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Title: Report on the Radiolaria Collected by H.M.S. Challenger During the Years 1873-1876, First Part: Porulosa (Spumellaria and Acantharia) - Report on the Scientific Results of the Voyage of H.M.S. Challenger During the Years 1873-76, Vol. XVIII
Author: Haeckel, Ernst, 1834-1919
Language: English
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BY H.M.S. CHALLENGER DURING THE YEARS 1873-1876, FIRST PART: PORULOSA
(SPUMELLARIA AND ACANTHARIA)***


images generously made available by Internet Archive (https://archive.org)



Note: Images of the original pages are available through
      Internet Archive. See
      https://archive.org/details/reportonradiolar01haecrich

      Second Part: Subclass Osculosa; Index
      Plates


Transcriber's note:

      Text enclosed by underscores is in italics (_Actissa_).

      Text enclosed by hash marks is in "gesperrt"
      (wide-spaced) type (#Larcoidea#).

      Page numbers enclosed by curly braces (example: {25}) have
      been incorporated to facilitate the use of the Index in
      Part II.

      Some typographical errors in the printed work have been
      corrected. They are listed at the end of the text.

      The Addenda & Errata (Second Part, pp. 1763-4) have been
      applied without further comment.



REPORT ON THE SCIENTIFIC RESULTS OF THE VOYAGE OF H.M.S. CHALLENGER
DURING THE YEARS 1873-76

Under the Command of Captain George S. Nares, R.N., F.R.S.
and the Late Captain Frank Tourle Thomson, R.N.

Prepared Under the Superintendence of
the Late Sir C. Wyville Thomson, KNT., F.R.S., &c.
Regius Professor of Natural History in the University of Edinburgh
Director of the Civilian Scientific Staff on Board
and Now of
John Murray
One of the Naturalists of the Expedition

ZOOLOGY--VOL. XVIII.

FIRST PART

Published by Order of Her Majesty's Government



Printed for Her Majesty's Stationary Office
and Sold by
London:--Eyre & Spottiswoode, East Harding Street, Fetter Lane
Edinburgh:--Adam & Charles Black
Dublin:--Hodges, Figgis, & Co.
1887

Price (in Two Parts, with a Volume of Plates) £5, 10s.



CONTENTS.



REPORT on the RADIOLARIA collected by H.M.S. CHALLENGER during the years
1873-1876.

By ERNST HAECKEL, M.D., Ph.D., Professor of Zoology in the University of
Jena.

FIRST PART.--PORULOSA.

(#SPUMELLARIA AND ACANTHARIA.#)



EDITORIAL NOTES.


The Report on the RADIOLARIA by Professor Ernst Haeckel of Jena occupies
the whole of the present Volume, the text being bound up in Two Separate
Parts and the Plates in a Third Part. The Report forms Part XL. of the
Zoological Series of Reports on the Scientific Results of the Expedition,
and is the largest single Report of the series which has up to this time
been published.

The Manuscript of the Systematic Part was written by Professor Haeckel in
the English language, and was received by me in instalments on the 12th
August 1884, 13th July and 4th December 1885, and 3rd June 1886. The
Introduction was written in German and was translated into the English
language by Mr. W. E. Hoyle of the Challenger Editorial Staff; the German
text being received in instalments between the 15th July 1886, and the 25th
January 1887.

The Challenger Naturalists found the representatives of this group of
animals to be universally distributed throughout ocean waters, and their
dead remains to be nearly equally widely distributed over the floor of the
ocean, the relative abundance and the species differing, however, with
change of locality, and their abundance or variety being intimately
connected with some of the most interesting and intricate problems of
general oceanography.

It was a fortunate circumstance that so distinguished a Naturalist, with
such an intimate knowledge of the RADIOLARIA, should have been willing to
undertake the laborious examination and description of the extensive
collections made during the Expedition. Professor Haeckel has devoted ten
years of his life to this work, and this Report sets forth the results of
his labours, on the conclusion of which he will be congratulated by all
Naturalists. The entire literature of the RADIOLARIA (from 1834 to 1884) is
completely recorded, and the older species (both living and fossil)
redescribed, so that the Report is a complete Monograph, which will be an
invaluable aid to all future Investigators.



  CHALLENGER OFFICE, 32 QUEEN STREET,
    EDINBURGH, _1st February 1887._



THE

VOYAGE OF H.M.S. CHALLENGER.



#ZOOLOGY.#



  Report on the RADIOLARIA collected by H.M.S. Challenger during the Years
  1873-76. By ERNST HAECKEL, M.D., Ph.D., Professor of Zoology in the
  University of Jena.



PREFACE.


The significance of the Radiolaria in regard to the relations of life in
the ocean has been increased in a most unexpected manner by the discoveries
of the Challenger. Large swarms of these delicate Rhizopoda were found not
only at the surface of the open ocean but also in its different
bathymetrical zones. Thousands of new species make up the wonderful
Radiolarian ooze, which covers large areas of the deep-sea bed, and was
brought up from abysses of from 2000 to 4000 fathoms by the sounding
machine of the Challenger. They open a new world to morphological
investigation.

When ten years ago (in the autumn of 1876) I accepted the enticing
invitation of Sir Wyville Thomson to undertake the investigation of these
microscopic creatures, I hoped to be able to accomplish the task with some
degree of completeness within a period of from three to five years, but the
further my investigations proceeded the more immeasurable seemed the range
of forms, like the boundless firmament of stars. I soon found myself
compelled to decide between making a detailed study of a selection of
special forms or giving as complete a survey as possible of the varied
forms of the whole class; and I decided upon the latter course, having
regard both to the general plan of the Challenger Reports, and to the
interests of our acquaintance with the class as a whole. I must, however,
confess at the close of my work that my original intention is far from
having been fulfilled. The extraordinary extent and varied difficulties of
the undertaking must excuse the many deficiencies.

The special examination of the Challenger collection was for the most part
completed in the summer of 1881; I collected its results in my Entwurf
eines Radiolarien-Systems auf Grund von Studien der Challenger-Radiolarien
(Jenaische Zeitschr. f. Naturw., Bd. xv., 1881). Since the manuscript of
this preliminary communication was completed only a few days before my
departure for Ceylon, and since I was unable to correct the proofs myself,
several errors have crept into the Prodromus Systematis Radiolarium
included in it. These have been corrected in the following more extensive
working out of it. Even at that time I had distinguished 630 genera and
more than 2000 species; but on the revision of these, which I undertook
immediately on my return from India, this number was considerably
increased. The total number of forms here described amounts to 739 genera
and 4318 species; of these 3508 are new, as against 810 previously
described. In spite of this large number, however, and in spite of the
astonishing variety of the new and marvellous forms, the riches of the
Challenger collection are by no means exhausted. A careful and patient
worker who would devote a second decade to the work, would probably
increase the number of new forms (especially of the smaller ones) by more
than a thousand; but for a really complete examination, the lifetime of one
man would not suffice.

The richest source of the Challenger material is the Radiolarian ooze of
the central Pacific Ocean (Stations 265 to 274). This remarkable deep-sea
mud consists for the greater part of well-preserved siliceous shells of
Polycystina (SPUMELLARIA and NASSELLARIA). Not less important, however,
especially for the study of the ACANTHARIA and PHÆODARIA, are the wonderful
preparations stained with carmine and mounted in Canada balsam on the spot
by Dr. John Murray. One such preparation (_e.g._, from Station 271) often
contains twenty or thirty, sometimes even fifty new species. In many of
these preparations the individual parts of the unicellular organism are so
well preserved that they show clearly the characteristic peculiarities of
the legions and orders. Since the material for these preparations was taken
with the tow-net, not only from the surface of the sea but also from
different bathymetrical zones, it furnishes valuable conclusions regarding
the chorology, as well as the physiology and morphology of the group. For
many new discoveries I am indebted to the study of such preparations, of
which I have examined about a thousand from 168 different Stations (compare
§ 240). In addition to these about 100 bottles were handed to me,
containing partly bottom-deposits, partly tow-net gatherings.

Sir Wyville Thomson, who directed the investigations of the Challenger with
so much devotion, and only partly saw its results, has laid me under a deep
debt of obligation; not less is this the case, however, with his successor,
Dr. John Murray. I am especially indebted to both gentlemen for the freedom
they have allowed me in the carrying out of my work, and especially for the
permission to include a description of all known Radiolaria in the
Challenger Report, which has thus become a second edition many times
enlarged of my Monograph published in 1862. Since all previous literature
of the subject has been consulted and critically revised, it is hoped that
this Report will form a useful foundation for future investigations. All
names of sufficiently described Radiolaria published during the first half
century of our knowledge of the class (from 1834 to 1884), are inserted in
alphabetical order in the index at the end of this work.

In addition to the treasures of the Challenger, my own collection of
Radiolaria has yielded many new forms whose description is here included.
On my journeys to the Mediterranean (an account of which is given in the
introduction to my Monograph of the Medusæ), I have given special attention
to these delicate microscopic organisms for more than thirty years. Besides
the various points on the Mediterranean, the Atlantic Ocean at the Canaries
(in the winter of 1866-67) yielded many interesting new forms; whilst my
voyage across the Indian Ocean, from Aden to Bombay, in November 1881,
thence to Ceylon and back by Socotra in March 1882, was still more
productive. In particular, some extended excursions which I had the
opportunity of making from Belligemma and Matura (at the southern extremity
of Ceylon) gave me an insight into the rich treasures of the Indian Ocean.

Most important, however, as regards the knowledge of the Indian Radiolaria,
are the collections which Captain Heinrich Rabbe of Bremen has so
beautifully preserved during his many voyages through that region. In the
neighbourhood of Madagascar and the Cocos Islands more especially, and also
in the Sunda Archipelago, he met with large swarms of Radiolaria, among
which were many new and remarkable forms. These were of special value for
completing the chorology, and the more so since the course of the
Challenger in the Indian Ocean lay very far to the southwards. I will
therefore take this opportunity of repeating my best thanks to Captain
Rabbe for the friendly donation of his valuable collection.

The Radiolarian fauna of the North Atlantic Ocean, which was previously but
little known and only slightly increased by the investigations of the
Challenger, received a valuable increase from the interesting collections
made by Dr. John Murray on various expeditions to the Færöe Islands (on the
"Knight Errant" in 1880 and on the "Triton" in 1882). A large number of new
Radiolaria were captured in the Færöe Channel, partly at the surface of the
Gulf Stream, partly at various depths, and the proof was thus furnished
that at certain points in the North Atlantic Ocean Radiolaria are very
richly developed. I am further indebted to Dr. John Murray for the free use
of this important material as well as for much other assistance in the
carrying out of my work. Another rich source of Radiolaria I found in the
alimentary canal of pelagic animals from all seas. Medusæ, Siphonophoræ,
Salpæ, Pteropoda, Heteropoda, Crustacea, &c., which live partly at the
surface of the sea and partly at various depths, and swallow large masses
of Radiolaria, often contain numbers of their shells well-preserved in
their intestine. The alimentary canal of Fishes and Cephalopods too, which
live upon these pelagic animal frequently contains considerable quantities
of siliceous shells; and another newly discovered source has been found in
the coprolites of the Jurassic period, which consist largely of Radiolarian
skeletons.

In the investigation of this complicated system of organisms, I have
endeavoured on the one hand to give accurately the forms and dimensions of
the species observed, and on the other hand to present a survey of the
relationships of the different genera and families; and in this I have
striven especially to combine the phylogenetic aims of the natural system
with the essentially artificial divisions of a practical classification.
Being, however, a conscientious supporter of the theory of descent, I can
of course lay no stress upon the value of the categories, which are here
distinguished as Legions, Orders, Families, Genera, &c. All these
artificial systematic grades I regard as of merely relative value; and from
the same cause I attach no importance to the distinction of all the species
here described; many of them are probably only developmental stages, and
like my predecessors I have determined their boundaries on subjective
grounds. In the systematic working out of so much material one always runs
the risk of doing either too much or too little in the way of creating
species; but in the light of the theory of descent this danger is of no
consequence.

In the carrying out of this extensive task the friendly aid of Dr. Reinhold
Teuscher of Jena was of the greatest benefit to me; at my request he was at
the trouble of making a large number of accurate drawings with the camera
lucida, and he also undertook a long series, amounting to some 8000,
accurate micrometric measurements, which were of the greatest value in the
attempt to settle the important question of the constancy of the various
species; I have alluded to this in a note at the conclusion of the Report
(p. 1760). My best thanks are due to Dr. Teuscher for the patient and
careful manner in which he discharged these tedious tasks.

The figures of new species of Radiolaria (about 1600 in number) which
appear in the atlas of one hundred and forty plates accompanying this
Report, were nearly all drawn with the camera lucida, partly by Mr. Adolph
Giltsch and partly by myself. The names of the genera which appear at the
bottom of the plates have in many cases been changed since they were
printed off, as may be seen from the explanations which accompany them. Had
it been possible to complete the examination of the material before the
plates were commenced this might have been avoided, and in many cases a
better selection of figures might have been made. All the drawings have
been made upon the stone by the practised hand of Mr. Adolph Giltsch, in
his usual masterly manner, and his lithographic work, which has lasted
fully ten years, is the more valuable since he has himself microscopically
studied the greater part of the species figured. The fact that the atlas
presents so full a picture of the marvellous wealth of form of the
Radiolaria is especially due to his lively interest in the work, to his
unwearying care, and to his morphological acuteness. May it be the means of
inducing many naturalists to study more deeply this inexhaustible kingdom
of microscopic life, whose endless variety of wonderful forms justifies the
saying--_Natura in minimis maxima_.



CONTENTS.



  FIRST PART.

  GENERAL INTRODUCTION--                                       PAGE

    I. Anatomical Section (§§ 1-140),                             i
          Chapter    I. The Unicellular Organism,                 i
             "      II. The Central Capsule,                   xxiv
             "     III. The Extracapsulum,                       li
             "      IV. The Skeleton,                        lxviii

   II. Biogenetical Section (§§ 141-200),                     xciii
          Chapter    V. Ontogeny (Individual Development),    xciii
             "      VI. Phylogeny (Genealogical Development),    ci

  III. Physiological Section (§§ 201-225),                  cxxviii
          Chapter  VII. Vegetative Functions,               cxxviii
             "    VIII. Animal Functions,                       cxl

   IV. Chorological Section (§§ 226-250),                     cxlvi
          Chapter   IX. Geographical Distribution,            cxlvi
             "       X. Geological Distribution,              clxiv

    V. Bibliographical Section (§§ 251-254),                 clxxvi

  SYSTEMATIC PART,                                                1

    I.  Subclass PORULOSA,                                        6
            Legion I. SPUMELLARIA vel PERIPYLEA,                  6
                 Order  1. Colloidea,                            10
                   "    2. Beloidea,                             28
                   "    3. Sphæroidea,                           50
                   "    4. Prunoidea,                           284
                   "    5. Discoidea,                           402
                   "    6. Larcoidea,                           599

            Legion II. ACANTHARIA vel ACTIPYLEA,                716
                 Order  7. Actinelida,                          728
                   "    8. Acanthonida,                         740
                   "    9. Sphærophracta,                       795
                   "   10. Prunophracta,                        859

  SECOND PART.

    II. Subclass OSCULOSA,                                      889
          Legion III. NASSELLARIA vel MONOPYLEA,                889
               Order 11. Nassoidea,                             895
                 "   12. Plectoidea,                            898
                 "   13. Stephoidea,                            931
                 "   14. Spyroidea,                            1015
                 "   15. Botryodea,                            1103
                 "   16. Cyrtoidea,                            1126

          Legion IV. PHÆODARIA vel CANNOPYLEA,                 1521
               Order 17. Phæocystina,                          1542
                 "   18. Phæosphæria,                          1590
                 "   19. Phæogromia,                           1642
                 "   20. Phæoconchia,                          1710

  Note on the Dimensions and Measurements,                     1760

  ADDENDA,                                                     1761

  ERRATA,                                                      1763

  INDEX,                                                       1765



GENERAL INTRODUCTION.


----


ANATOMICAL SECTION.

A SKETCH OF OUR KNOWLEDGE OF THE ORGANISATION OF THE RADIOLARIA IN THE YEAR
1884.


----


CHAPTER I.--THE UNICELLULAR ORGANISM.

(§§ 1-50.)

1. _Definition of the Radiolaria._--RADIOLARIA are marine Rhizopoda, whose
unicellular body always consists of two main portions, separated by a
membrane; an inner _Central capsule_ (with one or more nuclei) and an
_Extracapsulum_ (the external calymma, which has no nucleus, and the
pseudopodia); the endoplasm of the former and the exoplasm of the latter
are connected by openings in the capsule-membrane. The central capsule is
partly the general central organ of the Radiolarian cell, partly the
special organ of reproduction, since its intracapsular protoplasm, along
with the nuclei embedded in it, serves for the formation of flagellate
spores. The extracapsulum is partly the general organ for intercourse with
the outer world (by means of the pseudopodia), partly the special organ of
protection (calymma) and nutrition (sarcomatrix). The majority of
Radiolaria develop also a skeleton for support and protection, which
presents the utmost variety of form, and is generally composed of silica,
sometimes of an organic substance (acanthin). The Radiolarian cell usually
leads an isolated existence (Monozoa _vel_ Monocyttaria); only in a small
minority (of one legion) are the unicellular organisms united in colonies
or coenobia (Polyzoa _vel_ Polycyttaria).

  The extent of the Radiolaria, as limited by the above definition, which I
  have made as compact as possible, differs in several important respects
  from that allowed to the group by all previous diagnoses. The shortest
  expression of its scope might perhaps be:--Rhizopoda with central capsule
  and calymma; for the most important character of the Radiolaria, and that
  by which they are distinguished from all other Rhizopoda, is the
  differentiation of the unicellular body into two principal parts of equal
  importance and their separation by a constant capsule-membrane.


2. _The Two Subclasses of the Radiolaria._--The systematic catalogue of the
Radiolaria, which forms the second part of this Report, and is brought up
to the year {ii}1884, contains 20 orders, 85 families, 739 genera, and 4318
species. The consideration that but a small proportion of the ocean his yet
been investigated renders it likely, however, that even this large number
does not include the half of the recent species. The great progress which
our knowledge of the organisation of the Radiolaria has made, by means of
comparative study, renders it possible to arrange this enormous mass of
forms in four main divisions or legions, and these are again related in
pairs, so that two divisions of the highest rank or subclasses are
constituted, the _Porulosa_ (or _Holotrypasta_) and _Osculosa_ (or
_Merotrypasta_).

  The division of the Radiolaria into two subclasses and four legions (or
  principal orders), I sought to establish in 1883 in a communication on
  the Orders of the Radiolaria (Sitzb. Jena Gesellsch. Med. u. Naturwiss.,
  February 16, 1883). As a believer in the theory of descent, I regard all
  the systematic arrangements of specialists as artificial, and all their
  divisions as subjective abstractions, and hence I shall be guided in the
  establishment of such groups as subclasses, legions, orders, &c., by
  purely practical considerations, especially by the desire to give as
  ready a survey as possible of the complex multitude of forms (compare §§
  154 to 156).


3. _Porulosa or Holotrypasta._--The subclass Porulosa or Holotrypasta
includes the two legions, PERIPYLEA or SPUMELLARIA, and ACTIPYLEA or
ACANTHARIA, which agree in the following constant and important
characters:--(1) The _Central Capsule_ is primitively a sphere, and retains
this homaxon form in the majority of the species. (2) The _Membrane_ of the
central capsule is everywhere perforated by very numerous minute pores, but
possesses no larger principal aperture (osculum). (3) The _Pseudopodia_
radiate in all directions and in great numbers from the central capsule,
passing through its pores. (4) The _Equilibrium_ of the floating
unicellular body is in most Porulosa pantostatic (indifferent) or
polystatic (plural-stable), since a vertical axis is either absent, or, if
present, has its two poles similarly constituted. (5) The _Ground-forms_ of
the skeleton are therefore almost always either spherotypic or
isopolar-monaxon, very rarely zygotypic. The two legions of the Porulosa
are distinguished mainly by the skeleton of the SPUMELLARIA (or PERIPYLEA)
being siliceous, never centrogenous, nor composed of acanthin, whilst in
the ACANTHARIA (or ACTIPYLEA) it is always centrogenous and made up of
acanthin; hence in the former the nucleus is always central, in the latter
always excentric.


4. _Osculosa or Merotrypasta._--The subclass Osculosa or Merotrypasta
includes the two legions MONOPYLEA or NASSELLARIA, and CANNOPYLEA or
PHÆODARIA, which agree in the following constant and important
characters:--(1) The Central Capsule is originally monaxon (ovoid or
spheroidal) and retains this ground-form in most of the species. (2) The
_Membrane_ of the central capsule possesses a single large principal
aperture (osculum) at the basal pole of the vertical main axis. (3) The
_Pseudopodia_ radiate from a stream of sarcode which passes out from the
central capsule only on one side, namely, through the principal aperture.
(4) The _Equilibrium_ of the floating body is {iii}monostatic or unistable,
since the two poles of the principal axis are always more or less different
from each other. (5) The _Ground-forms_ of the skeleton are, therefore, for
the most part grammotypic (centraxon) or zygotypic (centroplan), rarely
spherotypic. The two legions of the Osculosa are distinguished chiefly by
the principal opening (osculum) being closed by a porous plate (porochora
with its podoconus) in the NASSELLARIA (or MONOPYLEA), and by a radiate
cover (operculum with its astropyle) in the PHÆODARIA (or CANNOPYLEA).


5. _The four Legions of Radiolaria._--The four principal groups of
Radiolaria, to which we have given the name "legions," are natural units,
since the most important peculiarities in the structure of the central
capsule are quite constant within the limits of the same legion, and since
all the forms in the same legion may be traced without violence to the same
phylogenetic stem. The four legions are, however, related to each other, in
so far as they all exhibit those characters which distinguish the
Radiolaria from other Protista. The two which compose the Porulosa (§ 3)
seem somewhat more nearly related to each other than to the two which make
up the Osculosa (§ 4). When, however, the attempt is made to bring them all
into a phylogenetic relationship, it undoubtedly appears that the
SPUMELLARIA (or PERIPYLEA) are the primitive stem, out of which the other
three have been developed as independent branches. All three have been
derived, probably independently, from the most ancient stem-form of the
SPUMELLARIA, the spherical _Actissa_.


6. _Peripylea or Spumellaria._--Those Radiolaria which we call "PERIPYLEA"
on account of the constitution of their central capsule, or "SPUMELLARIA"
on account of the nature of their skeleton, are separated from the other
three legions of the class by the combination of the following constant
characters:--(1) The _Membrane_ of the central capsule is single and evenly
perforated all over by innumerable fine pore-canals, but without any larger
principal opening (osculum). (2) The _Nucleus_ always lies centrally in the
SPUMELLARIA monozoa and is serotinous, for it divides only at a later
period into the nuclei of the spores; in the SPUMELLARIA polyzoa it is
precocious, and divides early into many small nuclei. (3) The _Pseudopodia_
are exceedingly numerous and distributed evenly over the whole surface of
the central capsule. (4) The _Calymma_ contains no phæodium. (5) The
_Skeleton_ is seldom wanting, is never centrogenous, and is always
siliceous. (6) The _Ground-form_ of the central capsule is originally
spherical (often modified); that of the skeleton is also spherical or, in
the majority of cases, derived in different ways from the sphere.


7. _Actipylea or Acantharia._--These Radiolaria which we call "ACTIPYLEA"
on account of the constitution of their central capsule, or "ACANTHARIA"
from the formation of their skeleton, are separated from the other three
legions by the combination of the following constant characters:--(1) The
_Membrane_ of the central capsule is single and {iv}perforated by numerous
fine pore-canals, which are regularly distributed in series or groups, but
without a larger principal opening (osculum). (2) The _Nucleus_ is always
excentric and generally precocious, since it divides early by a peculiar
process of budding into numerous small nuclei. (3) The _Pseudopodia_ are
very numerous and distributed regularly in groups (or series united into a
network). (4) The _Calymma_ contains no phæodium. (5) The _Skeleton_ is
generally present, always centrogenous, and composed of acanthin. (6) The
_Ground-form_ of the central capsule is originally spherical (often
modified), that of the skeleton polyaxon (often modified).


8. _Monopylea or Nassellaria._--Those Radiolaria which we call "MONOPYLEA"
from the formation of their central capsule, or "NASSELLARIA" from the
nature of their skeleton, are distinguished from the other three legions of
the class by the combination of the following constant characters:--(1) The
_Membrane_ of the central capsule is single, and has only one large
principal opening (osculum) at the basal pole of the vertical main axis;
this osculum is closed by a perforated lid (porochora or operculum porosum)
from which there arises within the central capsule a peculiar cone of
threads or pseudopodia (podoconus). (2) The _Nucleus_ is usually excentric
and is always serotinous, since it only divides at a comparatively late
period into spore-nuclei. (3) The _Pseudopodia_ are not very numerous and
arise by division of a single stem or bundle of threads of sarcode, which
issues from the porochora. (4) The _Calymma_ contains no phæodium. (5) The
_Skeleton_ (very rarely absent) is never centrogenous, but always
extracapsular and siliceous. (6) The _Ground-form_ of the central capsule
is always monaxon (with a vertical allopolar main axis), originally ovoid,
often modified; that of the skeleton is also generally monaxon, often
modified (triradial or bilateral).


9. _Cannopylea or Phæodaria._--Those Radiolaria which we call "CANNOPYLEA"
from the constitution of their central capsule, or "PHÆODARIA" on account
of their peculiar phæodium, are distinguished from the other three legions
by the combination of the following characters:--(1) The _Membrane_ of the
central capsule is double, consisting of a strong outer and delicate inner
capsule, and has only one principal opening (osculum) at the basal pole of
the vertical main axis; this osculum is closed by a radiate cover
(astropyle or operculum radiatum), from the centre of which arises an
external tubular spout (proboscis). Occasionally a few small accessory
openings (parapylæ) are present besides the principal opening. (2) The
_Nucleus_ lies centrally or subcentrally in the capsule (in the vertical
main axis), and is serotinous, inasmuch as it only divides at a late period
into spore-nuclei. (3) The _Pseudopodia_ are usually very numerous and
arise from a thick sarcomatrix, formed by the spreading out of a thick stem
of sarcode, which issues from the astropyle. (4) The _Calymma_ always
contains a phæodium or peculiar voluminous excentric mass of pigment. (5)
The _Skeleton_ (very rarely absent) is never centrogenous, always
extracapsular and formed of a silicate of carbon. (6) The {v}_Ground-form_
of the central capsule is always monaxon (with a vertical allopolar main
axis) and generally spheroidal; that of the skeleton is very varied.


10. _Synopsis of the Subclasses and Legions:--_

  +-----------------------------------------------------------------+
  |                        FIRST SUBCLASS.                          |
  +-----------------------------------------------------------------+
  |                  PORULOSA vel HOLOTRYPASTA.                     |
  |                                                                 |
  |   Central capsule originally spherical, without osculum or      |
  |      principal opening, with innumerable fine pores.            |
  +-----------------------------------------------------------------+
  |           Legion I.            |           Legion II.           |
  |          SPUMELLARIA.          |          ACANTHARIA.           |
  |          (PERIPYLEA).          |         (ACTIPYLEA).           |
  +--------------------------------+--------------------------------+
  |       _Central capsule_        |       _Central capsule_        |
  |      originally spherical,     |      originally spherical,     |
  |            homaxon.            |            homaxon.            |
  |                                |                                |
  |       _Capsule-membrane_       |       _Capsule-membrane_       |
  |            single,             |            single,             |
  |       pores innumerable,       |        pores numerous,         |
  |      distributed all over.     |     regularly distributed.     |
  |                                |                                |
  |      _Nucleus_ central,        |      _Nucleus_ excentric,      |
  |     originally spherical       |    (usually dividing early).   |
  |    (usually dividing late).    |                                |
  |                                |                                |
  |_Skeleton_ absent or siliceous, | _Skeleton_ always of acanthin, |
  |     never centrogenous.        |      always centrogenous.      |
  |                                |                                |
  |       _Calymma_ always         |       _Calymma_ always         |
  |       without phæodium.        |       without phæodium.        |
  +-----------------------------------------------------------------+
  |                       SECOND SUBCLASS.                          |
  +-----------------------------------------------------------------+
  |                  OSCULOSA vel MEROTRYPASTA.                     |
  |                                                                 |
  |     Central capsule originally monaxon, with an osculum at      |
  |           the basal pole of the vertical main axis.             |
  +-----------------------------------------------------------------+
  |           Legion III.          |           Legion IV.           |
  |          NASSELLARIA.          |           PHÆODARIA.           |
  |          (MONOPYLEA).          |          (CANNOPYLEA).         |
  +--------------------------------+--------------------------------+
  |       _Central capsule_        |       _Central capsule_        |
  |       originally ovoid,        |       always spheroidal,       |
  |            monaxon.            |            monaxon.            |
  |                                |                                |
  |      _Capsule-membrane_        |      _Capsule-membrane_        |
  |           single,              |        always double,          |
  |       a porous area            |        an astropyle            |
  |   (porochora) at the oral      |   (with radiate operculum)     |
  |    pole of the main axis.      |       at the oral pole         |
  |                                |       of the main axis.        |
  |                                |                                |
  |     _Nucleus_ excentric,       |  _Nucleus_ always spheroidal,  |
  |     near the aboral pole       |       in the main axis         |
  |        (dividing late).        |       (dividing late).         |
  |                                |                                |
  |      _Skeleton_ siliceous,     |   _Skeleton_ of a silicate,    |
  |        usually monaxon,        |     always extracapsular.      |
  |         extracapsular.         |                                |
  |                                |                                |
  |       _Calymma_ always         |       _Calymma_ always         |
  |       without phæodium.        |        with phæodium.          |
  +-----------------------------------------------------------------+


11. _Individuality of the Radiolaria._--Like other Protozoa the Radiolaria
are unicellular organisms, the whole fully developed organisation of which
falls under the category of a single cell, both morphologically and
physiologically. Since this view is based upon the composition of the
individual body out of two different morphological elements, nucleus and
protoplasm, it is at once justified in the case of the majority of
Radiolaria, in which the plasmatic body encloses only a single nucleus (the
so-called "Binnen-Bläschen"); such is the case in all the SPUMELLARIA
monozoa, NASSELLARIA and PHÆODARIA. This aspect of the case might appear
doubtful in those Radiolaria in which the simple primary cell-nucleus
divides early into numerous small secondary nuclei, as is the case in the
SPUMELLARIA polyzoa and most ACANTHARIA. Strictly speaking, the
multinucleate central capsule should in such cases be regarded as a
syncytium; but since the individual unity of the unicellular organism is as
clearly defined in these precocious multinuclear Radiolaria as in the
ordinary serotinous forms, the former must be considered unicellular
Rhizopods just as are the latter. This mode of regarding {vi}the case is
the more necessary, inasmuch as the early division of the nucleus has no
further influence upon the organisation. Just as in many other classes of
the Protista there are monozootic (solitary) and polyzootic (social) forms,
so also in the Radiolaria there are in addition to the ordinary monozootic
or monobious forms certain families in which colonies or coenobia are
formed by the association of individuals; this distinction may be expressed
by the terms "Monocyttaria" and "Polycyttaria."

  The unicellular nature of the Radiolaria was first established by Richard
  Hertwig in 1879 (L. N. 33),[1] and brought into conformity with our
  present histiological knowledge and the new reform of the cell-theory.
  Huxley, however, who was in 1851 the first to examine living Radiolaria
  accurately, declared _Thalassicolla nucleata_ to be a unicellular
  Protozoon, and the individual central capsules of _Sphærozoum punctatum_
  to be cells, but, owing to the then condition of the cell-theory, he was
  unable to give a conclusive demonstration of this view. Later, when
  Johannes Müller in 1858 and myself in 1862 recognised the peculiar
  "yellow cells" which occur in large numbers in many Radiolaria as true
  nucleated cells, it appeared impossible any longer to maintain the
  unicellular nature of the Radiolaria; also the great complication which I
  showed to exist in the structure of _Thalassicolla_ appeared to
  contradict it. Only after Cienkowski (1871) and Brandt (1881) had shown
  that the "yellow cells" do not belong to the Radiolarian organism, but
  are symbiotic unicellular algæ, was it possible to revive and demonstrate
  anew the unicellular nature of the Radiolaria.


12. _Morphological Individuality._--From the morphological standpoint the
individuality of the unicellular elementary organism is obvious in the
ordinary solitary Radiolaria (Monobia), and is to be so regarded that the
whole body with all its constituent parts, and not merely the central
capsule, is to be regarded as _a cell_. Naturally the xanthellæ or yellow
cells (§§ 76, 90), which as independent algæ live in symbiosis with many
Radiolaria, must be excluded. The unicellular organisation of the
Radiolaria is further to be distinguished from that of the other Protista,
inasmuch as an internal membrane (capsule-membrane) separates the central
(medullary) from the peripheral (cortical) portion. In the coenobia of the
social Radiolaria (or Polycyttaria), the morphological individuality
persists only as regards the medullary portions of the aggregated cells
(the individual central capsules), while the cortical portions fuse
completely to form a common extracapsulum. Hence in these SPUMELLARIA
polyzoa two different stages of morphological individuality must be
distinguished, the _Cell_ as a _Morphon of the first stage_, and the
_Coenobium_ as a _Morphon of the second stage_.


13. _Physiological Individuality._--From the physiological standpoint also
the individuality of the unicellular organism is immediately obvious in the
case of the ordinary solitary Radiolaria (Monobia); as in other Protista it
fulfils all the functions of life by itself alone. This physiological
individuality of the monobious Radiolarian cell is furthermore not
influenced by the xanthellæ, which live as independent algæ in symbiosis
with many Radiolaria; even though these often by the production of starch
assist in the {vii}nourishment of the Radiolaria, yet they are by no means
indispensable to them. On the other hand, the physiological individuality
offers more complicated relations in the social Radiolaria (Polycyttaria)
which live united in colonies or coenobia. Here the actual _Bion_ (or the
fully developed physiological individual) is not represented by the
individual cells, but by the whole multicellular coenobium, which in each
species has a definite form and size. In these coenobia, which are usually
spherical or cylindrical jelly-like masses, several millimeters in
diameter, numerous cells are so intimately united that only their medullary
portions (the central capsule with the endoplasm) remain independent; the
cortical portions (calymma and exoplasm) on the contrary uniting into a
common extracapsulum. This discharges, as a whole, the functions of
locomotion, sensation, and inception of nutriment, while the separate
central capsules act in the main only as reproductive organs (forming
spores) and partly also as the central organs of metastasis (digestion).
Each coenobium may also be regarded as a polycyttarium, _i.e._, a
"multicellular Radiolarian," whose numerous central capsules represent so
many sporangia or spore-capsules.

  On this head compare the section in my monograph of 1862 (L. N. 16),
  entitled Die Organisation der Radiolarien-Colonien; _Polyzoen_ oder
  _Polycyttarien?_ (pp. 116 to 126); and also R. Hertwig, Zur Histologie
  der Radiolarien, 1876 (L. N. 26, p. 23).


14. _Monocyttaria_ and _Polycyttaria_.--In the majority of the Radiolaria
each unicellular organism passes its individual life in an isolated
condition (as a Monocyttarium). Only in a part of the SPUMELLARIA numerous
unicellular individuals are united into societies which are regarded as
coenobia or colonies (Polycyttaria). This is the case in three different
families belonging to the PERIPYLEA, in the Collozoida (without a skeleton,
Pl. 3), the Sphærozoida (with a Beloid skeleton, Pl. 4), and the
Collosphærida (with a Sphæroid skeleton, Pls. 5-8). All three families of
Polycyttaria (or social Radiolaria), agree in their mode of forming
colonies, since the central capsules of the social individuals remain
separate and lie in a common jelly-like mass, which is formed by the fusion
of their extracapsulum. The chief part of the voluminous colonies, which
attain a diameter of several millimetres (sometimes more than 1 cm.), and
are generally spherical, ellipsoidal or cylindrical, consists therefore of
the jelly-like calymma, and this is penetrated by a sarcoplegma, to whose
meshes all the individual organisms contribute by means of the pseudopodia,
which radiate from their sarcomatrix. A further peculiarity in which the
social SPUMELLARIA differ from the solitary consists in the fact that the
former are precocious and the latter serotinous in the division of the
nucleus (§ 64). Whilst in the solitary or monozootic SPUMELLARIA the middle
of the central capsule is occupied by the simple nucleus, and this divides
only at a late period (immediately before the formation of spores) into the
numerous spore nuclei, in the colonial or polyzootic SPUMELLARIA this
division takes place very early, and the middle of each central capsule is
usually occupied by an oil-globule.

  {viii}The colonial Radiolaria were described as early as the year 1834 by
  Meyen, the first investigator of the class, under the name _Sphærozoum_,
  and, as _Palmellaria_, compared with the gelatinous colonies of the
  Nostochineæ. The first accurate observations upon their structure were,
  however, made in 1851 by Huxley, who described examples of all three
  families under the name _Thalassicolla punctata_.  More extended,
  however, were the investigations of Johannes Müller, who in his
  fundamental work (1858) divided the whole class Radiolaria into
  _Solitaria_ and _Polyzoa_.  The _Radiolaria solitaria_ he divided into
  Thalassicolla, Polycystina and Acanthometra, the _Radiolaria polyzoa_
  into Sphærozoa (without a shell) and Collosphæra (with a shell).  The
  most accurate delineation of the Polycyttaria was given by Hertwig in his
  beautiful memoir, Zur Histologie der Radiolarien (1876). Quite recently,
  however (1886), since the completion of my manuscript upon the Challenger
  Radiolaria, a very complete Monograph of the Polycyttaria has appeared by
  Karl Brandt, Die colonie-bildenden Radiolarien (Sphærozoen) des Golfes
  von Neapel und der angrenzenden Meeres-Abschnitte (276 pp., 8 pls.,
  Berlin).  It contains in particular most valuable contributions to the
  physiology and histology.


15. _The Central Capsule and Extracapsulum._--The special peculiarity of
the unicellular Radiolarian organism, by which it is clearly distinguished
from all other Rhizopoda (and indeed from most other Protista), is its
differentiation into two separate chief constituents, the central capsule
and extracapsulum, and the formation of a special membrane which separates
them. This, the capsule-membrane, is not to be compared with an ordinary
cell-membrane, as an external layer, but rather to be regarded as an
internal differentiated product. The extracapsulum or external (cortical)
portion of the body is in most Radiolaria more voluminous than the central
capsule or inner (medullary) portion. The exoplasm of the former (the
cortical or extracapsular protoplasm) is emphatically different from the
endoplasm of the latter (the medullary or intracapsular protoplasm).
Besides the most important vital processes are distributed by division of
labour so completely between them that they appear most distinctly
co-ordinated. The central capsule is on the one hand the general central
organ of the "cell-soul" for the discharge of its sensory and motor
functions (comparable to a ganglion-cell), on the other hand the special
organ of reproduction (sporangium). The extracapsulum, also, is not less
significant, since on the one hand its calymma acts as a protecting
envelope to the central capsule, as a support to the pseudopodia, and a
foundation for the skeleton or a matrix for the development of the shell,
and on the other hand its pseudopodia are of the utmost importance as
peripheral organs of movement and sensation as well as of nutrition and
respiration. The _central capsule_ and the _extracapsulum_ are therefore to
be regarded both morphologically and physiologically as the two
_characteristic co-ordinated principal parts_ of the unicellular
Radiolarian organism.

  In most of the more modern delineations of the Radiolaria the central
  capsule is regarded as the "cell proper" and its membrane as the
  "cell-wall." The following facts are opposed to the correctness of this
  interpretation:--1. In most Radiolaria the exoplasm is clearly different
  from {ix}the endoplasm, and the former is more voluminous than the
  latter. 2. In all Radiolaria the division of labour is so carried out
  between the central capsule and the extracapsulum, that the physiological
  significance and independence of both principal parts of the cell is
  almost equally great. 3. It is only in the ACANTHARIA that the formation
  of the skeleton takes place within the central capsule; in all the other
  three legions it is quite independent of it.


16. _The Malacoma and Skeleton._--Whilst the division of the unicellular
organism into central capsule and extracapsulum is undoubtedly the most
important character of the Radiolarian organism, the development of a
skeleton of peculiar and most varied form is of very striking significance.
This skeleton is _always a secondary product of the cell_, but is always
anatomically so independent, and so clearly marked off from the soft parts
or malacoma, that it seems advisable to regard both separately in a general
morphological survey. The skeleton stands in a different relation to each
of the two principal constituents of the malacoma. Only in the ACANTHARIA
is it centrogenous and developed from the central capsule outwards. In the
other three legions the skeleton never arises in the centre of the capsule;
in the NASSELLARIA and PHÆODARIA it is always extracapsular; in the
SPUMELLARIA it is also outside the central capsule originally, but
afterwards becomes often surrounded by it, and finally lies in most cases
partly within and partly without the central capsule. The chemical basis of
the skeleton in the ACANTHARIA is the curious acanthin (an organic
substance allied to chitin), in the PHÆODARIA a silicate of carbon, and in
the NASSELLARIA and SPUMELLARIA silica.


17. _Ground-Forms of the Radiolaria (Promorphology)._--The ground-forms of
the Radiolaria exhibit a greater variety than those of any other class in
the organic world, greater indeed than is to be found in all the remaining
groups together. For every conceivable ground-form which can be defined in
the system of promorphology is actually present in the Radiolaria; their
skeleton exhibits, as it were, in material existence, certain geometrical
ground-forms which are found in no other organisms. The cause of this
unexampled richness in different forms lies chiefly in the static relations
of the Radiolaria, which swim freely in the sea, partly also in the
peculiar plasticity of their protoplasm and the material of their
skeletons.

  Regarding the general system of ground-forms compare my Generelle
  Morphologie (1866, Bd. i. pp. 375-552; Bd. iv., Allgemeine
  Grundformenlehre). The ground-forms there proposed and systematically
  defined have, however, found but little acceptance (chiefly, no doubt,
  owing to the difficult and complicated nomenclature); but having now,
  twenty years after their publication, anew carefully revised and
  critically studied them, I can find no sufficient reason for abandoning
  the principles there adopted. On the contrary the study of the Challenger
  Radiolaria during the last ten years, with its incomparable wealth of
  forms, has only confirmed the accuracy of my system of ground-forms. The
  customary treatment of these in zoological and botanical handbooks (such
  as those of Claus and Sachs) is quite insufficient.


{x}18. _The Principal Groups of Geometrical Ground-Forms._--The great
variety of the geometrical ground-forms which are actually realised in the
variously shaped bodies of the Radiolaria, renders it desirable to classify
these in as small a number as possible of principal groups and a larger
number of subdivisions. As extensive principal groups four at least must be
distinguished; the _Centrostigma_ or Sphærotypic, the _Centraxonia_ or
Grammotypic, the _Centroplana_ or Zygotypic, and the _Acentrica_ or Atypic.
The natural centre of the body, about which all its parts are regularly
arranged, is in the first group a point (stigma), in the second a straight
line (principal axis), in the third a plane (sagittal plane), in the fourth
a centre is of course wanting.


19. _The Centrostigma or Sphærotypic Ground-Forms._--The first group of
geometrical ground-forms, here distinguished as sphærotypic or the
centrostigma, is undoubtedly the most important among the Radiolaria,
inasmuch as if these be considered monophyletic, it must be the original
one from which all the other ground-forms have been derived. The common
character of all these sphærotypic ground-forms is that their natural
centre is a point (stigma); thus there is no single principal axis (or
protaxon) such as is characteristic of the two following groups. The
sphærotypic ground-forms are subdivided into two important smaller groups,
the _spheres_ (Homaxonia) and the _endospherical polyhedra_ (Polyaxonia).
The spherical ground-forms, fully developed in the central capsule and
calymma of _Actissa_ and the #Sphæroidea# as well as in many ACANTHARIA,
present no different axes; all possible axes passing through the centre of
the body are equal (Homaxonia). In the endospherical polyhedra, on the
contrary, numerous axes (three at least) may be distinguished, which are
precisely equal to each other and different from all the remaining axes
(Polyaxonia). If the extremities of these axes, or the poles, which are all
equidistant from the common centre, be united by straight lines, a
polyhedral figure is produced whose angles all lie in the surface of the
sphere. According as the poles of the axes are at equal, subequal, or at
different distances from each other, we may divide the endospherical
polyhedra into regular, subregular and irregular. (See Gener. Morphol., Bd.
i. pp. 404-416.)


20. _The Centraxonia or Grammotypic Ground-Forms._--The second principal
group of organic ground-forms, here called grammotypic or centraxonia, is
characterised by the fact that a straight line (gramma) or a single
principal axis (protaxon) forms the natural centre of the body. This
important and extensive group is divided into two subgroups, those with one
axis (Monaxonia) and those with crossed axes (Stauraxonia); in the latter
different secondary transverse or cross-axes may be distinguished, but not
in the former. In the Monaxonia, therefore, every transverse section of the
body perpendicular to the principal axis is a circle, in the Stauraxonia,
on the contrary, a polygon. The Monaxonia are further subdivided into two
groups, in one of which the two poles of the principal axis {xi}are equal
and similar (Isopolar), in the other of which they are different
(Allopolar); in the former the two halves of the body, which are separated
by the equatorial plane (or the largest transverse plane, perpendicular to
the principal axis), are equal, in the latter unequal. Among the isopolar
uniaxial ground-forms (Monaxonia isopola) may be mentioned the ellipsoidal,
spheroidal, lenticular, &c.; to the allopolar uniaxial forms (Monaxonia
allopola) belong the conical, hemispherical, ovoid, &c. In the same way the
pyramidal ground-forms with crossed axes are divisible into two groups,
according as the two poles of the principal axis are equal or not. The
ground-form of the former is the double pyramid, that of the latter the
single pyramid. Both the double and the single pyramids may again be
subdivided, each into two important lesser groups, the regular and the
amphithect. In the first division the equatorial plane of the double and
the basal plane of the single pyramid is a regular polygon (square, &c.),
whilst in the other division it is an elongated or amphithect polygon
(rhombus, &c.); the crossed axes are equal in the former, unequal in the
latter. (See Gener. Morphol., Bd. i. pp. 416-494.)


21. _The Centroplana or Zygotypic Ground-Forms._--The third principal group
of ground-forms includes those which are bilaterally symmetrical in the
ordinary sense, or zeugitic or zygotypic; the natural centre of their body
is a plane. These forms are the only ones in which the distinction between
right and left is possible, since their body is divided by the median plane
(planum sagittale) into two symmetrical halves (right and left). In all
these zeugites the position of every part is determined by three axes
perpendicular to each other, and of these three dimensive axes two are
allopolar, one is isopolar. The two unlike poles of the principal (or
longitudinal) axis are the oral and aboral, the two unlike poles of the
sagittal (or vertical) axis are the dorsal and ventral; the two similar
poles of the frontal (or transverse) axis, however, are the right and left.
This important group of zeugitic or bilateral forms may also be divided
into two clearly distinct lesser groups, the _Amphipleura_ and the
_Zygopleura_. In the Amphipleura (or bilaterally radial ground-forms) the
"radial two-sided" body is produced by modification of a regular pyramid
(as _Spatangus_ from _Echinus_), and hence is composed of several (not less
than three) antimeres. In the Zygopleura (or bilaterally symmetrical
ground-forms) on the other hand, the bodies consist of two antimeres (as in
all the higher animals, Vertebrata, Arthropoda, &c.). (See Gener. Morphol.,
Bd. i. pp. 495-527.)


22. _The Acentrica or Atypic Ground-Forms._--Among the acentrica or
anaxonia are included all those ground-forms which are absolutely
irregular, and in which neither a definite centre nor constant axes can be
distinguished (_e.g._, most Sponges). These quite irregular ground-forms
are very rare among the Radiolaria, but nevertheless there may be referred
to them the amoeboid central capsule of some #Colloidea# (_Collodastrum_,
p. 27, Pl. 3, figs. 4, 5) among the SPUMELLARIA, the irregular shells of
many Collosphærida {xii}(Pl. 8, fig. 2), and the absolutely irregular
shells of the Phorticida and Soreumida among the #Larcoidea#. (See Gener.
Morphol., Bd. i. p. 400.)


23. _The Subsidiary Groups of Geometrical Ground-Forms._--The four natural
principal groups of ground-forms, which have just been defined according to
the nature of the centre of their bodies, may be divided again into
numerous subsidiary groups, defined by the relations of the constant axes
and the two poles of each axis, as well as by the number of the axes and
the differentiation of the secondary with respect to the principal axis.
The most important of these subsidiary groups into which the principal ones
are immediately divided are the following:--(1) The _Centrostigma_ (or
sphærotypic) are divided into spheres (Homaxonia) and endospherical
polyhedra (Polyaxonia). (2) The _Centraxonia_ (or grammotypic) into
uniaxial (Monaxonia) and those with crossed axes (Stauraxonia); among the
former of these may be distinguished the isopolar (phacotypic) and the
allopolar (conotypic); among the latter the double and single pyramids. (3)
The _Centroplana_ (or bilaterals) are divided into amphipleura (or
bilaterally radial) and zygopleura (or bilaterally symmetrical). (4) The
_Acentrica_ (or Anaxonia) or absolutely irregular ground-forms, present no
special subdivisions.

  For a complete system of the geometrical ground-forms and their relation
  to promorphological classification, see Gener. Morphol., Bd. i. pp.
  555-558.


24. _The Spherical or Homaxon Ground-Form._--The spherical is the only
absolutely regular ground-form, since only in it are all axes which pass
through the centre equal; it is very often realised among the Radiolaria,
especially in the SPUMELLARIA and ACANTHARIA, where it furnishes the common
original ground-form, but it is often to be seen in the shells of many
PHÆODARIA (in most #Phæosphæria#); on the other hand, it is never found
among the NASSELLARIA. Geometrical spheres, in the strict sense of the
term, are only to be found among the SPUMELLARIA and ACANTHARIA, namely, in
the central capsule of many #Collodaria# (Pls. 1, 2) and all #Sphæroidea#
(Pls. 11-30) as well as many Acanthometra and Acanthophracta (Pls.
128-138). Nevertheless, speaking generally, one includes those central
capsules and skeletons which have been distinguished here as endospherical
polyhedra. (On these ground-forms see Gener. Morphol., Bd. i. pp. 404-406.)


25. _The Endospherical Polyhedral Ground-Form._--The endospherical
polyhedron or polyaxon ground-form naturally follows the spherical or
homaxon. Under it are included all polyhedra whose angles fall in the
surface of a sphere; this ground-form is especially common among the
SPUMELLARIA, especially in the shells of #Sphæroidea#, but is also found
among the ACANTHARIA (especially in the Astrolophida and #Sphærophracta#),
as well as among the #Phæosphæria# (in most genera of the Orosphærida,
Sagosphærida, and Aulosphærida). Strictly speaking, all those
lattice-shells which have {xiii}been incorrectly called "spherical" belong
to this category, for they are none of them true spheres in the geometrical
sense (like the central capsules of the #Sphæroidea#), but rather
endospherical polyhedra, whose angles are indicated by the nodal points of
the lattice shell, or the radial spines which spring from them. These
endospherical polyhedra may be divided into three groups, the regular,
subregular, and irregular. Of _regular polyhedra_, properly so-called, it
may be shown geometrically that only five can exist, namely, the regular
tetrahedron, cube, octahedron, dodecahedron, and icosahedron. All these are
actually manifested among the Radiolaria, although but seldom.  Much more
common are the _subregular endospherical polyhedra_, _e.g._, spherical
lattice-shells with regular hexagonal meshes of equal size; they are never
exactly equal nor perfectly regular, but the divergences are so
insignificant that they escape superficial observation (Pl. 20, figs. 3, 4;
Pl. 26, figs. 1-3). On the contrary in the _irregular endospherical
polyhedra_ the meshes of the lattice-sphere are more or less different in
size and often in form also (Pl. 28, figs. 4, 8; Pl. 30, figs. 4, 6). The
five truly regular polyhedra require separate notice on account of their
importance. (See Gener. Morphol., Bd. i. p. 406.)


26. _The Regular Icosahedral Ground-Form._--The ground-form whose
geometrical type is the regular icosahedron (bounded by twenty equilateral
triangles) is rarely exemplified, but it occurs among the PHÆODARIA in the
Circoporid genus _Circogonia_ (Pl. 117, fig. 1), and also in certain
Aulosphærida, but, apparently, only as an accidental variation (_e.g._,
_Aulosphæra icosahedra_). Furthermore, this ground-form may also be assumed
to occur in those #Sphæroidea# whose spherical lattice-shells bear twelve
equidistant radial spines (_e.g._, many species of _Acanthosphæra_,
_Heliosphæra_, and other Astrosphærida); the basal points of these spines
indicate the twelve angles of the regular icosahedron. (See on this head
Gener. Morphol., Bd. i. p. 411.)


27. _The Regular Dodecahedral Ground-Form._--The ground-form whose
geometrical type is the regular dodecahedron (or pentagonal dodecahedron),
bounded by twelve equilateral and equiangular pentagons, is very rarely
found perfectly developed, as in _Circorrhegma dodecahedra_ (Pl. 117, fig.
2). This form is by no means so common among the Radiolaria as in the
pollen grains of plants (_e.g._, _Buchholzia maritima_, _Fumaria spicata_,
_Polygonum amphibium_, &c.). It can, however, be regarded as present in all
those #Sphæroidea# whose spherical lattice-shells bear twenty equal and
equidistant radial spines (_e.g._, many species of _Acanthosphæra_,
_Heliosphæra_, and other Astrosphærida); the basal points of these spines
mark out the twenty angles of the regular pentagonal dodecahedron. (See
Gener. Morphol., Bd. i. p. 412.)


28. _The Regular Octahedral Ground-Form._--The ground-form whose
geometrical type is the regular octahedron (bounded by eight equilateral
triangles), commonly appears among the SPUMELLARIA in the family
Cubosphærida (p. 169, Pls. 21-25). In {xiv}these #Sphæroidea# the typical
ground-form is usually indicated by six equal radial spines, which are
opposed to each other in pairs, and lie in three similar axes perpendicular
to each other; these are the three axes of the tesseral crystallographic
system; one of them is vertical, whilst the other two cross each other at
right angles in its centre. Occasionally, too, the spherical form of the
lattice-shell passes over into that of the regular octahedron (Pl. 22,
figs. 8, 10). The same form recurs in _Circoporus_ (Pl. 117, fig. 6) among
the PHÆODARIA. In the vegetable kingdom it is exhibited by the antheridia
of _Chara_. It is not found in the NASSELLARIA and ACANTHARIA. (See Gener.
Morphol., Bd. i. p. 412.)


29. _The Regular Cubic Ground-Form._--The ground-form whose geometrical
type is that of a die or cube, is actually presented in a very striking
manner by various Radiolaria. Among the SPUMELLARIA it occurs in certain
#Sphæroidea#, _e.g._, in the Astrosphærid genera _Centrocubus_ and
_Octodendron_ (Pl. 18, figs. 1-3); in these the central medullary shell is
a complete cube, bounded by six equal squares, from the eight angles of
which eight equal radial spines project. This form can also be regarded as
present in those #Sphæroidea# whose spherical lattice-shell bears eight
equal and equidistant radial spines (many Astrosphærida). Besides these the
cubic ground-form is to be seen in certain NASSELLARIA of the family
Tympanida, especially in _Lithocubus_ (Pl. 82, fig. 12; Pl. 94, fig. 13),
in many species of _Acrocubus_, _Microcubus_, &c.; the twelve bars of its
lattice-skeleton correspond often exactly to the edges of the cube. (See
Gener. Morphol., Bd. i. p. 413.)


30. _The Regular Tetrahedral Ground-Form._--The ground-form whose
geometrical type is the regular tetrahedron, bounded by four equilateral
triangles, occurs less frequently in the Radiolaria than the other four
regular polyhedra. Among the SPUMELLARIA it is found in the #Beloidea#, and
especially in those members of the Thalassosphærida and Sphærozoida whose
spicules bear four equal branches, diverging at equal angles from a common
centre. Precisely the same structure is seen also among the NASSELLARIA in
some #Plectoidea#, as in _Tetraplagia_ among the Plagonida, and
_Tetraplecta_ among the Plectanida. The skeleton of both these genera
consists of four equal rods, which radiate at equal angles from a common
centre, just as do the axes of the regular tetrahedron. The tetrahedral
form of these #Plectoidea# is the more important and interesting since on
the one hand it is related to the similar spicular form of the #Beloidea#,
and on the other perhaps furnishes the starting point from which _Cortina_
among the NASSELLARIA may be derived (_Plagoniscus_, _Plectaniscus_). (See
Gener. Morphol., Bd. i. p. 415.)


31. _The Isopolar-Monaxon or Phacotypic Ground-Form._--The isopolar
uniaxial or phacotypic ground-form is characterised by the possession of a
vertical main axis with {xv}equal poles, whilst no transverse axes are
differentiated. All horizontal planes which cut the axis at right angles
are circles, and increase in size from the poles towards the equator. The
most important ground-forms of this group are the _phacoid_ (the lens or
oblate spheroid) and the _ellipsoid_ (or prolate spheroid). Phacoids (or
geometrical lenses with blunt margins) are very often presented by the
central capsules of the #Discoidea# and of many ACANTHARIA (Quadrilonchida
and Hexalaspida), but the lattice-shells of many SPUMELLARIA and ACANTHARIA
exhibit the same form, as also do a few PHÆODARIA (_e.g._, _Aulophacus_).
True geometrical ellipsoids are seen in the central capsules of many
#Prunoidea# among the SPUMELLARIA, and of many Amphilonchida and
Belonaspida among the ACANTHARIA. Furthermore, the lattice shells of many
species of these groups retain the same essential form, _e.g._, many
Ellipsida, Druppulida, and Spongurida (Pls. 13-17, and 39), as well as most
Belonaspida. (See Gener. Morphol., Bd. i. p. 422.)


32. _Allopolar-Monaxon or Conotypic Ground-Form._--The allopolar uniaxial
or conotypic ground-form is characterised by the possession of a vertical
main axis whose two poles are unlike, while no transverse axes are
differentiated.  All horizontal planes cutting the main axis at right
angles are circles, and decrease more rapidly from the largest plane
towards the basal than towards the apical pole.  The most important
ground-forms of this group are the ovoid, the cone, and the hemisphere.
They often occur (and in geometrical perfection) in the egg-shaped central
capsule and podoconus of the NASSELLARIA, as well as in the shells of
several groups of this legion, particularly in the Cyrtocalpida or
Monocyrtida eradiata (Pl. 51, figs. 10-13), and in many Stichocyrtida
eradiata; furthermore, they are also seen among the PHÆODARIA, _e.g._,
certain Challengerida (Pl. 99, figs. 19-22). (See Gener. Morphol., Bd. i.
p. 426.)


33. _The Regular Dipyramidal or Quadrilonchial Ground-Form._--The
ground-forms whose geometrical type is the regular double pyramid are
characterised by a vertical main axis which possesses equal poles, and
which is crossed at its centre by several equal transverse axes. The
horizontal equatorial plane is therefore a regular polygon, and divides the
body into two equal regular pyramids.  The simplest and commonest form of
this group is the quadratic octahedron, the ground-form of the quadratic
crystallographic system; its equatorial plane is a square. This regular
dipyramidal ground-form occurs among the SPUMELLARIA in the shells of the
Staurosphærida as well as of many #Discoidea#, in which several equidistant
radial spines or arms lie in the quadratic equatorial plane of the body,
and project from the margin of the lenticular disc (_e.g._, _Sethostaurus_,
Pl. 31; _Histiastrum_, Pl. 46, &c.). It is, however, among the ACANTHARIA
that the most important part is played by this ground-form (and especially
by the quadratic octahedron); it forms the basis of all those
#Acanthometra# and #Acanthophracta# in which twenty radial spines are
disposed according to the Müllerian Law, and in which {xvi}the four
equatorial spines are of equal dimensions (Icosacantha). (See Gener.
Morphol., Bd. i. p. 436-446.)


34. _The Amphithect Dipyramidal or Lentelliptical Ground-Forms._--The
ground-forms whose geometrical type is the lenticular or "triaxial"
ellipsoid, may also be designated amphithect double pyramids; they are
characterised by the possession of a vertical main axis which has similar
poles, and is crossed at its middle by two transverse axes, unequal but
isopolar. The horizontal equatorial plane of the body is therefore an
amphithect or elongated polygon (a rhombus in the simplest case possible),
and divides the whole body into two equal amphithect pyramids. The simplest
and commonest form of this group is the rhombic octahedron, which is also
the ground-form of the rhombic crystallographic system. It plays an
important part in those ACANTHARIA in which twenty radial spines are
disposed according to the Müllerian Law, but in which the two pairs of
equatorial spines are unequal (different geotomical and hydrotomical axes,
see p. 719); to this category belong the Amphilonchida (Pl. 132),
Belonaspida (Pl. 136), Hexalaspida (Pl. 139), and Diploconida (Pl. 140). A
form essentially identical obtains also among the SPUMELLARIA in the
majority of the #Larcoidea#, both in their triaxial lattice-shells, and in
their lentelliptical central capsules, which present geometrically accurate
triaxial ellipsoids, with three unequal isopolar axes at right angles to
each other. (See Gener. Morphol., Bd. i. p. 446-452.)


35. _The Regular Pyramidal Ground-Forms._--The ground-forms whose
geometrical type is the regular pyramid, and which are the most conspicuous
in the Medusæ, Polyps, Corals, and regular Echinoderms (the Radiata of
earlier authors), are almost confined among the Radiolaria to the legion
NASSELLARIA; they occur, however, in the great majority of these, and
especially in those families which may be classed together as "#Cyrtoidea#
triradiata et multiradiata." Strictly speaking, however, almost all these
NASSELLARIA, at all events in their origin, are bilateral or dipleuric,
since the primary sagittal ring with its characteristic apophyses marks out
the sagittal median plane, and further, since the three feet of the basal
tripod are usually divided into an unpaired dorsal (pes caudalis) and two
paired ventral or lateral (pedes pectorales, dexter et sinister). On the
other hand, it is noteworthy, firstly, that among the primitive
#Plectoidea# there are perfectly regular radial forms, without any
indication of an original bilateral symmetry, and secondly, that similar
forms are also very common among the #Cyrtoidea#, probably as secondary
radial forms, developed from primitive bilateral ones. Similar cases also
occur in certain PHÆODARIA (_e.g._, the Medusettida and Tuscarorida, Pls.
100, 120), but they are entirely wanting among the ACANTHARIA and
SPUMELLARIA. The multiradial NASSELLARIA have arisen from the triradial by
the interpolation of three, six, nine, or more interradial and adradial
secondary apophyses between the three primary perradial ones. (See Gener.
Morphol., Bd. i. pp. 459-874.)


{xvii}36. _The Amphithect Pyramidal Ground-Forms._--The ground-forms whose
geometrical type is the amphithect pyramid, are distinguished from the
regular pyramidal forms, just discussed, chiefly by the form of the basal
plane, which is not a regular, but an amphithect or elongated polygon (in
the simplest case a rhombus). Hence in this case the allopolar main axis of
the body is crossed by two transverse axes which are isopolar and at right
angles, but are unequal; they cannot, however be distinguished as sagittal
and frontal axes as is the case in the zeugites. In the animal as well as
in the vegetable kingdom, an important part is played by this ground-form,
_e.g._, in the Ctenophora, where it is the rhombic pyramid.  Among the
Radiolaria it is not common, though it is clearly expressed among the
NASSELLARIA in a number of #Stephoidea# (Stephanida and Tympanida), as well
as in many #Spyroidea# (_e.g._, the bipedal Zygospirida). It is very
accurately developed among the PHÆODARIA in the bivalved #Phæoconchia#
(Pls. 121-128), where the two valves of the shell (dorsal and ventral) are
generally exactly alike, their median keels corresponding to the poles of
the sagittal axis. In the slit between the two valves lie the two secondary
openings (right and left) of the tripylean central capsule, corresponding
to the two poles of the frontal axis, and the main axis stands
perpendicularly to both these, its oral pole being indicated by the
astropyle, or principal aperture. (See Gener. Morphol., Bd. i. pp.
479-494.)


37. _The Amphipleural Ground-Forms._--By the term amphipleural ground-forms
are to be understood those usually defined as "bilaterally radial"; their
geometrical type is a half amphithect pyramid. The best known examples of
this form in the animal kingdom are the bilateral five-rayed Echinoderms
(_Spatangus_, _Clypeaster_), in the vegetable kingdom the symmetrical
five-rayed flowers (_Viola_, _Trifolium_). The three dimensive axes have
the same relation as in the zygopleura, to be next discussed, and which
also resemble them in being divisible only by one plane (the sagittal
median plane) into two equal halves. They differ, however, the amphipleural
body not being made up of two antimeres, but of at least three pairs of
antimeres (or three parameres), being therefore primitively radial. Hence
each of the symmetrical halves of the body contains more than one antimere.
Among the Radiolaria this form does not occur in the SPUMELLARIA,
ACANTHARIA, or PHÆODARIA; it is very common, however, among the
NASSELLARIA; many #Cyrtoidea# multiradiata and #Spyroidea# multiradiata
show this bilaterally radial ground-form, inasmuch as the body consists of
two symmetrical halves, and is also composed of numerous (usually three,
six, nine, or more) radial parameres. In the multiradiate Dicyrtida and
Tricyrtida the cephalis (the first joint) is usually bilateral, whilst the
thorax (the second joint) is multiradial. (See Gener. Morphol., Bd. i. pp.
495-506.)


38. _The Zygopleural Ground-Forms._--As zygopleural or dipleural
ground-forms, as opposed to the amphipleural, are classed those zeugites or
centroplana which are known {xviii}as "bilaterally symmetrical" in the
strictest sense of the term. This is the most important ground-form in the
animal kingdom, inasmuch as it obtains almost exclusively among the higher
animals (Vertebrata, Articulata, Mollusca, Vermes). The body consists of
only two antimeres, which correspond to the two symmetrical halves of the
body. Of the three dimensive axes two are allopolar, one isopolar; the oral
pole of the longitudinal main axis is different from the aboral; the dorsal
pole of the sagittal axis is different from the ventral; but the right pole
of the frontal axis is equal to the left. The right antimere is usually
precisely similar to the left (Eudipleura), more rarely it is slightly
dissimilar or asymmetrical (Dysdipleura). Among the Radiolaria this
ground-form is entirely wanting in the Porulosa or Holotrypasta
(SPUMELLARIA and ACANTHARIA), but on the contrary it is very common in the
Osculosa or Merotrypasta (NASSELLARIA and PHÆODARIA). In the NASSELLARIA it
is of special importance, for the typical _Cortina_ (the combination of the
primary sagittal ring with the basal tripod) exhibits the zygopleural
ground-form clearly sketched out; indeed it is usually clearly seen even in
the sagittal ring itself, for its ventral segment is more strongly curved
than the dorsal; its basal (or oral) pole is always different from the
apical (or aboral). Of the three feet of the basal tripod the unpaired
(caudal) one is directed dorsally and backwards, the two paired (pectoral)
ones ventrally and forwards. The majority of the NASSELLARIA may be
regarded as modifications of this original ground-form. Its relation to the
primitively triradiate tripod presents a still unsolved problem, and the
numerous relations of the zygopleural to the multiradiate ground-forms in
the NASSELLARIA are exceedingly complicated. The zygopleural ground-form is
less widely distributed among the PHÆODARIA, though it is very
characteristically developed in the rich and varied group of Challengerida
(Pl. 99). (See Gener. Morphol., Bd. i. pp. 507-527.)


39. _Synopsis of the Geometrical Ground-Forms:--_

  Principal Groups of Ground-Forms.
    Subsidiary Groups of Ground-Forms.
      Geometrical Type.
        Examples.

  I. CENTROSTIGMA.
  The geometrical centre of the body is a point. Main axis wanting.
  |
  +-I. HOMAXONIA.
  | All axes equal.
  | |
  | +-1. _Sphere_,
  |
  |     Central capsule of the #Sphæroidea# and of many ACANTHARIA.
  |
  +-II. POLYAXONIA.
    Endospherical polyhedra. All the angles of the body lie on the surface
    of a sphere. Numerous isopolar axes.
    |
    +-2. _Endospherical polyhedron_,
    |
    |   Lattice-spheres of the #Sphæroidea#, #Sphærophracta#, and
    |   #Phæosphæria#.
    |
    +-3. _Icosahedron_,
    |
    |   _Circogonia_.
    |
    +-4. _Dodecahedron_,
    |
    |   _Circorrhegma_.
    |
    +-5. _Octahedron_,
    |
    |   Cubosphærida, _Circoporus_.
    |
    +-6. _Cube_,
    |
    |   _Centrocubus_, _Lithocubus_, &c.
    |
    +-7. _Tetrahedron_,

        _Tetraplagia_, _Tetraplecta_, &c.

  II. CENTRAXONIA.                                                  {xix}
  The geometrical centre of the body is a straight line (the vertical main
  axis).

  Constant transverse axes (perpendicular to the main axis) are wanting in
  the Monaxonia (which have circular transverse sections); on the contrary
  they are differentiated in the Stauraxonia (which have polygonal
  transverse sections).
  |
  +-III. MONAXONIA.
  | Uniaxial ground-forms or centraxonia without transverse axes. The
  | transverse planes (perpendicular to the main axis) are circles.
  | |
  | +-8. _Monaxonia isopola._
  | | (Spheroids and ellipsoids; both poles of the main axis similar.)
  | |
  | | Central capsule and lattice-shell of of many #Discoidea# (lenses) and
  | | #Prunoidea# (ellipsoids), Belonaspida, &c.
  | |
  | +-9. _Monaxonia allopola._
  |   (Cone, ovoid and hemisphere; the two poles of the axis dissimilar.)
  |
  |     Central capsule and lattice-shell of many NASSELLARIA, especially
  |     the #Cyrtoidea# eradiata (Cyrtocalpida, &c.).
  |
  +-IV. STAURAXONIA.
    Pyramidal ground-forms or centraxonia with transverse axes. The
    transverse planes (perpendicular to the main axis) are either regular
    or amphithect polygons.
    |
    +-10. _Dipyramides regulares._
    | (Quadratic octahedron, or quadrilonchial forms and regular double
    | pyramids.)
    |
    |   ACANTHARIA with twenty radial spines, the four equatorial being
    |   equal. Multiradial #Discoidea# and Staurosphærida.
    |
    +-11. _Dipyramides amphithectæ._
    | (Rhombic octahedron, lentellipsoid, and amphithect double pyramids.)
    |
    |   ACANTHARIA with twenty radial spines, whose four equatorial spines
    |   are unequal but paired. Many #Larcoidea#.
    |
    +-12. _Pyramides regulares._
    | (Regular pyramids.)
    |
    |   Many NASSELLARIA (triradial and multiradial). Medusettida and
    |   Tuscarorida.
    |
    +-13. _Pyramides amphithectæ._
      (Rhombic pyramids.)

        #Phæoconchia#. Bipedal #Spyroidea# and #Stephoidea#.

  III. CENTROPLANA.
  The geometrical centre of the body is a plane (the sagittal plane).
  Constant transverse axes (perpendicular to the main axis) are wanting in
  the Monaxonia (which have circular transverse sections); on the contrary
  they are differentiated in the Stauraxonia (which have polygonal
  transverse sections).
  |
  +-V. BILATERALIA (or ZEUGITA).
    Bilateral forms in the general sense, with right and left halves.
    |
    +-14. _Amphipleura_
    | (Bilaterally radial ground-form.)
    |
    |   Many #Cyrtoidea# and #Spyroidea# multiradiata.
    |
    +-15. _Zygopleura._
      (Bilaterally symmetrical ground-form.)

        Most NASSELLARIA (primitively at least), many Challengerida.

  IV. ACENTRA.
  There is no geometrical centre.
  |
  +-VI. ANAXONIA.
    No definite axes can be determined.
    |
    +-16. _Irregularia._
      (Absolutely irregular ground-forms.)

        _Collodastrum_, _Collosphæra_, Phorticida, Soreumida.


40. _Mechanical Causes of the Geometrical Ground-Forms._--The great variety
of ground-forms exhibited by the Radiolaria is of special interest, since
in most instances their causes admit of recognition, and since they are so
intimately related to each other that even in the remaining cases the
assumption that they have arisen by purely mechanical _causæ efficientes_
seems justified. In this respect the first rank is taken by statical
conditions, especially the indifferent or stable equilibrium of the whole
organism, which floats freely in the water. With regard to these
fundamental statical relations, three principal groups of ground-forms may
be distinguished, pantostatic, polystatic, and monostatic.


41. _Pantostatic Ground-Forms._--By pantostatic or indifferently stable
ground-forms are meant those in which the centre of gravity coincides with
the centre of the body, so that they are in equilibrium in any given
position. Strictly speaking, the only form which possesses perfectly
indifferent equilibrium is the sphere, that being the only truly homaxon
and perfectly regular form. Nevertheless, in a somewhat wider sense many
Polyaxonia, especially the endospherical polyhedra with very numerous
sides, may be {xx}included in this category. Such indifferently stable
bodies are found among the SPUMELLARIA in many #Collodaria# and
#Sphæroidea#, as well as in the Astrolophida among the ACANTHARIA. On the
contrary they are entirely wanting among the NASSELLARIA and PHÆODARIA,
since their central capsule constantly presents a main axis with a
differentiated basal pole, and determines the position of stable
equilibrium.


42. _Polystatic Ground-Forms._--Those ground forms are defined as
polystatic or multistable in which the body is in equilibrium in several
different positions (though not in an infinite number). The number of these
positions is usually twice as many as that of the constant equal isopolar
axes exhibited by the form. Hence the regular polyhedra have as many
positions of equilibrium as they have angles or sides, the icosahedron
twenty, dodecahedron twelve, octahedron eight, cube six, tetrahedron four.
The isopolar monaxon ground-forms (lens, ellipsoid, cylinder) and the
diplopyramidal ground forms (quadrilonchial and lentelliptical) have two
positions of stable equilibrium, since the two poles of the vertical axis
are equal and similar and the body is divided into equal halves by the
equatorial plane. This is the case in many SPUMELLARIA (especially
#Discoidea#, #Prunoidea#, and #Larcoidea#), as well as in the great
majority of ACANTHARIA. Perhaps the same holds good also in certain
NASSELLARIA (_e.g._, isopolar Tympanida) and PHÆODARIA (_e.g._, isopolar
#Phæosphæria#), though here unistable equilibrium appears to be
necessitated by the constant main axis of the central capsule and the
differentiated basal pole of the main axis.


43. _Monostatic Ground-Forms._--Those ground-forms are classed as
monostatic or unistable in which the body is in equilibrium only in one
position, since the centre of gravity of the body lies in a constant
vertical axis below its centre. This fixed position is only rarely and
exceptionally found among the SPUMELLARIA (_e.g._, in _Xiphostylus_,
_Sphærostylus_, _Lithomespilus_, _Lithapium_) and among the ACANTHARIA
(_e.g._, in _Zygostaurus_ and _Amphibelone_). On the contrary it is quite
usual among the NASSELLARIA and PHÆODARIA (with but few exceptions); for
here a vertical main axis, with a differentiated basal pole, is determined
even by the formation of the central capsule, and usually also by the
corresponding structure of the skeleton. Among the NASSELLARIA this basal
pole, with the porochora of the central capsule, appears always to be the
lower; as also in most #Phæogromia# among the PHÆODARIA. In the peculiar
bivalved #Phæoconchia#, on the other hand, the basal pole with the
cannopyle is directed upwards; as also in the Challengerida and
Tuscarorida. The #Phæosphæria# and #Phæocystina# are probably to a large
extent polystatic. In general unistable equilibrium may be assumed in the
following categories of ground-forms:--(1) Allopolar monaxon (conical and
ovoid); (2) pyramidal (regular and amphithect); (3) Centroplana
(amphipleura and zygopleura); (4) Anaxonia.


{xxi}44. _Principal Axes._--From the foregoing consideration of the
statical conditions and their direct causal connection with the geometrical
ground-forms of the Radiolaria, the great mechanical significance of the
differentiation of definite axes in these unicellular free-swimming
organisms will be manifest. The most important of these is the primary main
axis (axis principalis, or protaxon), which in all cases has a vertical
direction. It is wanting in the Centrostigma (spheres and endospherical
polyhedra), and in the Anaxonia (acentra). It is isopolar in the phacotypic
forms (Monaxonia isopola), and in the double pyramids (Stauraxonia
isopola). It is allopolar in all monastatic ground-forms, in the conotypic
forms (Monaxonia allopola), pyramids (Stauraxonia allopola), and the
Centroplana (or bilateral forms).


45. _Secondary or Transverse Axes._--In contrast to the vertical main axis
all the other constant axes differentiated in the body may be called
"secondary axes," or "transverse axes," since they cross the former at
definite points. All ground-forms whose vertical axis is crossed by a fixed
number of such axes at definite angles may be called "Stauraxonia." They
are divided into two groups, double pyramids and single pyramids; in the
former the two poles of the main axis (or the two halves of the body
separated by the equatorial plane) are similar (Stauraxonia homopola), in
the latter dissimilar (Stauraxonia heteropola). If all the secondary axes
be equal, the stauraxon ground-form is regularly radial. If some of them be
unequal they are arranged in certain relations towards two primary
transverse axes, perpendicular to each other, to which all the other
secondary axes are subsidiary; the ground-forms are then either amphithect
or bilateral. The two primary transverse axes, which may also be designated
"ideal transverse axes" (euthyni), divide the vertical main axis in its
centre; one of them is the sagittal, the other the frontal. These three
dimensive axes give the factors which accurately determine the ground-form
and the dimensions in most Radiolaria; the vertical main axis determines
the length (principal axis); one horizontal transverse axis determines the
thickness (sagittal axis), and the other the breadth (frontal axis). Those
ground-forms in which the transverse axes are isopolar are termed
"amphithect," and those in which the one (frontal or lateral) is isopolar
and the other (sagittal or dorso-ventral) is allopolar, are termed
"bilateral," or better "zeugitic."


46. _Primary and Secondary Ground-Forms._--The geometrical sphere must be
regarded as the original ground-form of the Radiolaria; it being understood
that its monophyletic derivation from a single stem-form, _Actissa_, is
correct. The simplest forms of _Actissa_ (_Procyttarium_, Pl. 1, fig. 1)
are in fact geometrically _perfect spheres_; indeed even the individual
parts which compose their unicellular bodies (nucleolus, nucleus, central
capsule and calymma) are concentric spheres. But in addition the central
capsules of most other SPUMELLARIA, especially the #Sphæroidea#, as well as
of many ACANTHARIA {xxii}are true spheres. Furthermore the simple or
concentrically composed lattice-spheres of #Sphæroidea#, #Sphærophracta#,
and #Phæosphæria# may be regarded as spheres, although strictly speaking
they are endospherical polyhedra. From the primary spherical form of the
Radiolaria all other secondary forms may be derived in the following
order:--1. By the development of a main axis the Monaxonia arise. 2. By the
development of transverse axes the Stauraxonia arise. 3. In both groups
(Monaxonia and Stauraxonia) the two poles (or upper and lower halves of the
body) are at first similar (Isopola). 4. By differentiation in the two
poles or halves of the body (distinction between the basal pole and the
apical) the forms with different poles (Allopola) arise. 5. The transverse
axes of the Stauraxonia are at first equal (regular pyramids and double
pyramids). 6. By differentiation in the transverse axes (distinction
between the sagittal and the frontal axis) the amphithect pyramids and
double pyramids arise. 7. From the amphithect pyramids the Amphipleura
arise by differentiation of both poles of the sagittal axis. 8. The
zygopleural ground-form appears last, as the simplest form of the
Amphipleura.


47. _The Ground-Forms of the Spumellaria._--The SPUMELLARIA, being the
oldest and most primitive Radiolaria, have for the most part either
indifferent or multistable equilibrium; _e.g._, all #Colloidea# and
#Beloidea# which have a spherical central capsule, and also most
#Sphæroidea#. Among these primitive Centrostigma true spheres and
endospherical polyhedra are represented in the utmost variety, and the
regular polyhedra in particular. By the development of a vertical main axis
these Centrostigma have also given rise to very numerous Centraxonia, which
are usually isopolar, very rarely allopolar. Sometimes they are Monaxonia
(circular in transverse section), sometimes Stauraxonia (polygonal in
transverse section). The vertical main axis is longer in the #Prunoidea#,
shorter in the #Discoidea# than any of the other axes. The #Larcoidea# are
distinguished by their lentelliptical or triaxial ellipsoid form; the three
different but isopolar axes corresponding with those of the rhombic
octahedron; but even among the #Sphæroidea#, #Prunoidea#, and #Discoidea#,
this form is sometimes produced by the differentiation of two different
transverse axes at right angles to each other. Whilst these ground-forms
(Centraxonia and Centrostigma) occur in the utmost variety among the
SPUMELLARIA, the centroplanar (or true bilateral) ground-form is entirely
wanting.


48. _The Ground-Forms of Acantharia._--In the small family Astrolophida,
which contains the most archaic forms of the legion (_Actinelius_,
_Astrolophus_), the ACANTHARIA show a direct relation to the most primitive
SPUMELLARIA (_Actissa_), and like these have indifferent equilibrium; their
central capsule is a sphere, their calymma an endospherical polyhedron,
whose angles are indicated by the distal ends of the numerous {xxiii}equal
radial spines. In the great majority of ACANTHARIA, however (all
#Acanthonida# and #Acanthophracta#), twenty radial spines are present,
regularly distributed, according to Müller's icosacanthan law, in five
parallel circles, each containing four crossed spines (p. 717). Usually the
twenty spines are equal, and the ground-form is the quadratic octahedron,
or a regular double pyramid with sixteen sides. But in some groups (the
Amphilonchida and Prunophracta) two opposite equatorial spines are much
more strongly developed than the other eighteen, and therefore the
hydrotomical axis in the equatorial plane is larger than the geotomical
axis (p. 719); the isopolar stauraxonian form passes over into the
allopolar, and the ground-form becomes the rhombic octahedron or the
amphithect double pyramid (compare §§ 33 and 34, and p. 720). The
centroplanar ground-form is entirely wanting in the ACANTHARIA.


49. _The Ground-Forms of the Nassellaria._--The NASSELLARIA all possess
monostatic ground-forms, inasmuch as by the very structure of their
monopylean central capsule a vertical main axis is necessitated, whose
basal pole occupies the porochora. The same arrangement is also for the
most part clearly recognisable in the corresponding structure of the
skeleton, which is generally either centraxon or centroplanar. Among their
manifold skeletal forms different larger groups of ground-forms may be
recognised according as the vertical allopolar main axis is crossed by
differentiated transverse axes or not (Stauraxonia or Monaxonia); the
former are either triradial or multiradial. The triradial, with three
lateral or terminal radial apophyses, constitute the greater part of the
NASSELLARIA, and have probably been derived originally from the triradial
#Plectoidea# (_Triplagia_, _Triplecta_); a more careful examination,
however (especially with reference to the structure of the cortinar
septum), reveals the fact that the ground-form is not strictly regularly
pyramidal (with three equal radii), but amphipleural (with two paired
ventral and one unpaired dorsal radius), and that it usually passes over
into a distinctly zygopleural form. The same holds true of the multiradial
NASSELLARIA, where for the most part three interradial or six adradial
(sometimes more) apophyses are intercalated between the three primary
perradial ones; sometimes here also the ground-form is a quite regular
hexagonal or nonagonal pyramid, but usually it is more or less amphithect
or amphipleural. Among the eradial NASSELLARIA, which have no radial
apophyses, the ground-form is sometimes allopolar monaxon (conical, ovoid,
hemispherical, &c.), sometimes amphithect pyramidal (even in the simplest
Stephanida, _Archicircus_, &c.), or sometimes distinctly zygopleural or
bilateral (many #Plectellaria#).


50. _The Ground-Forms of the Phæodaria._--The PHÆODARIA agree with the
NASSELLARIA in the possession of a primitively centraxon ground-form, and
like them are monostatic, since a vertical main axis whose basal pole
passes through the astropyle is present, owing to the characteristic
structure of their cannopylean central capsule. In {xxiv}the great majority
of PHÆODARIA the spheroidal central capsule also possesses a pair of
parapylæ near the opposite apical pole of the main axis (Tripylea), and
these determine (as the right and left secondary openings) an isopolar
frontal axis. Hence, strictly speaking, in most PHÆODARIA the central
capsule has the geometrical ground-form of the amphithect pyramid (as in
the Ctenophora), with an allopolar vertical main axis, and two unequal, but
isopolar, horizontal transverse axes. In many PHÆODARIA the skeleton also
has this amphithect pyramidal ground-form, _e.g._, the bivalved
#Phæoconchia# and part of the #Phæogromia#. On the contrary, in the rest of
the PHÆODARIA the skeleton exhibits very various geometrical ground-forms,
independent of that of the central capsule. In the #Phæosphæria# it forms
preferably spheres or endospherical polyhedra, as also in the Castanellida
and Circoporida among the #Phæogromia#; among the Circoporida there are
also seen with remarkable distinctness the regular polyhedra (especially
the dodecahedron and icosahedron). Isopolar monaxonia are found among the
Aulosphærida (_Aulatractus_) and Orosphærida; allopolar monaxonia among the
Challengerida (_Lithogromia_). The Medusettida and Tuscarorida show various
forms of regular pyramids (allopolar Stauraxonia); and finally, the
Challengerida are for the most part centroplanar or bilateral. Thus the
PHÆODARIA present a great wealth of different geometrical ground-forms in
the development of their skeleton, not in that of their central capsule.



CHAPTER II.--THE CENTRAL CAPSULE.


51. _Components of the Central Capsule._--In all Radiolaria without
exception, at some period of life or other, the central portion of the soft
body is separated from the peripheral portion by an independent,
anatomically recognisable membrane; this membrane with all its contents is
designated the central capsule, and is the peculiar central organ of the
unicellular body, which distinguishes the Radiolaria most clearly from the
other Rhizopoda. In the great majority of the Radiolaria the volume of the
central capsule is less than that of the surrounding peripheral soft body
which we place in opposition to it as "extracapsulum." The
"capsule-membrane," which separates these two constituents, arises very
early in most Radiolaria, and persists throughout their whole life. In some
species, however, the membrane only appears later, immediately before the
formation of the spores, and hence is absent for a considerable period.
Regarded as a whole, then, the capsule consists of the following
parts:--(1) the capsule-membrane; (2) the enclosed endoplasm, or
intracapsular protoplasm; (3) the nucleus. But in addition, many other
non-essential structures may be enclosed in the central capsule, especially
hyaline spheres (vacuoles), fatty spheres, pigment granules, crystals, &c.

  The central capsule was first described in my Monograph in 1862 (pp.
  69-82) as the most characteristic component of the Radiolarian organism,
  and distinguished from the whole extracapsular {xxv}soft body. The fact
  that it has recently been reported as absent by various authors is due to
  their having observed young or unripe specimens, before the formation of
  the spores. In some species of #Polycyttaria# and ACANTHARIA the membrane
  persists only a very short time.


52. _The Primary Form of the Central Capsule._--The form of the central
capsule is originally a geometrical sphere; and if in accordance with our
monophyletic hypothesis all Radiolaria are to be derived from one common
stem-form (_Actissa_, see p. 12), then the central capsule of this common
stem-form must be regarded as perfectly spherical (_Procyttarium_, p. 13,
Pl. 1, fig. 1). Since, further, the enclosed nucleus and the surrounding
calymma of this primitive archaic form must also be spheres, and since the
nucleus lies in the centre of the body, and the protoplasm is evenly
distributed between it and the membrane, it follows that no axes or
excentrically differentiated parts are to be distinguished in this most
primitive Radiolarian. Rather in the primary central capsule all parts are
concentrically and evenly arranged round its centre. This primary spherical
form becomes modified in most Radiolaria into various secondary
ground-forms, which are correlated partly with the structure of the capsule
itself, and partly also with the development of openings in its membrane.
In general the ground-form of the central capsule is polyaxon in the
Porulosa (SPUMELLARIA and ACANTHARIA); but in the Osculosa centraxon forms
are more frequently observed; in the NASSELLARIA the ovoid (allopolar
monaxon) form is predominant, and in the PHÆODARIA the rhomboid or
amphithect pyramid. In these latter, the astropyle indicates the basal pole
of the vertical main axis, whilst the two parapylæ (right and left) mark
the poles of the frontal transverse axis. In the NASSELLARIA the centre of
the porochora corresponds with the basal pole of the main axis, whilst no
transverse axes are originally present.


53. _The Secondary Forms of the Central Capsule._--The original purely
spherical form of the central capsule persists only in the minority of the
Radiolaria, namely, the greater part of the SPUMELLARIA and ACANTHARIA; it
passes over into various other secondary forms in the majority of the
class, in the whole of the NASSELLARIA and PHÆODARIA, and in a considerable
portion of the SPUMELLARIA and ACANTHARIA. These secondary or derived forms
may be divided into two quite distinct groups, which may be designated
endometamorphic and exometamorphic; in the former the cause of the
divergence of the secondary form from the sphere lies in the internal
structure of the central capsule; in the latter it lies in the external
influence exerted by the growth of the skeleton. Obviously the former
series of modifications is more significant than the latter.


54. _The Endometamorphic Forms of the Central Capsule._--The secondary
forms of the central capsule, which are due to internal causes connected
with its growth, are as follows:--

  {xxvi}A. _The Ellipsoidal Central Capsule_, with one axis elongated, so
  that it becomes the vertical main axis of the body.

    _a._ Among the SPUMELLARIA, _Actiprunum_ (p. 14), _Colloprunum_ (p. 25,
    Pl. 3, fig. 9), most #Prunoidea# (p. 288).

    _b._ Among the ACANTHARIA, many Amphilonchida (p. 782, Pl. 132, figs.
    2, 6), and Belonaspida (p. 861).

    _c._ Among the NASSELLARIA, many #Plectoidea# (p. 905, Pl. 91, figs. 5,
    9), #Stephoidea# (p. 937, Pl. 81, fig. 16), Monocyrtida (Pl. 51, fig.
    3), &c.

  B. _The Cylindrical Central Capsule_, with considerable elongation of the
  vertical main axis, which is several times as long as the horizontal
  transverse axis.

    _a._  Amongst the SPUMELLARIA, _Collophidium_ (p. 26, Pl. 3, figs. 1-3)
    and many #Prunoidea# (_Spongurus_, &c.).

    _b._  Among the ACANTHARIA, some Amphilonchida.

  C. _The Discoidal, Spheroidal, or Lenticular Central Capsule_, with one
  axis shorter than the others, which becomes the vertical main axis.

    _a._ Among the SPUMELLARIA, _Actidiscus_ (p. 15), _Collodiscus_ (p.
    27), and the large group #Discoidea# (p. 408).

    _b._ Among the ACANTHARIA, many Quadrilonchida (p. 768, Pl. 131), and
    most Hexalaspida (p. 874).

    _c._ Among the NASSELLARIA, certain #Stephoidea# and #Cyrtoidea#.

    _d._ Among the great legion PHÆODARIA the spheroidal central capsule is
    almost always more or less flattened in the direction of the main axis
    (p. 1525, Pls. 101-128).

  D. _The Lentelliptical Central Capsule_ (or triaxial ellipsoid), with
  three unequal but isopolar axes at right angles to each other, the
  sections in all three dimensions of space being ellipses.

    _a._ Among the SPUMELLARIA, _Actilarcus_ and the large group
    #Larcoidea# (p. 604).

    _b._ Among the ACANTHARIA, certain Amphilonchida and Belonaspida.

  E. _The Polymorphic, Amoeboid or Irregular Central Capsule._

    _a._ Among the SPUMELLARIA, _Collodastrum_ (p. 28, Pl. 3, figs. 4, 5),
    and some #Larcoidea#.


55. _The Exometamorphic Forms of the Central Capsule._--The secondary forms
of the central capsule, which are brought about by external causes, chiefly
dependent on the formation of the skeleton, are very various and in many
cases devoid of special interest; in other instances, on the contrary, they
are of great importance, because of the clear relation of cause and effect
which can be traced between the development of the skeleton and of the
capsule. The most important phenomena to be recorded in this connection are
as follows:--

  {xxvii}I. SPUMELLARIA.--(A) In many of the #Sphæroidea#, the central
  capsule of which is originally enclosed by a simple lattice-sphere, it
  puts out protrusions through the meshes of the shell, thus forming
  club-shaped processes, corresponding in number with the meshes of the
  lattice (Pl. 11, figs. 1, 5; Pl. 20, fig. 1_a_; Pl. 27, fig. 3, &c.). The
  whole surface of the spherical capsule may thus be covered with numerous
  independent radial clubs of equal size, but usually they unite again
  outside the shell to form a simple sphere with smooth surface. (B) In
  many #Prunoidea# whose originally ellipsoidal body has become cylindrical
  by the marked prolongation of the main axis, the central capsule is
  divided by a series of constrictions into segments, which correspond with
  the annular constrictions of the skeleton (Pls. 39, 40). (C) In most
  #Discoidea# whose lentiform or discoidal shell develops radial arms at
  its margin, the central capsule sends out processes into these arms, and
  adapts itself to the stellate form of the skeleton (p. 409, Pl. 43, fig.
  15; Pl. 47, &c.) (D) In many #Larcoidea# whose growth is originally
  lentelliptical, but later spiral or irregular, the central capsule
  follows the mode of growth and develops irregular protuberances.


  II. ACANTHARIA.--Whilst the central capsule of most ACANTHARIA retains
  its primitive spherical form, in a minority of the group it passes over
  into various secondary forms, which are directly determined by the growth
  of the skeleton; especially common are lappet or club-shaped prominences
  which follow the larger radial spines. Hence the central capsule may
  assume the form of a violin, with two lobes corresponding to the two
  poles of the elongated main axis, as in many Amphilonchida (p. 782, Pl.
  132, fig. 10), and the Diploconida (p. 884, Pl. 140). On the other hand
  the central capsule becomes cruciform, with four lobes disposed at right
  angles, as in Lithoptera and other Quadrilonchida (p. 768, Pl. 131, fig.
  10, &c.).


  III. NASSELLARIA.--The primitive ellipsoid or ovoid form of the central
  capsule persists only in a few NASSELLARIA, such as the simplest and most
  archaic forms, the Nassellida, many #Plectoidea#, #Stephoidea#,
  Monocyrtida, &c. In the great majority of the NASSELLARIA, on the
  contrary, the ellipsoid or ovoid form passes over into a secondary form
  which is usually characterised by the presence of lobes, and is obviously
  dependent upon the previous development of the skeleton. In many
  #Stephoidea# and #Spyroidea# (probably the majority), a bilobed central
  capsule is formed (with symmetrically equal right and left lobes), since
  the primary vertical sagittal ring interferes with the growth in the
  median plane (Pl. 90, figs. 7-10). In other {xxviii}#Spyroidea#, on the
  contrary, and the majority of the #Cyrtoidea#, the central capsule forms
  at its basis rounded lobes, which protrude and hang down from the meshes
  of the cortinar plate; and since this latter has usually three or four
  large pores, the capsule similarly develops three or four processes (Pl.
  53, fig. 19; Pl. 55, figs. 4-11; Pl. 59, figs. 4-13; Pl. 60, figs. 3-7;
  Pl. 65, fig. 1).


56. _The Membrane of the Central Capsule._--The capsule-membrane or
envelope of the central capsule is both morphologically and physiologically
one of the most important parts of the Radiolarian body, for it separates
its two main constituents, the capsule with its nucleus and endoplasm and
the extracapsulum with the calymma and exoplasm. The capsule-membrane is
invariably present at some time or other during the life of the organism,
even though in a few species it may persist only for a short time. It is
characterised in general by its power of resistance to chemical and
physical reagents, and appears to be related to the elastic tissues or
perhaps even more to the chitinous substances. Its thickness is usually
less than 0.0001, though in certain groups it ranges between 0.001 and
0.002, and in many of the larger Radiolaria (such as Collida and PHÆODARIA)
it may attain a thickness of 0.003 to 0.006 or more. In the three legions
SPUMELLARIA, ACANTHARIA, and NASSELLARIA the capsule-membrane is single,
while in the PHÆODARIA it is always double, being composed of a firm outer
and a delicate inner membrane, which are in contact at only few points.
Usually it is quite structureless, except for its apertures; the thicker
membrane showing occasionally a fine concentric lamination. In certain
large #Colloidea# (_e.g._, _Thalassicolla_, Pl. 1, fig. 5_b_) the membrane
is covered on the inner surface by a network of polygonal ridges, and in
some large PHÆODARIA with remarkable small curved rods (Pl. 114, fig. 13).
In all Radiolaria the membrane is perforated by definite openings or pores,
through which the intracapsular and extracapsular protoplasm are in direct
communication. These openings (or "pylae") show very characteristic and
constant differences in the four legions, which have given rise to the
names--PERIPYLEA, ACTIPYLEA, MONOPYLEA, CANNOPYLEA.

  The capsule-membrane was first indicated as the most important and
  absolutely constant component of all Radiolaria, and as the differential
  character of the class, in my Monograph (1862, pp. 69-71). The careful
  investigations of R. Hertwig have confirmed this view and at the same
  time have yielded the most important conclusions regarding the nature and
  systematic significance of the openings in the capsule (_op. cit._, 1879,
  pp. 105-107). On the contrary, Karl Brandt has recently propounded the
  theory that the capsule-membrane is by no means a constant part of the
  Radiolarian organism, but is lacking in certain species of _Collozoum_
  and _Sphærozoum_ (1881, p. 392). This contradiction is explained by the
  fact that in some #Collodaria# and #Acanthometra# the formation of the
  central capsule takes place much later than in the other Radiolaria, in
  some {xxix}species indeed only just prior to the development of the swarm
  spores. I have recognised the presence of it in all species which I have
  investigated (more than a thousand), and even in those in which Brandt
  denies its existence. It is often very delicate and may easily be
  overlooked, especially when the contents of the capsule are colourless,
  but in all cases by the prudent application of staining fluids and other
  reagents its presence may be demonstrated. Even in those cases in which
  the contour of the capsule was not visible, and its contents appeared to
  pass without definite boundary into the matrix of the extracapsulum, it
  was possible by the use of appropriate stains or reagents, which would
  not penetrate the capsule, or of those solvents which were capable of
  dissolving its contents and of causing it to swell up like a distended
  bladder, to recognise the existence of the membrane. Those Radiolaria in
  which it is truly absent are young animals of species in which the
  membrane is only formed immediately before sporification, and persists
  but for a short time (_e.g._, species of _Collozoum_, _Sphærozoum_,
  _Acanthometra_, _Acanthochiasma_, &c.).


57. _The Capsule-Openings of the Peripylea (or Spumellaria)._--The
capsule-membrane of the PERIPYLEA is generally perforated by extremely fine
and numerous pores, which are distributed at equal distances over the whole
surface, and are precisely alike in all parts of the capsule. Hence the
SPUMELLARIA may be called "Holotrypasta" or "Porulosa"; they agree with the
ACTIPYLEA in being devoid of an osculum or operculum; they are
distinguished from the latter group mainly in that their pores are equally
distributed over the whole surface of the capsule, whilst in the ACTIPYLEA
the pores are disposed in definite groups or lines, separated by large
imporous areas.

  The central capsule of the SPUMELLARIA, with its innumerable fine and
  evenly distributed pores, must be regarded as the primitive arrangement,
  from which the different central capsules of the three other legions have
  been developed. The central capsule of the ACTIPYLEA has been derived
  from that of the PERIPYLEA by reduction in the number of the pores and
  their distribution in definite, regularly disposed areas in the membrane.
  The central capsule of the Osculosa is characterised by the formation of
  a special main-aperture (osculum) at the basal pole, which is closed in
  the MONOPYLEA by the porochora, and in the CANNOPYLEA by the astropyle;
  the remaining pores, with the exception of the accessory openings of many
  CANNOPYLEA, remain undeveloped in both these legions. In the same way
  Hertwig regards the central capsule of the PERIPYLEA as the primitive
  form (1879, L. N. 33, p. 107).


58. _The Capsule-Openings of the Actipylea (or Acantharia)._--The
capsule-membrane of the ACTIPYLEA is perforated by very numerous fine
pores, which are regularly distributed over the surface of the central
capsule, and separated by imporous intervals. Hence the ACANTHARIA belong
to the "Holotrypasta" or "Porulosa"; they have neither osculum nor
operculum, and agree in this particular with the PERIPYLEA; but they are
separated from these latter chiefly by the fact that their pores are much
less numerous, and marked off into regularly arranged groups or lines by
imporous intervals. In the PERIPYLEA, on the contrary, the pores are much
more numerous and are evenly distributed over the whole surface of the
capsule.

  {xxx}The central capsule of the ACANTHARIA has hitherto been for the most
  part confounded with that of the SPUMELLARIA, and no clear distinction
  has been drawn in this respect between the two legions of the Porulosa.
  Hertwig, who in 1879 first discovered the remarkably different structure
  of the Osculosa (NASSELLARIA and PHÆODARIA), recognised no distinction
  between the structure of the capsules in the PERIPYLEA and ACTIPYLEA (his
  Acanthometrea), and supposed that in both these legions "very fine pores
  were evenly distributed in large numbers over the capsule-membrane"
  (_loc. cit._, p. 106). I have, however, during the last few years
  convinced myself, by the careful comparative investigation of numerous
  ACANTHARIA, that in this respect they are quite distinct from the
  SPUMELLARIA (with perhaps the exception of the Astrolophida, which are
  nearly related to the primitive _Actissa_). The number of pores in the
  ACTIPYLEA is usually very much smaller than in the PERIPYLEA, and they
  are regularly arranged in groups.


59. _The Capsule-Openings of the Monopylea (or Nassellaria.)_--The
capsule-membrane of the MONOPYLEA always possesses a single large
main-opening, an osculum, which lies at the basal pole of the main axis,
and is closed by a circular perforated lid (operculum porosum). When seen
from the surface this lid appears as a clearly defined porous area
(porochora or area porosa), and forms the horizontal base of a peculiar
cone, which stands vertically in the interior of the capsule and may be
designated the "thread-cone" (podoconus). The NASSELLARIA may hence be
termed "Merotrypasta" or "Osculosa," like the CANNOPYLEA; the structure and
significance of the circular lid (operculum), which closes the main-opening
(osculum) is, however, quite different in the two legions. Whilst the lid
of the CANNOPYLEA (astropyle) is solid, traversed by radial ribs, and only
perforated in its centre by a short tube (proboscis), in the MONOPYLEA the
operculum (porochora) is always perforated by numerous vertical fine pores,
and is in connection with the peculiar internal "pseudopodial cone"
(podoconus, Pl. 51, figs. 5, 13; Pl. 81, fig. 16; Pl. 91, fig. 5; Pl. 98,
fig. 13). The pores are separated by small vertical, highly refractive rods
(opercular rhabdillæ); these become intensely stained by carmine, and are
either evenly distributed over the surface of the porochora or arranged in
definite groups. The outer or distal end of each rod is rounded, sometimes
thickened like a club or split into lobes; the inner or proximal end is
usually pointed, and stands in connection with a myophane thread of the
podoconus (see § 79). The primary circular form of the porochora, in which
the opercular rhabdillæ are evenly distributed in a horizontal plane,
undergoes various secondary modifications in many NASSELLARIA. The
triradial structure of the skeleton, which characterises the majority of
the legion, causes a splitting of the base of the central capsule into
three or four lobes; this division also affects the porochora, which lies
in the centre of the base, so that the rhabdillæ become arranged in three
or four equal circles. If, however, the lobes of the central capsule become
larger and protrude through the three or four collar pores of the cortinar
septum, the central porochora may separate entirely into three or four
elongated tracts, which lie on the axial side of the magnified lobes; the
rhabdillæ are then arranged over the whole surface of {xxxi}these tracts,
on the outer aspect of which run the longitudinal myophane fibrillæ of the
podoconus (compare §§ 79 and 99).

  The porous area of the MONOPYLEA was first described by Hertwig in 1879,
  and shown to be the characteristic main-opening of the central capsule in
  various families belonging to this legion (L. N. 33, pp. 71, 73, 83, 106,
  Taf. vii., viii.). According to his view "the capsule-membrane in the
  porous area becomes thickened around each pore into a rod, perforated by
  a canal," and the intracapsular protoplasm passes outwards through these
  fine canals (_loc. cit._, p. 106). I am not able to share this
  interpretation, but think rather that I have convinced myself by the
  examination of some living NASSELLARIA, and of many well-stained and
  preserved preparations in the Challenger collection, that the rods are
  _solid_, specially modified portions of the capsular wall, and that the
  protoplasm does not pass through them but through pores which lie between
  them.


60. _The Capsule-Openings of the Cannopylea (or Phæodaria)._--The
capsule-membrane of the CANNOPYLEA always possesses only a single large
main-opening or osculum, which lies at the basal pole of the vertical main
axis, and is closed by a circular radiated lid (operculum radiatum). This
operculum appears, when seen from the surface, as a sharply defined
stellate area (astropyle), from the middle of which arises a shorter or
longer cylindrical tube, the proboscis. Hence the PHÆODARIA, like the
MONOPYLEA, belong to the "Merotrypasta" or "Osculosa"; the structure and
significance of the circular operculum, which closes the main-opening
(osculum), are, however, quite different in the two legions. Whilst the
operculum of the MONOPYLEA (porochora) is perforated by numerous fine
vertical pores, and connected with the peculiar internal pseudopodial cone
(podoconus), this structure is entirely wanting in the CANNOPYLEA, and
instead of it there is a solid operculum, with radial ribs which originate
at the base of its central tubular mouth; this tube (proboscis) is
cylindrical, often conical at the base, of very variable length and with a
round aperture at either end. In spite of the great difference which the
various families of CANNOPYLEA exhibit in the formation of their skeleton
and its appendages, the constitution of this characteristic stellate
main-opening (astropyle) is always essentially the same; both the stellate
operculum itself, and the proboscis which rises from its centre, show only
slight differences in the various groups. In addition to this large
main-opening most PHÆODARIA possess several small accessory openings
(parapylæ); and usually two of these are present, placed symmetrically
right and left of the aboral pole of the main axis and in the frontal plane
(Pl. 101, figs. 2, 6, 10; Pl. 104, figs. 1, 2_a_). Sometimes there are more
numerous accessory openings (three to six or more) regularly arranged, as
in the two peculiar families, Circoporida and Tuscarorida; occasionally
also there is only a single parapyle, at the aboral pole of the main axis
(_e.g._, in _Tuscaridium_). The parapylæ seem to be quite absent in the
families Challengerida, Medusettida, Castanellida, and perhaps also in
other PHÆODARIA. The form and structure of the small accessory openings
appear to be always the same. The {xxxii}outer capsule-membrane is elevated
in the form of a short cylindrical tube or "apertural ring" (collare
paraboscidis), the external margin of which bends inwards, and at the base
of the ring passes over into the delicate internal capsule membrane. Upon
this apertural ring is situated a longer or shorter "apertural cone"
(paraboscis), which is a tubular, cylindrical or conical, prolongation of
the membrane, open externally.

  The peculiar capsule-openings of the PHÆODARIA were first discovered and
  carefully described by Hertwig in 1879 (L. N. 33, pp. 95, 107). He found
  in all the six genera which he examined _three_ openings, a main-opening
  at the basal pole of the main axis and two accessory openings, one on
  either side of the apical pole; hence he named the whole group
  "TRIPYLEA." This name, however, is not applicable to the numerous
  PHÆODARIA mentioned above, which have only a main opening without any
  accessory openings, nor to those genera in which the number of the latter
  is variable. I have, therefore, replaced Hertwig's designation by the
  term "CANNOPYLEA," which has reference to the peculiar tubular form of
  the opening. This I find much more developed in many PHÆODARIA than
  Hertwig has represented, and I must also, in certain particulars, dissent
  from his delineation of the minute structure, although this is in the
  main remarkably accurate.


61. _The Nucleus._--The nucleus, enclosed in the central capsule of all
Radiolaria, behaves in every respect like a true cell-nucleus, and thus
lies at the base of the now universal opinion, that the whole Radiolarian
organism, in spite of its varied development and remarkable variations, is
unicellular and remains throughout life a true individual cell. This
important theory is not invalidated by the fact that the nucleus undergoes
peculiar modifications in many groups, and in certain groups presents
appearances seldom or never seen elsewhere.


62. _Uninuclear and Multinuclear Radiolaria (Monocaryotic and
Polycaryotic)._--All Radiolaria present two different conditions in respect
of the behaviour of the nucleus, since in their young stages they are
uninuclear (_monocaryotic_), and in later stages multinuclear
(_polycaryotic_). This is readily explained by the fact that each
individual Radiolarian is developed from a simple unicellular swarm-spore,
and that afterwards, before the formation of swarm-spores, the single
nucleus divides into many small nuclei. Thus in the Radiolaria the nucleus
is pre-eminently the _organ of reproduction and inheritance_. The division
of the originally single nucleus into many small nuclei may take place,
however, at very different periods, so that the Radiolaria may be divided
in this respect into precocious and serotinous.


63. _Serotinous and Precocious Radiolaria._--In the great majority of the
Radiolaria the division of the nucleus takes place only at a late period, a
short time or even immediately before the process of spore formation; it
then breaks up rapidly into numerous small nuclei (always more than one
hundred, sometimes many thousands), and each of these {xxxiii}either
becomes itself the nucleus of a swarm-spore, or by repeated division gives
rise to a group of spore-nuclei. All those Radiolaria which are uninuclear
during the greater part of their existence, and in which the process of
division is late, and takes place rapidly, are called "serotinous" or
late-dividing forms. To this category belong all PHÆODARIA and NASSELLARIA,
as well as all the solitary or monozoic SPUMELLARIA and some ACANTHARIA. On
the other hand, the name "precocious," or early dividing, is applied to
those Radiolaria in which the division of the nucleus takes place very
early, and in which, therefore, the cell is multinuclear during the greater
part of its existence. This is the case in all the social or polyzootic
Radiolaria (Polycyttaria, Pls. 3-8), and also in the great majority of the
ACANTHARIA, both #Acanthometra# and #Acanthophracta#. In the last two
groups, however, there are numerous exceptions, and these are seen in
remarkably large species, characterised by the great size of the central
capsule. From a phylogenetic point of view, the conclusion is allowable
that the precocious forms are secondary, and have arisen by adaptive
modification from the primitive serotinous stem. In the Polycyttaria (or
social SPUMELLARIA, _i.e._, the three families Collozoida, Sphærozoida, and
Collosphærida), the cause of the adaptation lies most probably in the
formation of the colony itself, for all these three families are so closely
related to three corresponding families of serotinous, monozootic
Radiolaria (Thalassicollida, Thalassosphærida, Ethmosphærida), that certain
species of the latter are hardly to be distinguished from isolated
individuals of the former. Perhaps the remarkable formation of the large
central oil-globule, which particularly characterises the Polycyttaria, is
the prime cause of their early nuclear division. In the ACANTHARIA the
cause is most likely to be found in the characteristic _centrogenous
development_ of their acanthin skeleton, whose radial bars first of all
appear in the centre of the capsule. Hence arises directly the excentric
position of the nucleus, which in the archaic stem of ACANTHARIA
(_Actissa?_) was probably central. In any case, but little weight is to be
laid upon the precocious division of the nucleus in the ACANTHARIA in
general, inasmuch as in certain species (both #Acanthometra# and
#Acanthophracta#) the more usual serotinous division persists.


64. _Central and Excentric Nuclei._--The position of the nucleus in the
interior of the central capsule was no doubt primitively central, and this
situation in the geometrical centre of the original spherical central
capsule has been accurately retained in all monozootic SPUMELLARIA; in the
polyzootic families of this legion (Polycyttaria), on the contrary, it is
obscured by the precocious division of the nucleus. In the other three
legions, which may be phylogenetically derived from the SPUMELLARIA, the
position of the nucleus is rarely central, but usually excentric, or at
most subcentral. In the ACANTHARIA (both #Acanthometra# and
#Acanthophracta#) the central position of the nucleus is at once excluded
by the constantly centrogenous development of the skeleton; the nucleus is
therefore always excentric, and may lie at either side; it usually
{xxxiv}divides very early into numerous separate nuclei, which are usually
distributed in the peripheral portions of the central capsule. In the
NASSELLARIA the development of the porochora, and of the podoconus which
stands upon it, brings about the formation of a vertical axis, and in
consequence the central capsule assumes a monaxon form (usually ovoid or
conical); the nucleus then lies in the main axis, but excentrically between
the apex of the podoconus and the aboral pole. In many NASSELLARIA,
however, especially when the podoconus is so large that its apex approaches
the aboral pole of the central capsule, the nucleus is pressed to one side
and lies quite excentrically. The PHÆODARIA exhibit a different
arrangement; the large spheroidal nucleus is always subcentral, so that its
main axis corresponds with that of the concentric spheroidal central
capsule; but since the astropyle always occupies the oral pole of the
latter, and since the distance of the nucleus from this pole is always
somewhat different from its distance from the other, it follows that,
strictly speaking, the nucleus never lies accurately in the geometrical
centre.


65. _Homogeneous and Allogeneous Nuclei._--The nucleus of the Radiolaria
not only exhibits a similar structure and composition, and suffers similar
modifications to those which are found to occur in the case of other
cell-nuclei, but also to some extent shows very peculiar developmental
forms, which are seldom or never found in other cells. In the first place
the nuclei may be divided into homogeneous and allogeneous, the former are
structureless and consist of a uniform mass of nuclein, whilst the latter
are composed of different substances and show various structural relations.
_Homogeneous_ nuclei, whose whole mass is uniform and exhibits no
structural differentiation, are probably always to be found in the
swarm-spores; in the fully developed Radiolarian body they are found only
in the first legion, SPUMELLARIA, and that both in many Monozoa (especially
small #Sphæroidea# and #Prunoidea#) and in the Polyzoa (or Polycyttaria).
The whole mass of these homogeneous nuclei, which are usually spherical or
ellipsoidal, consists of uniform, perfectly clear and transparent nuclein,
and becomes evenly stained by carmine, hæmatoxyline, &c.  They may be
readily distinguished by these means from the clear vacuoles or "hyaline
vesicles," which are evenly distributed in the endoplasm of many
Radiolaria, and may be confused with the former. _Allogeneous_ nuclei,
which are always composed of different parts and often show complicated
structural relations, are found developed in the great majority of
Radiolaria. The most important differentiation exhibited by these secondary
forms is the separation of the nuclear mass into a firm nuclear substance
(caryoplasm) and a fluid nuclear juice (caryolymph). In addition in each
nucleus a nucleolus is visible, and often several or many may be seen (see
§§ 67 to 70).


66. _The Form of the Nucleus._--The nucleus of the Radiolaria shows greater
variations in form and structure than are to be found in the majority of
cell-nuclei; {xxxv}exception must, however, be made in the case of many
animal ovicells, which, in their peculiar form and composition, often
recall large Radiolarian nuclei. With respect to the external shape two
main forms may be distinguished, as primary and secondary. The _primary
form_ of the Radiolarian nucleus is the sphere; it occurs not only in most
swarm-spores, but also in most adult forms belonging to the legion
SPUMELLARIA, and in individual instances in other groups; indeed the nuclei
of most SPUMELLARIA, as also the concentric central capsules in which they
lie, are true geometrical spheres. The _secondary forms_ of the nucleus are
found in the majority of adult Radiolaria, and arise from the primary
spherical forms in various ways, either by the elongation or contraction of
one axis, or by the formation of apophyses or processes. The most important
of these secondary forms are as follows:--

  1. _Ellipsoidal nuclei_, arising by elongation of one principal axis;
  very common among the NASSELLARIA, as well as in many #Prunoidea# and
  #Larcoidea# among the SPUMELLARIA; also in several ACANTHARIA.

  2. _Discoidal nuclei_, arising by contraction of one principal axis,
  sometimes lenticular or spheroidal, biconvex, sometimes shaped like a
  disc or coin; especially common in the #Discoidea# among the SPUMELLARIA,
  also in some ACANTHARIA; the large nucleus of the PHÆODARIA is always
  spheroidal or almost spherical, with a slightly shortened main axis.

  3. _Stellate nuclei_, spherical, and armed with evenly distributed radial
  club-shaped or conical processes; rare but very characteristic,
  especially in the two large Thalassicollida _Thalassopila_ (Pl. 1, fig.
  3), and _Thalassophysa_ (Monogr. d. Radiol., Taf. i.); also in some
  #Sphærellaria# (Pl. 11, fig. 5).

  4. _Amoeboid nuclei_, with unequal processes irregularly arranged, in
  certain irregular forms of SPUMELLARIA and ACANTHARIA.

  5. _Lobate nuclei_, with several (usually two or three) large ovoid or
  pyriform lobes, which protrude into corresponding larger lobes of the
  central capsule, in many NASSELLARIA, especially the multiarticulate
  #Cyrtoidea# (Pl. 59, figs. 12, 13). The budding nucleus of the ACANTHARIA
  is also lobate (Pl. 129, figs. 6-11).


67. _The Nucleus of the Peripylea._--The nucleus of the SPUMELLARIA or
PERIPYLEA shows in certain groups a very primitive arrangement, indeed the
archaic structure from which the various forms of nuclei of other
Radiolaria may be derived; but on the other hand, in other groups it
exhibits very peculiar and remarkable differentiations. In the first place
it may be noted that the monozootic or solitary SPUMELLARIA usually possess
a single serotinous nucleus, which only divides into numerous swarm-spores
at a late period; {xxxvi}whilst, on the contrary, the polyzootic colonial
SPUMELLARIA (or Polycyttaria) are uninuclear only in the young state (Pl.
3, fig. 12), and speedily present numerous small homogeneous nuclei, which
have arisen by precocious division of a single nucleus; these are usually
spherical and 0.008 to 0.012 mm. in diameter. The serotinous nucleus of the
monozootic SPUMELLARIA, in many divisions of this large legion, and
especially in the simply constituted #Sphæroidea#, is a homogeneous sphere
of nuclein, lying in the middle of the central capsule. In many other cases
it assumes the form of a spherical vesicle ("Binnen-Bläschen"), whose fluid
or semi-fluid contents are enclosed by a more or less firm membrane. This
vesicle often contains a single central spherical _nucleolus_ (Pl. 1, figs.
1_l_, 4_l_), but sometimes a variable number of small excentric nucleoli
(Pl. 1, figs. 1_a_, 2_a_). The nuclear membrane is often somewhat thick,
presenting a double contour, and in such cases may even exhibit a fine
radial striation, the expression of minute pores (Pl. 1, fig. 2_a_). In the
colossal nuclei (as much as 1 to 2 mm. in diameter) of certain large
Thalassicollida the nucleolus presents a very remarkable form, becoming
stellate by the protrusion of processes, which may again branch in a
dendritic fashion (as in the common _Thalassicolla nucleata_), or it may
develop into a very long cylindrical thread, which is disposed in
serpentine coils, and in _Thalassophysa pelagica_ passes into the different
cæcal processes of the stellate nucleus. In many #Sphæroidea#, whose
skeleton is composed of numerous concentric lattice spheres, the small
central spherical nucleus lies at first within the innermost of these (the
medullary shell); but afterwards it grows through the meshes of the
lattice-work, and the radiating club-shaped processes thus formed (Pl. 11,
fig. 5) unite with each other outside the medullary shell, and form an
external nuclear sphere which completely encloses the latter. In the
Polysphærida (with several concentric lattice-shells) and in the
Spongosphærida (with spongy lattice-spheres), this process may be several
times repeated, so that eventually the central spherical nucleus attains
considerable dimensions, and encloses two or more concentric lattice-shells
with their radial connecting rods. The nuclear membrane is in these cases
usually penetrated by radial bars, which connect the outermost of the
enclosed shells with the remaining cortical shells which surround the
central capsule. The same remarkable arrangement is also very common among
the #Discoidea#. The small spherical primary nucleus is in such instances
immediately surrounded by the innermost earliest developed lattice-shell,
around which the concentric rings are subsequently deposited; it then grows
out through the meshes, and the processes fuse outside the ring to form a
homogeneous lentiform nucleus (Pl. 43, fig. 15). The same process recurs in
certain #Prunoidea# and #Larcoidea#, whilst in other SPUMELLARIA of these
groups (_e.g._, Pylonida) the lobate processes of the nucleus remain free.

  Both the simple serotinous nucleus of the monozootic SPUMELLARIA, and the
  numerous precocious nuclei of the Polycyttaria, were first described in
  my Monograph in 1862, the former as the "endocyst" ("Binnen-Bläschen"),
  the latter as "spherical transparent vesicles" ("Kugelige
  {xxxvii}wasserhelle Bläschen"). I was in error, however, in regarding the
  latter as identical with the so-called "hyaline spherules" in the central
  capsule of many Monozoa, which rather belong to the category of
  intracapsular vacuoles (see § 72). The credit of recognising, by the aid
  of the modern methods of staining, the distinctness of these two
  structures, which may readily be mistaken for each other, and of
  demonstrating the true nature both of the serotinous and precocious
  nuclei, belongs to Richard Hertwig (1879, L. N. 33).


68. _The Nucleus of the Actipylea._--The nucleus of the ACANTHARIA or
ACTIPYLEA shows very peculiar relations in respect of structure and
division, particularly special forms of lobular budding, which belong to
the characteristic peculiarities of this singular legion, and are not found
among other Radiolaria. The position of the nucleus is _always excentric_,
even in the youngest ACANTHARIA, for the centrogeneous formation of the
skeleton, the constant development of the earliest radial portions of it in
the middle of the central capsule, forces the nucleus from its normal
central position. The majority of the ACANTHARIA, like most Polycyttaria,
are precocious, the primary nucleus early dividing into numerous small
nuclei (see note A below). Nevertheless there are many exceptions to this
rule in different families, _e.g._, _Stauracantha_, _Xiphacantha_,
_Phatnacantha_, and _Pristacantha_ among the #Acanthometra#, and
_Stauraspis_, _Echinaspis_, _Dodecaspis_, and _Phatnaspis_ among the
#Acanthophracta#. In these instances the primary nucleus remains for a long
time as a simple excentric ellipsoidal or irregularly round body, even in
the fully developed stage, and only at a very late period (sometimes just
before the formation of the spores) divides into many small nuclei. Since
this serotinous division of the nucleus takes place in different genera of
very various groups, it can only be decided by further investigations how
widely it is spread among the ACANTHARIA, and upon what circumstances it is
dependent (see note B). The division of the nucleus appears to be
precocious in the majority of this legion, and a number of small nuclei
appear to be early formed by a peculiar process of budding; in most fully
developed ACANTHARIA these are disposed in one or two layers under the
surface of the central capsule, but if their numbers increase to any
considerable extent, the whole space between the skeletal rods becomes
filled with small nuclei; sometimes these are homogeneous, sometimes
vesicular, 0.002 to 0.012 mm. in diameter; usually they are spherical and
have a small nucleolus (compare Pl. 129, figs. 6-11, and note C).

  A.  The numerous nuclei, which are to be found in the central capsule of
  most mature ACANTHARIA, were first described in my Monograph (1862) as
  "spherical, transparent vesicles, provided with a small dark granule" (p.
  374, Taf. xv. figs. 2, 5; Taf. xvi. figs. 2, 4; Taf. xxi. fig. 7, &c.).
  Their more minute constitution and peculiar origin were first accurately
  delineated by R. Hertwig (1879, _loc. cit._, pp. 11-24, Taf. i-iii.).

  B. The fact that in a number of ACANTHARIA the nucleus does not divide
  early as in the majority of the legion, but only at a later period, was
  first observed by R. Hertwig in a species of #Acanthometra# (_Xiphacantha
  serrata_), and a species of #Acanthophracta# (_Phatnaspis
  {xxxviii}mülleri_ = _Haliommatidium mülleri_) (_loc. cit._, pp. 11 and
  27). This serotinous division of the nucleus seems, however, to be rather
  widely spread in both sublegions of the ACANTHARIA; I have found, not
  only in the forms above mentioned, but also in several others belonging
  to different genera, a single large excentric nucleus, even in those
  individuals in which the skeleton was fully developed.

  C. The peculiar mode of nuclear budding, by which these small nuclei
  arise, appears to proceed in the following manner (Pl. 129). The
  vesicular primary nucleus, which, in consequence of the centrogeneous
  development of the skeleton protrudes as it grows into irregular lobes
  (Pl. 129, fig. 9), assumes a peculiar concavo-convex form, sometimes that
  of a hood or dish, sometimes that of a kidney or sausage. The convex
  surface is apposed to the capsule-membrane, while the concave is turned
  towards the central star of the skeleton (fig. 6). There is now formed at
  the centre of the convex surface of the strong, doubly-contoured, nuclear
  membrane, a flask-shaped invagination with a narrow neck and expanded
  base; the membrane now becomes disposed in peculiar folds, which at the
  narrow aperture of invagination appear as folds, but on the expanded body
  of the flask take the form of concentric rings, laid closely side by side
  (Pl. 129, fig. 10). The convex bottom of the flask, which is directed
  towards the concave proximal side of the nucleus, becomes again
  invaginated by a central conical apophysis of the enlarged nucleolus,
  which is situated between them. Usually the nucleolus has already become
  flattened into a lentiform shape, and upon its distal face a conical
  apophysis has been developed, which is divisible into a darker proximal
  and clearer distal portion. The tip of the latter appears to be in direct
  connection with the nuclear membrane at the centre of the base of the
  flask-shaped invagination (figs. 6, 10). At this stage of development the
  nucleus of the ACANTHARIA generally presents the characteristic form of a
  hood-shaped, concavo-convex vesicle, whose radial axis is also the axis
  of the flask-shaped distal invagination, and of the depressed conical
  nucleolus, which lies between the latter and the concave side of the
  nucleus.  After this peculiar invagination has persisted for some time in
  connection with the enlarged nucleolus, both disappear, and then a
  remarkable growth of lobular processes takes place on the concave
  proximal side of the hood or kidney-shaped nucleus; from four to eight
  knobs of unequal size usually appear, and their thickened wall encloses a
  variable number of small of nucleoli; these are at first few but
  afterwards more numerous (fig. 7). Subsequently these knobs or lobes
  become completely separated by constriction from the original central
  mass of the nucleus, and appear as so many separate independent
  "sausage-shaped bodies" in the hollow central capsule (fig. 8). Each of
  the bodies now appears, and at first on its convex aspect, to form a
  large number of small nucleoli, which either separate by constriction
  from it or become free by its breaking up and lie in numbers in the
  central capsule. Finally the buds or lobes of the nucleus break up
  entirely into such nucleoli, which are evenly distributed in the central
  capsule, and become the nuclei of the swarm-spores (fig. 11). Compare R.
  Hertwig, L. N. 33, Taf. i.-iii. pp. 19-25.


69. _The Nucleus of the Monopylea._--The nucleus of the mature forms of the
NASSELLARIA or MONOPYLEA is generally simple or lobate, homogeneous or
vesicular and _excentric_, and appears only to divide into numerous small
nuclei just before the formation of the spores. Nevertheless I have
sometimes, though not often, seen in representatives of very various
families of the MONOPYLEA, the central capsule filled with many small
spherical homogeneous nuclei (Pl. 53, fig. 19). Hence all the families of
this legion appear to be serotinous, their simple primitive nucleus
persisting for a long period. It {xxxix}is commonly placed excentrically,
and most usually in the apical or aboral portion of the central capsule,
either between its apex and the podoconus, or quite excentrically on the
dorsal aspect. The simple nucleus of the NASSELLARIA usually appears to be
vesicular and to possess a somewhat firm membrane, clear contents, and a
rather large, dark coloured nucleolus. In many NASSELLARIA the nucleus is
spherical or ellipsoidal (Pl. 53, fig. 11); whilst in many #Stephoidea# and
#Spyroidea#, where the central capsule is constricted by the sagittal ring
and divided into two symmetrical lateral lobes, the nucleus partakes of the
same mode of growth and appears in the middle of the capsule as a
transversely placed ellipsoid or even as a short cylinder (Pl. 90, figs. 7,
9). The most remarkable modification in the form of the nucleus is to be
found in the multi-articulate #Cyrtoidea#. Here it is usually enclosed in
the cephalis and is spherical, ellipsoidal or spheroidal, often flattened
almost into a disc. If now the central capsule increase greatly in size and
put forth three or four clavate lobes which hang down through the pores of
the cortinar septum into the thorax (or even into the succeeding joints),
the nucleus usually undergoes similar modification, and three or four
finger-like apophyses are developed from its base, which project into the
corresponding lobes of the central capsule (Pl. 59, figs. 4, 12, 13).

  The numerous small, spherical, homogeneous nuclei which are to be found
  in the central capsules of those NASSELLARIA, which are ripe and about to
  develop spores, were described in 1862 in my Monograph, as "numerous,
  small, transparent, spherical cells" in the case of various #Cyrtoidea#
  (_Arachnocorys_, _Lithomelissa_, _Eucecryphalus_, _Eucyrtidium_, &c.)
  (_loc. cit._, pp. 302, 305, 309, 321, &c.), and I find them of the same
  form and dimensions, but deeply stained with carmine in many preparations
  in the Challenger collection. R. Hertwig has delineated them very
  accurately in the case of _Tridictyopus_ (1879, _loc. cit._, p. 84, Taf.
  vii. fig. 3). He was also the first to recognise the uninucleate
  condition of the NASSELLARIA, which is much more frequently observed than
  the serotinous multinucleate condition, and he described very clearly the
  peculiar lobed nuclei which arise in #Cyrtoidea#, owing to the protrusion
  of the nucleus through the cortinar septum (_loc. cit._, p. 85, Taf.
  viii. figs. 3-8).


70. _The Nucleus of the Cannopylea._--The nucleus presents the same
remarkable structures in all species of the PHÆODARIA or CANNOPYLEA which
have been examined, and closely resembles the germinal vesicle of an
amphibian ovum, being a large spherical or spheroidal vesicle with numerous
nucleoli. Its diameter usually amounts to half or two-thirds, sometimes
even three-quarters, that of the central capsule. The vertical main axis of
the latter is also that of the nucleus, which usually lies somewhat nearer
to the aboral pole. The nucleus is generally rather more strongly
compressed in the direction of the main axis than the capsule itself. The
membrane of the vesicular nucleus is thin, but firm, and encloses a clear
or finely granular mass of nuclein. The number and size of the contained
nucleoli are variable even in one and the same species, and stand in
inverse ratio to each other, an obvious result of the gradual process of
division. Commonly {xl}from twenty to fifty roundish or spherical, strongly
refracting nucleoli, are present; more rarely there are several hundred
very small ones.  Sometimes the nucleus is penetrated by fine trabeculæ, in
whose meshes lie the nucleoli (Pl. 101, fig. 2). In certain nuclei, which
contained a few large nucleoli, these were of irregular form, probably the
result of amoeboid movements (Pl. 101, fig. 1). In the formation of spores
in the CANNOPYLEA, the nucleus apparently becomes dissolved, and its
numerous nucleoli develop directly into the nuclei or mother-nuclei, which
produce the nuclei of the flagellate spores. Furthermore, many PHÆODARIA
seem to multiply by simple cell-division, since very commonly (especially
in the #Phæocystina# and #Phæoconchia#) two large nuclei (right and left),
may be met with in one central capsule; sometimes also a single large
nucleus, in which a sagittal constriction marks the commencing division of
the capsule (Pl. 101, figs. 2, 36; Pl. 104, fig. 3; Pl. 124, fig. 6, &c.).

  The large nucleus of the PHÆODARIA was first described in my Monograph in
  1862, in the case of _Aulacantha_ (p. 263), _Aulosphæra_ (p. 359), and
  _Coelodendrum_ (p. 361), as a "large, spherical, thin-walled endocyst,"
  from 0.1 to 0.2 mm. in diameter. More detailed descriptions, especially
  with respect to the behaviour of the nucleoli were given by R. Hertwig in
  1879 (L. N. 33, p. 97).


71. _The Endoplasm or Intracapsular Protoplasm._--In all Radiolaria the
intracapsular protoplasm, which, for the sake of brevity, may be termed
"endoplasm," constitutes originally, and especially in the earliest stages,
the only important content of the central capsule, except the nucleus. In
certain SPUMELLARIA and NASSELLARIA, of simple structure and of small
dimensions, this condition persists for a long period, and the endoplasm
then appears as a homogeneous, colourless, turbid or finely granular,
mucous, semi-solid mass, which cannot be distinguished from the ordinary
undifferentiated protoplasm of young cells; no definite structure, and in
particular, no fibrillar network, can be discovered in it even by the use
of the customary reagents. In the great majority of the Radiolaria,
however, this primitive homogeneous condition of the endoplasm is very
transient, and it soon undergoes definite modifications, becoming
differentiated into separate parts or producing new constituent contents.
Such products of the internal protoplasm are in particular hyaline spheres
(vacuoles and alveoles), oil-globules, pigment-bodies, crystals, &c. The
most important of the differentiations which take place in the endoplasm is
that into an internal, granular, _medullary_ substance and an external,
fibrillar, _cortical_ substance; although the various legions behave
somewhat differently in this respect (§§ 77-80).


72. _Intracapsular Hyaline Spheres._--The central capsule of very many
Radiolaria contains in its endoplasm numerous spherical bodies of varying
size, which consist of watery or albuminous fluid, and have previously been
regarded as nuclei, or described as products of the internal protoplasm,
under various names, such as "spherical transparent {xli}vesicles" (see
note A, below), "albumen spheres" (see B), "gelatinous spheres" (see C),
"alveolar cells" (see D), &c. Some of these spheres are perfectly
transparent, structureless and of varying refractive power, producing the
impression of drops of fluid; others contain various formed constituents,
such as oil-globules, fat-granules, pigment-granules, concretions,
crystals, &c. From a morphological point of view they may all be divided
into two categories, membraneless vacuoles and vesicular alveoles.  The
_vacuoles_ are simple spherical drops of fluid or of gelatinous material,
devoid of a special envelope, but immediately surrounded by the endoplasm.
The _alveoles_, on the other hand, are true vesicles with a thin spherical
envelope, enclosing a drop of fluid or jelly. This envelope is commonly
very thin, homogeneous, and often scarcely discernible, so that in practice
a sharp line of demarcation cannot be drawn between alveoles and vacuoles;
the former are usually somewhat larger than the latter. The fact is,
nevertheless, certain that the hyaline spheres, which may be isolated on
rupturing the central capsule of many Radiolaria, in certain cases,
particularly in large species, possess a clear, anatomically demonstrable
membrane, whilst in others no such appearance is presented.  It may be
assumed that the vesicular alveoles are developed from the drop-like
vacuoles by increase in size, and by the precipitation of a delicate
envelope from the endoplasm. The character common to all these hyaline
spheres, whether vacuoles or alveoles, is found in their aqueous, not
adipose, constitution, and in their clear transparent appearance, which
allows of no structure (the above-mentioned contained bodies excepted)
being recognised. Their refractive power and consistency vary somewhat, and
probably their chemical constitution still more. Sometimes they are
strongly refractive and shining, and sometimes feebly refractive and pale;
their consistency shows all intermediate stages between a thin fluid, which
readily disappears in water, and a firm, insoluble jelly. As regards their
chemical composition (which is probably very variable), the hyaline spheres
may be best divided into two groups, the organic and inorganic. The
_inorganic hyaline spheres_ are simple drops of saline solution without any
carbonaceous constituent; the _organic_, on the other hand, contain a small
quantity of organic matter dissolved in the watery fluid, and may be either
albuminous or gelatinous spheres.  The formed contents which are commonly
present are of very various natures, usually small fat-granules, more
rarely larger fat-granules or pigment-granules, sometimes concretions or
crystals. In many groups, especially among the large PHÆODARIA and
#Collodaria#, the numerous hyaline spheres are remarkable for their equal
size and even distribution throughout the endoplasm (Pl. 1, figs. 1, 4; Pl.
104, fig. 2, &c.). In some genera belonging to the Thalassicollida the
alveoles are of enormous size (Pl. 1,  figs. 2, 3); they then become
flattened by mutual pressure into polyhedra and distend the central capsule
to unusual dimensions (in _Physematium_ and _Thalassolampe_ 8 to 12 mm.).

  A. The "_spherical hyaline vesicles_,"  which I described in my Monograph
  (1862, p. 71) as among the most important and constant contents of the
  central capsule, are partly vacuoles, {xlii}partly homogeneous nuclei.
  Most recent investigators, Bütschli in particular (1882, L. N. 41), have
  pointed out and rightly criticised this confusion. The criticism might,
  however, have been more justly expressed by stating that, in the
  preparation of my Monograph (1859-1862), I did not make use of modern
  methods of demonstrating the nucleus by staining fluids, which were quite
  unknown at the time, and only discovered a decade later. In fact, without
  the aid of such reagents, it is quite impossible to distinguish between
  the various "spherical transparent vesicles," of which those found in the
  central capsule of the PHÆODARIA and many monozootic #Collodaria# are
  simple vacuoles lying in the endoplasm, whilst, on the other hand, those
  of the Polycyttaria and many other Radiolaria are true homogeneous
  nuclei. For not only are the general appearance of the small clear
  spheres, their refractive power, and regular distribution in the
  endoplasm quite similar, but they are also of much the same size, for the
  diameter ranges from 0.005 to 0.015 mm., being generally between 0.008
  and 0.012 mm. In addition to this there is generally in each hyaline
  sphere a dark brightly shining granule, which, in the case of the
  vacuole, is simply a fat-granule, whilst in the case of the nucleus, it
  is a true nucleolus. The small hyaline spheres in the young uninucleate
  capsules of the Polycyttaria are simple vacuoles (Pl. 3, fig. 12), whilst
  in the ripe multinucleate capsules they are true nuclei (Pl. 3, figs. 3,
  8, 9), and it is quite impossible to discriminate between these two
  conditions without the use of reagents. This has been expressly
  recognised by R. Hertwig, who has the merit of having been the first to
  clearly distinguish, by the aid of staining fluids, between these two
  different constituents (1879, L. N. 33, p. 108).

  B. The "_albumen spheres_," which were first observed by A. Schneider in
  1858 in the common cosmopolitan _Thalassicolla nucleata_ (L. N. 13, p.
  40), and which appear to occur in only a few other Thalassicollida, are
  distinguished from the ordinary hyaline spheres of about the same size by
  their higher refractive power and by certain albuminoid reactions,
  especially the coagulation of a membranous envelope under the influence
  of certain reagents (see my Monograph, p. 250, and Hertwig, L. N. 26,
  1876, p. 46). They often enclose various formed contents, and require
  further investigation.

  C. The _gelatinous spheres_ of various sizes, found in the endoplasm of
  the Radiolaria, agree in their reactions (especially in staining by
  certain reagents) with the common extracapsular jelly of the calymma, and
  are hence distinguishable both from the true (coagulable) "albumen
  sphere," and from the ordinary watery vacuoles.

  D. The _alveoles_, which are only accurately known in the case of certain
  large monozootic #Collodaria#, but which also seem to occur in the
  central capsule of other remarkably large Radiolaria, were described in
  my Monograph in the case of _Thalassolampe margarodes_ and _Physematium
  mülleri_, under the name "intracapsular alveolar cells" (1862, pp. 77,
  254, 257). They are not, however, true nucleated cells, and the body
  described as a nucleus is not such in reality. Nevertheless these large
  hyaline spheres do possess a special envelope, as I have recently
  convinced myself by the examination of ruptured central capsules of
  _Thalassolampe maxima_, _Thalassopila cladococcus_, and _Physematium
  atlanticum_ (Pl. 1, figs. 2, 3). The central capsule of these
  #Collodaria# becomes distended to most unusual dimensions (2 to 12 mm. in
  diameter) by the great development of these large hyaline vesicles, each
  of which measure from 0.1 to 0.5 mm. in diameter.


73. _The Intracapsular Fat-Globules._--Fat is present in the central
capsule of all Radiolaria in larger or smaller quantities, and generally
appears in the form of very {xliii}numerous, small, spherical granules,
which are either distributed evenly in the endoplasm (as an emulsion) or
enclosed in the vacuoles; the latter, in particular, is the case in most
PHÆODARIA, perhaps generally. In this group each vacuole contains as a rule
a single dark, shining fat-granule, and sometimes also an irregular bunch
composed of from two to five or more granules. In addition to these small
fat-granules (_granula adiposa_) which are always present, the central
capsule of many Radiolaria contains also larger fat-globules (_globuli
adiposi_). These appear to be generally wanting in the PHÆODARIA, and are
on the whole rare in the ACANTHARIA; whilst, on the contrary, they are very
common in the NASSELLARIA and SPUMELLARIA. The Polycyttaria or social
Radiolaria are as a rule distinguished by the possession of a single large
central oil-globule, which lies in the centre of the central capsule, and
is on an average about one-third of it in diameter (Pl. 3, figs. 4, 5).
This is absent, however, in those young capsules of the Polycyttaria in
which the primary nucleus is centrally situated (Pl. 3, fig. 12). Those
species of Polycyttaria whose central capsule reaches a considerable size,
often enclose numerous oil-globules, and in _Collophidium_ (species of
_Collozoum_ with an elongated cylindrical capsule, Pl. 3, figs. 1, 3) the
axis of each capsule is occupied by a row of numerous oil-globules.  In the
monozootic SPUMELLARIA, in which the nucleus is always centrally situated,
the large oil-globules are, of course, excentric, being in apposition to
the inner surface of the capsule-membrane (Pl. 1, fig. 3; Pl. 2, figs. 2,
5). In the #Discoidea# the oil-globules, which are often present in large
numbers, form elegant concentric rings around the central nucleus, and in
those species with segmented arms, there are one or more transverse rows in
each segment (Pl. 43, fig. 15). In the NASSELLARIA the number and
distribution of the oil-globules are dependent upon the form of the central
capsule. When this is simple, without lobes, and ovoid or conical, they
generally lie in its aboral half above the podoconus (Pl. 51, figs. 5, 13;
Pl. 97, fig. 1). When, on the contrary, the basal portion of the capsule
sends out three or four dependent processes (as in the majority of the
#Cyrtoidea#), a large globule may generally be seen in the swollen distal
part of each conical or ovoid lobe (Pl. 53, fig. 19; Pl. 60, figs. 4-7). In
many #Stephoidea# and #Spyroidea#, whose central capsule is separated into
two lateral portions by the constriction corresponding to the sagittal
ring, each of these contains either a single large globule or a group of
small ones (Pl. 90, figs. 7, 10). These oil-globules are usually colourless
and highly refractive; rarely they are yellow or brown, sometimes
rose-coloured, or an intense blood-red (_e.g._, in _Thalassophysa
sanguinolenta_) or even orange (in _Physematium mülleri_). In many
SPUMELLARIA, and particularly in the Polycyttaria, an albuminous substratum
may be recognised in them, which is sometimes disposed in layers, and after
extraction of the fat presents the appearance of a laminated sphere. The
physiological significance of the oil-globules is twofold; in the first
place they tend to diminish the specific gravity of the organism; in the
second they may be utilised as a reserve store {xliv}of nutriment. In the
latter respect they are of special importance in the process of
spore-formation, each flagellate spore usually containing a fat-granule.


74. _The Intracapsular Pigment-Bodies._--In the majority of Radiolaria when
observed alive, the central capsule is coloured, only in the minority is it
colourless.  The colour is never diffuse, but always due to the formation
of definite pigment granules or vesicles, which are sometimes distributed
evenly throughout the endoplasm, sometimes aggregated in the central or
peripheral regions.  Their form may be either spherical, irregularly
rounded, or polyhedral.  They vary much in dimensions, but in most cases
are immeasurably small, and appear under a high magnifying power as fine
dust; occasionally, however, their diameter may amount to from 0.001 to
0.005 or more. The chemical constitution of the intracapsular pigment is
unknown in most Radiolaria, and is probably very various. In many instances
the pigment-granules consist of fat, in others not.  The commonest colours
are yellow, red, and brown; violet and blue are rare, and green still
rarer. Sometimes a definite tone of colour prevails throughout a whole
group, and may then be attributed to inheritance, _e.g._, red is found in
most #Sphæroidea#, and blue in the Polycyttaria (see note A). One colour is
almost always constant in the members of the same species. True
pigment-cells, belonging to the Radiolarian organism, do not occur within
the central capsule. The peculiar yellow cells which are found in the
central capsule of many ACANTHARIA are symbiotic xanthellæ (see § 76).

  A. The number of Radiolaria whose pigment has been examined in the living
  state, is too small to allow of any general conclusions being drawn.
  Regarding the different colours known, see my Monograph, L. N. 16, p. 76.


75. _The Intracapsular Crystals._--The crystals found in the central
capsule of many Radiolaria may be divided into two groups, of very
different significance; small crystals, which are very widely distributed,
and large crystals, which occur in only a few genera. The _small crystals_
may also be termed "spore-crystals," since each swarm-spore often contains
such a crystal. They are rod-like or spindle-shaped, and consist of an
organic substance which probably serves as a reserve of nutriment for the
developing spores. Such spore-crystals have been observed in numerous
SPUMELLARIA and ACANTHARIA belonging to various families, and are probably
present throughout the two legions which make up the Porulosa. On the other
hand, they have not been noticed in the Osculosa (NASSELLARIA and
PHÆODARIA), the few swarm-spores belonging to these groups which have been
observed not exhibiting any crystals. The _large crystals_, which occur in
small numbers in the endoplasm, have hitherto only been observed in a few
species of SPUMELLARIA, belonging to the Polycyttaria. They were first
noticed in the common _Collosphæra huxleyi_, and regarded as coelestin.
They are also found in the central capsule of many other Collosphærida,
_e.g._, _Buccinosphæra_ (Pl. 5, figs. 11, 12). Crystal-masses,
crystal-sheaves, or spherical masses of radiating acicular crystals are
enclosed in {xlv}the vacuoles or "albumen globules" of _Thalassicola
nucleata_ and other Thalassicollida, as well as in the central capsule of
_Coelographis_ and some other PHÆODARIA (Pl. 127, figs. 4-7). All these
large crystals are probably to be regarded as excretory products.


75A. _The Intracapsular Concrements._--Concretions, either mineral or
organic, of varying form and constitution, are to be found in the endoplasm
of Radiolaria belonging to very different families. They are most abundant
and multiform in _Thalassicolla nucleata_, being usually circular or
elliptical discs, which are concentrically laminated and highly refractive,
resembling starch-grains. Among them twin forms may frequently be observed,
as though the concrements were in process of division (see note A). Similar
amyloid concretions are to be seen in the central capsule of different
SPUMELLARIA and NASSELLARIA, _e.g._, in _Cephalospyris triangulata_ (Pl.
96, fig. 28). Violin-shaped, highly refractive concrements have been
observed in the central capsule of numerous SPUMELLARIA, NASSELLARIA, and
ACANTHARIA, _e.g._, _Thalassosphæra_, _Spongosphæra_, _Plegmosphæra_,
_Cyrtocalpis_, _Peripyramis_, _Botryocella_, &c. (see note B). The chemical
constitution of these concrements is insufficiently known.

  A. The amyloid concretions of _Thalassicolla nucleata_ have been
  described in detail in my Monograph (pp. 80, 250, Taf. iii. figs. 2, 3),
  and by R. Hertwig in the Histologie der Radiolarien (1876, p. 47, Taf.
  iii. figs. 9-13).

  B. The violin-shaped concretions of _Thalassosphæra bifurca_ have been
  figured in my Monograph (pp. 80, 261, Taf. xii. fig. 1).


76. _The Intracapsular Xanthellæ._--The xanthellæ, zooxanthellæ, or
symbiotic "yellow cells" are found within the central capsule only in the
ACANTHARIA, whilst in other Radiolaria they only occur in the
extracapsulum. They are most frequent in the #Acanthometra#, rarer in the
#Acanthophracta#, but even in the former they are often wanting. Their
number is very variable, but usually small, from ten to thirty in one
capsule. They lie for the most part immediately below the capsule membrane,
in the cortical layer of the endoplasm. The form of the yellow cells is
either spherical or ellipsoidal, often also spheroidal or even lentiform.
The diameter varies from 0.01 to 0.03 mm. They possess a distinct membrane
and an excentric nucleus, and contain numerous yellow pigment-granules in
the endoplasm. This yellow pigment dissolves in mineral acids to form a
green fluid, and in other respects also behaves somewhat differently from
the yellow pigment in the extracapsular yellow cells of the SPUMELLARIA and
NASSELLARIA. In both cases, however, the xanthellæ are not integral
portions of the organism, but unicellular algae, living as parasites or
symbiontes in the body.

  A. The yellow cells in the central capsule of the ACANTHARIA were first
  observed by Joh. Müller (L. N. 12, pp. 14, 47). In my Monograph I
  described them at greater length, and indicated their differences from
  the extracapsular yellow cells of other Radiolaria (L. N. 16, pp. 77,
  86). Since then, R. Hertwig has demonstrated their cellular nature (L. N.
  33, pp. 12, 113), and still more recently {xlvi}Brandt has given further
  accurate information regarding their occurrence, constitution, and
  physiological significance (L. N. 39, ii. Art., p. 235, figs. 62-73).


77. _The Endoplasm of the Peripylea._--The intracapsular protoplasm of the
SPUMELLARIA or PERIPYLEA is usually distinguished by a more or less
complete radial arrangement, which does not occur in the same form in other
Radiolaria; it may be regarded as characteristic of this legion, for it
probably occurs in all the species at some period of life or other, and
stands in a direct causal relationship with the typical structure of the
capsule-membrane in all the "PERIPYLEA" (see note A). For as this is
commonly perforated by very numerous pores distributed at equal intervals
over the whole surface of the capsule, and since a communication between
the intra- and extracapsular sarcode takes place through these, the radiate
structure of the endoplasm may be readily explained as due to the influence
of radial currents which take place continuously or intermittently in the
endoplasm. This radiate structure is most obvious when the endoplasm
contains no secondary products or only an insignificant amount of these,
and thus appears colourless and almost homogeneous, or only finely
granular. Under these circumstances, an optical section of the central
capsule usually reveals a distinct radial striation; numerous narrow,
straight, dark streaks alternating regularly with still narrower clear
ones; the latter consist of homogeneous, the former of more or less
granular protoplasm (Pl. 20, fig. 1_a_). Often there may be distinguished
in each darker streak a single straight row of strongly refracting (fat?)
granules, sometimes several such rows. Occasionally the whole endoplasm
becomes divided up into a number of large "radial wedges," club-shaped,
conical or pyramidal masses of granular protoplasm, separated by clear
divisions of hyaline plasma (_e.g._, in _Actissa radiata_, p. 14, where in
the optical section of the central capsule, between the membrane and the
nucleus, twenty-five dark radial wedges of equal size were separated by
thick clear partitions of hyaline protoplasm). In the majority of the
SPUMELLARIA this radial striation is partially or entirely concealed by the
formation of pigment or of other products. Very often it is only visible in
the cortical layer, which lies immediately below the capsule-membrane (Pl.
1, figs. 1, 3). The remarkable "centripetal cones" which characterise the
Thalassicollid genus _Physematium_, and were formerly described as
"centripetal cell-groups," are probably a special development of these
cortical radial wedges; they are conical cortical bodies, regularly
distributed on the inner surface of the membrane of the central capsule,
and disposed with the apex turned towards the centre (see note B). More
rarely than in the cortical layer, a similar radial structure is to be
found in the innermost medullary layer immediately surrounding the nucleus.
Here the endoplasm sometimes breaks up into fine radial threads, which are
anatomically separable and hang down from the free nucleus as thin
processes (see note C). In some cases it is also possible to isolate radial
rods from the cortical layer of teased out central capsules.

  {xlvii}A. The radial structure of the endoplasm was first described in my
  Monograph (1862, p. 74), though R. Hertwig (1879, p. 112) was the first
  to indicate its typical significance in the case of the PERIPYLEA, and to
  demonstrate its causal relation with the radial currents in the central
  capsule of this legion. More recent investigations have led me to the
  conviction that this phenomenon is more widespread, and often more
  strongly developed, than was formerly imagined, and that it is probably
  one of the typical characters of all SPUMELLARIA (at least of the
  Monozoa).

  B. The centripetal cones of _Physematium_, which have hitherto been known
  only in these colossal Thalassosphærida, were fully described in my
  Monograph under the name "conical centripetal cell-groups"; by their
  first discoverer, A. Schneider (L. N. 13), they were termed "nests," and
  compared with the "nests" (central capsules) of the Polycyttaria. In the
  _Physematium mülleri_ of the Mediterranean (hitherto only observed by
  Schneider and myself at Messina) it appeared as though each centripetal
  cone were composed of a group of from three to nine (usually four or
  five) slender wedge-shaped cells, whose common centripetal apex was
  produced into a radial thread of sarcode (L. N. 16, p. 258, Taf. iii.
  fig. 7). Since then (1866) I have observed at Lanzerote, in the Canary
  Islands, a nearly related form, which I take to be _Physematium
  atlanticum_, Meyen.  In this, however, the "centripetal cell-groups" were
  wanting, and the whole cortical layer of the endoplasm was cleft into
  numerous radial portions, each enclosing a nucleus (probably the
  mother-cells of flagellate spores, see p. 35).

  C. The radial fibres of the medullary endoplasm which cling to an
  extracted nucleus have been observed by Hertwig in certain #Sphæroidea#
  (_Diplosphæra_, _Arachnosphæra_) (L. N. 33, p. 40).


78. _The Endoplasm of the Actipylea._--The intracapsular protoplasm of the
ACANTHARIA or ACTIPYLEA is often distinguished by a partial or complete
radial arrangement like that of the PERIPYLEA, but differing in the number,
size, form, and distribution of the radial portions into which the
endoplasm is differentiated. For since the pores of the capsule membrane
are distributed at equal distances all over the surface in the SPUMELLARIA,
whilst in the ACANTHARIA they are arranged in definite groups, and since
the number and arrangement of the pores has a direct influence upon the
internal currents of the endoplasm, it follows that the radial structure in
the latter legion must be very different from that in the former. In
addition to this there must not be forgotten the important influence which
the early centrogenous formation of the skeletal rods exercises upon the
disposition and growth of the intracapsular structures. Hence the endoplasm
of the ACANTHARIA does not separate into innumerable thin, closely packed
radial wedges or cortical radial rods, but into a small number of large
pyramidal portions between which run the radially disposed heterogeneous
portions of the contents of the capsule, viz., the radial bars of acanthin
and the peculiar intracapsular "axial threads." As a direct consequence of
the regular disposition of these heterogeneous radial portions, which is
often characteristic of the various families of the ACANTHARIA, a
corresponding differentiation of the endoplasm is brought about; it divides
into a number of conical or pyramidal portions (radial pyramids), whose
bases rest upon the capsule-membrane and whose apices are directed towards
the centre of {xlviii}the capsule (the central star of the skeleton).
These radial pyramids are, however, but rarely visible, being usually more
or less concealed by a dark pigment.

  The differentiations of the endoplasm in the central capsule of the
  ACTIPYLEA have been but little investigated, but they appear to vary
  somewhat in the different groups of this legion. In all ACANTHARIA in
  which the twenty radial bars are regularly arranged according to the
  Müllerian law (see p. 717) and in which axial threads constant in number
  and disposition run between them from the central star to the
  capsule-membrane, it obviously follows that the endoplasm must be divided
  into more or less distinct radial pyramids, and this must the case
  whether these take the form of continuous tracts or of actually separable
  portions. The regular polygonal figures, often seen on the surface of the
  central capsule (with special distinctness in _Acanthometron elasticum_
  and _Acanthometron pellucidum_) separated by a network of granular
  threads, are the bases of such radial pyramids (see Hertwig, L. N. 43, p.
  12, Taf. i. figs. 1-7).


79. _The Endoplasm  of the Monopylea._--The intracapsular protoplasm of the
NASSELLARIA or MONOPYLEA is distinguished from that of any of the other
three legions by the development of a quite peculiar fibrillar structure,
the axial "pseudopodial cone," which may shortly be termed the "podoconus"
(foot-cone). Since this is in direct correlation with the peculiar
structure of the capsular opening, the large "porochora," which is situated
at the basal pole of the main axis, it is quite as characteristic of the
legion as the latter itself (see note A). The podoconus is primitively a
vertical regular cone whose circular base occupies the horizontal porochora
or "basal porous area" of the central capsule, while its vertical axis
coincides with that of the latter. The apex of the cone, usually somewhat
rounded off, is therefore directed towards the aboral or apical pole of the
central capsule and separated from it by a larger or smaller interval. In
this interval the nucleus originally lies (as in Pl. 51, fig. 13; Pl. 98,
fig. 13); but it is usually displaced subsequently and lies excentrically.
The cone is of very variable height; on an average its vertical height is
about equal to the diameter of its horizontal base; these dimensions are,
however, dependent upon the form of the central capsule; the height being
greater in slender ovoid or conical capsules, and less in depressed
sphæroidal or discoidal ones, than the diameter of the base. The podoconus
consists of differentiated endoplasm, which becomes more deeply stained by
carmine and offers greater resistance to solvents than the surrounding
finely granular protoplasm. The apex, especially, becomes very intensely
stained. It always exhibits a very characteristic fine but distinct
striation, numerous straight radial lines diverging from the apex of the
cone towards the base. The number of these striæ appears to correspond with
that of the vertical rods in the porochora, and each of these latter stands
apparently in direct communication with the basal end of an apical stria (§
59). These threads are probably differentiated constant contractile threads
of endoplasm, or even myophanes, comparable with the contractile cortical
threads of the CANNOPYLEA and the permanent axial threads of the ACTIPYLEA.
 The numerous modifications, {xlix}undergone by the form and contents of
the central capsule in the different groups of MONOPYLEA, especially those
due to the formation of the skeleton, are not without influence upon the
podoconus. The most important divergencies from the above described primary
form are the following:--(1) The vertical axial cone becomes oblique, its
axis inclining in the sagittal plane and approaching either the dorsal or
the ventral wall of the capsule; the cause of this appears to be usually
the excentric development of the growing nucleus or the formation of a
large oil-globule. (2) The smooth mantle of the podoconus becomes divided
by three longitudinal furrows into three equal prominent ridges, which
correspond to three circular lobes in the porochora; the cause of this
basal triradial lobular formation lies probably in the triradial
development of the skeleton in many NASSELLARIA or in the cortinar
structure of the collar septum. (3) The simple podoconus splits into three
or four elongated lobes, which eventually become almost completely
separated and correspond to the lobes of the central capsule, in the axial
wall of which they lie as longitudinally striated bands. The behaviour of
these bands justifies the hypothesis that the podoconus is a muscular
differentiated portion of the endoplasm and is composed of myophane
fibrillæ, whose contraction determines the opening of the central capsule.

  A. The podoconus of the MONOPYLEA was first described by R. Hertwig in
  1879, and recognised as a characteristic component of the central capsule
  in the most various groups of this legion (in #Plectoidea#, #Stephoidea#,
  #Spyroidea#, and #Cyrtoidea#; see his figures, _loc. cit._, Taf. vii.,
  viii., and the description, pp. 71, 73, 83, 106). Hertwig called it the
  "pseudopodial cone," and regarded it as a conical process of the
  capsule-membrane, which is developed from this latter and projects from
  the porous area into the interior of the central capsule; "it is
  penetrated by fine canals which arise at the apex of the cone, diverge
  towards the base, and terminate there in the rods of the pseudopodial
  area. The intracapsular protoplasm penetrates at the apex of the
  pseudopodial cone into its fine canals, runs along them and emerges from
  the rods of the porous area in the form of slender threads" (_loc. cit._,
  p. 19). I cannot agree with this view of Hertwig, although I have been
  able to confirm the accuracy of his description by my own observations
  upon numerous excellently stained and preserved preparations in the
  Challenger collection. As I have proved by numerous teased out
  preparations, and as Hertwig himself correctly states, "the cone is more
  readily detached from the membrane than from the protoplasm, when the
  capsule is teased" (_loc. cit._, p. 73). Hence I regard the podoconus not
  as a differentiated portion of the capsule-membrane but as endoplasm, and
  believe that it is composed of myophanes or "contractile muscular
  fibrils" in the same manner as the cortical layer of the CANNOPYLEA.
  Probably the contraction of these fibrils serves to raise the opercular
  rods and hence to allow the exit of the endoplasm through the pores which
  lie between these opercular rhabdillae (compare § 59).


80. _The Endoplasm of the Cannopylea._--The intracapsular protoplasm of the
PHÆODARIA or CANNOPYLEA is distinguished from that of the other three
legions by several characteristic peculiarities, which are very important,
since they stand in causal relation to the typical structure of the
capsule-membrane and in particular of its {l}remarkable aperture. In the
case of many and perhaps of all PHÆODARIA the endoplasm is differentiated
into a granular medullary and a thin fibrillar cortical layer, the former
of which usually encloses numerous small vacuoles, while the latter
contains muscular fibrillæ. In the voluminous central capsule of large
PHÆODARIA the whole cortical layer of the endoplasm, which lies immediately
below the delicate inner capsule-membrane, sometimes appears delicately and
regularly striated, and most distinctly so under the apertures, towards the
centre of each of which the dark striæ are radially directed (see note A,
below). These striæ are probably contractile muscular fibrillæ; or
"myophanes," by whose contraction the openings are voluntarily widened. In
the Tripylea this fibrillar star is much more strongly developed under the
astropyle (the main opening) than under the parapylæ (or accessory
openings); and probably the peculiar radial structure of the operculum of
the former is due to the stronger development of these radial fibrils
(being their impression). In many PHÆODARIA, indeed, the fine myophane
fibrils are only visible under the apertures, whilst in others they form a
continuous fibrillar cortical layer on the whole inner surface of the inner
capsule-membrane; the fine fibrillæ run meridionally from one pole of the
main axis to the other; perhaps the whole central capsule may change its
form in consequence of their contractions. The medullary portion of the
endoplasm, which lies below this thin cortical layer, is usually finely
granular in the PHÆODARIA, and permeated by numerous spherical vacuoles,
which are noteworthy from their equal size and regular distribution. Each
clear vacuole usually contains a dark shining fat-granule, more rarely a
group of such granules (see note B). Compare § 60, and Pl. 101, figs. 1-3;
Pl. 104, figs. 1, 2; Pl. 111, fig. 2; Pl. 128, fig. 2, &c.

  A. The fine fibrillæ in the cortical layer of the endoplasm were first
  described by Hertwig in 1879 (L. N. 33, p. 98, Taf x. figs. 6-10). He
  found them, however, only below the three openings in the capsule of the
  Tripylea, where they form three stellate groups of fibrils. I find them
  very clearly shown, and with especial distinctness, under the astropyle
  in most PHÆODARIA of which I have had the opportunity of examining
  well-stained and preserved central capsules. In many cases, also, the
  striation is not confined to the apertures, but spreads over the whole
  cortical layer. Perhaps this constitutes in all PHÆODARIA a thin
  myophane-sheet, whose contractile fibrils run from one pole of the main
  axis to the other and cause by their contraction changes in the form of
  the spheroidal central capsule.

  B. The granular medullary portion of the endoplasm of the PHÆODARIA, with
  its numerous clear spherical vacuoles, was first described in my
  Monograph (1862), in the case of _Aulacantha_ (p. 263), _Aulosphæra_ (p.
  359), and _Coelodendrum_ (p. 361) as a "finely granular, mucous substance
  (intracapsular sarcode), packed more or less closely with clear spherical
  vesicles from 0.005 to 0.015 mm. in diameter, each of which contains one
  or two, rarely three, dark shining granules." That these clear spheres
  are true vacuoles was first clearly proved by Hertwig (L. N. 33, p. 98).
  As a rule all the vacuoles of the same central capsule are of equal size
  (generally from 0.008 to 0.012 mm. in diameter), and are distributed at
  equal intervals throughout the finely granular endoplasm.



{li}CHAPTER III.--THE EXTRACAPSULUM.

(§§ 81-100).

81. _The Components of the Extracapsulum._--The extracapsulum or
extracapsular malacoma, under which name are included all those parts of
the soft body which lie outside the central capsule, consists of the
following constant, and important constituents:--(1) The _calymma_ or
extracapsular jelly-veil; (2) the _sarcomatrix_ or layer of exoplasm
immediately surrounding the membrane of the central capsule; (3) the
_sarcodictyum_ or network of exoplasm, covering the surface of the calymma;
(4) the _pseudopodia_ or radial fibres of exoplasm, which may again be
subdivided into intracalymmar pseudopodia, uniting the sarcomatrix and
sarcodictyum, and extracalymmar pseudopodia, radiating freely into the
water outside the calymma.


82. _The Calymma._--The calymma or extracapsular jelly-veil of the
Radiolaria is always the most voluminous portion of the extracapsulum, and
in spite of its simple structureless constitution is of great morphological
and physiological importance. In all Radiolaria this gelatinous mantle
completely surrounds the central capsule, but is separated from its outer
surface by a continuous, though thin, layer of exoplasm, the sarcomatrix.
The pseudopodia radiating from the latter pierce the calymma, form the
sarcodictyum at its surface, and radiate from its nodal points freely into
the surrounding water. The calymma is rarely visible in living freshly
captured Radiolaria, examined in sea-water, for its gelatinous substance is
perfectly hyaline, colourless and pellucid, and possesses the same
refractive index as sea-water; but when the object is removed from this
fluid and transferred to carmine solution or some other colouring matter,
the extent and figure of the calymma become apparent, for the staining
fluid does not at first penetrate into the gelatinous material. When this
has taken place, however (after a longer or shorter time), and the
gelatinous material has become coloured, its form and size may be observed
by the converse experiment; the object is transferred once more to water
and the outlines of the calymma become as clear as those of the central
capsule. The same is the case with dead specimens in which the sticky
surface of the calymma has become covered with dust.

  The jelly-veil of the Radiolaria was recognised even by the earliest
  observers of the group, Meyen (1834), and Huxley (1851), and compared
  with that of the Palmellaria; the former noticed it in _Physematium_ and
  _Sphærozoum_ (L. N. 1, p. 283), and the latter in _Thalassicolla_ and
  _Collosphæra_ (L. N. 5, p. 433). In all these SPUMELLARIA, both in the
  monozootic _Thalassicolla_ and in the polyzootic _Sphærozoum_ and
  _Collosphæra_, the calymma is very voluminous and filled with large
  alveoli. Meyen called them "muco-gelatinous masses, in the interior of
  which are contained small equal-sized vesicles"; Huxley likewise found
  clear vesicles in the jelly and compared them with Dujardin's vacuoles.
  Johannes Müller observed the jelly-veil in many different Radiolaria, in
  particular in the #Acanthometra#, first discovered by him, but
  erroneously believed that it only originated {lii}after death by
  liquefaction of the sarcode (L. N. 12, p. 6). This mistake is, however,
  easy to understand, since in living Radiolaria the calymma is usually
  invisible on account of its perfect transparency, whilst in dead
  specimens it is usually quite distinct on account of the dust clinging to
  its adhesive surface. I myself believed that the formation of the
  voluminous hyaline jelly-veil was only partially due to liquefaction
  after death, but that it was to some extent present in the living
  organism and that it might vanish and subsequently reappear by means of
  imbibition (L. N. 16, pp. 109, 110). R. Hertwig was the first to
  demonstrate, in 1879, that the jelly-veil is constantly present in living
  Radiolaria, that it forms the basis of the extracapsular malacoma and
  surrounds the central capsule as a second protective sheath (L. N. 33, p.
  114).


83. _The Structure of the Calymma._--The extracapsular jelly-veil appears
structureless in most Radiolaria, inasmuch as it represents a homogeneous
pellucid excretion of the exoplasm and contains neither fibres nor other
formed structures. In some groups, however, definite structural characters
become secondarily developed. The most common and striking of these is the
formation of alveoles, which takes place in the extracapsulum (see § 86).
In consequence of this the calymma assumes a remarkable frothy consistency
and appears to be composed of large, clear, thin-walled vesicles; this is
especially the case in the #Collodaria# (#Colloidea#, Pls. 1, 3, and
#Beloidea#, Pls. 2, 4), and in many large PHÆODARIA, especially among the
#Phæocystina# (Phæodinida and Cannorrhaphida, Pl. 101, and Aulacanthida,
Pls. 102-104). More rarely the calymma is not permeated by vacuoles, but
there appear in it fine striæ parallel to the surface as though it were
composed of thin concentric laminæ like an onion; perhaps these are the
expressions of a different quantity of water in the various layers. In the
calymma of many Radiolaria thin, straight, radial lines are to be seen,
which are probably pseudopodia, and not to be attributed to any structural
modification, or they may be slender canals which serve for the exit of the
pseudopodia. On the outer surface of the calymma of different Radiolaria,
and especially in the ACANTHARIA, a peculiar network of fibres is to be
found, composed of polygonal meshes, like elastic fibres, probably due to a
local thickening of the jelly. These polygonal meshes are often very
regularly distributed between the radial spines of the #Acanthometra#, and
stand in a definite relation to them. The fibres which form the meshes are
often rather strong, resembling elastic fibres, as above-mentioned, and
either simple or composed of bundles of very fine fibrillæ (L. N. 33, p.
15, Taf. i. fig. 1, Taf. ii. fig. 4).


84. _The Consistency of the Calymma._--The gelatinous material of which the
calymma of the Radiolaria consists is a pellucid mass, rich in water and
usually quite hyaline and structureless; its consistency is very variable.
In the majority of the Radiolaria it may perhaps be about equal to that of
the jelly which composes the umbrella of most Medusæ; but as in these
latter it may vary between very wide extremes, constituting on the one hand
a very soft jelly-mantle, offering but little {liii}resistance to
mechanical influences and almost disintegrating under the eyes of the
observer, and on the other hand forming a firm gelatinous shell, comparable
to cartilage in hardness, elasticity, and power of mechanical resistance.
In many Radiolaria of large dimensions with an alveolar calymma (especially
in numerous #Collodaria# and PHÆODARIA) this may be split by means of
dissecting needles and the central capsule extracted like the stone from a
cherry, and then it is easy to ascertain that the firmness and elasticity
of this jelly-veil are not less than those of a cherry. The different
degrees of consistency in the various Radiolaria may be dependent either
upon the relative amount of water which they contain, or upon qualitative
or quantitative variations in the organic substance of which the jelly
consists. Great importance is to be attached to the considerable
consistency of the calymma, because it furnishes the indispensable
groundwork for the deposition of many parts of the skeleton and
particularly of the lattice-shells.


85. _The Primary and Secondary Calymma._--In most Radiolaria the external
form and volume of the calymma are different at different stages of growth,
and this difference is mainly dependent upon the development of the
skeleton. Hence it is advisable to distinguish in general the primary from
the secondary calymma. The _primary calymma_ is in the great majority of
Radiolaria a perfect sphere, in the middle of which lies the concentric
central capsule; on the surface of this gelatinous plate the primary
spherical lattice-shell is secreted in most SPUMELLARIA and
#Acanthophracta#, as well as in those PHÆODARIA which possess a spherical
shell; in the remaining PHÆODARIA also and in the NASSELLARIA, where the
lattice-shell is not spherical but monaxon, it is secreted on the surface
of the primary calymma. This takes place at a definite time, very important
in the development of the Radiolarian, which for the sake of brevity we
shall term the "_lorication-period_." Since the firm surface of the primary
calymma furnishes the necessary foundation for the deposition of the
primary lattice-shell, it is of the greatest mechanical significance in all
shell-bearing Radiolaria. The _secondary calymma_ arises only after the
lorication-period by further growth of the primitive jelly-mantle and in
the fully developed Radiolarian usually encloses wholly or partially the
external parts of the skeleton, in consequence of which it assumes the most
various forms. Very often the secondary calymma is polyhedral, being
stretched between the radial spines of the skeleton, the distal ends of the
latter then forming the fixed points of the gelatinous polyhedron.


86. _The Extracapsular Vacuoles and Alveoles._--The calymma of the
Radiolaria usually appears completely homogeneous and hyaline without any
structure; sometimes it encloses numerous clear vesicles, vacuoles or
alveoles, and then assumes a frothy appearance, the expression of a more or
less distinct alveolar structure. {liv}The clear vesicles to which this is
due are either spherical, or polyhedral from mutual pressure, and like the
similar ones in the central capsule may be divided into membraneless
vacuoles and vesicular alveoles. The _vacuoles_ are simple drops of fluid,
without a special envelope, and immediately surrounded by the gelatinous
substance of the calymma, in which they appear as simple cavities. The
_alveoles_ on the contrary are true vesicles, with a thin envelope, which
encloses a drop of fluid or a globule of jelly; in the latter case its
contents are different in refracting power and amount of contained water
from the substance of the surrounding calymma. A sharp boundary between the
membraneless vacuoles and the vesicular alveoles cannot be drawn in the
case of the extracapsular hyaline spheres any more than in the
intracapsular; the envelope of the alveoles is sometimes very distinct and
even anatomically separable, whilst at other times it is very thin and
scarcely recognisable; it may occasionally arise and disappear within a
very short time (see note A). There is no doubt that in the calymma as in
the central capsule the vesicular alveoles are secondary products, which
have arisen from the vacuoles by the secretion of an enveloping membrane.
This membrane is either a delicate sheath of exoplasm, or a firmer and more
resistant skin, distinct from the exoplasm, and probably an excretion from
it (_e.g._, Pl. 4, figs. 2, 3). In many cases the outer surface even of the
vacuoles is covered by a network of pseudopodia, which form a sarcoplegma
similar to a fenestrated alveolar membrane. The colourless pellucid fluid
in the vacuoles and alveoles is usually simple sea-water, more rarely it
contains a small quantity of albumen ("albumen-spheres") or jelly
("gelatinous spheres"). The size of these spheres is very variable. Quite
small vacuoles may be found in the calymma of many Radiolaria. Large
vacuoles, on the other hand, producing the appearance of an alveolar
structure, are confined to but few groups, to a part of the SPUMELLARIA
(#Colloidea#, #Beloidea#, and a few #Sphæroidea#), and to the #Phæocystina#
(PHÆODARIA with incomplete skeleton); besides they occur only rarely in
individual genera, _e.g._, _Nassella_ among the skeletonless NASSELLARIA.
Since the volume of the calymma is much increased by the development of
vacuoles, and the power of mechanical resistance is at the same time much
increased, the fact is explained that the vacuoles occur mainly in
Radiolaria which have no skeleton or only an incomplete one (see note B).
Among the monozootic #Collodaria# the alveolar structure is especially well
developed in the following genera; _Thalassicolla_ (Pl. 1, figs. 4, 5),
_Thalassophysa_, _Thalassoplancta_, _Lampoxanthium_ (Pl. 2, figs. 1, 2);
among the PHÆODARIA in most genera of the Phæodinida, Cannorrhaphida and
Aulacanthida (Pls. 101-104), and probably also in other voluminous
PHÆODARIA (_e.g._, #Phæosphæria#). The alveoles or vacuoles in the calymma
of these large Radiolaria lie usually in several layers, one above another,
and increase in size from within outwards. The Polycyttaria or social
Radiolaria (the three families Collozoida, Sphærozoida and Collosphærida)
without exception have an alveolar structure, and the special form of
{lv}their colonies or coenobia is to a great extent determined by the
development, number, size and arrangement of the alveoles in their calymma
(compare Pls. 3-8). In these cases there is not unfrequently developed a
large central alveole (see note C) whose thickened wall encloses a globe of
jelly and serves as the central support of the whole colony (Pl. 5, fig.
1). Still more striking, however, is the arrangement of certain
Polycyttaria, where each individual of the colony (or each central capsule
with its calymma) is enclosed in a large alveole, whose firm wall often
attains considerable thickness (Pl. 4, figs. 2, 3). The whole colony then
appears as an aggregate of numerous cells, each of which possesses two
envelopes, the inner central capsule and the outer alveolar membrane;
between these lies in the Collosphærida the siliceous lattice-shell (Pl. 6,
fig. 2). These pericapsular alveoles may be regarded as an outer cell-wall
more correctly than the membrane of the central capsule itself, but the
arrangement may also be compared to the temporary encystation of other
Protista (see note D).

  A. The extracapsular vacuoles in the calymma were first observed in 1851
  by Huxley, in _Thalassicolla_ and _Sphærozoum_, and compared with
  Dujardin's sarcode vacuoles (L. N. 5). Afterwards J. Müller noticed that
  generally these "large clear vesicles are covered by a fine membrane,"
  and hence he called them "alveoles" (L. N. 12, pp. 3, 7, &c.). In my
  Monograph I have described them more in detail as "extracapsular
  alveoles" (1862, p. 88, Tafs. i.-iii. xxxii.-xxxv.). Ever since then the
  point has been debated whether these clear spaces are simple vacuoles in
  the sense of Huxley or vesicular alveoles as stated by J. Müller. This
  contention is unnecessary, for both varieties are present, and often no
  sharp line can be drawn between them. R. Hertwig has recently come to the
  conclusion that they are as a rule "membraneless vacuoles," but that they
  "sometimes become surrounded by a special envelope" (L. N. 33, p. 31). He
  even succeeded "in extracting from a _Collosphæra_ the large vesicle
  which lies in the centre of many colonies and removing its covering of
  central capsules and jelly."

  B. The _mechanical importance_ of the alveolar structure, which certainly
  increases the elasticity and mechanical resistance of the voluminous
  calymma, has not yet been sufficiently realised; in the case of those
  Radiolaria which have no skeleton, or at all events no lattice-shell, it
  may take the place of this as a protective envelope. Furthermore, by
  taking in and giving out water it may discharge a hydrostatic function,
  causing the organism to rise or sink in the water.

  C. The _large central alveole_ found in the colonies of many Polycyttaria
  (especially Collosphærida) and first described in my Monograph (Taf.
  xxxiv. fig. 1), has since then been observed by Hertwig, Bütschli, and
  other investigators, and recognised as the "central support of the whole
  colony, surrounded by a delicate membrane" (compare L. N. 33, p. 31, and
  L. N. 41, p. 436). In a colony of _Trypanosphæra transformata_ (Pl. 5,
  fig. 1), which I observed living while in Ceylon in 1881, the membrane of
  the large central alveole was surrounded by a firm network of
  sarcoplegma, and could be mechanically isolated from the central
  jelly-sphere which it enclosed.

  D. The _pericapsular alveoles_, figured in Pl. 4, figs. 2, 3, from a
  _Sphærozoum_, and in Pl. 6, fig. 2, from a _Siphonosphæra_, were very
  well preserved in some preparations in the Challenger collection; perhaps
  their development coincides with the formation of spores, and may be
  regarded as an encystation.


{lvi}87. _The Extracapsular Fat-Globules._--Fat is probably as widely
distributed in the exoplasm as in the endoplasm of the Radiolaria; a
considerable proportion of the small, dark, highly refractive granules
appear to consist of fat; most likely they are for the most part direct
products of metastasis. These widely-spread granules, which are sometimes
coloured, and which by their passive motion produce the phenomenon of
granular circulation in the exoplasm, are not the only fatty structures in
the extracapsulum; larger globules sometimes occur. In certain large
#Collodaria# (_e.g._, _Thalassicolla melacapsa_, Pl. 1, fig. 5;
_Thalassophysa sanguinolenta_, &c.) radial series of oil-globules are found
in the calymma, especially in its proximal portion; in others the central
capsule is surrounded by a layer of oil-globules (situated in the
sarcomatrix). In the PHÆODARIA a part of the phæodium appears to consist of
fat-globules.


88. _The Extracapsular Pigment._--The formation of colouring matters in the
extracapsulum is on the whole rare in the Radiolaria, apart from the
"yellow cells" (see § 91) and from the peculiar phæodium of the PHÆODARIA,
which will be separately treated of in the next paragraph. Considerable
masses of extracapsular pigment, usually black or blue, rarely brown or
red, are found only in a few Radiolaria belonging to the first three
legions; most often in the SPUMELLARIA. Some large #Collodaria#, _e.g._,
the common _Thalassicolla nucleata_ and a few other species of this genus
(Pl. 1, fig. 4), are characterised by a rich deposit of black or blue
pigment in the sarcomatrix and in the proximal portion of the calymma.
Brown pigment is deposited in the calymma of many #Sphæroidea# and
#Discoidea#, as well as of some NASSELLARIA (_Cystidium_, _Tridictyopus_,
&c.). In a part of the ACANTHARIA red pigment granules are thickly strewn
in the sarcoplegma and pass along the free pseudopodia, as for example in
_Actinelius purpureus_ and _Acanthostaurus purpurascens_. The composition
and significance of these extracapsular pigments are not completely known.

  On the extracapsular pigment of _Thalassicolla nucleata_, compare my
  Monograph, pp. 87, 251. On the red extracapsular pigment-granules of the
  ACANTHARIA, see L. N. 19, pp. 345, 364, &c.


89. _The Phæodium of the Phæodaria._--The PHÆODARIA, which are
distinguished from the other three legions of Radiolaria by the double
membrane of the central capsule, and the peculiar structure of the
main-opening (astropyle), differ also in other points, the most important
of which is the constant presence of a voluminous mass of extracapsular
pigment. This possesses a peculiar constitution and special significance,
and is not to be confounded with the extracapsular pigment-granules of
other Radiolaria (_e.g._, _Thalassicolla_), and hence it has been
distinguished by the name "Phæodium," and the individual granules which
compose it as "Phæodella" (see note A). The phæodium is always excentric in
position relatively to the central capsule, of which it {lvii}surrounds the
oral half in the form of a voluminous concavo-convex cap, hiding the
astropyle at its basal pole so completely that the latter is rarely visible
until the phæodium has been removed (Pls. 99-104; Pl. 115, fig. 8; Pl. 123,
&c.). The central capsule is generally almost completely embedded in the
phæodium, so that only its aboral pole (with the two parapylæ in the
TRIPYLEA) projects. In the #Phæogromia#, in which the lattice-shell
possesses a special opening and the central capsule lies excentrically in
the aboral position of its interior, the phæodium occupies the oral aspect,
between the capsule and the aperture (Pls. 99, 100, 118-120, &c.). In the
peculiar family Coelographida (Pls. 126-128) a special receptacle (galea
with its rhinocanna) for the phæodium is developed outside the bivalve
shell, within which the central capsule lies. The proboscis, which in all
PHÆODARIA arises from the centre of the astropyle, lies in the vertical
axis of the phæodium and is entirely surrounded by it. The volume of the
phæodium in the majority of the PHÆODARIA may be said to be about as great
as that of the central capsule, although in some species it is considerably
larger. Its colour is always dark, usually between green and brown,
commonly olive-green or blackish-brown, rarely reddish-brown or black. The
phæodellæ or pigment-granules which make up the greater part of the
phæodium (see note B) are irregular in form and unequal in size and show no
definite structure; usually they are spherical or ellipsoidal, and exhibit
fine parallel striæ which run transversely or obliquely (Pl. 101, fig. 3,
6, 10; Pl. 103, fig. 1, &c.). Between the larger granules is usually found
a thick dust-like mass of innumerable very small grains. The physiological
significance of this peculiar phæodium is still unknown, but is probably
considerable, judging from its large size and especially from its constant
topographical relation to the astropyle; the latter consideration would
lead to the supposition that it plays an important part in the nutrition
and metastasis of the PHÆODARIA (see note C).

  A. The phæodium of _Aulacantha_, _Thalassoplancta_, and _Coelodendrum_
  was first described in 1862, in my Monograph, as an excentric
  extracapsular mass of pigment of blackish-brown or olive-green colour
  (pp. 87, 262, 264, 361, Taf. ii. iii. xxxii.). Since then John Murray,
  who investigated many living PHÆODARIA during the Challenger expedition,
  has shown its general distribution in this legion (Proc. Roy. Soc. Lond.,
  vol. xxiv. p. 536, 1876). From the constancy of its presence I gave the
  legion the name PHÆODARIA in 1879 (L. N. 34).

  B. With regard to the special composition of the phæodium and the
  constitution of the phæodellæ, see the general description of the
  PHÆODARIA, pp. 1533-1537.

  C. Perhaps the phæodellæ are to some extent symbiontes with the
  PHÆODARIA; the xanthellæ present in most other Radiolaria are absent in
  this legion.


90. _The Extracapsular Xanthellæ._--Xanthellæ or Zooxanthellæ, symbiotic
"yellow cells," are very commonly found in the extracapsulum of the
Radiolaria, especially in many SPUMELLARIA and NASSELLARIA; whilst in the
ACANTHARIA similar yellow cells usually only occur within the central
capsule, and in the PHÆODARIA their {lviii}presence has not been certainly
demonstrated. The extracapsular Xanthellæ are found most abundantly in the
#Collodaria#, both in the monozootic Thalassicollida and in the polyzootic
Sphærozoida. They occur in smaller numbers in the #Sphærellaria#, and in
many divisions of the latter they seem to be entirely absent. Also it
sometimes happens that, though present in large numbers in some
SPUMELLARIA, they are entirely absent in others nearly related to them;
indeed, this has also been observed in the case of different individuals of
the same species. This fact alone is sufficient to show that the Xanthellæ
are not an integral part of the Radiolarian organism (as was formerly
believed) but parasites or more correctly symbiontes, which live as
inhabitants of the calymma. More recent investigations have shown, that
besides the yellow pigment-grains they contain starch or an amyloid
substance, that is to say, vegetable reserve materials, that their thin
envelope contains cellulose, and that their yellow colouring-matter
resembles chlorophyll and is related to that of the Diatomaceæ
("Diatomin"). Hence they are now generally regarded as unicellular Algæ,
nearly related to those which occur as symbiontes in other marine animals
(_Exuviella_, &c.). The starch, which they develop with the formation of
oxygen, may serve as nutriment to the Radiolaria, while the carbonic acid
yielded by the latter is also beneficial to the Xanthellæ. The form of the
Xanthellæ is usually spherical and elliptical, often also sphæroidal or
discoidal. Their diameter is usually between 0.008 and 0.012 mm., rarely
more or less. The differences exhibited by Xanthellæ which live in
different groups of Radiolaria demand further investigation, which will
perhaps lead to the establishment of several species of the genus
_Zooxanthella_. At present _Zooxanthella extracapsularis_, in the calymma
of SPUMELLARIA and NASSELLARIA, may be clearly distinguished from
_Zooxanthella intracapsularis_, in the central capsule of the ACANTHARIA.

  The "yellow cells" were first described in 1851 by Huxley, in the
  #Collodaria#, and afterwards by J. Müller (1858) in many SPUMELLARIA and
  NASSELLARIA. In my Monograph (1862, pp. 84-87) I gave a detailed account
  of their structure and increase by division, and laid special emphasis on
  the fact that they are the only elements in the Radiolarian organism
  which "are _undoubtedly cells_ in the strict histological sense of the
  word." Afterwards, in my Beiträge zur Plastiden-Theorie, I showed the
  constant presence of "starch in the yellow cells of the Radiolaria"
  (1870, L. N. 21). Shortly afterwards Cienkowski observed that the yellow
  cells live independently and reproduce themselves after the death of the
  Radiolaria, and in consequence first put forth the hypothesis that they
  do not belong to the Radiolarian organism, but that they are unicellular
  Algæ parasitic upon it (1871, L. N. 22). This view was ten years later
  more fully established by Karl Brandt, and elucidated by comparison with
  the symbiosis of the gonidia of Algæ, and the hyphæ of Fungi in the
  formation of Lichens, which had in the meantime become known (1881, L. N.
  38). Brandt gave this unicellular yellow Alga the name _Zooxanthella
  nutricola_, and afterwards gave fuller details regarding its remarkable
  vital relations (L. N. 39). Patrick Geddes, who named it _Philozoon_,
  supplemented this account and showed experimentally that it gives off
  oxygen under the influence of sun-light (1882, L. N. 42, 43).  In
  consequence {lix}of this there is no doubt that all Xanthellæ (the
  _Zooxanthella extracapsularis_ of SPUMELLARIA and NASSELLARIA, and the
  _Zooxanthella intracapsularis_ of the ACANTHARIA, and possibly also the
  _Zooxanthella phæodaris_ of the PHÆODARIA) do not originally belong to
  the Radiolarian organism, as was believed up to the time of Cienkowski,
  but penetrate actively into it from without, or are taken in passively by
  means of the pseudopodia. In any case their symbiosis, when they are
  associated with the Radiolarian cell in large numbers, may be of great
  advantage to both parties, since the metastasis of the Xanthella is
  vegetable, that of the Radiolarian animal in character. In any case their
  symbiosis is to a large extent accidental, by no means as necessary as in
  the case of the Lichens. See on these points in addition to Brandt and
  Geddes (_loc. cit._) also Geza Enz, Das Consortial-Verhältniss von Algen
  und Thieren, Biol. Centralbl., Bd. ii. No. 15, 1883, Oskar Hertwig, Die
  Symbiose oder das Genossenschaftsleben im Thierreich, Jena, 1883, and
  Bütschli, Die Radiolarien, in Bronn's Klass. u. Ord. d. Thierreichs, 1882
  (L. N. 41, pp. 456-462).


91. _The Exoplasm or Extracapsular Protoplasm._--The extracapsular
protoplasm, which may be shortly termed the "exoplasm" (or ectosarc), is
primitively in all Radiolaria (and especially in their earliest development
stages) the only important constituent of the extracapsulum, besides the
calymma. Although the extracapsular and intracapsular protoplasm of the
Radiolaria are everywhere in direct communication, and although the
openings in the membrane of the central capsule bring about an interchange
between them, still the two portions of sarcode show certain constant and
characteristic differences, which are due to the physiological division of
labour between the central and peripheral parts of the body and their
corresponding morphological differentiation. The extracapsular, like the
intracapsular, protoplasm is originally homogeneous, but may afterwards
become differentiated in various ways, producing the special constituents
of the extracapsulum. Such "external protoplasmic products" are vacuoles,
pigment-bodies, &c. More important, however, are the topographically
different sections into which the exoplasm may be divided according to its
relations to the central capsule and the calymma. In this respect the
following parts may be generally distinguished--(1) the _Sarcomatrix_, or
fundamental layer of the exoplasm, which surrounds the central capsule as a
continuous sheath of sarcode and separates it from the calymma; (2) the
_Sarcoplegma_, an irregular network of the exoplasm, which spreads
throughout the gelatinous material of the calymma; (3) the _Sarcodictyum_
or network of sarcode on the outer surface of the calymma; and (4) the
_Pseudopodia_, which project outwards from the latter and radiate into the
water.


92. _The Sarcomatrix._--The sarcomatrix, being "the fundamental layer of
the pseudopodia" (or "matrix of the exoplasm"), constitutes the proximal
innermost section of the extracapsular sarcode, and in all Radiolaria forms
a thin continuous mucous layer, which covers the whole outer surface of the
central capsule and separates it from the surrounding calymma (see note A,
below). The sarcomatrix communicates internally {lx}through the openings of
the central capsule with the endoplasm, whilst externally the pseudopodia
or mucous threads arise from it, which by their union form the sarcoplegma.
The sarcomatrix is only interrupted in the SPUMELLARIA and ACANTHARIA by
those parts of the skeleton which perforate the membrane of the central
capsule. In all NASSELLARIA and PHÆODARIA, as in the #Collodaria#, it
appears as a perfectly continuous sarcode-envelope of the central capsule.
Its thickness is variable; in general it is most strongly developed in the
SPUMELLARIA and PHÆODARIA, less so in the NASSELLARIA, and is thinnest in
the ACANTHARIA. The thickness seems, however, to vary even in one and the
same individual, the difference depending partly upon the different stages
of development and partly upon nutritional conditions. After abundant
inception of nutriment the thin protoplasmic layer of the matrix is
thickened and turbid, rich in granules and irregular masses, which are
probably due to enclosed but only half-digested food; xanthellæ also, as
well as foreign bodies taken up with the nutriment, such as frustules of
Diatoms and shells of smaller Radiolaria, and of pelagic infusoria, larvæ,
&c., are often, especially in large individuals, aggregated in considerable
quantities in the matrix. After long fasting, on the contrary, this is poor
in these enclosed bodies and in granules; it then forms a thin colourless
more or less hyaline mucous coating to the central capsule. From a
physiological standpoint the sarcomatrix is to be regarded as the _central
organ of the extracapsulum_, and as of pre-eminent significance. Probably
it is not only the most important organ for the nutrition of the Radiolaria
(especially for digestion and assimilation in particular), but perhaps is
also the central organ of perception. On the other hand the sarcomatrix
belongs to those components of the Radiolarian organism which take no part
in the formation of the skeleton.

  A. The sarcomatrix was first described in my Monograph in 1862 (p. 110)
  as the "Mutterboden der Pseudopodien," possessing a pre-eminent
  physiological importance. Compare also my paper on the sarcode elements
  of the Rhizopoda (Zeitschr. f. wiss. Zool., Bd. xv. p. 342, 1865).


93. _The Sarcoplegma._--By the name sarcoplegma, as distinguished from the
remaining extracapsular sarcode, is understood the intracalymmar web of
exoplasm or "ectosarcode network," which ramifies within the gelatinous
mass of the calymma. Internally it is in direct connection with the
continuous sheath (sarcomatrix), which encloses the central capsule, whilst
externally it is in contact with the superficial sarcode network
(sarcodictyum) which surrounds the calymma. The configuration of this
exoplasmic web, which penetrates the jelly-veil in all directions, is
exceedingly variable; in most Radiolaria it is extremely irregular in form,
like the protoplasmic network in the ground-substance of many kinds of
connective tissue. In some groups, however, it assumes a rather regular
shape which it appears to retain (_e.g._, in many ACANTHARIA). It must be
assumed also that in those instances where the consistency {lxi}of the
calymma approaches that of cartilage, the tracks of the exoplasmic threads
remain constant, but accurate observations are wanting as to how far the
configuration of the sarcoplegma is constant or variable in the different
groups, as well as regarding its peculiar behaviour in those Radiolaria
whose calymma is characterised by the formation of vacuoles or alveoles
(see § 86). Usually it envelops the larger alveoles in the form of a
reticulate veil. In many #Collodaria# the exoplasm is aggregated at certain
points of the intracalymmar web, so that large balls or amoeboid bodies
appear to be distributed between the alveoles, _e.g._, in _Thalassophysa
pelagica_ and _Thalassicolla melacapsa_ (Pl. 1, figs. 4, 5). The
sarcoplegma is metamorphosed directly into silex in the Radiolaria
spongiosa, or those genera which possess a spongy cortical skeleton, and
were formerly known as Spongurida; to this category belong the
Spongosphærida (Pl. 18) and Spongodiscida (Pl. 47) as well as certain
NASSELLARIA and PHÆODARIA. The single siliceous spicules, which are
irregularly interwoven to form the spongy web, are to be regarded as the
silicified threads of the intracalymmar sarcode network. From a
physiological point of view the sarcoplegma is of importance both for the
nutrition and motion of the Radiolaria, since it brings the sarcomatrix and
the sarcodictyum, with the pseudopodia which radiate from it, into direct
communication.


94. _The Sarcodictyum._--The sarcodictyum may be defined as the
extracalymmar network of exoplasm, and is a reticular covering which lies
upon the outer surface of the gelatinous calymma. Internally, the
sarcodictyum is in direct communication with the sarcoplegma, or the web of
exoplasmic threads which ramifies in the gelatinous substance of the
calymma; externally, on the other hand, the pseudopodia radiate freely from
it; thus its relation to these is similar to that which the sarcomatrix
bears to the roots of the sarcoplegma. Relations similar to those which
have led to the separation of the primary from the secondary calymma,
induce us to distinguish also a primary and secondary sarcodictyum. The
original or _primary sarcodictyum_ ramifies over the surface of the
original or primary calymma, and like this is of pre-eminent importance in
the formation of the primary lattice-shell; if we regard the surface of the
primary calymma as the indispensable foundation for the deposition of this
latter, then the primary sarcodictyum furnishes the material from which it
is developed: silex in the SPUMELLARIA and NASSELLARIA, a silicate of
carbon in the PHÆODARIA, and acanthin in the ACANTHARIA. It may indeed be
said that the primary lattice-shell of the Radiolaria arises by a direct
chemical metamorphosis of the primary sarcodictyum, by a chemical
precipitation of the dissolved skeletal material (silex, silicate, or
acanthin), which was stored up in the exoplasm of the sarcodictyum. Hence a
deduction from the special conformation of the former to that of the latter
is permissible. The particular form of the primary lattice-sphere with its
regular or irregular meshes is due to the corresponding form of the primary
sarcodictyum; both regular and irregular forms of this {lxii}commonly
occurring. The form of the _regular sarcodictyum_ with circular or regular
polygonal, usually hexagonal, meshes is constantly maintained during the
formation of the regular lattice-shells (_e.g._, Pl. 12, figs. 5-10; Pl.
52, figs. 8-20; Pl. 96, figs. 2-6; Pl. 113, figs. 1-6). The form of the
_irregular sarcodictyum_, on the other hand, with irregular polygonal or
roundish meshes, persists during the development of the irregular
lattice-shells (_e.g._, Pls. 29, 70, 97, 106). All this is true also of the
_secondary sarcodictyum_, or the exoplasmic network which ramifies over the
surface of the secondary calymma. The secondary lattice-shells, which are
deposited on the surface of the latter, retain the configuration of the
secondary sarcodictyum, by the chemical metamorphosis of which they have
originated; this is the case in many SPUMELLARIA which develop several
concentric lattice-shells (Pl. 29), in some NASSELLARIA (Pl. 54, fig. 5),
in the Phractopeltida among the ACANTHARIA (Pl. 133), and in the
double-shelled PHÆODARIA, Cannosphærida, and part of the Coelodendrida and
Coelographida (Pls. 112, 121, 128). In those Radiolaria which form no
lattice-shell whatever, the conformation of the sarcodictyum is usually
irregular, with meshes of irregular form and unequal size; sometimes,
however, they seem to be very regular, as in many #Acanthometra# (Pl. 129,
fig. 4).


95. _The Pseudopodia._--On the whole the pseudopodia or thread-like
processes of the exoplasm exhibit in the Radiolaria the same characteristic
peculiarities as in all true Rhizopoda; they are usually very numerous,
long and thin, flexible and sensitive filaments of sarcode, which show the
peculiar phenomena of granular movement. Their physiological significance
is in several respects very great, for they serve as active organs for the
inception of nutriment, for locomotion, sensation, and the formation of the
skeleton (see note A, below). The presence of a calymma, however, which
distinguishes the Radiolaria from the other Rhizopoda, brings about certain
modifications in the behaviour of the pseudopodia. If in general all the
threads, which arise from the sarcomatrix or fundamental layer and radiate
outwards, be called "pseudopodia," then that part of them which is included
in the gelatinous substance of the calymma and forms the sarcoplegma may be
termed the "collopodia" (or intracalymmar pseudopodia), and the remaining
portion, which passes outwards from the sarcodictyum freely into the water,
may be described as "astropodia" (or extracalymmar pseudopodia). In many
Radiolaria these two portions present some differences in morphological and
physiological respects, and certain distinctions are probably generally
present (see note B). Apart from this universal differentiation in the
different groups of the Radiolaria, specially modified forms of pseudopodia
may be recognised as the axopodia and myxopodia of the ACANTHARIA (see §
95, A), and the sarcode-flagellum of certain SPUMELLARIA (see note C).

  A. The pseudopodia of the Radiolaria have been so fully described in my
  Monograph, in 1862, both morphologically and physiologically, that I need
  only refer to the account there given {lxiii}(pp. 89-127); for
  supplementary observations see R. Hertwig (1879, L. N. 33, p. 117) and
  Bütschli (1882, L. N. 41, pp. 437-445).

  B. The _Astropodia_, or free radiating pseudopodia, are in many
  Radiolaria more or less clearly distinguishable from the collopodia,
  which form the sarcoplegma within the calymma; how far these distinctions
  depend upon a permanent differentiation (especially in the ACANTHARIA and
  PHÆODARIA) needs further investigation.

  C. The _sarcode-flagellum_ (perhaps better termed _axoflagellum_) was
  first described in my Monograph (1862, p. 115) in the case of various
  #Discoidea# (Taf. xxviii. figs. 5, 8; Taf. xxx. fig. 1). Hertwig has
  given a substantially similar account of the organ in some other
  #Discoidea# (L. N. 33, p. 67, Taf. vi. figs. 10, 11); probably this
  peculiar structure is confined to the order #Discoidea# among the
  SPUMELLARIA, but is widely distributed within its limits. The
  axoflagellum is a thick cylindrical thread of sarcode, finely striated
  and pointed towards its free end. It always lies in the equatorial plane
  of the discoidal body, and always unpaired in one of its axes; in the
  triradiate #Discoidea# it is in the axis of the unpaired principal arm
  and opposite to it (Pl. 43, fig. 15). In the Ommatodiscida (p. 500, Pl.
  48, figs. 8, 19, 20) the axoflagellum probably passes out through the
  peculiar marginal ostium of the shell. Perhaps it is always connected
  with the central nucleus by intracapsular axial fibres, and is to be
  regarded as a specially differentiated bundle of pseudopodia (or
  axopodia?).


95A. _The Myxopodia and Axopodia._--The two forms of pseudopodia which we
distinguish as myxopodia and axopodia differ markedly from each other both
morphologically and physiologically. The _myxopodia_, or ordinary free
pseudopodia, which are found in large numbers in all Radiolaria, and
constitute their most important peripheral organs, are simple homogeneous
exoplasmic threads, which arise from the sarcodictyum or extracalymmar
sarcode network, and radiate freely into the water; here they may branch
and combine by anastomosis to form a changeable network, but they never
contain an axial thread. The _axopodia_, on the other hand, are
differentiated pseudopodia, which consist of a firm radial thread, and a
soft covering of exoplasm; they penetrate the whole calymma in a radial
direction and project freely from its surface, and generally (if not
always) they are produced inwards to the middle of the central capsule,
perforating its membrane; their proximal end is lost in a dark central heap
of granules. Such axopodia are at present known with certainty only in the
ACANTHARIA, where they are widely, and perhaps universally, distributed.
Their development in this legion probably stands in direct causal relation
to the peculiar structure of the central capsule and the centrogenous
formation of the skeleton. Since the radial skeletal rods of the
#Acanthometra# possess originally a thin coating of protoplasm, it may be
said that the centrogenous axopodia of this group became differentiated in
two ways, the firm axial threads of one section remaining very thin and
covered by protoplasm, whilst those of the other section became
metamorphosed into radial bars of acanthin. This hypothesis acquires more
probability from the regular distribution and arrangement of the axopodia
in the ACANTHARIA; they usually stand at fixed intervals {lxiv}between the
radial bars, singly or in groups; sometimes their number seems to be not
greater than that of the bars, whilst in other cases a circlet or group of
axopodia corresponds to each radial bar. Perhaps their fine axial thread
consists of acanthin. At all events the axopodia are constant organs
(probably sensory, like the "palpocils") and not retractile like the
movable myxopodia.

  The axial threads in the pseudopodia of the #Acanthometra# were first
  discovered by R. Hertwig, who accurately described their peculiar
  structure and arrangement (L. N. 33, pp. 16, 117).


96. _The Myophriscs of the Acanthometra._--The #Acanthometra# are
characterised by a very peculiar differentiation of the exoplasm, namely,
by the formation of myophriscs or contractile threads from the
sarcodictyum. In most (and perhaps in all) ACANTHARIA of this order each
radial bar is surrounded by a circlet of such contractile threads, which
was first described as a "ciliary corona" (see note A, below). The number
of contractile threads in each circlet usually amounts to from ten to
twenty, rarely being more than thirty and less than eight; it often appears
to be constant in the individual species (see note B). In the living state
the myophriscs are long, thin filaments, the pointed distal end of which is
inserted into the radial bar, whilst the thicker proximal end is attached
to the surface of the calymma, which is elevated round the base of each rod
into the form of a gelatinous cone or skeletal sheath (see note C).
Probably the myophriscs lie on the outer surface of the apical portion of
this gelatinous cone, and are hence to be regarded as exoplasmic threads
differentiated from the sarcodictyum. Sometimes, however (as in
_Acanthochiasma_), they fuse into a contractile membrane and form the
envelope of a cone, whose interior is occupied by a gelatinous papilla of
the calymma. On mechanical irritation the myophriscs contract rapidly and
suddenly, like muscle-fibrillæ, becoming at the same time thicker, and
hence are very different from pseudopodia. Their distal point of insertion
being fixed to the firm acanthin rod, they raise by their contraction the
skeletal sheath, to which their bases are attached or in the surface of
which they lie. The result of their contraction is therefore a distention
and increase in volume of the calymma, with which is no doubt connected an
inception of water into the gelatinous mass, and hence a diminution in its
specific gravity. Probably the #Acanthometra# contract their myophriscs
voluntarily when they wish to rise in the water; when these relax the
calymma collapses owing to its elasticity, water is then expelled and the
specific gravity increases. From a physiological point of view, then, the
myophriscs are to be regarded as a hydrostatic apparatus, morphologically
as myophanes or muscular fibrillæ, such as also occur in the intracapsular
protoplasm (see §§ 77-80). On more violent irritation and after the death
of the #Acanthometra# the myophriscs separate from the radial bars and
remain attached to the distal ends of the conical gelatinous sheaths as
free "ciliary coronas." At the same time, {lxv}they melt into short, thick,
hyaline rods, the so-called "gelatinous cilia." The myophriscs are found
only in the order #Acanthometra#, and are wanting in the #Acanthophracta#,
as well as in the other three legions of Radiolaria.

  A. The "_ciliary coronas_" on the skeletal rods of dead #Acanthometra#
  were first described by the discoverer of this order, Johannes Müller,
  and referred to as "the stumps of the contracted, thickened threads" (L.
  N. 12, p. 11, Taf. xi.).

  B. The "_number of the gelatinous cilia_" I found constant in certain
  species of #Acanthometra#, and stated in my Monograph (L. N. 16, p. 115)
  "that here is to be found the first differentiation of the diffuse
  sarcode into definite organs of regular definite number, size, and
  position, which deserve the name tentacles rather than pseudopodia."

  C.  The nature of the myophriscs as fibrillæ allied to muscles was first
  discovered by R. Hertwig, who described them as "structures of peculiar
  nature," under the name of "contractile threads," and pointed out in
  detail their histological and physiological peculiarities (L. N. 33, pp.
  16-19, Taf. i.).


97. _The Exoplasm of the Peripylea._--The extracapsular protoplasm of the
SPUMELLARIA or PERIPYLEA is in communication with the intracapsular sarcode
by the innumerable fine pores of the capsule-membrane, and like these pores
is evenly distributed over the whole surface. The sarcomatrix which
immediately surrounds the central capsule is moderately strong, and sends
out innumerable long, thin pseudopodia, which probably correspond to the
pores of the membrane. Their number is markedly greater in the SPUMELLARIA
than in the other three legions. The ramifications and communications which
the radiating fibres of the sarcomatrix undergo within the calymma,
apparently present the most manifold variations, so that the sarcoplegma or
intracalymmar network thus formed has very diverse forms. On the surface of
the calymma the exoplasmic threads constitute a variously disposed
sarcodictyum, a regular or irregular exoplasmic network, by the
silicification of which a primary lattice-shell arises in the majority of
the SPUMELLARIA. The free ends of the pseudopodia, which arise from this
extracalymmar network and radiate out into the water, appear in most
SPUMELLARIA to be relatively short, but exceedingly numerous. Specially
modified pseudopodia and axial threads in particular do not seem to occur
in this legion. Perhaps, however, among the latter may be reckoned the
remarkable pseudopodia which combine to form the sarcode flagellum in many
#Discoidea# (and perhaps in other SPUMELLARIA). This axoflagellum is a
particularly strong thread of sarcode, arising from a definite point in the
central capsule; it is cylindrical or slenderly conical in form, much
longer, stronger, and more contractile than the ordinary pseudopodia; it
contracts in a serpentine fashion on mechanical irritation and seems to
originate by the fusion of a bundle of pseudopodia (compare § 95, C).


98. _The Exoplasm of the Actipylea._--The extracapsular protoplasm of the
ACANTHARIA or ACTIPYLEA differs in several important respects from that of
other {lxvi}Radiolaria, and appears to undergo more significant
differentiations than that of the three other legions. Since the pores in
the wall of the central capsule are not distributed evenly and at equal
intervals over its whole surface (as in the PERIPYLEA), but rather exhibit
a regular disposition in groups at unequal intervals, the number of
projecting pseudopodia is much less and the law of their arrangement
different from that which obtains in the PERIPYLEA (§ 58). In many and
probably in all ACANTHARIA they are divided into two groups, those which
arise from the centre of the capsule and possess firm axial threads, and
those which have not these characters (compare § 95, A). The axopodia, or
stiff pseudopodia with axial threads, arise from the centre of the capsule,
are present in much smaller numbers than the soft and flexible myxopodia,
and are regularly disposed between the radial bars of acanthin, usually so
that they are as far removed from them as possible, _i.e._, in the centre
between each three or four bars; these latter may indeed be regarded as
strongly developed axial threads, which have become changed into acanthin
(§ 95, A). The soft myxopodia, or pseudopodia without axial threads, are
much more numerous than the others, and arise from the sarcodictyum or
exoplasmic network which ramifies over the surface of the calymma. Their
number and arrangement seem, however, in many (if not in all) ACANTHARIA to
be regular and not to possess the extraordinary variability seen in the
other three legions. In many #Acanthometra# the sarcodictyum exhibits a
symmetrical conformation, with regular or subregular, polygonal (mostly
hexagonal) meshes, and generally the stronger threads of the sarcodictyum
secrete a firm, homogeneous or fibrillar, striated substance, which forms a
network of ridges on the surface of the calymma. In the #Acanthophracta#
the place of this is taken by the acanthin network of the primary
lattice-shell. The axopodia of the #Acanthometra# are usually about as long
as the radial spines between which they stand; their stiff axial thread is
surrounded by a soft sheath of protoplasm, communicating with the thin
sarcomatrix which surrounds the central capsule. Numerous branches pass
into the calymma from the exoplasmic sheath of the axial threads, and form
by their interweaving a loose sarcoplegma. The most peculiar differentiated
products of the exoplasm of the ACANTHARIA, however, are the myophane
fibrillæ of the #Acanthometra#, which have already been described under the
name of myophriscs (§ 96).


99. _The Exoplasm of the Monopylea._--The extracapsular protoplasm of the
NASSELLARIA or MONOPYLEA arises only from the porochora, or the
intracapsular podoconus, the oral base of which is formed by this porous
area. The pseudopodia or protoplasmic threads which pass through the pores
of the latter, united into a bundle, are not very numerous (in most
NASSELLARIA probably between thirty and ninety), and unite just outside it
to form a thick discoid sarcomatrix; this covers the porochora completely
below, and spreads out in the form of a thin envelope of exoplasm over the
whole {lxvii}surface of the central capsule; at the apical portion of the
latter the sarcomatrix is often so thin that it can only be recognised by
the aid of reagents; it separates the membrane of the central capsule from
the surrounding calymma. The pseudopodia, which penetrate the latter and by
loose anastomoses from a wide-meshed sarcoplegma within it, are usually not
very numerous. The greater part of them radiate in a bunch downwards from
the basal disc of the sarcomatrix, and a smaller number arise from the
thinner envelope which covers the remainder of the central capsule (Pl. 51,
fig. 13; Pl. 65, fig. 1; Pl. 81, fig. 16). On the outer surface of the
calymma the collopodia, which have passed through it, unite to form the
sarcodictyum, and through the silicification of this the primary
lattice-shell arises in the great majority of the NASSELLARIA. From the
surface of the sarcodictyum arise the astropodia, or free pseudopodia which
radiate outwards into the water. Their number in most MONOPYLEA is
relatively small, but their length appears to be very great.


100. _The Exoplasm of the Cannopylea._--The extracapsular protoplasm of the
PHÆODARIA or CANNOPYLEA is much better developed as regards volume than in
the other three legions, and is connected with the intracapsular sarcode by
only a few apertures in the capsule-membrane. In most PHÆODARIA three of
these are present, the astropyle or main-opening at the oral pole of the
main axis, and the two lateral parapylæ or accessory openings on either
side of the aboral pole (§ 60). In several families the latter appear to be
wanting, whilst in others their number is increased; these families have
not yet, however, been observed during life. The protoplasm projects both
from the oral main-opening and from the two aboral accessory openings in
the form of a thick cylindrical rod; the tube into which each opening is
produced in many PHÆODARIA (longer in the case of the astropyle, shorter in
the parapylæ) being regarded as an excretion from this protoplasmic
cylinder. The sarcode threads within the tube appear like a bundle of
fibrils, either quite hyaline or finely striated. After issuing from the
mouth of the aperture they pass over into a thick sarcomatrix, which
surrounds the central capsule entirely and separates it from the enclosing
calymma. In the neighbourhood of the basal astropyle the sarcomatrix is
usually swollen into a thick lenticular disc, which is in direct contact
with the peculiar phæodium of this legion (§ 89). The pseudopodia, which
radiate from the sarcomatrix, and form by anastomosis a wide-meshed
sarcoplegma within the calymma, are usually not very numerous in the
PHÆODARIA, but are very strong. Sometimes two stronger bundles of
collopodia may be distinguished at the two poles of the main axis, an oral
bundle (in the direction of the proboscis of the astropyle) and an aboral
bundle (at the opposite pole between the parapylæ). The collopodia of the
sarcoplegma unite at the surface of the calymma into a regular or irregular
sarcodictyum, which, in most PHÆODARIA produces by the secretion of a
peculiar silicate the primary lattice-shell. {lxviii}The free astropodia,
which pass outwards from the sarcodictyum into the water, are in most
PHÆODARIA very numerous (Pl. 101, fig. 10). Since, however, only a few
species of this great legion have been observed in a living state, their
pseudopodia require further accurate examination.



CHAPTER IV.--THE SKELETON.

(§§ 101-140).

101. _The Significance of the Skeleton._--The skeleton of the Radiolaria is
developed in such exceedingly manifold and various shapes, and exhibits at
the same time such wonderful regularity and delicacy in its adjustments,
that in both these respects the present group of Protista excels all other
classes of the organic world. For, in spite of the fact that the
Radiolarian organism always remains merely a single cell, it shows the
potentiality of the highest complexity to which the process of skeleton
formation can be brought by a single cell. All that has been brought to
pass in this direction by single tissue-cells of animals and plants does
not attain the extremely high stage of development of the Radiolaria. Only
very few Rhizopoda of this very rich and varied class fail to exhibit the
power of forming this firm supporting and protecting organ--indeed, only
ten of the seven hundred and thirty-nine genera which are enrolled in the
list of the Challenger collection, namely, six genera of SPUMELLARIA (five
Thalassicollida, _Actissa_, _Thalassolampe_, _Thalassopila_,
_Thalassicolla_, _Thalassophysa_, Pl. 1, and one genus of Collozoida,
_Collozoum_, Pl. 3), and in addition two genera of NASSELLARIA (the
Nassellida, _Cystidium_ and _Nassella_, Pl. 91, fig. 1), and two genera of
PHÆODARIA (the Phæodinida, _Phæocolla_ and _Phæodina_, Pl. 101, figs. 1,
2). These skeletonless forms of Radiolaria are, however, of extreme
interest, since they include the original stem-forms of the whole class as
well as of its four legions. All Radiolaria which form skeletons have
originated from soft and skeletonless stem-forms by adaptation, and that
polyphyletically, for the skeletal types of the four legions have been
developed independently of each other (§ 108).


102. _The Chemical Peculiarities of the Skeleton._--The chemical
composition of the skeleton shows very marked variations in the different
legions of the Radiolaria. The two legions SPUMELLARIA and NASSELLARIA
(united formerly as "Polycystina") form their skeleton of pure silica (see
note A, below); the legion PHÆODARIA of a silicate of carbon (see note B),
and the ACANTHARIA of a peculiar organic substance--acanthin (see note C).
This explains the well-known fact that the deposits of fossil Radiolaria
(or Polycystine marls) are composed exclusively of the skeletons of
SPUMELLARIA and NASSELLARIA, those of the ACANTHARIA and PHÆODARIA being
entirely absent (in the case of the last group, however, exception must be
made in favour of the Dictyochida, or those PHÆODARIA {lxix}whose skeleton
is made up of isolated scattered tangential siliceous fragments). The
enormous deposits of Radiolarian skeletons in the deep sea of today, which
constitute the Radiolarian ooze, consist, like the fossil Polycystine
marls, almost exclusively of the shells of SPUMELLARIA and NASSELLARIA,
though here the acanthin skeletons of the ACANTHARIA may be present in very
small numbers, and the silicate skeletons of the PHÆODARIA, which offer
more resistance to the solvent action of sea-water, somewhat more
abundantly. Calcareous skeletons do not occur in the Radiolaria (see note
D).

  A. The pure siliceous skeletons of the Polycystina were first recognised
  in 1833 by Ehrenberg in chalky marls (L. N. 2, p. 117).  Since the two
  legions ACANTHARIA and PHÆODARIA were entirely unknown to Ehrenberg, his
  name Polycystina has reference only to the SPUMELLARIA and NASSELLARIA.

  B. The silicate skeleton of the PHÆODARIA was formerly taken by me for a
  purely siliceous one. When I described the first PHÆODARIA in my
  Monograph in 1862, I was only acquainted with five genera and seven
  species, whilst the number of PHÆODARIA here described from the
  Challenger amounts to eighty-four genera and four hundred and sixty-five
  species. In the vast majority of these (though not in all) the skeleton
  becomes more or less intensely stained by carmine, and is also more or
  less charred at a red heat, in some even becoming of a blackish-brown. In
  many PHÆODARIA, furthermore, the hollow skeletal tubes are destroyed by
  the continued action of heat. They are also, for the most part, strongly
  acted upon, or even destroyed by boiling caustic alkalis, whilst boiling
  mineral acids have no effect upon them. The best method of cleaning the
  skeletons of PHÆODARIA from their soft parts is to heat them in
  concentrated sulphuric acid, and then add a drop of fuming nitric acid;
  in this they are not dissolved even on prolonged heating. From these
  facts it would appear that the skeletons of the PHÆODARIA consist of a
  compound of organic substance and silica, or a "carbonic silicate." The
  more intimate composition yet remains to be discovered, as also the
  manifold differences which the various families of PHÆODARIA seem to show
  in respect of its composition. The small skeletal fragments of the
  Dictyochida (the only remains of PHÆODARIA which occur as fossils) appear
  to consist of pure silica.

  C. The acanthin skeleton of the ACANTHARIA was first described as such in
  my Monograph (1862, pp. 30-32). Johannes Müller, the discoverer of this
  legion, took them for siliceous skeletons and defined the #Acanthometra#
  as "Radiolaria without lattice-shell, but with siliceous radial spines"
  (L. N. 12, p. 46). I formerly supposed that the acanthin skeletons in
  some of the ACANTHARIA were partially or wholly metamorphosed into
  siliceous skeletons, but, according to the investigations of R. Hertwig,
  this does not appear to be the case; he showed that the skeletons of the
  most varied #Acanthometra# and #Acanthophracta# are completely dissolved
  under the longer or shorter action of acids, and supposes that in all
  ACANTHARIA, without exception, the skeleton is composed of acanthin
  (1879, L. N. 33, p. 120). Quite recently Brandt has found that the
  acanthin spines dissolve not only in acids, alkalis, and "liquor
  conservativus" (as I had shown), but also in solutions of carbonate of
  soda (1 per cent.), and even of common salt (10 to 20 per cent.); he
  concludes from this that they consist of an albuminoid substance
  (vitellin) (L. N. 38, p. 400). I am unable to share this view, for I have
  never been able to see some of the most important reactions of albumen in
  any of the skeletons which I have examined, such for example as the
  xanthoproteic reaction, the red coloration with Millon's test, &c. They
  do not become {lxx}yellow either with nitric acid or with iodine. In
  dilute mineral acids they dissolve more rapidly than in concentrated. My
  usual method of cleansing the skeleton of ACANTHARIA (which has been
  practised with the same result on thousands of specimens) consists in
  heating the preparation in a small volume of concentrated sulphuric acid
  and then adding a drop of fuming nitric acid; all other constituents (the
  whole central capsule and the calymma) are thus very rapidly destroyed;
  the skeleton remains quite uninjured and withstands the combined action
  of the mineral acids for a longer or shorter time, though on prolonged
  heating it also is dissolved. I do not therefore regard acanthin as an
  albuminous substance, but as one related to chitin.

  D. Calcareous skeletons have not been certainly demonstrated in the
  Radiolaria, and probably do not occur. Sir Wyville Thomson in his
  Atlantic (1877, L. N. 31, vol. i. p. 233, fig. 51) described under the
  name _Calcaromma calcarea_, a Radiolarian which contained scattered in
  its calymma numerous calcareous corpuscles "resembling the rowels of
  spurs." These are identical with the "toothed bodies, recalling crystal
  balls," which Johannes Müller figured in the Mediterranean _Thalassicolla
  morum_ so early as 1858, and compared with the "siliceous asterisks of
  _Tethya_" (L. N. 12, p. 28, Taf. vii. figs. 1, 2). I formerly regarded
  these peculiar calcareous corpuscles, whose solubility in mineral acids I
  had observed, as spicules of a Thalassicollid, and hence described the
  species in my Monograph as _Thalassosphæra morum_ (L. N. 16, p. 260). I
  have, however, seen reason to change my view, and am now led to suppose
  that those peculiar calcareous corpuscles, which may be named
  "_Calcastrella_," are not formed by the Radiolarian itself, but are
  foreign bodies which have been accidentally incorporated into the calymma
  of a Thalassicollid (_Actissa_). These corpuscles occur, often in large
  numbers, in many preparations in the Challenger collection, and in the
  calymma of other Radiolaria, chiefly #Discoidea#, hence it would appear
  that they are foreign bodies taken up by the pseudopodia and carried into
  the calymma by the circulation of the sarcode. The Radiolaria which Sir
  Wyville Thomson figured as _Calcaromma calcarea_, and Müller as
  _Thalassicolla morum_, I regard as species of _Actissa_ (see p. 13),
  perhaps _Actissa radiata_ of the Pacific, and _Actissa primordialis_ of
  the Mediterranean (compare the description of the Thalassosphærida of the
  Challenger collection, pp. 30, 31).


103. _The Physical Properties of the Skeleton._--The skeletons of all
Radiolaria are characterised pre-eminently by a high degree of _firmness_,
which fits them to serve as protective and supporting apparatus. This is
obvious in the case of the pure siliceous shells of the Polycystina; but
the acanthin framework of the ACANTHARIA also possesses a degree of
stiffness but little inferior, whilst the silicate skeletons of the
PHÆODARIA seem on the whole to be not so firm. The hollow skeletal tubes of
the last-named, which are filled with gelatinous material, are very brittle
on account of the delicacy of their walls. Their _elasticity_ also is very
small, whilst that of the acanthin spines is considerable. The thin long
needles of many ACANTHARIA are very elastic, as are also the bristle-like
siliceous spicules of many SPUMELLARIA. The _refractive power_ of the
skeleton in the various legions is very different, depending upon the
chemical constitution. The siliceous skeleton of the Polycystina
(SPUMELLARIA and NASSELLARIA) and the silicate skeleton of the PHÆODARIA
have the same refractive index as glycerine, and hence become invisible
when mounted in that fluid; they then become visible only on addition of
{lxxi}water, and are clearer in proportion to the quantity of water which
is added. The refractive index of acanthin is, however, very different from
that of glycerine, so that the skeletons of ACANTHARIA are readily visible
when mounted in this fluid. In water, the skeletons of all Radiolaria
appear about equally refractive, as also in Canada balsam. The substance of
the skeleton appears almost entirely hyaline, colourless, and transparent.
Very rarely it is faintly coloured (in some ACANTHARIA). A cloudy opaque
constitution is seen in some PHÆODARIA (especially in the "porcellanous
shells" of Tuscarorida and Circoporida, Pls. 100, 114-117); when dried,
these appear by reflected light milky-white or yellowish-white; the cause
of this opacity lies partly in the peculiar "cement-like structure" of
these porcellanous shells, partly in their fine porosity, and the minute
air-bubbles contained in their thick walls.


104. _The Elementary Structure of the Skeleton._--The general constitution
of the skeleton--or more accurately expressed, of the morphological
elements of which the skeleton consists--is of such a nature that it may be
termed structureless. Both the organic acanthin skeletons of the ACANTHARIA
and the silicate skeletons of the PHÆODARIA, as well as the inorganic
siliceous skeletons of the SPUMELLARIA and NASSELLARIA, appear under the
microscope perfectly homogeneous, transparent, colourless, and crystalline.
Only very rarely do they show traces of a concentric striation, which
arises from the deposition of the skeletal substance in layers; as, for
example, the thick spines of some PHÆODARIA (Pls. 105-107, &c.). Some of
the PHÆODARIA, however, form an exception to this rule, inasmuch as their
partially tubular skeletal elements possess a remarkable porcellanous
structure. In the tubular or Cannoid skeleton, which occurs in most
CANNOPYLEA, the lumen of the thin-walled flinty tube is filled with jelly,
and frequently a thin siliceous thread runs in its axis, and is connected
with the wall by transverse threads (§§ 127, 139). The elementary structure
of the opaque porcellanous shells, which distinguish the two families
Circoporida (Pls. 114-117) and Tuscarorida (Pl. 100), is quite peculiar.
Numerous fine siliceous spicules lie scattered irregularly in a finely
granular or porous matrix.


105. _Complete and Incomplete Lattice-Shells._--In the great majority of
Radiolaria (in all four legions) the skeleton has the form of a delicate
lattice-shell or a receptacle in which the central capsule is enclosed. In
a small minority, however, this is not the case. The skeleton then consists
only of isolated rigid pieces (radial or tangential spicules), or of a
simple ring (sagittal ring of the #Stephoidea#), or of a basal tripod with
or without a loose tissue of trabeculæ, &c. (#Plectoidea#); the central
capsule is then not surrounded by a special latticed receptacle, but only
rests upon the skeletal trabeculæ. According to these different
arrangements, two principal groups or sublegions may be distinguished in
each legion, of which one set (Cataphracta) are characterised by a complete
{lxxii}lattice-shell, whilst the others (Aphracta) are without it. The
RADIOLARIA APHRACTA, then, or Radiolaria without a complete skeleton, are
the #Collodaria# (p. 9), the #Acanthometra# (p. 725), the #Plectellaria#
(p. 895), and the #Phæocystina# (p. 1543). On the other hand, the
RADIOLARIA CATAPHRACTA, or Radiolaria with a complete skeleton, are the
#Sphærellaria# (p. 49), the #Acanthophracta# (p. 791), the #Cyrtellaria#
(p. 1015), and the #Phæocoscina# (p. 1590).

  Upon this basis the first subdivision of the Radiolaria was made by
  Johannes Müller, who recognised three groups:--"I. _Thalassicolla_,
  without receptacle, naked or with spicules; II. _Polycystina_, with a
  siliceous receptacle; III. _Acanthometra_, without receptacle, but with
  siliceous radial spines" (L. N. 12, p. 16).


106. _The Ectolithia and Entolithia (Extracapsular and Intracapsular
Skeletons)._--The relation of the skeleton to the central capsule in the
Radiolaria is very various in many respects; in the first instance two
great groups, _Ectolithia_ and _Entolithia_ (see note A), may be
distinguished topographically by mere external observation; in the former
the skeleton lies entirely outside the central capsule; in the latter,
partially at all events, within it. The _Ectolithia_, with a completely
extracapsular skeleton, include all NASSELLARIA and PHÆODARIA, as well as a
great part of the SPUMELLARIA (all #Collodaria# and the most archaic forms
of #Sphærellaria#); the _Entolithia_, on the other hand, in which the
skeleton lies partly within, partly without the central capsule, include
all ACANTHARIA and the majority of the SPUMELLARIA (most #Sphærellaria#,
see note B).

  A. The difference between Ectolithia and Entolithia was applied in my
  Monograph in 1862 (p. 222) to separate the Monocyttaria into two main
  groups. The arrangement was, however, quite artificial, being contrary to
  the natural relations of the larger groups, as was shown seventeen years
  later by the discovery of the different structural relations of the
  central capsule.

  B. Among the ACANTHARIA, which all possess primitively an intracapsular
  and centrogenous skeleton, the remarkable _Cenocapsa_ (Pl. 133, fig. 11),
  seems to furnish the single exception; in it the skeleton consists of a
  simple spherical shell which encloses the concentric central capsule. The
  exception is, however, only apparent; the twenty perspinal pores of the
  shell show that they were originally in connection with twenty
  centrogenous acanthin spines, and that those have disappeared by
  retrograde metamorphosis.


107. _Perigenous and Centrogenous Skeletons._--Much more important than the
topographical relation of the skeleton to the central capsule, according to
which the Ectolithia and Entolithia are separated from each other (§ 106),
is the original development of the skeleton within or without the central
capsule, which gives rise to the distinction between perigenous and
centrogenous skeletons. _Centrogenous skeletons_ are found only in the
ACANTHARIA, which are further distinguished from all other Radiolaria by
their skeleton being formed of acanthin; in all ACANTHARIA the formation of
the skeleton begins in the middle of the central capsule, from which twenty
(the number is inconstant only in the {lxxiii}small group #Actinelida#)
radial spines are centrifugally developed. The three other legions, on the
contrary, possess on the whole a _perigenous_ skeleton, which _originally_
develops outside the central capsule and never in its middle. In the
NASSELLARIA and PHÆODARIA the skeleton retains this extracapsular position,
as also in the #Beloidea# and part of the #Sphærellaria# among the
SPUMELLARIA; in the great majority of the latter, however, the primary
perigenous skeleton is subsequently enveloped by the growing central
capsule, so that it lies partially within it (§ 109).


108. _Polyphyletic Origin of the Skeleton._--The skeleton of the Radiolaria
has undoubtedly originated polyphyletically, for it is impossible to derive
its manifold varieties from a single ground-form, or to regard them as
modifications of one type. It is much more probable that the different
skeletonless Radiolaria have entered upon different ways of skeleton
formation quite independently of each other. At the outset it is quite
clear that the skeletons of the _four legions have originated independently
of each other_. Further, it is certain that within the legion of the
SPUMELLARIA the Beloid skeletons of the #Collodaria# are not connected with
the Sphæroid skeletons of the #Sphærellaria# and the forms derived from
them (see § 109). In the same way the skeletons of the PHÆODARIA are
polyphyletic; probably in this legion the Beloid, Sphæroid, Cyrtoid, and
Conchoid skeletons have been developed quite independently (see § 112). In
the NASSELLARIA, on the other hand, it is possible that all the skeletal
forms are to be derived monophyletically from a single simple primitive
form (either the sagittal ring or basal tripod?) (see § 111). Still more
probable is it that the ACANTHARIA have arisen monophyletically, for all
the forms of their acanthin skeleton may be derived without violence from
_Actinelius_ (see § 110).


109. _The Skeleton of the Spumellaria._--The skeletons of the SPUMELLARIA
or PERIPYLEA consist of silica, and are very different and of independent
origin in the two orders of this legion. The first order, #Collodaria#,
have either no skeleton whatever (#Colloidea#, p. 10, Pls. 1, 3), or their
skeleton is _Beloid_, a loose extracapsular envelope of spicules,
consisting of numerous unconnected portions; the separate parts are usually
disposed tangentially, either as simple or compound siliceous spicules
(#Beloidea#, p. 28, Pls. 2, 4). The second order of SPUMELLARIA, on the
other hand (#Sphærellaria#, p. 49), develops a siliceous lattice-shell
which consists of a single piece, and is remarkable for the extraordinary
variety of its forms (pp. 50-715, Pls. 5-50). To this order belong not less
than three hundred genera and seventeen hundred species of the Challenger
Radiolaria (that is, about two-fifths of all the genera and species). In
spite of this extreme richness in different forms this large group must be
regarded as _monophyletic_, since all its forms may be quite naturally
derived from a common stem-form, a _simple lattice-sphere_ (_Cenosphæra_,
p. 61, Pl. 2). The twenty-eight families of #Sphærellaria# may be
distributed in four suborders, among which the #Sphæroidea# constitute the
{lxxiv}stem-forms, since they retain the original spherical shape (Pls.
5-8, 11-30). In the other three suborders a vertical main axis is
developed, which in #Prunoidea# is longer, in #Discoidea# shorter than the
other axes of the shell. Hence the shell of the #Prunoidea# (p. 284, Pls.
13, _bis_, 17, 39, 40) is ellipsoidal or cylindrical, that of the
#Discoidea#, on the other hand, lenticular or discoidal (p. 402, Pls.
31-38, 41-48). Finally, the shell of the fourth suborder, #Larcoidea#, is
lentelliptical; it has the ground-form of a triaxial ellipsoid, and is
characterised by the possession of three unequal dimensive axes, or three
isopolar axes of different lengths perpendicular to each other (p. 599,
Pls. 9, 10, 49, 50).


110. _The Skeleton of the Acantharia._--The skeletons of the ACANTHARIA or
ACTIPYLEA are distinguished from those of all other Radiolaria by two very
important peculiarities; in the first place, they consist not of silica but
of a peculiar organic substance, _Acanthin_, and secondly, their
development is centrogenous, numerous radial spines or acanthin spicules
being formed which are united in the middle of the central capsule. Hence
the ACANTHARIA are the only Radiolaria in which the skeleton originates
from the first in the middle of the central capsule. The number of radial
spines is primitively indefinite, variable, and often considerable (more
than a hundred), but in the great majority it is limited to twenty. In
accordance with this the legion may be divided into two orders, the more
archaic small group Adelacantha, with an indefinite number of spines, and
the more recent group, Icosacantha, which has been developed from them and
possesses twenty regularly disposed spines; of the three hundred and
seventy-two species of ACANTHARIA which have been hitherto described, about
five per cent. belong to the former, about ninety-five per cent. to the
latter division (see note A, below). The numerous genera of Icosacantha may
then be again divided into two suborders, of which the #Acanthonida# (p.
740, Pls. 130-132) produce no complete lattice-shell, and thus agree with
the #Actinelida#, with which they may be united as #Acanthometra# in the
broader sense (or ACANTHARIA without a lattice-shell). The
#Acanthophracta#, on the other hand (p. 791, Pls. 133-140), produce a
complete lattice-shell, usually by means of two opposite or four crossed
transverse processes, which arise from each radial spine and unite with
each other (see note B, below). In most #Acanthophracta# the lattice-shell
remains single; only in the Phractopeltida does it consist of two
concentric lattice-spheres (p. 847, Pl. 133, figs. 1-6). Furthermore, the
whole order #Acanthophracta# may be subdivided into two suborders according
to the different ground-form of the lattice-shell; this remains spherical
in the #Sphærophracta# (the three families Sphærocapsida, Dorataspida,
Phractopeltida, Pls. 133-138). On the other hand, it assumes another form
in the #Prunophracta#; it becomes ellipsoidal in the Belonaspida (Pl. 136,
figs. 6-9), discoidal or lentiform in the Hexalaspida (Pl. 139); and
finally takes the shape of a double cone in the Diploconida (Pl. 140).

  {lxxv}A.  The group Adelacantha consists only of the suborder
  #Actinelida#, with the three families Astrolophida, Litholophida, and
  Chiastolida (p. 728, Pl. 129, figs. 1-3); the number of the radial spines
  is very different and variable, sometimes only from ten to sixteen, but
  usually from thirty to fifty, and often more than one hundred; they are
  generally irregularly distributed, and not as in the second main
  division. This latter, the Icosacantha, always possesses _twenty_ radial
  spines, which are regularly disposed according to a constant law, the
  so-called "Müllerian" or "Icosacanthan" law; the twenty spines are always
  so placed between the poles of a spineless axis that they form five zones
  each of four spines; the four spines of each zone are equidistant from
  each other, and also from the same pole, and alternate with those of the
  neighbouring zones, so that the whole twenty lie in four meridian planes,
  which cut out an angle of 45° (compare pp. 717-722, Pls. 130-140). In
  spite of the manifold variations in form which are developed in the
  Icosacantha, they may all be derived from a common stem-form,
  _Acanthometron_ (p. 742), since the law of distribution of the twenty
  spines is constantly inherited.

  B.  An exception is found in the peculiar family Sphærocapsida (p. 797,
  Pl. 133, figs. 7-11; Pl. 135, figs. 6-10). Here the shell is composed of
  innumerable small, perforated plates, which arise on the surface of the
  calymma independently of the spines.


111. _The Skeleton of the Nassellaria._--The skeletons of the NASSELLARIA
or MONOPYLEA consist of silica, and are never composed of separate
portions, but constitute always a single continuous piece. The ground-form
is originally monaxon, corresponding to that of the central capsule, with a
constant difference between the two poles of the vertical main axis. The
ground-form is never spherical or polyaxon as in the lattice-shells of the
SPUMELLARIA, and the skeleton never consists of hollow tubes, as in the
PHÆODARIA. The legion NASSELLARIA may be divided into two orders; in the
#Plectellaria# (three suborders #Nassoidea#, #Plectoidea#, #Stephoidea#)
the skeleton does not form a complete lattice-shell; in the #Cyrtellaria#,
on the other hand, which are derived from these, the siliceous skeleton
forms a complete lattice-shell enclosing the central capsule. The number of
forms thus developed is astonishingly great, so that among the NASSELLARIA
no less than two hundred and seventy-four genera and sixteen hundred and
eighty-seven species may be distinguished, almost as many as in the
#Sphærellaria#. In spite of this great variety of forms the legion
MONOPYLEA is probably monophyletic; at least all the different skeletal
forms may be derived from three elements which are combined in the most
manifold fashion; (1) the _sagittal ring_, a simple siliceous ring, which
lies vertically in the sagittal plane of the body, encircles the central
capsule and comes into contact with it at the basal pole of the main axis
(§ 124); (2) the _basal or oral tripod_, composed of three diverging radial
spines, which meet in the middle of the basal pole of the central capsule
(or in the centre of the porochora) (§ 125); (3) the _cephalis_, or
lattice-head, a simple ovoid or subspherical lattice-shell, which encloses
the central capsule and stands in connection with it at the basal pole of
its main axis. Any one of these three important structural elements of the
NASSELLARIAN skeleton may possibly be the starting-point {lxxvi}for all the
remaining forms of the MONOPYLEA; the great difficulty in their
phylogenetic derivation lies in the facts that, on the one hand, any one of
the three elements may alone constitute the skeleton, and on the other
hand, in the great majority of the legion, two or three are united together
(compare §§ 182-185).


112. _The Skeleton of the Phæodaria._--The skeleton of the PHÆODARIA or
CANNOPYLEA is always extracapsular, usually consists of a silicate of
carbon (more rarely of pure silica), and in the majority of the legion is
composed of hollow cylindrical tubes, whose siliceous wall is very thin,
and whose lumen is filled with gelatinous material (§ 127). The manifold
and remarkable skeletal forms occurring in this legion are not
monophyletic, since they cannot be derived from a common stem-form; they
are, on the contrary, polyphyletic, various skeletonless PHÆODARIA
(Phæodinida) have independently acquired skeletons of different form and
composition. The legion PHÆODARIA can be subdivided into four orders, the
skeletons of which present the following important distinctions:--(1) The
#Phæocystina# possess only incomplete Beloid skeletons (§ 115), composed of
many separate pieces, sometimes tangentially (Cannorrhaphida, Pl. 101),
sometimes radially arranged (Aulacanthida, Pls. 102-105). (2) The
#Phæosphæria# form Sphæroid skeletons (§ 116), usually only a simple
lattice-shell without special aperture (Pls. 106-111); two concentric
shells united by radial bars occur only in the Cannosphærida (Pl. 112). (3)
The #Phæogromia# are distinguished by the formation of a simple Cyrtoid
skeleton (§ 123) resembling that of the Monocyrtida; the monothalamus
lattice-shell is usually ovoid or helmet-shaped, more rarely polyhedral or
almost spherical; a vertical main axis can always be distinguished, at the
basal pole of which is an aperture usually armed with teeth or spines (Pls.
99, 100, 113-120). (4) The #Phæoconchia# are distinguished from all other
Radiolaria by the possession of a bivalved shell like that of the
Conchifera; the two valves of this Conchoid skeleton must be distinguished
as dorsal and ventral, as in the Brachiopoda (Pls. 121-128). The fifteen
families of PHÆODARIA which are arranged in the four orders just mentioned,
present such great differences among themselves, that the skeleton must be
regarded as probably polyphyletic even within the limits of each order.


113. _Types of Skeletal Formation._--No less than twelve different
principal forms may be distinguished as morphological types of the
formation of the skeleton in the Radiolaria; some of these are peculiar to
a single legion or even to a smaller group; but sometimes the same form
occurs in several legions. Some types occur only in an isolated manner,
independently of the others, but most exist in various combinations with
other types. Of the twelve described below the Conchoid and Cannoid occur
only in the PHÆODARIA; the Plectoid and Circoid only in the NASSELLARIA;
the Astroid only in the ACANTHARIA; the remaining seven types are found in
several legions in the same form and hence are polyphyletic.


{lxxvii}114. _The Astroid Skeleton._--Under the name "Astroid" we place the
peculiar star-shaped skeletons of the ACANTHARIA in opposition to those of
all other Radiolaria, for they are separated from them not only
fundamentally by reason of the chemical nature of their substance
(Acanthin, § 102), but also by their centrogenous origin, and the resulting
stellate form (Pls. 129-140). The ACANTHARIA are the only Radiolaria in
which the skeleton arises within the central capsule by the formation of
numerous rays or radial spines of acanthin which project on all sides from
the centre. Originally these are united at this point, their conical or
pyramidal points meeting and being supported one upon another. In the great
majority of ACANTHARIA this loose apposition is constant, so that when the
soft parts are destroyed the skeleton falls to pieces. Only in a few forms
in this legion are the central ends of the spines fused so that the whole
skeleton forms a connected star (_Astrolithium_). The small group
Chiastolida (or Acanthochiasmida) is characterised by the fact that the two
rays which are opposite to one another in each axis unite and form a
diametral bar. The skeleton is almost always composed of twenty radial
spines, which are regularly disposed (Icosacantha), only in the small
primitive group #Actinelida# is the number variable (Adelacantha, § 110).


115. _The Beloid Skeleton._--As Beloid or spicular skeletons are grouped
together all those which consist of several disconnected portions; these
always lie outside the central capsule, either within the calymma or on its
surface. Such extracapsular Beloid skeletons are entirely wanting in the
ACANTHARIA and NASSELLARIA; they occur only in the #Beloidea# among the
SPUMELLARIA, and in the #Phæocystina# among the PHÆODARIA; the individual
Beloid portions of the former are solid, those of the latter hollow. In
both groups the simplest forms of the separate portions are simple
unbranched needles (_Thalassosphæra_, _Thalassoplancta_, _Physematium_,
_Belonozoum_, among the SPUMELLARIA; _Cannobelos_ and _Cannorrhaphis_ among
the PHÆODARIA); usually these spicules are disposed tangentially over the
surface of the calymma. Among the #Beloidea# branched spicules occur more
commonly than these simple ones; they are either stellate (with many rays
united in a centre) or twin-like, with a tangential bar, from each pole of
which two or three (seldom more) radial branches project (Pls. 2, 4). Among
the PHÆODARIA the subfamily Dictyochida is characterised by the annular
shape of its Beloid portions, either simple rings, or hat-shaped or
pyramidal bodies with a latticed cap over the ring (Pl. 101, figs. 3-14;
Pl. 114, figs. 7-13). The family Aulacanthida among the PHÆODARIA, alone
possesses hollow _radial tubes_, which penetrate the whole calymma, and
project distally over its surface, whilst their proximal ends rest upon the
surface of the central capsule. Although in these cases the enclosed
proximal end is always simple, the free distal end develops the most
various processes in adaptation to its prehensile functions (Pls. 102-105).


{lxxviii}116. _The Sphæroid Skeletons or Lattice-Spheres._--The
"lattice-spheres" or sphæroid skeletons are the simplest and most primitive
forms of lattice shells, and are widely distributed in the three legions
SPUMELLARIA, ACANTHARIA, and PHÆODARIA, whilst they are entirely wanting in
the NASSELLARIA. The round lattice-shell is either a true sphere in the
geometrical sense, or an endospherical polyhedron, _i.e._, a polyhedron,
all whose angles lie in the surface of a sphere (§ 25). In general,
_primary_ and _secondary_ lattice-spheres may be distinguished, of which
the former are secreted on the outer surface of the primary, the latter on
that of the secondary calymma (§ 85). Furthermore, _simple_ and _compound_
lattice-spheres may be distinguished, the latter of which consist of two or
more concentric lattice-spheres firmly united by radial bars; in such cases
the innermost lattice-sphere is always to be regarded as the oldest or
primary, all the succeeding ones as secondary, and the outermost as the
youngest (§ 129). The simple lattice-spheres are usually to be regarded as
primary; they may, however, occasionally be secondary, in which case the
primary shell, originally enclosed, has been lost by degeneration (as, for
example, in the case of the Aulosphærida and some #Sphærellaria#).


117. _The Lattice-Spheres of the Spumellaria._--The lattice-spheres or
Sphæroid skeletons of the SPUMELLARIA exhibit in spite of their simple type
of structure, an extraordinary variety in the formation of the lattice-work
and radial apophyses, so that in the systematic portion of this work no
less than one hundred and seven genera and six hundred and fifty species
are distinguished; these are united in one suborder, the #Sphæroidea# (pp.
50-284, Pls. 5-8, 11-30). It may be divided into two main divisions, the
_Monosphærida_ with a single primary lattice-sphere (Pls. 12-14, 21, 26,
27), and _Pliosphærida_ (or Sphæroidea concentrica) whose skeleton consists
of two or more concentric lattice-spheres united by radial bars. The latter
are subdivided into Dyosphærida with two concentric lattice-spheres (Pls.
16, 19, 20, 22, 28); Triosphærida, with three spheres (Pls. 17, 24, 29);
Tetrasphærida, with four (Pls. 23, 30); Polysphærida, with five or more
(Pls. 15, 23); and Spongosphærida, with spongy lattice-spheres (Pls. 18,
25). A special group is made up of the simple lattice-spheres of the social
Collosphærida (or Sphæroidea polyzoa) (Pls. 5-8); these are usually more or
less irregular, and characterised by the development of peculiar tubular
processes; the latter are generally wanting in the Sphæroidea monozoa,
whose lattice-shell is very regularly formed. This distinction is
interesting and important, inasmuch as the regular lattice-spheres are
explained by the independent development of the free-swimming Monozoa,
whilst the irregular spheres are due to the mutual dependence of the social
Polyzoa.


118. _The Lattice-Spheres of the Acantharia._--The lattice-shells or
Sphæroid skeletons of the ACANTHARIA are immediately distinguishable from
those of all other Radiolaria by their centrogenous development and the
central union of the radial spines by which they are supported; the only
exception is furnished by the remarkable genus _Cenocapsa_ {lxxix}(Pl. 133,
fig. 11), in which the radial spines are absent, not primitively, however,
but in consequence of degeneration; for the twenty cross-shaped perspinal
pores, originally due to the twenty radial spines, are still present. In
the most nearly allied genera, _Porocapsa_ (Pl. 133, fig. 7) and
_Cannocapsa_ (Pl. 133, fig. 8), the proximal part of the twenty radial
spines is still present, while their distal portion has degenerated; hence
in this case they do not stand in direct communication with the spherical
shell. On the other hand, this primitive connection persists in the genera
_Astrocapsa_ (Pl. 133, figs. 9, 10), and _Sphærocapsa_ (Pl. 135, figs.
6-10). The five genera just mentioned form the peculiar family
Sphærocapsida (pp. 795-802); the spherical shell is in these cases composed
of very numerous small plates disposed like a pavement, each plate or aglet
being perforated by a pore canal; in addition to which there are twenty
larger (perspinal) pores (or twenty cross-shaped groups each of four
aspinal pores) at those important points where primitively the twenty
radial spines penetrate the calymma. This peculiar porous "pavement shell"
has probably been developed (independently of the twenty radial spines)
upon the calymma of the #Acanthonida# (_Acanthonia_, p. 749) by the action
of the sarcodictyum; it has, therefore, quite a different morphological
significance from the spherical lattice-shell of the Dorataspida, which is
composed of tangential apophyses of the twenty Acanthonid spines (pp.
802-847, Pls. 134-138). Each radial spine here forms either two opposite or
four crossed transverse processes, and since their branches spread over the
surface of the spherical calymma and are united suturally at their
extremities, the peculiar lattice-sphere of the Dorataspida arises. This
extensive family is again divided into two subfamilies:--the Diporaspida
(Pls. 137, 138) possess always only two opposite apophyses, and form by the
union of their branches two opposite primary apertures or aspinal meshes.
The Tessaraspida, on the other hand (Pls. 135, 138), have always four
crossed transverse processes, and form by their union four primary aspinal
meshes. From the Diporaspida are probably to be derived the Phractopeltida
(p. 847, Pl. 133, figs. 1-6), the only ACANTHARIA which possess a double
lattice-sphere; their double concentric spherical shell may be compared
with that of the Dyosphærida.


119. _The Lattice-Spheres of the Phæodaria._--The lattice-spheres or
Sphæroid skeletons of the PHÆODARIA, which are generally developed quite
regularly, though occasionally in a modified form, fall in the order
#Phæosphæria# into two groups of very different structure, each of which
includes two families. The first group (_Phæosphæria inarticulata_)
contains the families Orosphærida (Pls. 106, 107) and Sagosphærida (Pl.
108); the lattice-work of the former consists of irregular polygonal meshes
and very coarse, partially hollow trabeculæ; in the latter, on the other
hand, it consists of triangular meshes and very slender filiform trabeculæ;
in both families the whole sphæroid skeleton forms a single unsegmented
piece as in most #Sphæroidea#. In the second group of {lxxx}#Phæosphæria#
(_Phæosphæria articulata_), on the other hand, the lattice-sphere is
segmented in quite a peculiar manner, and composed of hollow cylindrical
tangential tubes, which are separated by astral septa at the nodal points
of the network; this remarkable structure characterises the two families,
Aulosphærida (Pls. 109-111) and Cannosphærida (Pl. 112); the segmented
lattice-sphere of the former is simple and hollow; while that of the latter
is connected by centripetal radial tubes with a simple concentric inner
shell, which is sometimes solid, sometimes latticed, and provided with a
main-opening corresponding to the astropyle of the enclosed central
capsule. Since in the Aulosphærida also, hollow centripetal radial tubes
project from the segmented lattice-sphere, it is possible that they have
been derived from the Cannosphærida by the loss of the primitive internal
shell. A special peculiarity of many #Phæosphæria# (_Oroscena_,
_Sagoscena_, _Auloscena_, &c.) consists in the fact that the whole surface
of the lattice-sphere is regularly covered with pyramidal or tent-shaped
prominences (Pl. 106, fig. 4; Pl. 108, fig. 1; Pl. 110, fig. 1). A simple
lattice-sphere quite similar to that of most Monosphærida also constitutes
the skeleton of the Castanellida (Pl. 113), but since it possesses a
special main-opening, it must be referred promorphologically to the Cyrtoid
shells of the #Phæogromia#.


120. _The Prunoid Skeleton or Lattice-Ellipsoid._--The "lattice-ellipsoids"
or Prunoid skeletons have arisen from the lattice-spheres or Sphæroid
skeletons by more energetic growth and elongation of one axis; this is the
main axis of the body and is probably always vertical; its two poles are
commonly equal. The Prunoid skeleton is either a true ellipsoid in the
geometrical sense or an "endellipsoidal polyhedron" (_i.e._, a polyhedron,
all the angles of which lie in an ellipsoidal surface). By further
elongation of the main axis, the ellipsoidal form passes over into the
cylindrical, the polar surfaces of the cylinder being usually rounded,
rarely truncated. The rich order #Prunoidea# (pp. 284-402) contains
numerous modifications of this form of shell which arise on the one hand by
the formation of transverse constrictions, on the other by the apposition
of concentric secondary shells. In respect of the latter, simple and
compound Prunoid shells can be distinguished as in the case of the Sphæroid
shells. In the compound Prunoid shells either all the concentric
lattice-shells may be ellipsoidal or the inner may be spherical. More
important differences are found in the transverse annular constrictions,
which give the Prunoid skeleton a segmented appearance; in this respect,
three principal forms may be distinguished (p. 288):--(A) _Monoprunida_,
with unsegmented shell, having no transverse constriction (Pls. 15-17); (B)
_Dyoprunida_, having a shell with two segments and one (equatorial)
transverse constriction (Pl. 39); (C) _Polyprunida_, with three or more
parallel transverse constrictions, by means of which the shell is divided
into four or more segments (Pl. 40). In the same manner as the #Prunoidea#
have arisen from the #Sphæroidea# among the SPUMELLARIA by greater
{lxxxi}development of the vertical main axis, the ellipsoidal Belonaspida
have arisen from the spherical Dorataspida among the ACANTHARIA (p. 859;
Pl. 136, figs. 6-9; Pl. 139, figs. 8, 9). The main axis of the ellipsoid in
this case is always occupied by the opposite equatorial spines of the
hydrotomical axis (pp. 719, 860). In the legion PHÆODARIA a similar
prolongation of the main axis rarely occurs; it is found, however, in
_Aulatractus_ (Pl. 111, figs. 6, 7), the lattice-shell of this Aulosphærid
being sometimes truly fusiform, sometimes rather ellipsoidal or even
double-conical.


121. _The Discoid Skeletons or Lattice-Discs._--The "lattice-discs" or
Discoid skeletons are characteristic of the SPUMELLARIAN group #Discoidea#,
and have arisen from the lattice-spheres of the #Sphæroidea# by a less
development of one axis, which is the main axis of the body, and is
probably usually vertical; its two poles are always equal. The Discoid
lattice-shell is either a biconvex lens (with a thin margin), or a plane
disc (a shortened cylinder with thick margin), or some form intermediate
between the two. All Discoid shells show a horizontal median plane or
equatorial plane, by which they are divided into two equal halves, an upper
and lower; the margin of the lens itself is originally the equator. The
main axis, the shortest of all the axes of the shell, stands vertically in
the centre of the equatorial plane. Among the PHÆODARIA Discoid shells
rarely occur (_Aulophacus_), as also among the ACANTHARIA (Hexalaspida).


122. _The Larcoid Skeleton or Lentelliptical Lattice-Shell._--The
lentelliptical lattice-shells, which may be shortly designated "Larcoid,"
are especially characteristic of the #Larcoidea#, a large order of
SPUMELLARIA (pp. 599-715; Pls. 9, 10, 49, 50). In addition they recur among
the ACANTHARIA, in the small family Hexalaspida (p. 872, Pl. 139), and the
family Diploconida (p. 881, Pl. 140), which is derived from it. These
lentelliptical lattice-shells are all characterised by the clear
differentiation of three unequal, but isopolar dimensive axes, _i.e._, the
three geometrical axes, perpendicular to one another, which determine the
form of the shell, are of unequal length; the two poles of each are,
however, equal. The geometrical ground-form is, therefore, a triaxial
ellipsoid (§ 34). In the rich order #Larcoidea# the lentelliptical
lattice-shell shows many variations in its development.


123. _The Cyrtoid Skeleton._--Cyrtoid skeletons are those lattice-shells
which possess a vertical main axis with two different poles (Monaxonia
allopola); the upper pole is usually termed the apical, the lower the
basal. Such Cyrtoid shells are characteristic of the great majority of the
NASSELLARIA or MONOPYLEA (and especially of the #Cyrtellaria#); they are
also found in a large division of the PHÆODARIA (the #Phæogromia#), and in
some SPUMELLARIA. In general the manifold Cyrtoid shells may be divided
into two large groups, those with one and those with several chambers. The
_monothalamous_ Cyrtoid shells are usually ovoid, conical, cap- or
helmet-shaped; their {lxxxii}internal cavity is simple, without
constrictions or septa. Among the NASSELLARIA they occur in the Monocyrtida
(Pls. 51-54, 98), where they have received the name "Cephalis." A form of
shell, essentially the same, is found amongst the PHÆODARIA in the order
#Phæogromia#, more especially in the Challengerida (Pl. 99), Medusettida
(Pls. 118-120), and Tuscarorida (Pl. 100), many of these latter closely
resembling many Monocyrtida. Such monothalamous Cyrtoid shells occur much
more rarely among the SPUMELLARIA (_e.g._, among the #Prunoidea# in
_Lithapium_, _Lithomespilus_, _Druppatractus_, Pls. 13, 14, &c.).
Polythalamous Cyrtoid shells (Pls. 55-80) occur exclusively in the
NASSELLARIA, and exhibit in this legion an astonishing variety of
structure; they are distinguished from the monothalamous forms by the
development of internal septa, or of annular incomplete diaphragms, which
usually correspond to the external constrictions; their interior is thus
divided into two or more communicating compartments. Among the
polythalamous Cyrtoid shells may be distinguished three principal groups,
the Stichocyrtid, Zygocyrtid, and Polycyrtid. Zygocyrtid shells are
characteristic of the #Spyroidea# (Pls. 84-90), and are distinguished by a
bilobate cephalis (cephalis bilocularis); the median sagittal ring, or a
corresponding constriction, divides the shell into right and left
compartments. Polycyrtid shells (Pl. 96) are peculiar to the #Botryodea#,
and characterised by a multilobate cephalis (cephalis multilocularis).
Stichocyrtid shells are those in which the primary cephalis remains simple,
and new joints are successively added to its basal pole; such shells occur
in the majority of the #Cyrtoidea#. Secondary chambers are sometimes added
in the other two groups (#Botryodea# and #Spyroidea#). When, as often
happens in these polythalamous Cyrtoid shells, two or three distinct joints
follow each other, the first is called the "cephalis," the second the
"thorax," and the third the "abdomen" (Tricyrtida Pls. 64-75).


124. _The Circoid Skeleton._--This is a very important and remarkable type
of skeletal formation, which occurs exclusively in the legion NASSELLARIA,
where it plays a very prominent part; its characteristic element is the
"sagittal ring," a simple, vertical, siliceous ring, which surrounds the
central capsule in its sagittal plane, and is specially differentiated in
its basal portion. This "primary sagittal ring" whose vertical allopolar
main axis coincides with that of the Monopylean central capsule embraced by
it, is characteristic of all members of the order #Stephoidea# (p. 931,
Pls. 81-83, 92-94); here it forms by itself the skeleton of the Stephanida
(Pl. 81); in the Semantida (Pl. 92) it is combined with a horizontal basal
ring, in the Coronida (Pls. 82, 93) with a vertical frontal ring and in the
Tympanida (Pls. 83, 94) with two horizontal rings, an upper mitral and a
lower basal. In the great majority of these #Stephoidea# there often
develop in definite places characteristic processes or apophyses, whose
branches combine to form a loose tissue or an incomplete lattice-shell.
This becomes complete in the #Cyrtellaria#, the majority of which retain
more or less {lxxxiii}distinct traces of the sagittal ring. Hence the
skeletons of all NASSELLARIA may be derived monophyletically (Hypothesis A,
p. 893) from a simple sagittal ring (_Archicircus_ and _Lithocircus_, Pl.
81). This theory, however, encounters the great difficulty that in many
#Stephoidea# (_Cortina_, _Cortiniscus_, &c.) it is combined in a remarkable
manner with the basal tripod of the #Plectoidea#, whilst in these latter it
is entirely wanting (compare p. 894).


125. _The Plectoid Skeleton._--Those forms are distinguished as Plectoid in
which three, four, or more radial siliceous spines proceed from a common
point, which lies excentrically outside the central capsule and at the
basal pole of its vertical allopolar main axis. This peculiar type of
skeletal formation only occurs in the legion NASSELLARIA, and is specially
characteristic of the order #Plectoidea# (p. 898, Pl. 91). But since the
essential elements of this remarkable skeleton also occur in many other
NASSELLARIA, sometimes combined with the Circoid, sometimes with the
Cyrtoid skeleton, it perhaps has a fundamental significance in this legion;
at all events it is possible to derive monophyletically all the other forms
of this legion from it (Hypothesis B, p. 893). The simplest form of the
Plectoid skeleton is a tripod, the three feet of which either lie in a
horizontal plane (_Triplagia_, Pl. 91, fig. 2), or correspond to the three
edges of a low pyramid (_Plagiacantha_). A fourth ray is sometimes added,
which stands vertically upon the summit of the pyramid (_Plagoniscus_,
_Plagiocarpa_, Pl. 91, figs. 4, 5). In other #Plectoidea# three secondary
rays are intercalated between the three primary (Hexaplagida, &c.); seldom
the number is greatly increased (Polyplagida, &c.). The rays are rarely
simple, but usually branched; in the Plagonida (Pl. 91, figs. 2-6) the
branches remain free; in the Plectanida (Pl. 91, figs. 7-13) they are
united to form a loose wicker-work. From such a web a perfect Cyrtoid shell
may arise. Several forms of Plagonida may also be readily confounded with
the isolated triradiate or quadriradiate spicula of many Beloid skeletons
(_Sphærozoum_, _Lampoxanthium_, &c.).


126. _The Spongoid Skeleton._--From the simple lattice-skeleton which the
majority of Radiolaria possess, some of them develop a spongy shell; the
trabeculæ of the lattice-work, situated in one plane in the former, are
developed in the latter in different planes and cross irregularly in all
directions; thus arises a kind of wicker-work of more or less spongy
structure, usually with very thin trabeculæ and irregular meshes. Such
Spongoid shells are most common among the SPUMELLARIA, especially in the
#Sphæroidea# (Spongosphærida, Pl. 18) and #Discoidea# (Spongodiscida, Pls.
41-47), more rarely in the #Prunoidea# and #Larcoidea#. Lattice-work of
similar spongy structure occurs very seldom among the NASSELLARIA, _e.g._,
in some #Plectoidea# (Pl. 91) and #Cyrtoidea# (_Spongocyrtis_,
_Spongopyramis_, _Spongomelissa_, &c., Pl. 56, fig. 10; Pl. 64, figs. 5-10,
&c.). Among the PHÆODARIA spongy skeletons are very rare; they {lxxxiv}are
to be seen in some #Phæosphæria# (_Oroplegma_, Pl. 107, fig. 1;
_Sagoplegma_, Pl. 108, fig. 2; _Auloplegma_, Pl. 111, fig. 8). No Spongoid
skeletons are known among the ACANTHARIA.


127. _The Cannoid Skeleton._--Cannoid or tubular skeletons are those which
are composed of hollow tubes; they occur exclusively in the PHÆODARIA or
CANNOPYLEA. Tubular processes, nevertheless, occur in some other
Radiolaria, as, for example, among the SPUMELLARIA in a portion of the
Collosphærida (_Siphonosphæra_, _Caminosphæra_, Pls. 6, 7), and of the
#Prunoidea# (_Pipetta_, _Cannartus_, &c., Pl. 39, figs. 6-10, &c.), also
among the NASSELLARIA in _Theosyringium_ (Pl. 68, figs. 4-6), _Cannobotrys_
(Pl. 96, figs. 3, 4, 8-11, 20-22), &c. In all these cases, however, the
tubes are direct processes of the cavity of the shell, the trabeculæ of the
lattice-work being solid. Only in the CANNOPYLEA are the lattice-bars
themselves, the radial spines and appendicular organs, generally tubular
(hence the designation "Pansolenia"). The lumen of the thin-walled
siliceous tubes is filled with jelly, and hence the specific gravity of the
relatively large skeleton is considerably diminished. This peculiarity is
not found in all CANNOPYLEA; it is wanting in all Sagosphærida and
Concharida, as well as in a part of the Orosphærida and Castanellida; in
the latter there are found intermediate stages between hollow and solid
skeletal rods. Very often a fine siliceous thread runs in the axis of the
tubes, which is connected with its wall by lateral branches (Pl. 110, figs.
4, 6; Pl. 115, figs. 6, 7). More seldom the tubes are divided by horizontal
septa into a series of chambers (Medusettida, Pls. 118-120). The two
families Aulosphærida (Pls. 109-111) and Cannosphærida (Pl. 112) are
distinguished from all other PHÆODARIA by the fact that their tubes are
separated by astral septa in the nodal points of the lattice-shell (§§ 112,
134).


128. _The Conchoid Skeleton._--By the name "Conchoid skeletons" are
distinguished the bivalved lattice-shells which occur exclusively in the
legion PHÆODARIA; they are quite characteristic of the #Phæoconchia# or
_Phæodaria bivalvia_, which embrace three families:--Concharida (Pls.
123-125), Coelodendrida (Pls. 121, 122), and Coelographida (Pls. 126-128).
The two valves of the lattice-shell of the Concharida are simple,
hemispherical, or boat-shaped, whilst in the Coelodendrida and
Coelographida tubes grow out from them, which branch and usually give rise
by anastomosis to a second external bivalved shell. In all #Phæoconchia#
the two valves are so disposed about the central capsule that an open slit
remains between them, into which open the apertures of the central capsule;
and since all these _Phæodaria conchoidea_ are TRIPYLEA, with three typical
openings in the central capsule, and since the two lateral accessory
openings lie at either side of the aboral pole, and the unpaired
main-opening at the oral pole of the main axis, it follows that the two
valves are to be regarded as dorsal and ventral as in the Brachiopoda (not
right and left as in the Lamellibranchiata). The dorsal and ventral
{lxxxv}valves are usually equal, but in a portion of the Concharida they
present constant differences. In this family the two valves are attached to
each other by their free edges, just as in the bivalved Mollusca and
Diatoms; and these edges may either be smooth (Conchasmida, Pl. 123, figs.
1-6), or dentate (Conchopsida, Pls. 124, 125); the valvular connection of
the latter is sometimes strengthened by a special ligament which unites the
two valves at the aboral pole (Pl. 123, figs. 8, 9). The form of the valve
is sometimes hemispherical, sometimes boat-shaped, with a sagittal keel.


129. _Medullary and Conical Shells._--In all Radiolaria whose skeleton
consists of a double shell or of two concentric lattice-shells united by
radial bars, an inner medullary shell (testa medullaris) and an outer
cortical shell (testa corticalis) may be distinguished (see note A, below).
The medullary shell is usually to be regarded as a primary, the cortical as
a secondary structure. Such double shells occur among the SPUMELLARIA in
the Dyosphærida (Pls. 19, 20), as well as in many #Prunoidea# (Pls. 39,
40), #Discoidea# (Pls. 33, 34), and #Larcoidea# (Pls. 9, 10); among the
ACANTHARIA only in the family Phractopeltida (Pl. 133); among the
NASSELLARIA only in very few #Cyrtoidea# (_e.g._, _Periarachnium_, Pl. 55,
fig. 11), and finally among the PHÆODARIA in the Cannosphærida (Pl. 112) as
well as in part of the Coelodendrida (Pl. 121) and Coelographida (Pls. 127,
128). In most cases (if not always?) the cortical shell arises by the
growth of radial spines from the surface of the medullary shell; these
become united at equal distances from the centre by transverse apophyses,
the surface of the secondary calymma furnishing the basis for their
secretion (§ 85). Nevertheless, it seems that in many #Sphærellaria# the
formation of the whole cortical shell proceeds simultaneously (at a
definite dictyotic period) like that of the primary medullary shell (see
note B). Whilst in the PHÆODARIA, ACANTHARIA, and NASSELLARIA, at most two
concentric shells are formed, in many SPUMELLARIA their number increases
continuously with additional growth; in many #Sphærellaria# it rises to
four, eight, or even more, as well as in many #Discoidea# (if the
concentric, peripherally disposed rings of chambers be regarded as
incomplete flattened shells). In these cases either only the innermost
primary lattice-shell is to be styled "medullary shell," or at most the two
innermost (inner and outer medullary shells), all the others being
cortical.

  A. The distinction between medullary and cortical shells was originally
  based in my Monograph (1862, p. 50) upon the topographical relation of
  the lattice-shells to the central capsule, inasmuch as I regarded all
  intracapsular shells as medullary, all extracapsular as cortical.
  Hertwig, however (1879, p. 122), rightly pointed out that this
  distinction is unpractical, "because the same lattice-shell in the same
  species may lie within or without the central capsule, according to the
  size of the latter." He proposes, therefore, to restrict the term
  medullary shell to the innermost, and to call all the others cortical; a
  course which seems justified by the special significance of the primary
  innermost lattice-shell ("as the point of origin of the radial spines").
  But in most #Sphærellaria# which form three or more concentric shells,
  the two innermost, which lie near together within the {lxxxvi}central
  capsule, are very different in size and dictyosis from all the others
  which lie outside, and are separated by wider interspaces (compare Pls.
  17, 24, 29-32, 40, &c.). In these cases it appears better to regard the
  two inner as inner and outer medullary shells, and all the others as
  cortical shells. The character of the dictyosis in the intracapsular and
  extracapsular shells is often so different that I have made it the basis
  of separation of _Thecosphæra_ and _Rhodosphæra_ among the Liosphærida
  (p. 60), of Elatommatida and Diplosphærida among the Astrosphærida (p.
  208), &c.

  B.--R. Hertwig (1879, L. N. 33, pp. 40, 123) separates the true
  (simultaneously formed) "cortical shells" (_e.g._, of _Actinomma_,
  _Cromyomma_) from the arachnoid "siliceous networks" (_e.g._, of
  _Diplosphæra_ and _Arachnosphæra_) which are formed by the successive
  union of tangential apophyses of the radial spines. Whether this
  principle is right in the theory or not, it cannot be carried out
  practically. Compare also Pl. 25, fig. 4.


130. _Dictyosis or Lattice Formation of the Skeleton._--In the great
majority of Radiolaria the dictyosis or formation of lattice-work, and
especially the formation of a variously-shaped "lattice-shell," plays such
an important part that the whole class has long been popularly known in
Germany by the name "lattice animalcules" ("Gitterthierchen" or
"Gitterlinge") (_Protista dictyota_). The old name Polycystina also (1838),
although referring only to the SPUMELLARIA and NASSELLARIA, is derived from
the lattice-work of the siliceous skeleton. The extremely various forms in
which this is manifested furnish the means of distinguishing species. The
specific conformation of the skeletal lattice-work is usually caused by the
special disposition of the sarcodictyum (§ 94), whose exoplasmatic threads
become silicified or (in the ACANTHARIA) converted into bars of acanthin.
In many cases, however, the form of the lattice is mainly dependent upon
the situation and form of the radial spines or of special processes from
them. With respect to their origin, two varieties of lattice may be
distinguished--simultaneous and successive. _Simultaneous dictyosis_ occurs
especially in the simple lattice-shells of the #Sphærellaria# and
PHÆODARIA, where, at a given moment ("dictyotic moment") the _whole_
lattice of the shell is excreted on the surface of the calymma. _Successive
dictyosis_, on the other hand, is found more particularly in the
lattice-shells of the ACANTHARIA (and in the concentric cortical shells of
many #Sphærellaria#), which develop from the separate lattice-plates formed
by the apophyses of the radial spines, and hence not at the same moment.
The lattice-shells of the #Cyrtellaria#, which gradually grow out from a
sagittal ring or a basal tripod, arise by successive dictyosis.


131. _Dictyosis of the Spumellaria._--Siliceous lattice-structures are
wanting in the first section of the SPUMELLARIA, the #Collodaria#, but in
the second section, #Sphærellaria#, they are developed in extraordinary
variety of details. In spite of this extreme richness in different forms,
the lattice-shells of the SPUMELLARIA may all be derived from one and the
same primitive ground-form, a simple lattice-sphere with regular hexagonal
meshes (_Phormosphæra_, p. 61, Pl. 12, figs. 9-11; _Heliosphæra_, &c.).
{lxxxvii}The siliceous bars which bound these regular and subregular meshes
are at first exceedingly then and filiform; afterwards they become thicker
or spread out laterally, whence the meshes often become round with a
hexagonal frame (Pl. 12, fig. 5; Pl. 28, fig. 1). If the latter vanish, a
lattice-shell with simple circular meshes is formed. Very commonly the
regular form of the meshes or pores becomes more or less irregular,
polygonal, or roundish. Hence, in general, four different principal forms
of dictyosis may be distinguished among the SPUMELLARIA; viz. (1) regular
or subregular _hexagonal_ meshes; (2) regular or subregular _circular_
meshes; (3) irregular _polygonal_ meshes; (4) irregular _roundish_ meshes.
The three latter forms are to be regarded as secondary, derived from the
primary first form. In those SPUMELLARIA which possess several concentric
lattice-shells enclosed one within another, either these have all the same
form of dictyosis, or the lattice-work of the innermost primary shell is
different from that of the outer secondary shells (Pls. 19, 20); sometimes
these latter also differ more or less among themselves (§ 129).


132. _Dictyosis of the Acantharia._--The lattice-structures of the
ACANTHARIA differ essentially from those of other Radiolaria in several
particulars. Firstly, they consist not of silica but of acanthin (§ 102);
secondly, they are always secondary formations, usually developed from
transverse processes of the primary centrogenous radial spines; thirdly,
their formation is not simultaneous (at the same time over the same shell),
but successive (proceeding from the individual radial spines tangentially
towards the middle of the intervals); fourthly, the configuration of the
network is due to the relative position of the spines and the mode of union
of their transverse apophyses. Since they are at right angles to the
spines, and since the branches of the apophyses are at right angles to
them, the original ground-form of their dictyosis is a lattice-work with
quadrangular meshes; these are often quite regular and square (Pl. 130,
figs. 5, 6; Pl. 136, figs. 2, 9, &c.); more commonly they are rectangular
or irregularly quadrangular (Pl. 131, fig. 10; Pl. 133, figs. 2, 3, &c.).
In the majority of the ACANTHARIA the quadrangular form of the meshes
passes over into an irregularly polygonal or roundish one (Pls. 137, 138).
Very often the primary meshes of the lattice-shells, which immediately
surround the radial spines, are larger and more regular ("aspinal pores"),
whilst the numerous secondary meshes between them are smaller and irregular
("coronal pores"; Pl. 135, figs. 1-4, &c.).


133. _Dictyosis of the Nassellaria._--The siliceous lattice-structures of
the NASSELLARIA are formed on the whole like those of the SPUMELLARIA, with
which they were formerly united under the name "Polycystina." In this group
also there may be distinguished as two main forms the regular and
irregular. In the NASSELLARIA the regular lattice-structures generally
exhibit hexagonal or circular meshes, whilst the irregular are either
polygonal or roundish; the irregular forms are, however, much more abundant
than the {lxxxviii}regular, and a further distinction from the SPUMELLARIA
consists in the fact that the primary skeletal elements, from which the
lattice is secondarily developed, exercise a predominant influence upon
their form. These primary elements in the majority of the NASSELLARIA are
to be seen in two morphologically most important structures:--first, the
_primary sagittal ring_, which embraces the central capsule in the median
plane (§ 124); and secondly, the _basal tripod_ (§ 125), whose three
diverging rays proceed from the base of the central capsule, whilst
commonly a fourth vertical ray supports the dorsal side of latter (compare
Pls. 81-91, p. 892). In the majority of the NASSELLARIA these two primary
elements appear in combination, whilst in others only one of them is
recognisable. In addition there occur numerous monaxon lattice-shells in
which neither of these elements can be recognised, but a simple ovoid
lattice-shell (cephalis) alone forms the whole skeleton or its primary part
(Pl. 51, fig. 13; Pl. 98, fig. 13). The great difficulty in the
morphological interpretation and phylogenetic derivation of the
NASSELLARIAN skeleton lies in the fact that each of these three
elements--the primary sagittal ring, the basal tripod, and the latticed
cephalis--may form the whole skeleton by itself or be combined with one or
both of the others (p. 893). Even nearly related or at all events very
similar forms may differ very greatly in this respect. With regard to the
manifold forms of their dictyosis it follows that it is partly dependent
upon one of the two first elements, partly independent. In the
#Plectellaria# (or those NASSELLARIA which do not possess a complete
lattice-shell) the lattice-work is usually irregular and arises by union of
the ramifications, which proceed either from the primary sagittal ring
(Pls. 81, 82, 92-94) or from the basal tripod (Pl. 91). In the
#Cyrtellaria# (or NASSELLARIA with a complete lattice-shell, Pls. 51-80),
on the other hand, the lattice-work is sometimes regular, sometimes
irregular, being often very different in the different joints of a
segmented shell (Pl. 72); a great part of it arises independently of the
two chief morphological elements, and develops according to laws similar to
those which regulate the dictyosis of the SPUMELLARIA.


134. _Dictyosis of the Phæodaria._--The lattice-structures of the
PHÆODARIA, which consist of a silicate of carbon (§ 102), are on the whole
not developed in such variety as those of the other Radiolaria, but exhibit
several essentially different types of structure, not reducible to a common
primitive type of lattice-work. In one portion of this legion there occurs
an ordinary simple lattice-work (as in SPUMELLARIA and NASSELLARIA), with
solid trabeculæ; of these the Castanellida (Pl. 113) and Concharida (Pls.
123-125) have usually regular or subregular, circular meshes, sometimes
hexagonally framed; the Orosphærida (Pls. 106, 107) large irregular
polygonal meshes with thick trabeculæ, the Sagosphærida (Pl. 108) large
triangular meshes with thin filiform trabeculæ. The Challengerida (Pl. 99)
are characterised by a very delicate regular lattice-work, with minute
hexagonal pores, like a Diatomaceous frustule. The Medusettida (Pls.
118-120) {lxxxix}show a peculiar alveolar structure, numerous small
compartments being enclosed between two parallel plates. In the Circoporida
(Pls. 114-117) and Tuscarorida (Pl. 100) the opaque porcellanous shell has
a peculiar cement structure (§ 104), and the lattice-structure is confined
for the most part to characteristic rings of pores at the base of the
hollow tubes, which arise from the shell. The most peculiar lattice-work,
however, appears in the segmented shell of the Aulosphærida (Pls. 109-111)
and Cannosphærida (Pl. 112). In the former the large meshes of the
lattice-work are usually subregular and triangular, in the latter
polygonal; the trabeculæ are hollow cylinders, filled with jelly, and
containing usually a central axial thread. In each nodal point of the
lattice, in which three or more tangential tubes meet, these are separated
by stellate or astral septa.


135. _Radial Spines of the Skeleton._--The skeleton in the great majority
of Radiolaria is armed with radial spines, which are of great importance in
the development of their general form and of their vital functions. From a
morphological point of view the number, arrangement, and disposition of the
spines is usually the determining factor as regards the general form of the
skeleton. Physiologically they discharge distinct functions, as organs of
protection and support; they act also, like the tentacles of the lower
animals, as prehensile organs, since their points, lateral branches, barbed
hooks, &c. serve to hold fast nutritive materials. In general main-spines
and accessory spines may be distinguished in most Radiolaria; the former
are of pre-eminent importance in determining the figure of the skeleton;
the latter are merely appendicular organs. The main-spines present such
characteristic and important differences in the various legions of
Radiolaria that they must be considered separately.


136. _Radial Spines of the Spumellaria._--The radial spines, which exhibit
most manifold variations in the large order #Sphærellaria#, present
characteristic differences in its four suborders. In the #Sphæroidea# their
number and disposition serve for the separation into families (p. 59); the
Cubosphærida (Pls. 21-25) always possess six radial main-spines, which
stand opposite to each other in pairs and lie in three diameters of the
shell, which are at right angles to each other and correspond to the axes
of the regular crystallographic system. The Staurosphærida (Pl. 15) have
four spines, which form a regular cross and stand opposite to each other in
pairs, in two axes at right angles. The Stylosphærida (Pls. 13-17) show
only two main-spines, which are opposed to each other in the vertical main
axis of the body. Finally, the Astrosphærida (Pls. 18-20, 26-30) are
characterised by a larger and variable number of radial spines (eight,
twelve, twenty or more), sometimes regularly, sometimes irregularly
arranged. Among the other #Sphærellaria# the #Prunoidea# (Pls. 13-17, 39,
40) are most allied to the Stylosphærida with two opposite main-spines; the
#Discoidea# (Pls. 31-47), on the other hand, to the Staurosphærida with
four crossed spines; there exist, however, #Discoidea# with two opposite,
three marginal, or numerous radial main-spines; it is {xc}characteristic of
this suborder that they all usually lie in the horizontal median plane of
the lenticular shell, arising from its equatorial margin. The #Larcoidea#
(Pls. 9, 10, 49, 50) show a great variety in the number and arrangement of
their radial main-spines, which in the different families of this suborder
stand in direct causal relation to the various forms of growth of the
shell; usually the primary main-spines lie either in the three different
dimensive axes, at right angles to each other, whose differentiation is
characteristic of the lentelliptical Larcoid shell (§§ 34, 122) or in
definite diagonal axes, which cut the former obliquely. The radial spines
of the SPUMELLARIA are _never_ united in the centre of the body, but arise
separately from the surface of the primary central lattice-shell (medullary
shell), more rarely from one of the secondary (cortical) shells, which
enclose it. Their form is originally three-edged (sometimes pyramidal,
sometimes prismatic); the cause of this is to be found in their origin from
the nodal points of the lattice-shell, whose meshes are primitively
hexagonal; hence three trabeculæ unite in each nodal point, and are
produced into three edges of the spine. Very commonly, however, the spines
are round (conical or cylindrical), more rarely polygonal. The three edges
are often delicately toothed, not unfrequently spirally twisted around the
axis of the spine (Pl. 21, figs. 1, 12).


137. _Radial Spines of the Acantharia_.--The radial spines of this legion
have a much greater significance than in the other three classes of
Radiolaria, since here alone they are the primary determining factors in
the skeletal structure, and grow outwards from the middle of the central
capsule. This centrogenous origin of the radial spines is as characteristic
of the ACANTHARIA as their chemical constitution, which is not siliceous
but acanthinic (§ 102). Furthermore, their form is in most cases so
peculiar that even an isolated ACANTHARIAN spine can be generally
distinguished from one belonging to either of the other three legions. In
the great majority of the ACANTHARIA (all #Acanthonida# and
#Acanthophracta#) twenty radial spines are constantly present, which,
disposed according to a definite geometrical law, make up the skeleton
(compare § 110 above and p. 717). The twenty spines are generally simply
apposed to each other in the centre (either by the surfaces or the edges of
their pyramidal base); more rarely they are completely united and form a
single star-like piece of acanthin (_Astrolithium_). Very rarely
(_Acanthochiasma_) each two opposite spines are united so that ten
diametric bars cross in the middle of the central capsule. Whilst in the
great majority of ACANTHARIA these twenty radial spines are present, the
small group #Actinelida# is characterised by the possession of an
inconstant, often very large number, sometimes over one hundred. Among
these #Actinelida# are probably to be found the stem-forms of the whole
legion. The variously modified spines of the ACANTHARIA may be grouped in
three main categories: (1) round (cylindrical or conical); (2) four-edged
(prismatic or pyramidal); (3) two-edged (leaf- or sword-shaped). The latter
very commonly bear two {xci}opposite transverse processes, the former four
crossed ones. By ramification and union of these apophyses arise the
lattice-shells of the #Acanthophracta# (excepting the Sphærocapsida).


138. _Radial Spines of the Nassellaria._--The radial spines in this legion
show as great a variety in their form as in the SPUMELLARIA, and, as in
them, are solid, siliceous bars, usually three-edged (prismatic or
pyramidal), or round (cylindrical or conical); more seldom they are
polygonal in section. The great majority of the NASSELLARIA are, however,
distinguished by a triradial structure, three primary radial bars diverging
from the base of the central capsule (usually from the centre of the
porochora); there is usually in addition a fourth apical spine, which
passes upwards vertically or obliquely on the dorsal aspect of the central
capsule. These three or four typical radial spines of the NASSELLARIA may
be derived with great probability from the basal tripod of the #Plectoidea#
(_Plagoniscus_, _Plectaniscus_, &c., Pl. 91); and since this tripod is very
characteristically combined in _Cortina_ and _Cortiniscus_ with the primary
sagittal ring of the #Stephoidea#, the three typical rays may be generally
designated "cortinar feet," in contradistinction to the other radial
processes of the NASSELLARIAN skeleton.  One of the three descending basal
feet ("pes caudalis," Pls. 91-95, C) is always unpaired, and lies in the
vertical median plane (or sagittal plane), just as does the vertically
directed apical spine, which originally forms the dorsal bar of the
sagittal ring, and is produced upwards into the "apical horn," (marked _a_
on the plates). The other two basal feet are paired, and diverge right and
left, forwards and downwards ("pedes pectorales," _p.p._). Six-rayed
NASSELLARIA, in which three secondary (interradial) feet are intercalated
between the three primary (perradial) cortinar feet, are less common than
the three-rayed forms. In some groups the number rises still higher, nine,
twelve, or even more secondary feet being intercalated between the three
primary. Besides, accessory radial spines may be developed on different
parts of the shell, which have sometimes a definite relationship to the
typical radial spines, sometimes not. Their form and ramification are very
various (Pls. 51-98).


139. _Radial Spines of the Phæodaria._--The radial spines of the PHÆODARIA
are very clearly distinguished from those of other Radiolaria by the fact
that they are usually hollow tubes, rarely solid bars. As a rule, the tubes
are cylindrical, often slightly fusiform or conical, their siliceous wall
is very thin, and their lumen filled with jelly; a fine thread of silica
usually runs in the axis, and in several families is connected by fine
transverse threads with the wall of the tube (Pl. 110, figs. 4, 6; Pl. 115,
figs. 6, 7). The peculiar family Medusettida is characterised by a very
remarkable segmentation of the hollow spines (Pls. 118-120). Each tube is
divided by a series of septa into chambers, which communicate by a central
or excentric opening in each septum, an arrangement resembling the
siphuncle of the chambered Cephalopod shells. The number and
{xcii}arrangement of the radial tubes in most PHÆODARIA is indefinite and
very variable; only in a few families is the number constant in each
species and genus, and the disposition regular. The Medusettida (Pls.
118-120) resemble the NASSELLARIA, inasmuch as equal radial feet diverge
from the base of their shell, sometimes three in number (_Cortinetta_, Pl.
117, fig. 9), sometimes four (_Medusetta_, Pl. 120, figs. 1-4), sometimes
six (_Gazelletta_); _Gorgonetta_ is specially distinguished by the
possession of six ascending and six descending spines regularly alternating
(Pl. 119). The Tuscarorida (Pl. 100) usually have three or four equidistant
feet. The Circoporida (Pls. 115-117), on the other hand, rather approach
the #Sphæroidea#, their spherical or regular polyhedral shell having a
definite number of tubular radial spines, which arise at regular intervals
from their angles; _Circoporus_ has six, _Circospathis_ nine, _Circogonia_
twelve, and _Circorrhegma_ twenty radial tubes. Very rarely the tubes of
the PHÆODARIA are angular, usually they are round, more or less
cylindrical, though they are often bifurcated or even ramified, and exhibit
a great wealth of the most delicate appendages; siliceous hairs, bristles,
spines, barbed or anchor-like hooks, spathillæ, brushes, circlets, &c.
(compare Pls. 99-128).


140. _Main-Spines and Accessory Spines._--As accessory spines (Paracanthæ)
we oppose to the main-spines (Protacanthæ), just described, all those
processes which have no determining influence upon the formation of the
skeleton as a whole, but are to be regarded as secondary constituents of
the skeleton, or appendicular organs of inferior significance. They are
developed in the utmost variety, sometimes as hairs or bristles, sometimes
as thorns or clubs, either straight or curved (often zigzag), smooth or
barbed; sometimes standing vertically upon the shell, or directed towards
the centre, sometimes obliquely, or rising at a definite angle. In those
SPUMELLARIA whose lattice-shell consists of several concentric spheres, the
accessory spines generally arise from the outermost, the main-spines, on
the contrary, from the innermost. In the NASSELLARIA, multifarious forms of
accessory spines are especially developed in the order #Plectellaria#. In
the PHÆODARIA they are often furnished with delicate appendages, _e.g._,
anchor-hooks, spathillæ, coronets, &c. Among the ACANTHARIA the accessory
spines which arise from the surface of the shell in the #Acanthophracta#
are very characteristic. They are not radially disposed (like the similar
superficial spines of the SPUMELLARIA), but parallel to the radial
main-spines from whose transverse processes they arise. Since in all these
#Acanthophracta# the twenty radial main-spines are opposite to each other
in pairs, all the accessory spines (often several hundred) are parallel to
ten different regularly disposed axes of the lattice-shell (Pls. 134-138).

  The skeletons of the Radiolaria, in addition to the general relations
  which have been discussed above, present numerous and important special
  differences in the various larger and smaller groups. These are indicated
  in detail in the descriptions of the legions, orders, and families in the
  systematic portion of this Report.



{xciii}BIOGENETICAL SECTION.

A SKETCH OF OUR KNOWLEDGE OF THE DEVELOPMENT OF THE RADIOLARIA IN THE YEAR
1884.


----


CHAPTER V.--ONTOGENY OR INDIVIDUAL DEVELOPMENT.

(§§ 141-152.)

141. _Individual Developmental Stages._--The germinal history of the
Radiolaria presents great obstacles to direct observation, and hence is
very incompletely known. The fragmentary observations, however (having been
made on Radiolaria of very various groups and supplemented by comparative
anatomical considerations), allow us to draw a general picture of the
essential developmental processes in this great class. It may probably be
assumed that in all Radiolaria, after maturation, the central capsule
discharges the function of a sporangium, and its contents are broken up
into numerous flagellate swarm-spores (zoospores). After these flagellate
swarm-spores (resembling _Astasia_) have emerged from the ruptured central
capsule, they probably pass over into a _Heliozoan_-stage (_Actinophrys_)
and then after the formation of a jelly-veil into the condition of
_Sphærastrum_. Afterwards, when a membrane is formed between the outer
jelly-veil and the inner nucleated cell-body, an _Actissa_-stage arises,
which exhibits in its simplest form the differentiation of the spherical
unicellular body into the central capsule and calymma. _Actissa_ thus
represents both ontogenetically and phylogenetically the primitive
condition of the Radiolarian organism, and may thus be regarded as the
point of departure of all other forms.


142. _The Astasia-Stage._--The formation of flagellate zoospores in the
mature central capsule is probably to be regarded as the common form of
individual development in all Radiolaria; since the whole contents are
utilised in the formation of these swarm-spores, and since the
extracapsulum takes no share in the process and perishes after they are
evacuated, the _central capsule_ may be regarded as a _sporangium_ (see
note A, below). The zoospores of the Radiolaria generally arise in the
following way:--the nucleus of the unicellular organism, sometimes early,
sometimes late (and in several different ways, §§ 63-70) breaks up into
numerous small nuclei, and each of these surrounds itself with a small
portion of the endoplasm. Very often, perhaps generally, this endoplasm
contains one or several fat-granules and sometimes also a small oblong
crystal; from the protoplasm {xciv}of the small roundish or ovoid cells
protrudes one or more vibratile flagella. The fully developed spores, which
commence their vibrations even within the central capsule, emerge when it
ruptures, and swim about freely in the surrounding water by means of the
flagellum. At this stage of its existence the young Radiolarian represents
essentially the simplest form of the Flagellata, such as _Astasia_ or
_Euglena_; the unicellular body is for the most part ovoid or
subcylindrical, sometimes fusiform or reniform, usually from 0.004 to 0.008
mm. in diameter (Pl. 1, fig. 1_c_; Pl. 129, fig. 11). In the anterior part
of the flagellate cell, immediately behind the base of the flagellum, lies
a homogeneous, spherical nucleus, whilst in the posterior part are usually
several small fat-granules and often also a small oblong crystal (hence the
name "crystal-spore," "Krystall-Schwärmer"). The number of vibrating
flagella, which are extremely long and fine, seems to be variable, usually
one, sometimes two, occasionally perhaps three, or even four or more (see
note B).

  A. The formation of the motile spores in the central capsule was first
  observed by J. Müller in _Acanthometra_ (1856, L. N. 10, p. 502), then by
  A. Schneider in _Thalassicolla_ (1858, L. N. 13, p. 41), and finally by
  myself in _Sphærozoum_ (1859, L. N. 16, p. 141). These older observations
  were, however, incomplete, for the origin of the motile corpuscles from
  the contents of the central capsule was not observed. The first complete
  and detailed observations upon the formation of spores in the Radiolaria
  were published in 1871 by Cienkowski (L. N. 22, p. 372, Taf. xxix.); they
  relate to two different Polycyttaria, _Collosphæra_ and _Collozoum_.
  These investigations were supplemented by R. Hertwig on _Collozoum_ and
  _Thalassicolla_ (1876, L. N. 26, pp. 28, 43, &c.); on _Collozoum_ he made
  the important discovery that the Polycyttaria form two kinds of spores,
  one with and the other without crystals, and that the latter are divided
  into macrospores and microspores (compare the chapter on "Reproduction,"
  §§ 212-216). Quite recently Karl Brandt has confirmed these observations,
  and has extended them to all the genera of Polycyttaria (1881, L. N. 38,
  p. 393, and 1885, _loc. cit._).

  B. The number of flagella, projecting from each spore, is very difficult
  to determine, owing to their extraordinary length and slenderness. It
  appeared to me that in the majority of those Radiolaria whose spores I
  investigated only a single flagellum could be demonstrated with
  certainty, although sometimes two, springing from a common base, seemed
  to be present. Compare the chapter on "Reproduction," (§ 215) and the
  recent work of Karl Brandt on Sphærozoea (1885, L. N. 52, pp. 145-174).


143. _The Actinophrys-Stage._--The fate of the flagellate zoospores which
emerge from the mature central capsule of the Radiolaria has not hitherto
been decided by actual observation; all attempts to rear the swarming
zoospores have been in vain, for they have soon died. From what we know,
however, of the comparative morphology of the Protista, the hypothesis is
fully justified, that between the _Astasia_-stage of the flagellate
swarm-spores, and the well-known _Actissa_-stage of the simplest
Radiolaria, there lies an intermediate developmental stage, which may be
regarded as being essentially the simplest Heliozoan form, _Actinophrys_ or
_Heterophrys_. The swarm-spore is very probably converted directly in to a
simple floating _Heliozoon_ by its elongated or ovoid body {xcv}becoming
spherical and by fine pseudopodia protruding all round instead of a single
flagellum; the nucleus at the same time assuming a central position.


144. _The Sphærastrum-Stage._--The _Actinophrys_-stage of the young
Radiolaria, which proceeds immediately from the flagellate zoospore, is
probably connected with the _Actissa_-stage by an intermediate form, which
may be regarded as a simple skeletonless _Heliozoon_ with a jelly-veil; a
well-known example of such a form is _Sphærastrum_ (in the solitary, not
the social condition) and _Heterophrys_. This important intermediate form
has arisen from the simple _Actinophrys_-stage by the excretion of an
external structureless jelly-veil, such as is formed in many other Protista
(_e.g._, in the encystation of many Infusoria). The young Radiolarian in
this second _Heliozoon_-stage becomes a simple cell with pseudopodia
radiating on all sides; its body consists of three concentric spheres, the
central nucleus, the protoplasmic body proper, and the surrounding calymma
or jelly-veil. When a firm membrane is developed between the last two
spheres this _Sphærastrum_-stage passes over into the _Actissa_.

  The gap in our empirical knowledge which still exists between the
  flagellate stage (§ 142) and the simplest Radiolarian stage (_Actissa_, §
  145), can be filled hypothetically only by the assumption of several
  _Heliozoon_-stages following one upon another. It is possible also that
  the capsule-membrane is not formed between the endoplasm and exoplasm (as
  here supposed), but that the membrane was formed first outside the cell
  and the extracapsulum subsequently secreted around it.


145. _The Actissa-Stage._--The first SPUMELLARIAN genus, _Actissa_, is not
only the simplest form actually observed among the Radiolaria, and the true
prototype of the whole class, but also the simplest form under which the
Radiolarian organisation can be conceived. It is therefore extremely
probably that _Actissa_ not only forms the common stem-form of the whole
class in a phylogenetic sense, but is also its common ontogenetic or
germinal form. Probably in all Radiolaria the _Sphærastrum_-stage develops
immediately into the typical _Actissa_-stage, by the formation of a firm
membrane between the protoplasmic body of the spherical Heliozoan cell and
its jelly-veil. Thus arises the characteristic central capsule, which is
wanting in the nearly related Heliozoa. It is further probable that all
Radiolaria in their early stage will so far conform to the state of things
in _Actissa_ as to have the capsule-membrane of the spherical skeletonless
cell perforated everywhere by fine pores. This structure is retained in all
SPUMELLARIA, whilst in the other three legions those structural relations
of the capsule which are characteristic of each develop from the
_Actissa_-stage.


146. _The Ontogeny of the Spumellaria._--In the simplest case the
individual development in the SPUMELLARIA ceases with the _Actissa_-stage.
In all other genera of this legion diverging forms proceed from this, of
which the different growth of the three dimensive {xcvi}axes on the one
hand (§§ 44, 45), and the differentiation of the various parts of the
unicellular organism with the formation of the skeleton on the other, are
of pre-eminent significance. Even in the varying growth of the central
capsule in the different dimensions of space in the skeletonless
#Colloidea#, four different modes may be distinguished, which further, in
the corresponding development of the skeleton, furnish the basis for the
origin of the four orders of #Sphærellaria#. The most primitive and
simplest form of growth, equal extension in all directions, is found in the
spherical central capsule and the concentric spherical skeletons
(_Procyttarium_, #Sphæroidea#). When the growth of the central capsule
proceeds more rapidly in the direction of the vertical main axis than in
any other direction, the ellipsoidal or cylindrical central capsule
(_Actiprunum_) arises, and the vertically elongated skeleton of the
#Prunoidea#, which is derived from it. When, on the contrary, the growth of
the central capsule and lattice-shell is less in the direction of the
vertical main axis than in any other direction, the lenticular or discoid
central capsule (_Actidiscus_) arises, and the corresponding lenticular
shell of the #Discoidea#. Finally, even quite early in many SPUMELLARIA,
the growth of the central capsule and of the corresponding lattice-shell in
the three dimensive axes is different, and hence arise the lentelliptical
forms whose geometrical type is the triaxial ellipsoid or the rhombic
octahedron (_Actilarcus_, #Larcoidea#). Thus the origin of the four orders
of #Sphærellaria# is simply explained by a varying growth in the different
dimensive axes. The _primary_ (innermost) lattice-shell is in this legion
always _simultaneously_ developed (suddenly excreted at the moment of
lorication from the sarcodictyum). The _secondary_ lattice-shells, on the
other hand, which surround the former concentrically, and are united with
it by radial bars, arise _successively_ from within outwards.


147. _The Ontogeny of the Acantharia._--The individual development of the
ACANTHARIA in the simplest case (_Actinelius_) stops at a point which
differs from the _Actissa_-stage only in the change of radial axial threads
into acanthin spines. In the small group #Actinelida#, their number remains
variable and usually indeterminate (Adelacantha), whilst in the great
majority of the legion (#Acanthonida# and #Acanthophracta#) the number is
constantly twenty, and those spines are regularly arranged according to the
Müllerian law in five parallel circles, each containing four crossed spines
(Icosacantha). The simplest form among these latter is _Acanthometron_,
which may be regarded both ontogenetically and phylogenetically as the
common starting-point of all the Icosacantha. Within this extensive group
variations in the length of the dimensive axes appear, similar to those
observed in the SPUMELLARIA. In the Astrolonchida and #Sphærophracta# the
central capsule remains spherical, extending equally in all directions; and
correspondingly the lattice-shell, which is excreted on the surface of the
spherical calymma, remains spherical. In the Belonaspida (just as in the
#Prunoidea#) {xcvii}this form passes over into an ellipsoid by prolongation
of one axis; on the contrary, in the Hexalaspida (as in the #Discoidea#)
the discoidal or lenticular form arises by shortening of an axis. Finally,
in the Diploconida, and in some Hexalaspida in which the growth is
different in all three dimensive axes (as in the #Larcoidea#), both the
central capsule and the shell assume the lentelliptical form. The
lattice-shell of the #Acanthophracta# is usually successive in its
development, since from each of the twenty radial spines two or four
tangential apophyses proceed, whose branches subsequently unite and combine
to form the lattice-shell. Only in the peculiar Sphærocapsida can the
pavement-like shell arise simultaneously or in a moment of lorication.


148. _The Ontogeny of the Nassellaria._--The individual development of the
NASSELLARIA in the simplest instance remains stationary at the skeletonless
Nasselid stage (_Cystidium_, _Nassella_), which can be immediately derived
from the foregoing _Actissa_-stage by the disappearance of the pores in the
upper (apical) hemisphere of the central capsule, whilst in the lower
(basal) portion they are modified to form a porochora; the podoconus is
developed within the endoplasm upon this latter. Usually the spherical form
of the central capsule passes over into an ovoid or ellipsoidal one, the
vertical axis which passes through the centre of the porochora being
elongated. From the skeletonless Nassellida the other NASSELLARIA may be
derived both ontogenetically and phylogenetically by the excretion of an
extracapsular siliceous skeleton. Unfortunately, the earliest stages in the
formation of this skeleton are unknown, and hence no answer can at present
be given to the important question, in what order the three primary
skeletal elements of the NASSELLARIA (the basal tripod, sagittal ring, and
latticed cephalis) appear (compare §§ 111 and 182). If, for example, in
_Cortina_ and _Tripospyris_ the basal tripod were to appear first in the
ontogeny, and the sagittal ring were developed from this, then the
#Plectoidea# would be rightly considered to be the oldest forms in the
phylogeny of the skeleton-forming NASSELLARIA; and in the contrary case the
#Stephoidea# would be so regarded. The relations of growth in the three
dimensive axes are very variable in the NASSELLARIA; the three most
important factors in this respect (partly separately and partly in
combination) are; (1) the development of the basal tripod to a triradial
stauraxon form (the ground-form being a three-sided pyramid); (2) the
development of the sagittal ring in the median plane of the body (the
vertical axis having the poles different); (3) the development of the
latticed cephalis outside the central capsule (the poles of the vertical
axis being again different). Since the development both of the skeleton and
of the malacoma is characterised in most NASSELLARIA by the stronger growth
of the vertical axis and the differentiation of the two poles, the
allopolar monaxon ground-form acquires a predominant significance in this
legion (§ 32); the starting point of most of the further modifications is
the basal pole of the vertical main axis. Next to this the sagittal axis is
usually the most important determining factor (its dorsal and ventral poles
being {xcviii}usually different), more rarely the frontal axis (with equal
right and left poles). In the zygothalamous #Spyroidea# (as in the
#Stephoidea#) the formation of the shell proceeds from the sagittal ring,
whilst in the polythalamous #Cyrtoidea# the latticed cephalis is always the
starting point, from which a series of joints (thorax, abdomen, and in the
Stichocyrtida, the numerous post-abdominal joints) successively arise
(unipolar growth).


149. _The Ontogeny of the Phæodaria._--The individual development of the
PHÆODARIA in the simplest case stops with the skeletonless condition of the
Phæodinida (_Phæodina_, _Phæocolla_), which can be immediately derived from
the foregoing _Actissa_-stage by the disappearance of the pores in the
greater part of the central capsule, the characteristic astropyle being
developed at the basal pole (§ 60). Since this particular form and
structure of the spheroidal central capsule remains the same in all
PHÆODARIA, whilst the formation of their skeleton follows very different
directions, it follows that further common paths of development are
excluded both ontogenetically and phylogenetically. What will be laid down
in this respect as regards the phylogeny of the different groups of
PHÆODARIA (§§ 194-199) holds true also of their ontogeny. The relations of
growth in the three dimensive axes are hence very different in the
skeletons of the various groups of PHÆODARIA. This difference is best
marked in the #Phæoconchia#, whose bivalved lattice-shells have as their
ground-form the rhomboid pyramid of Ctenophora. In most #Phæogromia# the
monaxon lattice-shell may develop simultaneously by sudden excretion at a
particular moment of lorication; this is also the case with the polyaxon
lattice-shells of the #Phæosphæria#. In their future growth the development
of basal or radial apophyses is of special importance. In the majority of
the PHÆODARIA these apophyses are tubes of silicate filled with jelly
(often provided with an axial siliceous thread); thus their development is
distinguished by complications which are absent in the case of the other
three legions.


150. _Growth._--The growth of the body in the Radiolaria, as in all other
organisms, is the fundamental function of individual development (see note
A). All structural relations which this richest class of the Protista
exhibits may be referred to different forms of growth, either of the
unicellular malacoma or of the skeleton which it produces. In general the
special development of the skeleton is dependent upon that of the central
capsule, and of the sarcodictyum on the surface of the calymma; in the
further growth, however, the conditions are reversed, and the condition of
the skeleton already formed directly determines the further development of
the central capsule and of the calymma with its sarcodictyum. The four
legions of Radiolaria show, speaking generally, certain characteristic
differences in growth, which are due in great part to the different
structure and ground-form of their central capsule. In the two legions of
the Porulosa (SPUMELLARIA and ACANTHARIA), in which the central capsule is
originally spherical and {xcix}the ground-form of the skeleton either
polyaxon or isopolar monaxon, two fundamental and variously combined
directions of growth are recognisable; firstly, the _concentric_ growth
(equal increase of volume in all directions), and secondly, multipolar or
_diametral_ growth (hypertrophy of certain parts in the direction of
definite pairs of radii). A different state of things obtains, however, for
the most part, in the two legions of the Osculosa (NASSELLARIA and
PHÆODARIA), in which the central capsule possesses a vertical main axis
with different poles, and the structure of the skeleton is determined by
this allopolar monaxon ground-form. The two fundamental directions of
growth here combined in the most various ways are, firstly, _unipolar_
growth (starting from the basal pole of the vertical main axis), and
secondly, radial or _pyramidal_ growth (characterised by the different
development of separate parts in the direction of definite radii). Whilst
the growth of the _malacoma_ is dependent on intussusception (as in most
organic structures capable of imbibing), the growth of the _skeleton_ in
all Radiolaria takes place by apposition (see note B).

  A. The earliest investigations into the modes of growth in the Radiolaria
  are due to J. Müller (L. N. 12, pp. 21-33). More detailed communications
  I gave myself in my Monograph (L. N. 16, pp. 150-159). The relations
  there sketched have now, in consequence of the examination of the
  Challenger collection, undergone many important additions, and in some
  divisions, important modifications; these are for the most part treated
  of in the general account of the separate families.

  B. The view here maintained, that the skeleton of all Radiolaria grows
  only by apposition, appeared formerly to have certain exceptions. I
  thought I had shown that in _Coelodendrum_ the thin-walled tubes grew not
  only in length but also in thickness, with continuous increase in the
  lumen (L. N. 16, pp. 152, 360). Further K. Brandt concluded, from the
  varying size of the median bars in the twin-spicules of _Sphærozoum_,
  that these siliceous structures grow by intussusception (L. N. 38, p.
  401). Both suppositions have been proved erroneous and I have come to the
  opinion that in all Radiolaria the skeleton grows by apposition.


151. _Regeneration._--Whilst the general course of individual development
(perhaps without any exception in the Radiolaria), begins with the
formation of zoospores in the central capsule, there yet occurs in some
groups a different form of ontogeny, introduced by simple division of the
unicellular organism, and coming under the term "regeneration" in its wider
sense. This spontaneous division occurs quite commonly in the Polycyttaria
(or social SPUMELLARIA), and produces their colonies (compare the chapter
on Reproduction, § 213). On the contrary, it has not been observed in the
solitary SPUMELLARIA, nor in the ACANTHARIA and NASSELLARIA; possibly,
however, the peculiar ACANTHARIAN family, Litholophida, has arisen by the
division of Acanthonida (compare p. 734). Among the PHÆODARIA division is
commonly observed in the order #Phæocystina# (which have an incomplete
Beloid skeleton or none), and also in the #Phæoconchia#. In all these cases
the increase by division is nothing else than an ordinary case of
cell-division, in which bisection of the nucleus precedes that of the
central capsule. The regeneration by {c}which each of the two
daughter-cells develops to a complete mother-cell depends upon simple
growth. Another form of regeneration, different from this, has been
observed in _Thalassicolla_. If the central capsule be extracted
artificially from the large concentric calymma, the enucleated central
capsule produces a new extracapsulum, with sarcomatrix, pseudopodia, and
calymma. This experiment may be repeated several times with the same
result. (Compare A. Schneider, 1867, L. N. 20.)


152. _The Formation of Colonies._--The individual development of colonies
takes place in all three families of the Polycyttaria (Collozoida,
Sphærozoida, Collosphærida) in the same simple way, by the repeated
division of a single monozootic SPUMELLARIAN. Since these divisions only
affect the central capsule and not the extracapsulum, the sister-cells,
which arise by repeated division of the mother, remain enclosed in a common
rapidly growing calymma. Probably in all Polycyttaria the commencement of
the formation of colonies immediately follows the _Actissa_-stage of the
monozootic mother-cell (or takes place in the _Thalassicolla_-stage, which
arises from the former by the development of alveoles in the calymma). The
simple central nucleus separates (by direct nuclear division) into two
halves, and the central capsule follows this process of bisection, becoming
constricted in the middle between the two daughter nuclei (Pl. 3, fig. 12).
In the further growth of the colony the process of division proceeds in the
older, now multinucleate, central capsules, in which an oil-globule has
taken the place of the original nucleus; then the division of the
oil-globules precedes that of the central capsule (Pl. 5, fig. 1). Another
mode of growth of the colonies is the multiplication of the central
capsules by gemmulation, or the formation of the so-called "extracapsular
bodies" (Gemmulæ, § 214). The characteristic skeletal structure of the
different species appears at a later stage. Whether ripe central capsules
can emerge from the social bond of a coenobium, and, having become
isolated, establish the formation of a new colony, is very doubtful. The
various forms which the coenobium assumes in the different species of
Polycyttaria, are due partly to simple growth, partly to the development of
large vacuoles in the calymma.

  The _form and size_ of the coenobia appear in many fully developed
  Polycyttaria to exhibit specific differences, which require further
  investigation; in the young stage, on the contrary, they are simple
  spheres or ellipsoids, often cylindrical or sausage-shaped (Pl. 3, figs.
  1, 4, 6, 11).  In some species the cylindrical gelatinous bodies become
  moniliform, and separated by transverse constrictions into many segments,
  each of which encloses a large alveole (Pl. 3, fig. 10). The rare
  ring-shape (Pl. 4, fig. 1) which I figured in 1862 in the case of
  _Collozoum_ (L. N. 16, p. 522, Taf. xxxv. fig. 1), I have recently
  observed in different species of Polycyttaria; it is capable of a very
  simple mechanical explanation, both ends of a sausage-shaped colony
  having been accidentally brought into contact by a wave and having united
  by agglutination. Quite recently Brandt has given a very complete account
  of the development, form, and growth of Polycyttarian colonies in his
  work on the colonial Radiolaria of the Bay of Naples (1885, L. N. 52, pp.
  71-85).



{ci}CHAPTER VI.--PHYLOGENY OR GENEALOGICAL DEVELOPMENT.

(§§ 153-200.)

153. _Sources of Phylogenetic Knowledge._--For the purpose of constructing
a hypothetical genealogical tree of the Radiolaria, as of all other
organisms, three sources of information are open to us, viz., palæontology,
comparative ontogeny, and comparative anatomy. In the present case,
however, these three sources are of very different value; the first two are
at present only very inadequately known and have only been partially
investigated, hence they can only be utilised to a very slight extent. The
comparative anatomy of the Radiolaria, on the other hand, is so completely
known, and affords such certain glimpses into the morphological relations
of the related groups, that by its aid we are in a position at all events
to lay down the general features of their phylogeny with some probability,
and to lay the foundation of a natural system.


154. _Natural and Artificial Systems._--Although in the classification of
the Radiolaria, as in the case of all other organisms, the natural system
must be regarded as the goal of systematic classification, our phylogenetic
knowledge of the Radiolaria is too fragmentary and inadequate to admit of
the systematic arrangement here adopted being regarded as a thoroughly
consistent natural system, that is, as representing the true genealogical
tree of the class. Owing, however, to the extraordinary variety of form of
the Radiolaria, and the complicated relationships of the larger and smaller
groups, a synoptical grouping of the different categories and the erection
of a complete, even if to some extent artificial, system, becomes a logical
necessity. Under these circumstances, and regard being had to both these
conditions, the following systematic treatment of the Radiolaria will
appear as a _compromise between the natural and artificial systems_, like
all other zoological and botanical classificatory attempts. On the one
hand, the attempt is made to arrange the larger and smaller groups as
nearly as possible according to their phylogenetic relationships, whilst,
on the other hand, the practice of circumscribing each by a definition as
clear and logical as possible has been carried out. Since these two efforts
naturally often come into contact, the insufficiency of many parts of the
arrangement is obvious, hence its hypothetical and provisional character is
emphatically stated.


155. _Systematic Categories._--The categories or different orders of
divisions have in the Radiolaria, as in all other organisms, no _absolute_
significance, but only a _relative_ value. In itself it is quite
unimportant whether the whole group be regarded, as at first, as a _family_
(Ehrenberg, 1847), or as an _order_ (J. Müller, 1858), or as a _class_
(Haeckel, {cii}1881). These different views are regulated, on the one hand,
by the known extent of the group and by the amount of our acquaintance with
it, and on the other, by comparison with related groups and by reference to
their conventional disposition. When, therefore, the whole class,
Radiolaria, is here divided into two subclasses, four legions, eight
orders, eighty-five families, &c., these artificial categories are drawn up
only in the conviction that by this means the easiest survey and most
thorough insight into the system as a whole may be attained; this latter
will indeed approach as far as possible the ideal of a natural system, but
must on numerous practical grounds always remain more or less artificial.
Since it is to be expected that with the progress of our systematic
knowledge the rank of the various categories will rise, it is possible that
in the future the arrangement of the group may be somewhat as
follows:--_Phylum_, RADIOLARIA; _Four Classes_, SPUMELLARIA, NASSELLARIA,
ACANTHARIA, PHÆODARIA; _Eight Legions_ (Nos. I.-VIII. in the following
Table); _Twenty Orders_ (Nos. 1-20 in the Table), &c.

  Four Legions. Eight Sublegions.   Twenty Orders.    Typical Families.
               {                   {1. Colloidea,  { 1a. Thalassicollida.
               {I. COLLODARIA      {               { 1b. Collozoida.
               { (Spumellaria      {
               {  palliata)        {2. Beloidea,   { 2a. Thalassosphærida.
               {                   {               { 2b. Sphærozoida.
  I. Legion    {
  (or Subclass){                   {                  { 3a. Ethmosphærida.
  SPUMELLARIA  {                   {3. Sphæroidea,    { 3b. Collosphærida.
  (PERIPYLEA)  {                   {
               {                   {4. Prunoidea,     { 4a. Ellipsida.
  [Porulosa    {II. SPHÆRELLARIA   {                  { 4b. Zygartida.
   peripylea.] { (Spumellaria      {
               {   loricata)       {5. Discoidea,     { 5a. Phacodiscida.
               {                   {                  { 5b. Porodiscida.
               {                   {
               {                   {6. Larcoidea,     { 6a. Larnacida.
               {                   {                  { 6b. Pylonida.

               {                   {7. Actinelida,    { 7a. Astrolophida.
               {                   {                  { 7b. Litholophida.
               {III. ACANTHOMETRA  {                  { 7c. Chiastolida.
               { (Acantharia       {
  II. Legion   {   palliata)       {                  { 8a. Astrolonchida.
  (or Subclass){                   {8. Acanthonida,   { 8b. Quadrilonchida.
  ACANTHARIA   {                   {                  { 8c. Amphilonchida.
  (ACTIPYLEA)  {
               {                   {                  { 9a. Sphærocapsida.
  [Porulosa    {                   {9. Sphærophracta, { 9b. Dorataspida.
   actipylea.] {IV. ACANTHOPHRACTA {                  { 9c. Phractopeltida.
               { (Acantharia       {
               {   loricata)       {                  {10a. Belonaspida.
               {                   {10. Prunophracta, {10b. Hexalaspida.
               {                   {                  {10c. Diploconida.
               {                   {11. Nassoidea,     11.  Nassellida.
               {                   {
               {V. PLECTELLARIA    {12. Plectoidea,   {12a. Plagonida.
               { (Nassellaria      {                  {12b. Plectanida.
               {   palliata)       {
               {                   {13. Stephoidea,   {13a. Stephanida.
               {                   {                  {13b. Tympanida.
               {
  III. Legion  {                   {14. Spyroidea,    {14a. Zygospyrida.
  (or Subclass){                   {                  {14b. Androspyrida.
  Nassellaria  {                   {
  (MONOPYLEA)  {                   {                  {15a. Cannobotryida.
               {VI. CYRTELLARIA    {15. Botryodea,    {15b. Lithobotryida.
  [Osculosa    { (Nassellaria      {                  {15c. Pylobotryida.
   monopylea.] {   loricata)       {
               {                   {                  {16a. Monocyrtida.
               {                   {16. Cyrtoidea,    {16b. Dicyrtida.
               {                   {                  {16c. Tricyrtida.
               {                   {                  {16d. Stichocyrtida.

               {                   {                  {17a. Phæodinida.
               {                   {17. Phæocystina,  {17b. Cannorrhaphida.
               {                   {                  {17c. Aulacanthida.
               {VII. PHÆOCYSTINA   {
  IV. Legion   { (Phæodaria        {                  {18a. Orosphærida.
  (or Subclass){   palliata)       {18. Phæosphæria,  {18b. Aulosphærida.
  Phæodaria    {                   {                  {18c. Cannosphærida.
  (CANNOPYLEA).{
               {                   {                  {19a. Challengerida.
  [Osculosa    {                   {19. Phæogromia,   {19b. Castanellida.
   cannopylea.]{VIII. PHÆOCOSCINA  {                  {19c. Circoporida.
               { (Phæodaria        {
               {    loricata)      {                  {20a. Concharida.
               {                   {20. Phæoconchia,  {20b. Coelodendrida.
               {                   {                  {20c. Coelographida.


156. _Formation of Species._--The totality of similar forms, which we unite
in one species, and which in the earlier dogmatic systems was regarded as a
category of absolute value, possesses only a _relative value_ like all
other systematic categories (§ 155). According to the individual views of
the systematist and the general survey which he has attained of the smaller
and larger systematic groups, the conception of a species adopted in his
practical work will be wider or narrower. In the present systematic
arrangement a medium extent has been adopted. It is shown that in the
Radiolaria, as in all other extensive groups of organisms, the constancy of
the species is very variable in the different groups. Many families of
Radiolaria are very rich in "bad species," _i.e._, very _variable_ forms,
in which the process of the formation of species is seen in progress; such,
for example, are--among the SPUMELLARIA, the Sphærozoida, Stylosphærida,
Phacodiscida and Pylonida; among the ACANTHARIA, the Amphilonchida and
Phractopeltida; among the NASSELLARIA, the #Stephoidea# and #Botryodea#;
and among the PHÆODARIA, the Aulacanthida, Sagosphærida, Castanellida and
Concharida. On the {civ}other hand, in some families numerous "good
species" may be distinguished, since the intermediate connecting forms are
no longer present and the forms have become _relatively constant_. As
instances of such families may be mentioned, among the SPUMELLARIA, the
Astrosphærida, Cyphinida, Porodiscida and Tholonida; among the ACANTHARIA
the Quadrilonchida and Dorataspida; among the NASSELLARIA, the #Spyroidea#
and #Cyrtoidea#; among the PHÆODARIA, the Challengerida, Medusettida,
Circoporida and Coelographida. The more carefully the different groups are
studied, the more numerous the individuals of each species under
comparison, the greater becomes the number of "bad" species among the
Radiolaria, and the smaller the number of good ones. Originally, no doubt,
all "species bonæ" were "malæ." There may be observed in the manifold
skeletal forms of the Radiolaria, on the one hand, the utmost accuracy of
configuration, and on the other, the greatest variability, and hence a
careful comparative study of them leads to a firm conviction of the gradual
"Transformation of Species," and of the truth of the "Theory of Descent."


157. _Palæontological Development._--The palæontology of the Radiolaria
already offers very considerable material for study; but in consequence of
its incompleteness this is of little value for the study of the phylogeny
of the class. By far the larger portion of the fossil Radiolaria belong to
the Tertiary period; only quite recently have numerous well-preserved
fossil Radiolaria been described from the Mesozoic period, and especially
from the Jura. Of Palæozoic Radiolaria (from the coal measures) only slight
traces are known. Moreover, the fossil Radiolaria hitherto known have been
found only in very circumscribed and widely separated localities. The
majority of all the species belong to the small island of Barbados.
Although our palæontological acquaintance with the Radiolaria must
necessarily be incomplete for this reason, it is still more so since at
least thirty out of the eighty-five families (that is more than a third)
could not possibly leave any fossil remains, either because they possess no
skeleton, or because of its chemical composition.

  Of the four legions of the Radiolaria, the ACANTHARIA (on account of the
  solubility of their astroid acanthin skeletons) have entirely vanished
  and have never been found fossil. Of the PHÆODARIA, whose silicate
  skeleton is not as a rule capable of fossilisation, only one section
  (Dictyochida) of a single family (Cannorrhaphida) has been observed
  fossil. Hence the fossil remains of the Radiolaria belong almost
  exclusively to the two legions, SPUMELLARIA and NASSELLARIA, which were
  formerly united under the term "Polycystina." Among these, however, the
  skeletonless Thalassicollida, Collozoida, and Nassellida could leave no
  traces. Hence there only remain fifty-five families of which we might
  expect to find fossil siliceous skeletons. Even of these, however,
  scarcely the half are certainly known in the fossil condition, whilst of
  the remainder nothing certain is known; for example, of the large order
  #Larcoidea# (among the SPUMELLARIA) and of the #Stephoidea# (among the
  NASSELLARIA) with a few isolated exceptions, no fossils are known. The
  great majority of fossil Radiolaria belong to the two NASSELLARIAN orders
  #Cyrtoidea# and #Spyroidea# (two relatively very highly developed
  groups); next to these follow the orders {cv}#Discoidea# and #Sphæroidea#
  among the SPUMELLARIA. From these palæontological facts it is obvious
  that our present very incomplete acquaintance with the fossil Radiolaria
  is quite insufficient to warrant us in drawing any conclusions from it
  regarding the phylogenetic development or palæontological succession of
  the individual groups.


158. _Origin of the Four Legions._--The agreement of all Radiolaria in
those constant and essential characters of the unicellular body, which
distinguish them from all other Protista (especially the differentiation of
the malacoma into a central capsule and extracapsulum), justifies the
conclusion that all members of this class have been developed from a common
undifferentiated stem-form. Only the simplest form of the SPUMELLARIA, a
skeletonless spherical cell with concentric spherical nucleus and calymma,
can be regarded as such. The simplest form of the Thalassicollida which is
now extant (_Actissa_, _Procyttarium_, p. 12), corresponds so exactly to
the morphological idea of that hypothetical stem-form that it may
unhesitatingly be regarded in a natural system as the common point of
origin of the whole class. On the other hand, _Actissa_ is so closely
related to the simple Heliozoa (_Actinophrys_, _Actinosphærium_,
_Heterophrys_, _Sphærastrum_, &c.) that its origin from this group of
Rhizopoda is exceedingly probable. The three legions ACANTHARIA,
NASSELLARIA, and PHÆODARIA are to be regarded as three main diverging
branches of the genealogical tree, which have been developed in different
directions and are only connected by their simplest stem-forms
(_Actinelius_, _Nassella_, _Phæodina_) with the stem-form of the
SPUMELLARIA, the primordial _Actissa_.


159. _Phylogeny of the Spumellaria._--The legion SPUMELLARIA or PERIPYLEA
is to be regarded as the common stem-group of the Radiolaria, and its
simplest form, _Actissa_, as the primitive genus or radical form of the
whole class; for it possesses in the simplest and most undifferentiated
form all those characters by which the Radiolaria are distinguished from
other Protista; all the other genera of the class may be derived from it by
successive modifications. Considered as a legion the whole group
SPUMELLARIA is undoubtedly monophyletic, for all its members possess those
essential characters by which it is distinctively marked off from the other
three legions, more especially a simple capsule-membrane, which is
everywhere evenly perforated by innumerable small pores; the nucleus lies
originally in the centre of the spherical central capsule. Furthermore, all
SPUMELLARIA lack those positive characters which distinguish the three
remaining legions--the centrogenous acanthin skeleton of the ACANTHARIA,
the basal porochora and the monaxon podoconus of the NASSELLARIA, the
astropyle and phæodium of the PHÆODARIA.


160. _Origin of the Spumellaria._--The genus _Actissa_ (p. 12, Pl. 1, fig.
1) presents the Radiolarian type in its simplest and most primitive form--a
spherical central capsule, which encloses in its middle a spherical
nucleus, and which is surrounded by a spherical calymma. The whole
unicellular body consists, therefore, of three concentric spheres, {cvi}and
possesses neither skeleton nor alveoles, nor other differentiated parts.
The innumerable fine pseudopodia, which issue from the central capsule
through the evenly distributed pores in its membrane, radiate in all
directions through the calymma and pass out over its surface. _Actissa_
can, therefore, be directly derived phylogenetically from the simplest
skeletonless Heliozoa (_Actinophrys_, _Heterophrys_, _Actinosphærium_,
_Sphærastrum_). The only essential difference between the two consists in
the development of the _central capsule_, which in _Actissa_ separates as a
distinct membrane the endoplasm from the exoplasm. This differentiation
which we regard is the most important distinguishing character of the
Radiolaria, has been transmitted by inheritance, along with the formation
of flagellate spores in the central capsule, from _Actissa_, the primitive
parent to all the other Radiolaria.

{cvii}161. _Hypothetical Genealogical Tree of the Spumellaria_:--


                          LARCOIDEA                   DISCOIDEA
                          ~~~~~~~~~~~~~          ~~~~~~~~~~~~~~~~~~~~~~~
                          Streblonida           PHACODISCARIA
                               |                  Coccodiscida
                               |   THOLONIDA           |
                               |        |              |
       PRUNOIDEA               |        |              |
  ~~~~~~~~~~~~~~~~~~  Soreumida|        |              |
                          |    |        |              |
  Zygartida               |    |        |              |
      |                   |    |        |              |
      |                   |    |Zonarida|              |
      |                   |Lithelida|   | SPHÆROIDEA   |CYCLODISCARIA
      |                   |    |    |   |~~~~~~~~~~~~~ |   Spongodiscida
      |                   |    |    |   |Stylosphærida |Pylodiscida|
      |              Phorticida|    |   |     |        |     |     |
      |                   |    |    |   |     |        |     |     |
  Panartida               |    |    |   |     |        |     |     |
      |          Artiscida|    +----+---+     |        |     |     |
      |                |  |         |         |        |     |     |
      |                |  |         |         |  Phacodiscida|     |
      |Spongodruppida  |  |         |         |        |     |     |
      |     |          |  |         |   Staurosphærida |     +-----+
      |     |          |  |     Pylonida      |        |        |
      |     |          |  |         |         |        |        |
  Cyphinida |          |  +---------+         |        |        |
      |     |          |       |              |        |   Porodiscida
      |     |          |       | Astrosphærida|        |        |
      +-----+          |       |        |     |        |        |
        |              |       |        |     |   Cenodiscida   |
        |Spongellipsida|   Larnacida    |     |        |        |
        |      |       |       |        |     |        |  Archidiscida
        |      |       |       |        |Cubosphærida  |        |
   Druppulida  |       |       |        |     |        +--------+
        |      |       |       |        |     |              |
        |      |       |       |        |     |Collosphærida |
        |      |       |       |        |     |     |        |
        |      |       |   LARNACILLA   +-----+-----+        |
        |      |       |   (Trizonium)        |              |
        | Spongurida   |       |              |              |
        +------+-------+       |              |              |
               |               |              |              |
           Ellipsida       Larcarida      Liosphærida    Cenodiscida
         (CENELLIPSIS)   (CENOLARCUS)    (CENOSPHÆRA)   (CENODISCUS)
               |               |              |              |
         [Actiprunum?]    [Actilarcus?] [Procyttarium]  [Actidiscus?]
               |               |              |              |
               +---------------+------+-------+--------------+
                                      |
               CENOSPHÆRA (Common stem-form of all Sphærellaria?)
                     |     |
                     |     |        POLYCYTTARIA
                     | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
                     |Collosphærida  Collozoida  Sphærozoida  }
                     |     |             |          |         } BELOIDEA
                     +-----+             |   Thalassosphærida }
                        |                |          |
                   Ethmosphærida         |          |
                        |                |          |
                        +----------------+----------+
                                         |
                                    COLLOIDEA
                                         |
                                  Thalassicollida
                                         |
                                      ACTISSA


{cviii}162. _Collodaria and Sphærellaria._--Whilst in all SPUMELLARIA the
malacoma agrees in possessing the characteristic features of the legion,
and thus justifies its derivation monophyletically from the common
stem-form _Actissa_, the different forms of skeleton, on the other hand,
cannot all be referred to the same fundamental form. More especially the
_spherical lattice-shell_, from which all the numerous skeletal forms of
the #Sphærellaria# may be derived, cannot have arisen from the incomplete
Beloid skeleton which characterises the #Beloidea# among the #Collodaria#.
It is probable rather that the formation of the skeleton has taken place
independently in those two groups of SPUMELLARIA. From the skeletonless
#Colloidea#, as the common stem-group of the SPUMELLARIA, two different
main groups have diverged, on the one hand the #Beloidea#, whose skeleton
consists of separate spicules scattered in the extracapsulum, and on the
other hand, the #Sphærellaria#, which have formed a simple lattice-sphere
around the central capsule; from this the manifold forms of the remaining
SPUMELLARIA may be derived.


163. _Descent of the Sphærellaria._--The extensive order #Sphærellaria#,
which includes all SPUMELLARIA with a complete lattice-shell, develops an
extraordinary variety of skeletal structures; these may, nevertheless, all
be derived without violence from a common stem-form, or simple spherical
lattice-shell, _Cenosphæra_. The main stem of the order, the extensive
suborder #Sphæroidea# (Pls. 5-30), is derived immediately from _Cenosphæra_
(p. 61, Pl. 12); three diverging branches of it being represented by the
other three suborders, the #Prunoidea# (Pls. 16, 17, 39, 40) being
developed by elongation, and the #Discoidea# (Pls. 31-48) by shortening of
the vertical main axis, whilst the #Larcoidea# (Pls. 9, 10, 49, 50) have
originated by the modification of the spherical lattice-shell into a
lentelliptical or triaxial ellipsoidal one. Although the monophyletic
derivation of all #Sphærellaria# from _Cenosphæra_ is exceedingly probable,
the possibility of a polyphyletic origin for the group is by no means
excluded. For even in the skeletonless primitive genus of all the
SPUMELLARIA, _Actissa_ (as well as in the social _Collozoum_), there are
found, in addition to the usual spherical types, other species (or
subgenera, p. 12) whose central capsule is not spherical but a modification
of the sphere; in _Actiprunum_ ellipsoidal; in _Actidiscus_ lenticular; in
_Actilarcus_ lentelliptical; if such modified forms of _Actissa_ were to
develop their lattice-shells independently, then their form would
correspond to that of the central capsule; and such simple ellipsoidal,
discoidal, and lentelliptical lattice-shells might have been the primitive
forms of the #Prunoidea#, #Discoidea# and #Larcoidea#.


164. _Genealogical Tree of the Sphæroidea._--_Cenosphæra_, the simplest
form of the spherical lattice-shell, may be unhesitatingly regarded as the
common stem-form of all the #Sphæroidea# (pp. 50-284, Pls. 5-30).
_Cenosphæra_ (p. 61, Pl. 12) arose directly from _Actissa_ simply by the
silicification of the spherical exoplasmatic network of the sarcodictyum
around the central capsule, on the surface of the concentric calymma. From
this simple siliceous extracapsular lattice-sphere all other forms of
#Sphæroidea# have arisen, in the main by the manifold combination of two
simple processes, first by the formation of radial spines on the surface of
the lattice-sphere, and second, the addition of concentric spherical
lattice-shells. Both processes may be utilised as the foundation for a
systematic treatment of the #Sphæroidea# (compare pp. 52-58).

  If in the #Sphæroidea# the characteristic number and disposition of the
  _radial spines_ be regarded as the most important heritable peculiarity
  of the different families, then we have the following natural
  arrangement:--(1) Liosphærida, without radial spines; (2) Cubosphærida,
  with six radial spines (opposite in pairs in three axes perpendicular to
  each other); (3) Staurosphærida, with four radial spines (in two axes
  crossed at right angles); (4) Stylosphærida, with two opposite radial
  spines (in the vertical main axis); and (5) Astrosphærida, with numerous
  regularly or irregularly distributed radial spines (eight to twenty or
  more). If, on the contrary, more stress be laid upon the number of the
  concentric lattice-shells, then we have the following artificial
  grouping:--(1) Monosphærida, with one simple lattice-sphere; (2)
  Dyosphærida, with two concentric lattice-spheres; (3) Triosphærida, with
  three; (4) Tetrasphærida, with four; (5) Polysphærida, with numerous
  (five to twenty or more) concentric lattice-shells; (6) Spongosphærida,
  with a spongy spherical shell. In general the former arrangement appears
  more natural than the latter, since the number of primary radial spines,
  which grow out from the primary lattice-sphere, determines their
  ground-form from the outset, whatever may be the number of secondarily
  added shells. Strictly speaking, according to the view adopted, these
  Liosphærida which have several shells, on the outer surface of which
  there are no radial spines, ought to be classified according to the
  number and arrangement of their internal radial connecting beams and
  distributed among the other families. The practical application of this
  correct principle meets, however, with great difficulties. Also in many
  cases the phylogenetic relations of the different #Sphæroidea# are more
  complicated than would appear from both these classificatory principles.
  In general their phylogeny will quite correspond with their ontogeny,
  since from the innermost first formed {cix}lattice-shell (primary
  medullary shell) a number of radial spines arises, and upon these the
  secondary shells are formed from within outwards.


165. _Genealogical Tree of the Prunoidea._--The suborder #Prunoidea# is
very closely related to the #Sphæroidea#, and is distinguished from it by
the elongation of one axis; from the simple lattice-sphere (_Cenosphæra_)
is developed a latticed ellipsoid (_Cenellipsis_, Pl. 39, fig. 1). The
development of this vertical isopolar main axis is foreshadowed even among
the #Sphæroidea#, in that family in which two opposite radial spines grow
out of the primary lattice-sphere at the two poles of the vertical main
axis (Stylosphærida, Pls. 13, 14). These latter pass over without any sharp
boundary into those forms of #Prunoidea# whose ellipsoidal lattice-shell
bears two opposite main-spines (Stylatractida, Pls. 15, 16). Other very
intimate relationships between the #Sphæroidea# and #Prunoidea# are
indicated in certain of the latter by the fact that of the two concentric
lattice-shells the inner (medullary) shell is spherical, the outer
(cortical) shell ellipsoidal (Pl. 39, figs. 3, 7, 8, 14, 19); often three
concentric lattice-shells are present, of which the two inner are spherical
intracapsular medullary shells, whilst the outer is an extracapsular
cortical shell, ellipsoidal or cylindrical in form (Pl. 39, figs. 4, 12,
17, 18). Owing to the manifold nature of these phylogenetical relations and
the variety of their combinations, the derivation of the individual
#Prunoidea# from the #Sphæroidea# is rendered very difficult; in addition
to which it is possible that the simplest #Prunoidea# (_Cenellipsis_,
_Ellipsidium_) have been directly developed from the skeletonless
_Actiprunum_ (a form of _Actissa_ with ellipsoidal central capsule, p. 14)
by the excretion of a simple ellipsoidal lattice-shell on the surface of
their calymma.

  The phylogeny of the #Prunoidea# is especially complicated by the
  formation of peculiar transverse constrictions, perpendicular to the
  longitudinal axis. They are wanting only in the Monoprunida (Ellipsida,
  Druppulida, and Spongurida); the Dyoprunida (Artiscida and Cyphinida, Pl.
  39, figs. 9-19) possess only one such constriction (in the equatorial
  plane); the Polyprunida, on the other hand, have three, five, or more
  parallel constrictions (Panartida and Zygartida, Pl. 40). The chambers,
  which are separated off by these constrictions, may be regarded as polar
  sections of incomplete cortical shells.


166. _Genealogical Tree of the Discoidea._--The suborder #Discoidea# is
closely related to the #Sphæroidea#, but separated from it by shortening of
one axis; from a simple lattice-sphere (_Cenosphæra_) a latticed lens or
flattened spheroid is developed, whose circular equatorial plane is larger
than any other section (_Cenodiscus_, Pl. 48, fig. 1). The formation of
this horizontal equatorial plane is perhaps indicated in that family of
#Sphæroidea# in which four crossed radial spines, lying in one plane, are
developed (Staurosphærida, Pls. 15, 31, 42). The morphological and
phylogenetical relations of the #Discoidea# to the #Sphæroidea# are
precisely the converse of those of the #Prunoidea#; in the latter the
vertical axis appears longer, in the former shorter than any {cx}other axis
of the body. The #Discoidea# are probably polyphyletic, having originated
from several different groups of #Sphæroidea#; at least two essentially
different main groups may be distinguished among them; of these the one is
characterised by the formation of a large extracapsular lenticular cortical
shell (Phacodiscaria), whilst in the other this typical "Phacoid shell" or
lattice-lens is wanting (Cyclodiscaria, compare pp. 403-409).

  The Phacodiscida (Pls. 31-35) perhaps constitute the primitive group of
  the Phacodiscaria, their lenticular or Phacoid cortical shell being
  connected by radial bars with one or two concentric spherical medullary
  shells; they may have originated directly from the Dyosphærida or
  Triosphærida by flattening of the spheroidal cortical shell. From the
  Phacodiscida the Cenodiscida (if indeed they be not the primitive
  stem-form) have been developed by retrogression and loss of those
  medullary shells. The Coccodiscida (Pls. 36-38), on the other hand, have
  been developed from the Phacodiscida by the addition of concentric rings
  of chambers, which may be regarded as incomplete cortical shells, only
  the equatorial portion of which is developed. Perhaps the Porodiscida,
  the primitive group of the Cyclodiscaria, have arisen in a similar way;
  they lack, however, the typical Phacoid shell, the concentric rings of
  chambers being directly applied to a small spherical medullary shell in
  the equatorial plane (Pls. 41-46). If those rings from the commencement
  be interrupted by three interradial gaps (gates) the family Pylodiscida
  arises (Pl. 38, figs. 6-20). If, on the contrary, the concentric radially
  divided chambers of the Porodiscida become quite irregular and spongy,
  they pass over into the Spongodiscida (Pls. 46, 47). It is not, however,
  impossible that part of the #Discoidea# (especially the Cenodiscida) have
  originated directly from skeletonless #Collodaria# with a lenticular
  central capsule, such as are found in a subgenus of _Actissa_
  (_Actidiscus_, p. 15).


167. _Genealogical Tree of the Larcoidea._--The suborder #Larcoidea#
presents in the structure, composition, and development of its variously
formed lattice-shells much more complicated relations than the other
#Sphærellaria#; it is essentially distinguished from them by the
characteristic ground-form of its lattice-shells, which is a "lentellipsis"
or a triaxial ellipsoid (also the ground-form of the rhombic
crystallographic system, the rhombic octahedron). Hence all parts of the
body are regularly disposed with respect to three different dimensive axes;
all three axes, perpendicular one to another, are isopolar but of different
lengths; the longest is the vertical main axis, the mean the horizontal
frontal axis, the shortest the horizontal sagittal axis. In the great
majority of the #Larcoidea# the lentelliptical ground-form is indicated in
the central capsule, even when it is not at once obvious in the skeleton.
Since such lentelliptical central capsules are developed even in _Actissa_
(_Actilarcus_, p. 16), it is possible that the simplest #Larcoidea# may
have arisen directly from these by deposition of a simple lentelliptical
lattice-shell in the sarcodictyum, on the surface of the calymma
(_Cenolarcus_, Pl. 50, fig. 7). It is more probable, however, that these
simplest forms (_Cenolarcus_, _Larcarium_) have been developed from the
simplest #Sphæroidea# (_Cenosphæra_), by the spherical body growing
unequally in the three dimensions of space. It appears especially likely
{cxi}from a study of the concentrically disposed lattice-shells of some
#Larcoidea# (_Coccolarcus_, _Larcidium_, Pl. 50, fig. 8), in which the
inner medullary shell is spherical, the outer cortical shell more or less
elliptical. In the great majority of #Larcoidea# the latter arises in quite
a peculiar manner, three broad lattice-zones, which are developed in three
planes at right angles to each other, growing out from a small spherical or
lentelliptical medullary shell, _Trizonium_, _Larnacilla_ (compare pp. 600,
615, 628, &c.).

  The trizonal _Larnacilla_-shell commences by the formation of a
  transverse girdle, by the union of two lateral latticed processes, which
  spring right and left in the equatorial plane from the poles of the
  frontal axis of a lentelliptical medullary shell (_Monozonium_, p. 633,
  Pl. 9, fig. 1). This is followed by a second lateral girdle, which lies
  in the frontal plane and proceeds from its lateral poles (_Dizonium_, p.
  634, Pl. 9, figs. 2, 3). Finally the sagittal girdle is formed, lying in
  the sagittal plane and arising from the lateral girdle on the two poles
  of the main axis (_Trizonium_, p. 637, Pl. 9, fig. 4). Whilst the gaps
  between the three zones of this trizonal shell remain open in the
  Pylonida, in _Larnacilla_, the important primitive form of the Larnacida,
  they are closed by lattice-work (Pl. 50, figs. 3-8). From this trizonal
  _Larnacilla_-shell the great majority of Larcoid shells may be derived.
  Such a system of zones may be repeated (Diplozonaria) or even developed a
  third time (Triplozonaria, p. 632). In most #Larcoidea# the zones are
  secondarily connected by lattice-work. In the Tholonida (Pl. 10) each of
  the two opposite latticed wings of a zone becomes a closed dome. In the
  Zonarida (Pl. 50, figs. 9-12) these domes are partially or wholly
  bisected by constrictions or latticed septa which are developed in the
  three dimensive planes. The Lithelida (Pl. 49, figs. 1-7) are
  characterised by the fact that one of each pair of opposite latticed
  processes (or half zones) grows more strongly than the other, and that
  the larger completely embraces the smaller so as to form a complicated
  spiral. Whilst in this case the spiral lies in a plane, in the
  Streblonida (Pl. 49, figs. 8, 9) it becomes turbinoid like a gastropod
  shell and forms an ascending spiral. Finally, two small families of
  #Larcoidea# are characterised by quite irregular growth (a very rare
  occurrence among the Radiolaria); these are the simple-chambered
  Phorticida (Pl. 49, figs. 10, 11) and the many chambered Soreumida (Pl.
  49, figs. 12, 13). The phylogenetic relationship of these families of
  #Larcoidea# is probably very complicated and demands closer investigation
  (compare pp. 599-604).


168. _Descent of the Polycyttaria._--The polyzootic or colonial Radiolaria,
which we unite in the group Polycyttaria (sometimes known as "Sphærozoea"),
belong without doubt to the legion SPUMELLARIA, for they possess all the
peculiarities by which these PERIPYLEA are distinguished from the other
legions of the Radiolaria. Only the morphological position of the
Polycyttaria in that legion, and their phylogenetic relation to the
monozootic or solitary SPUMELLARIA, can be variously interpreted. The three
families which we distinguish among the Polycyttaria are so closely related
to three different families of the Monocyttaria, that they may be directly
derived from them by the formation of colonies. According to this
_triphyletic hypothesis_ the social skeletonless Collozoida (Pl. 3) would
be descended from the solitary Thalassicollida (Pl. 1), the polyzootic
Sphærozoida with a Beloid skeleton (Pl. 4) from the monozootic
{cxii}Thalassosphærida (Pl. 2), and the colonial Collosphærida with a
Sphæroid skeleton (Pls. 5-8) from the solitary Ethmosphærida (Pl. 12, &c.).
Many species of monozootic and polyzootic forms in all three groups are so
alike that they can only be distinguished by the fact that the one series
are colonial, the others solitary. On the other hand, there are some
reasons which would justify a monophyletic hypothesis for the Polycyttaria,
_e.g._, the precocious nuclear division; in this case it would be most
natural to hold that the Sphærozoida and Collosphærida have arisen as two
diverging branches from the Collozoida, whilst the latter are nothing else
than colonial Thalassicollida.


169. _Phylogeny of the Acantharia._--The legion ACANTHARIA or ACTIPYLEA is
distinguished by its peculiar acanthin skeleton, which develops
centrogenously, as well as by the disposition in groups of the pores in its
central capsule, and its excentric usually precocious nucleus; it is thus
so different from all other Radiolaria as undoubtedly to furnish,
phylogenetically considered, an independent stem (§ 7). This stem is only
connected at the root by _Actinelius_ with the primitive form of the
SPUMELLARIA, _Actissa_. The stem is monophyletic, since all the forms
belonging to it may be derived without violence from _Actinelius_ as a
common primitive form.


170. _Origin of the Acantharia._--The genus _Actinelius_ (p. 730, Pl. 129,
fig. 1), which may naturally be regarded as the common primitive form of
all ACANTHARIA, possesses a spherical central capsule, which in consequence
of the early division of the nucleus (§ 63), encloses numerous small
nuclei; from its centre arise many simple radial spines of equal size,
which penetrate the central capsule. A large number of radial pseudopodia
issue between the spines from the sarcomatrix which surrounds the capsule.
_Actinelius_ may have been directly derived from _Actissa_, the common
stem-form of all Radiolaria, by the division of the pseudopodia into two
groups, myxopodia, which remained soft, and axopodia, which became firm (§
95A). As the latter became changed into strong acanthin rods, and touched
each other in the centre, they forced the nucleus from its originally
central position and brought about its early division. _Actinelius_ is also
of all Radiolaria the form which, next to _Actissa_, most nearly approaches
the Heliozoa. If the stiff axial threads of _Actinosphærium_ be conceived
of as partially converted into acanthin spines, and its nucleated medullary
substance as separated from the alveolar cortical layer by a membrane
(central capsule), then _Actinelius_ would be produced.


{cxiii}171. _Hypothetical Genealogical Tree of the Acantharia_:--

                                Diploconida
                                     |
                                     |
    Phractopeltida              Hexalaspida             Cenocapsida
         |                           |                       |
         |          Phatnaspida      |     Lychnaspida       |
         |               |           |          |            |
         |               |           |          |       Porocapsida
         |               |      Coleaspida      |            |
         |               |           |          |            |
         |  Ceriaspida   +-----+-----+          |            |
         |     |               |                |            |
         +--+--+               |                |            |
            |             Belonaspida           |            |
            |                  |                |            |
       Phractaspida            |           Stauraspida       |
            |                  |                |            |
            |                  |                |       Astrocapsida
            |                  |                |       Sphærocapsida
            +-------+----------+          ------+------      |
                    |                           |            |
                Diporaspida                Tessaraspida      |
            (Dorataspida dipora)     (Dorataspida tetrapora) |
                 |        |                 |          |     |
                 |        +--------+--------+          |     |
                 |                 |                   |     |
                 |           [Dorataspida]             |     |
                 |                                     |     |
                 |                                     |     |
                 |                Quadrilonchida       |     |
                 |                     |               |     |
          Phractacanthida              |      Stauracanthida |
                 |                     |               |     |
                 |    Amphilonchida    |               +--+--+
                 |         |           |                  |
                 |         |           |              Acanthonia
                 |         |           |                  |
                 +---------+--------+--+------------------+
                                    |
                              Astrolonchida
                                    |
             Litholophida           |              Chiastolida
                  |                 |                   |
                  |           Zygacanthida              |
                  |            Acanthonida         Actinastrum
                  |           Acanthometron             |
  Astrolophida    |                 |                   |  Acanthochiasmida
       |          |                 |                   |         |
       |          |                 |                   |   Acanthometron
       |          |                 |                   |         |
       +----------+-----------------+-------------------+---------+
                                    |
                                Actinelida
                                Actinelius
                                    |
                                    |
                                 Actissa


{cxiv}172. _Adelacantha and Icosacantha._--The numerous forms of
ACANTHARIA, here disposed in twelve families and sixty-five genera, may be
divided phylogenetically into two main groups of very different
extent--_Adelacantha_ and _Icosacantha_. The more primitive group,
_Adelacantha_, have an indefinite and variable number of radial spines,
which are always quite simple in form and usually irregularly distributed;
this main division includes only the one order #Actinelida#, with six
genera, among which is _Actinelius_, the common stem-form of all the
ACANTHARIA. The more recent group, Icosacantha, includes all the other
ACANTHARIA (fifty-nine genera), and is very markedly distinguished from the
Adelacantha by the fact that the radial spines are always twenty in number,
and arranged according to Müller's law (compare pp. 717-725, and § 110).
Since this regular disposition (in five alternating zones each of four
spines) has been retained by inheritance in the whole of the Icosacantha,
it is probable that this large group has been developed monophyletically
from a twig of the Adelacantha; _Actinastrum_ (p. 732) and _Chiastolus_ (p.
738) still present connecting links between the former and the latter,
between _Actinelius_ and _Acanthometron_.


173. _Acanthonida and Acanthophracta._--The extensive main division
Icosacantha (§ 110), which embraces all ACANTHARIA with twenty radial
spines, disposed according to Müller's law, may be subdivided into two
large groups or orders:--the #Acanthonida# (p. 740, Pls. 130-132) and the
#Acanthophracta# (p. 791, Pls. 133-140). The latter possess a complete
extracapsular lattice-shell, which the former have not. The more recent
#Acanthophracta# may be derived phylogenetically from the more primitive
#Acanthonida# simply by the development of this lattice-shell, with which
process are usually (perhaps always) connected certain alterations in the
malacoma, _e.g._, degeneration of the myophriscs (§ 96). The most primitive
form of all Icosacantha is the genus _Acanthometron_ (p. 324), in which all
the twenty acanthin spines are of the simplest constitution and of equal
dimensions.


174. _Differentiation of the Acanthonida._--The order #Acanthonida#, which
embraces all Icosacantha which have no complete lattice-shell, divides
early into three main branches, the three families Astrolonchida,
Quadrilonchida, and Amphilonchida (p. 727, Pls. 130-132). The first of
these constitutes the common stem-group from which the other two as well as
the whole group #Acanthophracta# have been developed; the common stem-form
of all is _Acanthometron_ (§ 173). All the Astrolonchida (p. 740, Pl. 130)
have twenty radial spines of equal size and similar form. On the other
hand, in the Quadrilonchida (p. 766, Pl. 131) the four equatorial spines
differ from the others in size and sometimes also in form. In the
Amphilonchida (p. 781, Pl. 132) two opposite equatorial spines (lying in
the hydrotomical axis) are much larger than the other eighteen and of a
different shape. Of the three families of the #Acanthonida# the most
important is the primitive group Astrolonchida, for from this the various
stem-forms of the #Acanthophracta# arise. They are subdivided according to
the formation of the spines into three subfamilies: the Zygacanthida, with
simple spines without apophyses (or transverse processes); the
Phractacanthida, with two opposite apophyses on each radial {cxv}spine, and
the Stauracanthida, with four crossed apophyses on each radial spine. The
three genera of the Zygacanthida represent the stem-forms of the three
families, since the radial spines in _Acanthometron_ (the most primitive
form of #Acanthonida#) are cylindrical, in _Zygacantha_ two-edged, and in
_Acanthonia_ four-edged (p. 741).


175. _Capsophracta and Cladophracta._--The extensive order
#Acanthophracta#, which embraces all ACANTHARIA with a complete
lattice-shell, is polyphyletic, its main subdivisions have been developed
independently from different branches of the #Acanthonida#. The whole order
may be divided directly into two main groups, the #Capsophracta# and
#Cladophracta# (p. 793), which differ in the structure and the origin of
their lattice-shell. The group (or suborder) #Capsophracta# includes only
the single family Sphærocapsida (p. 795, Pl. 133, figs. 7-11; Pl. 135,
figs. 6-10); the lattice-shell arises independently of the twenty radial
spines, being made up like a pavement of innumerable small acanthin plates,
united by a kind of cement; each plate being perforated by a fine pore. In
addition twenty larger main pores (or groups of four pores each) are
present, corresponding to the twenty radial spines; these are always equal,
quadrangular prismatic, without transverse processes as in _Acanthonia_. In
the #Cladophracta#, which include the five remaining families of the
#Acanthophracta#, the structure and origin of the lattice-shell are quite
different; the lattice-shell is here made up of the branches of the
transverse processes, which radiate tangentially from the twenty radial
spines and are only united secondarily.


176. _Ascent of the Dorataspida._--The group #Cladophracta#, or those
ACANTHARIA whose lattice-shell arises by the union of transverse
processes of the twenty radial spines, includes five different
families, whose stem-group is the family Dorataspida, with a simple
spherical lattice-shell. This family itself is, however, diphyletic in
origin, being composed of two essentially and originally different
subfamilies--Diporaspida and Tessaraspida (p. 803). The Diporaspida (p.
808, Pls. 137, 138) have been developed from the Phractacanthida, and as
each radial spine of the latter bears two opposite apophyses, so the
lattice-shell of the former has forty primary aspinal pores (two on the
base of each spine). On the other hand, the Tessaraspida (p. 830, Pls. 135,
136) have been developed from the Stauracanthida, and as each radial spine
of the latter bears four crossed apophyses, so the lattice-shell of the
former has eighty primary aspinal pores (four at the base of each spine).


177. _Descent of the Diporaspida._--Whilst the Tessaraspida (§ 176) have
given rise to no new groups which could take rank as independent families,
no less than four separate families of ACANTHARIA have arisen from the
Diporaspida. The Phractopeltida (Pl. 133, figs. 1-6) are distinguished from
all other ACANTHARIA by the possession of two concentric spherical
lattice-shells, and have probably been developed from the {cxvi}Diporaspida
in the same way as the Dyosphærida from the Monosphærida among the
#Sphæroidea#; in that case the smaller inner lattice-sphere (medullary
shell) would be the primary, and the larger outer sphere (cortical shell)
the secondary; this latter shows forty primary aspinal pores like those of
the Diporaspida. The possibility is not excluded, however, that the small
inner lattice-sphere of the Phractopeltida is a secondary product. The
three remaining families, which must be regarded as descendants of the
Diporaspida, form together a single phylogenetic series, and are separated
from the primitive group mainly by the fact that the original spherical
form of the lattice-shell has been modified into one distinguished by an
elongated equatorial axis (the hydrotomical axis); hence the #Prunophracta#
(pp. 794-859). The ellipsoidal Belonaspida have arisen directly by
hypertrophy of the two opposite equatorial spines of this hydrotomical axis
(p. 859, Pl. 136, figs. 6-9; Pl. 139, figs. 8, 9; perhaps they have also
arisen directly from the Amphilonchida). In the lentelliptical Hexalaspida
(Pl. 139) all six spines which lie in the hydrotomical meridian plane (two
equatorial and four polar) are very strongly developed, the remaining
fourteen being rudimentary. Finally, in the Diploconida the two conical
sheaths of the two opposite hydrotomical equatorial spines are so
predominant that they take the chief part in the formation of the
hour-glass-shaped shell.


178. _Phylogeny of the Nassellaria._--The legion NASSELLARIA or MONOPYLEA
is so clearly characterised by the peculiar porochora, which closes the
osculum at the oral pole of the monaxon central capsule, and by the
podoconus connected with it, that there can be no doubt that
phylogenetically it represents an independent stem (§ 8). This stem is only
connected at its base by means of _Cystidium_ and _Nassella_ with _Actissa_
and _Thalassicolla_, the stem-forms of the SPUMELLARIA. This stem is
monophyletic, inasmuch as all its members may be derived without violence
from the skeletonless Nassellida (_Nassella_, _Cystidium_, p. 896, Pl. 91,
fig. 1).


179. _Origin of the Nassellaria._--The Nassellida (p. 896), which may
naturally be considered as the common stem-group of the NASSELLARIA, are
most nearly related among other Radiolaria to the Thalassicollida, and in
both these skeletonless families the simplest forms, _Cystidium_ and
_Actissa_ correspond; on the other hand, those which have arisen from them
by the formation of alveoles in the calymma (_Nassella_ and
_Thalassicolla_) also correspond. The origin of the simplest Nassellida
from these primitive Thalassicollida may be explained by supposing that the
numerous (formerly evenly distributed) pores of the capsule membrane became
obliterated in the upper (apical) half of the central capsule, whilst in
the lower (basal) half they became correspondingly more strongly developed;
hence the porochora was formed at the oral pole of the vertical main axis,
and a differentiation of the endoplasm proceeding from this gave rise to
the characteristic podoconus. Both these organs still at present exhibit
very various degrees of progressive development.


{cxvii}180. _Hypothetical Genealogical Tree of the Nassellaria._

                               CYRTOIDEA.
                         ~~~~~~~~~~~~~~~~~~~~~~~~~
             BOTRYODEA        _Triradiata_
           ~~~~~~~~~~~~~
            Pylobotryida       Podocampida
                 |                  |
                 |   _Eradiata_     |    _Multiradiata_       SPYROIDEA
                 |        |         |                     ~~~~~~~~~~~~~~~~~
                 |   Lithocampida   |     Phormocampida   Androspyrida
                 |        |         |            |            |
            Lithobotryida |     Podocyrtida      |            |
                 |        |         |            |            |
                 |    Theocyrtida   |      Phormocyrtida      |
      Tholospyrida
                 |        |         |            |            |        |
            Cannobotryida | Tripocyrtida         |      Phormospyrida  |
                 |        |         |            |            |        |
                 |   Sethocyrtida   |       Anthocyrtida      |        |
                 |        |         |            |            |        |
                 |        |    Tripocalpida      |            |        |
                 |        |         |            |            |        |
                 |   Cyrtocalpida   |       Phænocalpida      +---+----+
                 |        |         |            |                |
  STEPHOIDEA     |        +---------+------------+           Zygospyrida
  ~~~~~~~~~~~~   |                  |                 (Spyroidea
      triradiata)
       Tympanida |             Tripocalpida                       |
           |     |    (Cyrtoidea triradiata monocyrtida)          |
           |     |                  |                             |
  Coronida |     +------------------+-----------------------------+
    |      |                        |
    |   Semantida                   |
    |      |                        |
    +--+---+                   Cyrtellaria
       |                            |
       |      Cortiniscus           |
       |            |               |
  Stephanida        |               |
       |            |               |
       +-----+------+               |
             |                      |
           Cortina  *---------  Cortinida          (PLECTELLARIA)
                                (Cortina)
                                    |
             Plectaniscus ---- Plagoniscus   ---- }
                                    |             }
             Tetraplecta  ---- Tetraplagia   ---- }  PLECTOIDEA
                                    |             }  Plectanida
             Plectophora  ----  Plagiacantha ---- }      |
                                    |             }      |
             Triplecta    ----  Triplagia    ---- }  Plagonida
                                    |             }
                                Nassoidea
                               (Nassellida)
                                    |
                                Nassella
                               (Cystidium)
                                    |
                                 Actissa


{cxviii}181. _Plectellaria and Cyrtellaria._--The extensive legion
NASSELLARIA far surpasses the other three legions in the endless variety of
its skeletal structures, and owing to the complicated relationships of its
numerous families presents no lack of difficult phylogenetic problems. All
NASSELLARIA may be divided first into two main groups or sublegions,
#Plectellaria# and #Cyrtellaria#; the latter having a complete
lattice-shell, the former not. Probably the #Cyrtellaria# have been
polyphyletically developed from several different groups of #Plectellaria#.
These groups are, however, connected in such manifold ways that a
monophyletic origin of all the NASSELLARIAN skeletons from one original
element is possible. Such a primitive element may have been furnished by
any one of three different skeletal parts, the sagittal ring, the basal
tripod, and the latticed cephalis (compare pp. 891-895, Bütschli, L. N. 40,
41).


182. _Phylogenetic Skeletal Elements of the Nassellaria._--The multiform
skeleton of the NASSELLARIA may be referred in different ways to one of the
three above-mentioned structural elements. Each of these (p. 891) may by
itself form the skeleton; the sagittal ring in the simplest #Stephoidea#
(_Archicircus_, _Lithocircus_), the basal tripod in the simplest
#Plectoidea# (_Triplagia_, _Plagiacantha_), the latticed cephalis in the
simplest #Cyrtoidea# (_Cyrtocalpis_, _Archicapsa_). In the great majority
of the NASSELLARIA, however, two of these elements, or even all three, are
found combined. In most #Cyrtellaria#, more especially, both the sagittal
ring and the basal tripod may be recognised in the lattice-shell, though
often only in slight rudiments or scarcely perceptible traces. In the
#Plectellaria# also (which possess no latticed cephalis) there are
individual genera with complete development both of the sagittal ring and
basal tripod; this important combination is especially well represented in
the Cortinida (_Cortina_, _Cortiniscus_, _Stephanium_, _Stephaniscus_,
_Tripocoronis_, &c.). The greatest difficulty as regards the phylogeny of
the NASSELLARIA lies in the fact that the most various combinations of the
three elements are presented by closely related or very similar forms. If,
in spite of this, a monophyletic hypothesis as to the origin of the
NASSELLARIA seems essential all sides of the three possible hypotheses must
receive full consideration and critical comparison (§§ 183-191).


183. _Ascent of the Nassellaria from the Plectoidea._--The monophyletic
hypothesis (No. 2, p. 893) which regards the basal tripod as the common
origin of the skeleton of all NASSELLARIA, starts from the simplest forms
of the #Plectoidea# (_Triplagia_, _Plagoniscus_, _Triplecta_,
_Plectaniscus_, &c., Pl. 91). All #Plectoidea# may be immediately derived
as diverging twigs of these, as well as all triradial and multiradial forms
of #Cyrtoidea# and #Spyroidea#; for in all these cases the distinctive
triradial (or the derived multiradial) form of skeleton appears directly
derivable from the simple basal tripod of the former. The same is perhaps
also true of many #Botryodea#. {cxix}Furthermore, certain important forms
of #Stephoidea# (_Cortina_, _Cortiniscus_, _Stephanium_, _Stephaniscus_,
&c.), which have a characteristic combination of the sagittal ring and
basal tripod, may be immediately derived from such forms of #Plectoidea# as
_Plagoniscus cortinaris_, _Plagiocarpa procortina_, _Plectaniscus
cortiniscus_, &c. On the contrary, those #Stephoidea# and #Cyrtoidea# in
which the basal tripod is wanting can only be derived from the #Plectoidea#
by the assumption that this structure has disappeared in consequence of
phylogenetic degeneration. The monophyletic derivation of the NASSELLARIA
from the #Plectoidea# has more internal probability than that from the
#Stephoidea#, since it is easier to suppose that the Cortinida (_Cortina_,
_Stephanium_, &c.) have been derived from the #Plectoidea# (_Plagoniscus_,
_Plagiocarpa_) than the converse. This view is the basis of the
hypothetical tree shown in § 180.


184. _Ascent of the Nassellaria from the Stephoidea._--The monophyletic
hypothesis (No. 1, p. 893) which regards the primary sagittal ring as the
common starting point of the skeleton in all NASSELLARIA, starts from the
simplest forms of #Stephoidea# (_Archicircus_, _Lithocircus_, &c., Pl. 81).
All #Stephoidea# and #Spyroidea# may be immediately derived from these, as
also the majority of the #Cyrtoidea# and probably of the #Botryodea#. Those
numerous forms of the last two groups, however, which possess no trace of a
sagittal ring, can only be derived from the former by the supposition that
the latter has completely disappeared in in consequence of gradual
phylogenetic degeneration. The same holds true also of the #Plectoidea#,
although certain forms (_e.g._, _Plagiocarpa procortina_, Pl. 91, fig. 5;
_Plectaniscus cortiniscus_, Pl. 91, fig. 9) appear to indicate the
commencing formation of the sagittal ring by the concrescence of two
branches, which approach each other from the upper part of the apical rod
and the ventral part of the basal rod. In any case, it is a fact of great
phylogenetic significance, that the primary sagittal ring in the cephalis
of the #Cyrtoidea# shows all conceivable stages of degeneration (compare
Bütschli, L. N. 40, 41, as well as the general account of and critical
comparison of the NASSELLARIA, pp. 889-895, &c.).


185. _Ascent of the Nassellaria from the Cyrtoidea._--The monophyletic
hypothesis (No. 3, p. 894) which regards the latticed cephalis as the
common point of origin of all the skeletons of the NASSELLARIA, starts from
the simplest forms of the #Cyrtoidea#, that is, from the Cyrtocalpida or
eradial Monocyrtida (_Archicorida_, _Archicapsida_, Pls. 51, 52, 98). All
#Cyrtoidea# and #Botryodea# may be regarded as divergent forms of these
monothalamous #Cyrtoidea#; the polythalamous simply by the addition of
fresh joints at the basal pole, the triradiate and multiradiate by the
development of three or more apophyses. The origin of the sagittal ring
(which presents every stage of development and degeneration in the
#Cyrtoidea#) may be regarded as a mechanical thickening of the latticed
plate in the sagittal circumference of the cephalis. By stronger
{cxx}development of this ring and coincident sagittal constriction of the
cephalis the order #Spyroidea# may be derived from the #Cyrtoidea#.  On the
other hand, the #Plectellaria#, which possess no cephalis, and indeed no
complete lattice-shell whatever, may be derived from the Monocyrtida by the
assumption of a degeneration of this structure; the sagittal ring having
been preserved in the #Stephoidea#, and the tripod of the Tripocalpida in
the #Plectoidea#. Although such a monophyletic derivation of the
NASSELLARIA from the Cyrtocalpida is possible, and though here, too, the
Cortinida play an important part as connecting links, this hypothesis has
less internal probability than that of the derivation from the #Stephoidea#
(§ 184) or #Plectoidea# (§ 183).


186. _Genealogical Tree of the Plectoidea._--The order #Plectoidea#
includes those NASSELLARIA whose rudimentary skeleton does not contain the
characteristic sagittal ring of the #Stephoidea#, but consists of several
(at least three) radial spines, which proceed from a point in the centre of
the porochora. The branches of these radial spines remain free in the
Plagonida, whilst in the Plectanida they unite with each other to form a
loose meshwork (not, however, a complete lattice-shell). The number and
arrangement of the radial spines, which serve for generic distinctions, are
the same in both families, so that each genus of the Plectanida has arisen
from a corresponding genus of the Plagonida. The simplest Plagonida, which
possess a basal tripod (_Triplagia_ or _Plagiacantha_ with three rays,
_Tetraplagia_ with four rays) are probably to be regarded as forming the
common origin of the whole order. These agree with certain three- and
four-rayed skeletal pieces of the #Beloidea# (Thalassosphærida and
Sphærozoida); and also the four and six-rayed twinned pieces of the latter
(spicula bigemina and trigemina) repeat in the same fashion the skeleton of
the former (_Plagonidium_, _Plagonium_). This similarity, however, is a
mere analogy and possesses no phylogenetic significance. On the other hand,
certain Plagonida (_Plagoniscus_, _Plagiocarpa_), and the corresponding
genera of Plectanida (_Plectaniscus_, _Periplecta_) seem to have important
phylogenetic relations to certain #Stephoidea# (_Cortina_, _Cortiniscus_,
&c.); the sagittal ring of the latter having perhaps arisen by the vertical
apical spine of the former having been connected with their horizontal
basal rod by two ventral apophyses growing out opposite to each other
(compare pp. 902, 914, _Plagiocarpa procortina_, Pl. 91, fig. 5). In this
case the Plectanida would belong to the simplest stem-forms of the
NASSELLARIA.


187. _Genealogical Tree of the Stephoidea._--The order #Stephoidea#
includes all those NASSELLARIA whose skeleton does not form a complete
lattice-shell, but consists of one or more rings, and often of a loose
meshwork which arises by the union of branches of the rings. A _vertical
sagittal ring_ is constantly present, embracing the central capsule in the
median sagittal plane, and forming at its basal pole various processes, the
starting point for other skeletal forms. The most important of these is the
tripodal _Cortina_ {cxxi}(p. 950, § 182). The Stephanida are the most
archaic family among the #Stephoidea# (p. 937, Pl. 81), perhaps indeed
among all the NASSELLARIA (§ 184); in them the sagittal ring and its
processes alone constitute the skeleton; secondary rings and meshes are
wanting. Two diverging families, the Semantida and Coronida, have been
developed from the Stephanida, and from one of them the family Tympanida
has arisen.

  The Semantida (p. 953, Pl. 92) develop a horizontal basal ring at the
  oral side of the vertical sagittal ring; the basal meshes or lattice
  gates, which remain between the former and the latter, are the important
  cortinar pores (one pair jugular, one pair cardinal, p. 954); they
  usually appear inherited in the cortinar septum of the #Cyrtellaria#. In
  the Coronida (p. 967, Pls. 82, 94) a second vertical ring (the frontal
  ring) appears in addition to the sagittal ring; it lies in the frontal
  plane at right angles to the latter. Finally the Tympanida (p. 987, Pls.
  93, 94) have probably arisen from the Semantida by the formation of a
  second horizontal ring (mitral ring) parallel to the basal and attached
  to the upper portion of the sagittal ring.


188. _Genealogical Tree of the Spyroidea._--The extensive order #Spyroidea#
is of especial interest in connection with the phylogeny of the
NASSELLARIA, since all its members show two well-developed skeletal
elements in combination, the sagittal ring of the #Stephoidea# and the
latticed cephalis of the #Cyrtoidea#; the majority possess also the basal
tripod of the #Plectoidea# (or a radial skeleton derived from it). Hence
there is a possibility of deriving the stem-forms of the #Spyroidea# from
each of these three groups. The four families of this order exhibit similar
relationships to those of the four families of #Cyrtoidea#; the common
stem-group is the family Zygospyrida; from this the Tholospyrida have
arisen by the development of a galea on the apical pole, the Phormospyrida
by the addition of a thorax on the basal pole. The Androspyrida may be
derived either from the Tholospyrida by the formation of a basal thorax, or
from the Phormospyrida by the development of an apical galea. Some groups,
however, such as the peculiar Nephrospyrida (Pl. 90) have probably been
developed directly from the #Stephoidea#.


189. _Genealogical Tree of the Botryodea._--The peculiar order #Botryodea#
(p. 1103), which is both difficult to investigate and insufficiently known,
presents great phylogenetic difficulties both as to its ascent and descent.
Probably the different genera of this order have been polyphyletically
developed from different groups of #Cyrtoidea# (perhaps also to some extent
of #Spyroidea#) by the formation of lobes in the cephalis. The three
families of #Botryodea# are related to each other in the same way as are
the three first families of the #Cyrtoidea#. From the single-jointed
Cannobotryida (corresponding to the Monocyrtida), the two-jointed
Lithobotryida (corresponding to the Dicyrtida), may be derived by the
development of a basal thorax, and from the latter the three-jointed
Pylobotryida (like the Tricyrtida) by the addition of an abdomen. In the
last two families the forms with an open basal mouth {cxxii}(Botryopylida
and Botryocyrtida) are to be regarded as primitive: the Botryocellida and
Botryocampida have arisen by the closure of this mouth with a basal
lattice-plate.


190. _Genealogical Tree of the Cyrtoidea._--The multiform and extensive
group #Cyrtoidea# presents the greatest difficulties to be found in the
phylogeny of the NASSELLARIA, because their morphological relations are
most complicated, and because similar forms very often appear to be of
quite different origin. The great majority of the #Cyrtoidea# show more or
less clearly a combination of the three structural elements: sagittal ring,
basal tripod, and latticed cephalis (p. 891). There are also, however,
numerous #Cyrtoidea#, whose skeleton no longer shows any trace of the
sagittal ring. Many of these show as the basis of the skeleton a strong
basal tripod with an apical spine, around which the cephalis has obviously
been secondarily developed, _e.g._, the remarkable Euscenida (p. 1146, Pls.
53, 97) and the interesting Callimitrida (p. 1217, Pls. 63, 64). These may
have been derived immediately from the #Plectoidea# without any relation to
the #Stephoidea#. There are also numerous true Monocyrtida, whose shell
consists of a simple latticed cephalis without a trace of the sagittal ring
or basal tripod (Cyrtocalpida, Pl. 51, figs. 9-13; Pl. 98, fig. 13); these
may have been developed directly from the skeletonless Nassellida by the
formation of a simple ovoid _Gromia_-like shell, and may have no relation
either to the #Stephoidea# or #Plectoidea#. On these grounds, as well as
from the complicated relationships of the many smaller groups of
#Cyrtoidea#, it is probable that the whole order has been developed
polyphyletically from different divisions of the #Plectellaria#.


191. _Systematic Arrangement of the Cyrtoidea._--Although for the reasons
just given no systematic arrangement of the #Cyrtoidea# can at present, or
for a long time in the future, be regarded as other than artificial, yet
some general principles of classification for this extensive group can be
laid down, which may serve as starting points for some future natural
disposition. This is especially true of the relations which in an
artificial system (p. 1129) were primarily utilised for the distinction of
twelve families and twenty-four subfamilies; the number of segments in the
shell, the number of radial apophyses (and parameres), and the constitution
of the basal aperture of the shell.

  As regards the _number of segments_, separated by transverse
  constrictions, of which the shell is composed, it is dependent upon the
  secondary addition of new joints at the basal pole of the main axis.
  Hence all many-jointed #Cyrtoidea# are to be derived from single-jointed
  ones, and the four sections thus distinguished (Monocyrtida, Dicyrtida,
  Tricyrtida, Stichocyrtida) form a phylogenetic series. Very often,
  however, the primary cephalis disappears owing to retrograde
  metamorphosis; and in such cases the single joint of the apparent
  Monocyrtida is formed of the thorax (_e.g._, {cxxiii}Pls. 52, 54, &c.).
  As regards the _number of radial apophyses_, three sections of
  #Cyrtoidea# may be distinguished;  the Pilocyrtida with three, the
  Astrocyrtida with numerous apophyses, and the Corocyrtida with none (p.
  1129). The last two may in general be regarded as two divergent branches
  from the first, for the eradiate Corocyrtida have probably been formed
  from the triradial Pilocyrtida by entire loss of the radial apophyses,
  whilst on the other hand the multiradiate Astrocyrtida have arisen from
  them by additions to the primary apophyses (interpolation of interradial
  between the perradial ones). As regards the _constitution of the
  shell-aperture_, the #Cyrtoidea# may be divided into Cyrtaperta and
  Cyrtoclausa (p. 1129); in general the Cyrtoclausa (with latticed
  shell-aperture) have arisen from the Cyrtaperta (with simple open mouth);
  in many Monocyrtida the converse may be supposed, the  simple basal mouth
  having been formed by degeneration of a basal lattice.


192. _Phylogeny of the Phæodaria._--The legion PHÆODARIA or CANNOPYLEA is
so clearly marked off from other Radiolaria by the double membrane of the
central capsule and the astropyle at its oral pole, as well as by the
extracapsular phæodium, that it must be regarded phylogenetically as an
independent stem (§ 9). This stem is only connected at its root by
_Phæodina_ with the stem-form of the SPUMELLARIA, _Actissa_. The stem
itself is monophyletic, inasmuch it its members may be derived without
violence from the skeletonless Phæodinida (_Phæodina_, _Phæocolla_). On the
other hand, the formation of the skeleton of the PHÆODARIA is undoubtedly
polyphyletic, different Phæodinida having independently commenced the
formation of a skeleton and having carried it out in very different ways.


193. _Origin of the Phæodaria._--The Phæodinida (p. 1544, Pl. 101), which
may naturally be regarded as the common stem-group of the PHÆODARIA, have
their nearest relations among other Radiolaria in the Thalassicollida (p.
10); and since this family is to be regarded as the primitive group of all
Radiolaria, they may be directly derived from them phylogenetically. The
essential modifications by which the primitive Phæodinida have arisen from
the more archaic Thalassicollida are of three kinds; (1) the doubling of
the membrane of the central capsule; (2) the reduction of the numerous fine
pores in the membrane and the formation of an osculum, and of an astropyle
closing it, at the oral pole of the main axis; (3) the production of an
extracapsular phæodium.  This last may, perhaps, be regarded as a
unilateral hypertrophy of the voluminous pigment masses which are deposited
in the sarcomatrix of certain Thalassicollida. Of the two genera of
Phæodinida hitherto known, probably _Phæodina_ (Pl. 101, fig. 2) approaches
the original stem of the PHÆODARIA more nearly than _Phæocolla_ (Pl. 101,
fig. 1), for the latter exhibits only the large main opening of the central
capsule (astropyle), whilst the former possesses also a pair of accessory
openings (parapylæ). The hypothetical stem-form (_Phæometra_) presumably
had a larger number of small parapylæ (like many Circoporida and
Tuscarorida), and the astropyle was probably but little differentiated from
them.


{cxxiv}194. _Hypothetical Genealogical tree of the Phæodaria:_--

                             PHÆOCONCHIA
                         ~~~~~~~~~~~~~~~~~~~~
        PHÆOSPHÆRIA        Coeloplegmida           PHÆOGROMIA
     ~~~~~~~~~~~~~~~~~~~        |                ~~~~~~~~~~~~~~~~~~
  Aularida                      |                Tuscarorida
     |                          |                   |
     |Aulonida                  |  Coelodrymida     |
     |   |                      |        |          |
     +---+                Coelotholida   |          |
       |                  Coelographida  |          |   Haeckelinida
       |                        |        |          |           |
       |            Conchopsida |  Coelodorida      |           |
  Aulosphærida           |      | Coelodendrida     |Circogonida|
       |                 |      +----+---+          |     |     |
       |            Conchasmida      |              |     |     |
       |             Concharida      |              |     |     |
       |   Sagmarida     +-----------+              |     +--+--+
       |        |                |                  |        |
  Cannosphærida |                |Castanellida      |  Circoporida
       |        |                |     |            |        |
       |        |Oroscenida  Concharida|            +------+-+
       |        |     |          |     |                   |
       |    Sagenida  |          |     |                   |
       | Sagophærida  |          |     |Gazellettida       |
       |        |     |          |     |     |             |
       |        |  Oronida       |     |     |Pharyngellida|
       |        |Orosphærida     |     |     |      |      |
       |        |     |          |     |     |      |      |
       +--------+-----+          |     |     |      |      |
                |                |     |     |      |      |
                +--------------+-+     |     |      |      |
                               |       |Euphysettida|      |
                               |       |Medusettida |      |
                               |       |     |      |      |
                               |       |     |Lithogromida |
                               |       |     |Challengerida|
                           Phæodinida  |     |      |      |
                               |       |     |      |      |
            PHÆOCYSTINA        |       +-----+-+----+      |
       ~~~~~~~~~~~~~~~~~~~~    |               |           |
   Aulacanthida                |               |           |
       |Cannobelida Catinulida |               +------+----+
       |    |             |    |                      |
       |    | Dictyochida |    |                      |
       |    |     |       |    |                      |
       |    +-----+-------+    |                      |
       |          |            |                  Phæodinida
       |    Cannorrhaphida     |       Phæodinida     |
       |          |            |           |          |
       +----------+------------+----+------+----------+
                                    |
                                 Phæodina
                                    |
                               (Phæometra)
                                    |
                                 Actissa


{cxxv}195. _Phæocystina and Phæocoscina._--Whilst the malacoma of all
PHÆODARIA possesses the characteristics of the legion, and hence justifies
the assumption of a monophyletic origin, the skeleton, on the other hand,
shows in the different groups such manifold and fundamental variations that
a polyphyletic origin of the latter is indubitable. Different Phæodinida
have commenced the formation of the skeleton independently, and it has
progressed in different directions. In the #Phæocystina# it remained
incomplete and led to the formation of various Beloid skeletons, whilst the
#Phæocoscina# developed complete lattice-shells. Both of these divisions
too are to be regarded as polyphyletic, since the skeletal forms of the
different groups cannot be derived without violence from a common primitive
form.


196. _Phæocystina with a Beloid Skeleton._--The order #Phæocystina#
includes all PHÆODARIA which have no complete lattice-shell; it contains,
firstly, the skeletonless Phæodinida (the common stem-group of the legion),
and secondly, the Phæacanthida, or PHÆODARIA with a Beloid skeleton (§
115). The latter are divisible into several very different groups (at least
two or three) which are probably different in origin. The Aulacanthida
(Pls. 102-105) form radial tubes which perforate the calymma, their
proximal end resting upon the surface of the central capsule, whilst the
distal extremity projects freely outwards. The skeleton of the
Cannorrhaphida, on the other hand, is composed of many separate portions
which are never radially arranged but are either placed tangentially to the
surface of the calymma or scattered irregularly in its gelatinous mass.
Furthermore, in the three subfamilies of which this family is composed, the
individual skeletal portions are so different that they have probably
arisen independently of each other; in the Cannobelida they form
cylindrical tangential tubes (Pl. 101, figs. 3-5), in the Catinulida flat
basin or cap-like structures (Pl. 117, fig. 8), in the Dictyochida hollow
rings, from which small pyramids are developed by unilateral formation of
lattice-work (Pl. 101, figs. 9-14; Pl. 114, figs. 7-12).


197. _Phæosphæria with a Sphæroid Skeleton._--The order #Phæosphæria#
includes those PHÆODARIA which possess a spherical (sometimes slightly
modified) lattice-shell without the characteristic aperture of the
#Phæogromia#. They have probably arisen independently of these, though they
may have been derived from the Castanellida by loss of the shell-aperture,
which was present originally. The four families which we have distinguished
among the #Phæosphæria#, are so different in the structure of their
lattice-shell that their phylogenetic connection is doubtful. In the
Orosphærida (Pls. 106, 107) and the Sagosphærida (Pl. 108) the whole
lattice-shell consists of a single piece and is unjointed (without astral
septa); in the former it is very firm and massive, with thick laminated
trabeculæ and polygonal meshes; in the latter it is very delicate and
brittle, with filiform trabeculæ and large {cxxvi}triangular meshes.  On
the other hand, the voluminous shell of the Aulosphærida (Pls. 109-111),
and of the Cannosphærida (Pl. 112), is characterised by a very peculiar
system of joints; it is composed of numerous separate cylindrical tubes,
which are placed tangentially and united at the nodes by stellate
partitions or astral septa. The Cannosphærida possess further a simple
central Cyrtoid shell, connected with the outer jointed shell by hollow
radial trabeculæ. Since many Aulosphærida possess rudiments of such
centripetal trabeculæ it is possible that these latter have been derived
from the former by the loss of the central Cyrtoid shell; the formation of
this monaxon shell perhaps indicates descent from the #Phæogromia#
(Castanellida).


198. _Phæogromia with a Cyrtoid Skeleton._--That order of the PHÆODARIA
which we designate #Phæogromia#, contains many very different forms, all
agreeing in the possession of a Cyrtoid skeleton, or a monaxon
lattice-shell, which has a large aperture at one pole of its vertical main
axis (§ 123). This Cyrtoid skeleton is sometimes ovoid or conical,
sometimes lentiform or helmet-shaped, sometimes polyhedral or almost
spherical. Although the principle of its structure is simple and often like
that of the Monocyrtida among the NASSELLARIA, yet the structure of the
wall and of the apophyses is so different in the various groups of the
#Phæogromia#, that the order is probably polyphyletic, and its Cyrtoid
shells have arisen independently of each other. Only in the Castanellida
(Pl. 113) does the shell-wall usually consist of simple lattice-work; in
the Challengerida, on the other hand (Pl. 99), it has an extremely fine
Diatom-like structure; in the Medusettida (Pls. 118-128) a peculiar
alveolar structure, and in the Circoporida (Pls. 114-117) and Tuscarorida
(Pl. 100) it possesses a characteristic porcellanous constitution (with
tangential spicules in a porous cement-mass); in the latter of these groups
the surface is smooth, in the former peculiarly tabulate; the two families
have also different stem-forms.


199. _Phæoconchia with a Conchoid Shell._--The order #Phæoconchia# (Pls.
121-128) is separated not only from all other PHÆODARIA, but also from all
other Radiolaria, by the possession of a bivalved shell resembling that of
a Lamellibranch; the two valves of this Conchoid skeleton are to be
interpreted as dorsal and ventral (§ 128). Probably these bivalved shells
are independent products, but possibly they may have been formed by the
bisection of a simple spherical lattice-shell; in the former case the
#Phæoconchia# would be directly descended from the Phæodinida, in the
latter from the Castanellida. The three families which we have
distinguished among the #Phæoconchia#, probably constitute a connected
stem, the most primitive group of which are the Concharida (Pls. 123-125).
From these the Coelodendrida (Pls. 121, 122) have next arisen by the
formation of a "galea" upon the apex of each valve, and the growth of
hollow tubes from this helmet-like structure. Finally, the Coelographida
{cxxvii}(Pls. 120-128) have been developed from the Coelodendrida by the
formation of a basal nasal tube (rhinocanna) from each galea, and the
formation of a median or paired frenulum, which connects the opening of the
nasal tube with the apex of the galea. In the Coelodendrida, as well as in
the Coelographida, there are two different subfamilies, of which the more
primitive (Coelodorida, Coelotholida) have free branches from the hollow
radial tubes, whilst the more recent (Coelodrymida, Coeloplegmida) form an
outer bivalved shell by anastomosis of the branches of the tubes.


200. _The Fundamental Biogenetic Law._--The causal connection between
ontogeny and phylogeny, which finds its most precise statement in the
fundamental biogenetic law, holds in general for the Radiolaria as for all
other organisms. In order to furnish direct proof of this, however, a
complete empirical knowledge both of individual and of palæontological
development would be necessary. In both these directions, as has been shown
in the foregoing chapters, our knowledge of the Radiolaria is very
incomplete and fragmentary, but still we are able to convince ourselves
indirectly of the validity of the law as applied to Radiolaria by the aid
of comparative anatomy. This is now so fully known to us (§§ 1-140) that we
are able not only to draw a complete and satisfactory picture of their
morphology, but also to arrive at most important conclusions regarding the
ontogeny and phylogeny of the individual groups. As regards the formation
of the multiform skeleton of the Radiolaria, most of the ontogenetic series
of forms, with which we have become acquainted by comparative anatomy, are
of _palingenetic_ nature; that is, they are primarily due to inheritance
and thus of direct phylogenetic significance. On the other hand, among the
ontogenetic phenomena of the Radiolaria, as far as they have yet been
investigated, only very few are _cenogenetic_, that is, brought about by
adaptive modification and without direct significance as regards phylogeny.



{cxxviii}PHYSIOLOGICAL SECTION.


----


CHAPTER VII.--VEGETATIVE FUNCTIONS.

(§§ 201-217.)

201. _Mechanism of the Functions._--The vital phenomena of the Radiolaria
are dependent upon the mechanical functions of their unicellular body, and
like those of all other organisms, are to be referred to physical and
chemical natural laws. All processes which appear in the life of the
Radiolaria are, therefore, ultimately to be explained by the attraction and
repulsion of the smallest particles, which compose the different portions
of their unicellular body; and the sensation of pleasure or the opposite is
in its turn the exciting cause of these elementary movements. Many adaptive
arrangements in the Radiolarian organism may produce the appearance of
being the premeditated result of causes working towards an end
("zweckthätig," _causæ finales_), but as opposed to this deceptive
appearance it must here be expressly stated that these may be recognised in
accordance with the developmental theory as the necessary consequence of
mechanical causes (_causæ efficientes_).

  Our _physiological_ acquaintance with the Radiolaria has by no means
  progressed so far as our _morphological_, so that the incomplete
  communications which are placed here for the sake of completeness must be
  regarded merely as preliminary fragments, not as fully elaborated
  results. Since my recent investigations have been mainly in the direction
  of morphology, I can add but little to the physiological conclusions,
  which I stated at length in my monograph twenty-four years ago (L. N. 16,
  pp. 127-165). Recently the vegetative physiology of the Radiolaria has
  been much advanced by the recognition of the symbiosis with the Xanthellæ
  (§ 205, L. N. 22, 39, 42). In addition Karl Brandt has recently (1885)
  published several important contributions to the physiology of the
  Polycyttaria or Sphaerozoea (L. N. 52).


202. _Distribution of Functions._--The distribution of the functions among
the various parts of the unicellular organism of the Radiolaria corresponds
directly to their anatomical composition, so that physiologically as well
as morphologically the central capsule and the extracapsulum appear as the
two coordinated main components. On the one hand the _central capsule_ with
its endoplasm and enclosed nucleus is the central organ of the "cell-soul"
(Zellseele), the unit regulating its animal and vegetative functions, and
the special organ of reproduction and inheritance. The _extracapsulum_
forms, on the other hand, by its calymma the protective envelope of the
central {cxxix}capsule, the support of the soft pseudopodia and the
substratum of the skeleton; the calymma acts also as a hydrostatic
apparatus, whilst the radiating pseudopodia are of the greatest importance
both as organs of nutrition and adaptation, as well as of motion and
sensation (§ 15). If, however, the vital functions as a whole be divided in
accordance with the usual convention into the two great groups of
_vegetative_ (nutrition and reproduction) and _animal_ (motion and
sensation), then the central capsule would be mainly the organ of
reproduction and sensation, and the extracapsulum the organ of nutrition
and motion.

  The numerous separate vital phenomena, which by accurate physiological
  investigation may be distinguished in the unicellular Radiolarian
  organism, may be distributed in the above indicated conventional fashion
  into a few larger and several smaller groups; it must always be borne in
  mind, however, that these overlap in many respects, and that the division
  of labour among the different organs in these Protista is somewhat
  complicated, notwithstanding the apparent simplicity of their unicellular
  organization. A general classification of the groups of functions is
  difficult, because each individual organ discharges several different
  functions. Thus the central capsule is pre-eminently the organ of
  reproduction and inheritance, but not less (though less conspicuous) is
  its importance as the psychical central organ, the unit regulating the
  processes of sensation, motion, and also nutrition. In this last respect
  it is comparable to the nerve-centres of the Metazoa, whilst the
  peripheral nervous system of the latter (including the organs of sense
  and the muscles) are in the present instance represented by the
  pseudopodia, which are at the same time the most important organs of
  nutrition and adaptation. In the calymma also in similar fashion several
  different physiological functions are united.


203. _Metastasis._--The functions of metastasis and nutrition have in all
Radiolaria a purely animal character, so that these Rhizopoda from the
physiological standpoint are to be regarded as truly _unicellular animals_,
or Protozoa ("Urthiere"). Since they do not possess, like plants, the power
of forming synthetically the compounds (protoplasm, carbohydrates, &c.)
necessary for their sustenance, they are compelled to obtain them
ready-formed from other organisms. Like other true animals they evolve
carbon dioxide by the partial oxidation of those products, and hence they
successively take up the oxygen necessary to their existence from their
environment.

  The question whether the Radiolaria are to be regarded as true animals I
  discussed fully from various points of view in 1862, and finally answered
  in the affirmative (L. N. 16, pp. 159-165). Afterwards, when in my
  Generelle Morphologie (1866) I sought to establish the kingdom Protista,
  I removed the Radiolaria along with the other Rhizopoda from the animal
  kingdom proper and placed them in the kingdom Protista (Bd. i. pp.
  215-220; Bd. ii. p. xxix). Compare also my Protistenreich (L. N. 32) and
  my Natürliche Schöpfungsgeschichte (vii. Aufl., 1879, p. 364). Both these
  steps appear fully justified when considered in the light of our present
  increased knowledge. From the _physiological_ standpoint the Radiolaria
  appear as unicellular _animals_, for in this respect the animal character
  of their metastasis (that proper to an oxidising organism) furnishes the
  sole {cxxx}criterion. On the other hand, from the morphological
  standpoint, they are to be classed as neutral Protista, for in this
  respect their unicellular character is the prominent feature, and
  distinguishes them from all true multicellular animals (Metazoa). Compare
  my Gastræa Theorie (1873, Jena. Zeitschr. für Naturwiss., Bd. viii. pp.
  29, 53).


204. _Nutrition._--The nutritive materials which the Radiolaria require for
their sustenance, especially albuminates (plasma) and carbohydrates
(starch, &c.), they obtain partly from foreign organisms which they capture
and digest, and partly directly from the Xanthellæ or Philozoa, the
unicellular Algæ, with which they live in symbiosis (§ 205). _Zooxanthella
intracapsularis_, found in the ACANTHARIA (§ 76), is probably of the same
significance in this respect as _Zooxanthella extracapsularis_ of the
SPUMELLARIA and NASSELLARIA (§ 90); and perhaps the same is true also of
_Phæodella extracapsularis_ (or _Zoochlorella phæodaris_?) of the PHÆODARIA
(§ 89). The considerable quantity of starch or amyloid bodies, elaborated
by these inquiline symbiontes, as well as their protoplasm and nucleus, are
available, on their death, for the nutrition of the Radiolaria which
harbour them. Nutrition by means of other particles obtained by the
pseudopodia from the surrounding medium is by no means excluded; indeed it
may be regarded as certain that numerous Radiolaria (especially such as
contain no symbiotic Algoid cells) are nourished for the most part or
exclusively by this means. Diatoms, Infusoria, Thalamophora (Foraminifera)
as well as decaying particles of animal and vegetable tissues can be seized
directly by the pseudopodia and conveyed either to the sarcodictyum (on the
surface of the calymma) or to the sarcomatrix (on the surface of the
central capsule) in order to undergo digestion there. The indigestible
constituents (siliceous shells of Diatoms and Tintinnoidea, calcareous
shells of small Monothalamia and Polythalamia, &c.) are here collected
often in large numbers and removed by the streaming of the protoplasm.

  The inception and digestion of nutriment, as it usually appears to take
  place by the pseudopodia, has already been so fully treated in my
  Monograph (L. N. 16, pp. 135-140), and since then in my paper on the
  sarcode body of the Rhizopoda (L. N. 19, p. 342), that I have nothing of
  importance to add. Quite recently Karl Brandt has expressed a doubt as to
  whether the taking up of formed particles by the pseudopodia and their
  aggregation in the calymma be really connected with the process of
  nutrition. He is disposed rather to believe that these foreign bodies are
  usually only accidentally and mechanically brought into the calymma, and
  that the nourishment of the Radiolaria is derived exclusively or
  pre-eminently from the symbiotic Xanthellæ (L. N. 52, pp. 88-93). I must,
  however, maintain my former opinion, which I have only modified insomuch
  that I now regard the sarcodictyum (on the outer surface of the calymma,
  § 94) rather than the sarcomatrix (on the outer surface of the central
  capsule, § 92) as the principal seat of true digestion and assimilation.
  From the sarcodictyum the dissolved and assimilated nutritive matters may
  pass by the intracalymmar pseudopodia (or sarcoplegma, § 93) into the
  sarcomatrix, and hence may reach the endoplasm through the openings in
  the central capsule. To what an extent the Radiolaria are capable of
  taking up even large formed bodies into the calymma, is shown by the
  {cxxxi}striking instance of _Thalassicolla sanguinolenta_, which becomes
  so deformed by the inception of numerous coccospheres and coccoliths,
  that I described it as a special genus under the name _Myxobrachia_
  (compare pp. 23, 30; also L. N. 21, p. 519, Taf. xviii., and L. N. 33, p.
  37).


205. _Symbiosis._--Very many Radiolaria, but by no means all members of
this class, live in a definite commensal relation with yellow unicellular
Algæ of the group Xanthellæ. In the ACANTHARIA they live within the central
capsule (_Zooxanthella intracapsularis_, § 76), in the SPUMELLARIA and
NASSELLARIA, on the other hand, within the calymma but outside the central
capsule (_Zooxanthella extracapsularis_, § 90); in the PHÆODARIA a special
form of these symbiotic unicellular Algæ appears to inhabit the phæodium in
the extracapsulum, and to compose a considerable portion of the phæodellæ
(_Zooxanthella phæodaris_, § 90, or better perhaps _Zoochlorella
phæodaris_, § 89). Undoubtedly this commensal life is in very many cases of
the greatest physiological significance for both the symbiontes, for the
animal Radiolarian cells furnish the inquiline Xanthellæ not only with
shelter and protection, but also with carbon dioxide and other products of
decomposition for their nutriment; whilst on the other hand the vegetable
cells of the Xanthellæ yield the Radiolarian host its most important supply
of nutriment, protoplasm and starch, as well as oxygen for respiration.
Hence it is not only theoretically possible, but has been experimentally
proved, that Radiolaria which contain numerous Xanthellæ can exist without
extraneous nutriment for a long period in closed vessels of filtered
sea-water, kept exposed to the sunlight; the two symbiontes furnish each
other mutually with nourishment, and are physiologically supplementary to
each other by reason of the opposite nature of their metastasis. This
symbiosis is not necessary, however, for the existence of the Radiolaria;
for in many species the number of Xanthellæ is very variable and in many
others they are entirely wanting.

  The symbiosis of the Radiolaria and Xanthellæ, or "yellow cells" (§§ 76,
  90) was first discovered by Cienkowski in 1871 (L. N. 22). Ten years
  later this important and often doubted fact was established by extended
  observations and experiments almost simultaneously by Karl Brandt (L. N.
  38, 39) and Patrick Geddes (L. N. 42, 43). This commensal life may be
  compared with that of the lichens, in which an organism with vegetable
  metastasis (the Algoid gonidia) and an organism with animal metastasis
  (the Fungoid hyphæ) are intimately united for mutual benefit. But the
  symbiosis of the Xanthellæ and Radiolaria is not as in the lichens a
  phenomenon essential for their development, but has more or less the
  character of an accidental association. The number of the inquiline
  Xanthellæ is so variable even in one and the same species of Radiolaria,
  that they do not appear to be exactly essential to its welfare; and in
  many species they are entirely wanting. Their significance is
  questionable in the case of those numerous deep-sea Radiolaria which live
  in complete darkness, and in which, therefore, the Xanthellæ, even if
  present, could excrete no oxygen on account of the want of light.
  Nevertheless it is possible that the phæodellæ of the PHÆODARIA (usually
  green, olive, or brown in colour), which are true cells, represent
  vegetable symbiontes, {cxxxii}which in the absence of sunlight are able
  to evolve oxygen by the aid of the phosphoresence of other abyssal
  animals. Since the PHÆODARIA are, for the most part, dwellers in the
  deep-sea, and since the voluminous phæodium must be of great
  physiological importance, a positive solution of this hypothetical
  question would be of no small interest (compare § 89).


206. _Respiration._--The respiration of the Radiolaria is animal in nature,
since all Protista of this class, like all other true Rhizopoda, take in
oxygen and give off carbon dioxide. Probably this process goes on
continuously and is tolerably active, as may be inferred from the fact that
Radiolaria cannot be kept for long in small vessels of sea-water unless
either they contain numerous Xanthellæ or the water is well aërated. The
oxygen is obtained from two sources, either from the surrounding water or
from the enclosed Xanthellæ, which in sunlight evolve considerable
quantities of this gas. Correspondingly, the carbon dioxide which is formed
during the process of oxidation of the Radiolaria is either given up to the
surrounding water or to the inquiline Xanthellæ, which utilise it for their
own sustenance (§§ 204, 205).

  The significance of the symbiotic Xanthellæ for the respiration of the
  enclosing Radiolaria may be shown experimentally in the following way. If
  two Polycyttarian colonies of equal size, both of which contain numerous
  Xanthellæ, be placed in equal quantities of filtered sea-water in sealed
  glass tubes, and if one tube be placed in the dark the other in the
  light, the colony in the former rapidly perishes, but not that in the
  latter; the Xanthellæ excrete only under the influence of sunlight the
  oxygen necessary for the life of the Radiolarian (compare Patrick Geddes,
  L. N. 42, p. 304).


207. _Circulation._--In the protoplasm of all Radiolaria, both inside and
outside the central capsule, slow currents may be recognised which fall
under the general term circulation, and have already been compared to the
cyclosis in the interior of animal and vegetable cells, as well as to the
sarcode streams in the body of other Rhizopoda. These plasmatic currents or
"plasmorrheumata" probably continue throughout the whole life of the
Radiolaria, and are of fundamental importance for the performance of their
vital functions. They depend upon slow displacements of the molecules of
the plasma (plastidules or micellæ) and cause a uniform distribution of the
absorbed nutriment and a certain equalisation of the metastasis.
Furthermore they are of great importance also in the inception of
nutriment, the formation of the skeleton, locomotion, &c. Sometimes the
circulation is directly perceptible in the plasma itself; but usually it is
only visible owing to the presence of granules (sarcogranula), which are
suspended in the plasma in larger or smaller numbers. The movements of
these granules are usually regarded as passive, due to the active
displacement of the molecules of the plasma. Although the intracapsular
protoplasm is in communication with the extracapsular through the openings
in the capsule membrane, nevertheless the currents exhibit certain
differences {cxxxiii}in the two portions of the malacoma. It is sometimes
possible, however, to recognise the direct connection between them and to
observe how the granules pass through the openings in the capsule-membrane.


208. _Currents in the Endoplasm._--Intracapsular circulation or a certain
slow flowing of the plasma within the central capsule is probably just as
common in the Radiolaria as without it, but it is not so easy to observe in
the former case as in the latter. A more satisfactory proof of these
endoplasmatic currents is furnished by the arrangement of the protoplasm
within the central capsule, since this is (at all events in part) an effect
produced by them. In this respect the two main divisions of the class show
characteristic differences. In the Porulosa (the SPUMELLARIA, § 77, and the
ACANTHARIA, § 78) the endoplasm is in general distinguished by a more or
less distinct radial structure, which is to be regarded as the effect of
alternating centripetal and centrifugal radial streams. In the Osculosa, on
the other hand, this radial structure is absent and the intracapsular
plasmatic streams converge or diverge towards the osculum or main-opening
in the central capsule which lies at the basal pole of its main axis, and
through which the mass of the endoplasm issues into the calymma. The two
legions of the Osculosa, however, present differences in this respect. In
the NASSELLARIA (§ 79) the endoplasmatic currents appear to unite in an
axial main stream at the apex of the monaxon central capsule, and this
apical stream seems to split into a conical bundle, the individual threads
of which pass diverging between the myophane fibrillæ of the podoconus
towards the basis of the central capsule, and issue through the pores of
the porochora. In the PHÆODARIA (§ 80), on the other hand, meridional
currents of endoplasm are probably present on the inner surface of the
capsule, which flow from the aboral pole of the vertical main axis to its
basal pole, and return in the reverse direction.


209. _Currents in the Exoplasm._--Extracapsular circulation, or a distinct
flowing of the plasma outside the central capsule, may be readily observed
in all Radiolaria which are examined alive; this is most readily seen in
the astropodia, or those free pseudopodia which radiate from the
sarcodictyum on the surface of the calymma into the surrounding water. The
granular movement is often quite as clear in the sarcodictyum itself, and
may be recognised in the collopodia, which compose the irregular plasmatic
network within the calymma. More rarely it is possible to follow the
granular stream thence through the sarcomatrix, and further into the
interior of the central capsule. In general the direction of the
extracapsular protoplasmic streams is radial, and it is frequently
possible, even in a single free astropodium, to observe two streams
opposite in direction, the granules on one side of the radial sarcode
thread moving centripetally, those on the other side centrifugally. If the
threads branch, and neighbouring ones {cxxxiv}become united by connecting
threads, the circulation of the granules may proceed quite irregularly in
the network thus formed. The rapidity and character of the extracapsular
currents are subject to great variations.

  The different forms of extracapsular sarcode currents have been already
  very fully described in my Monograph (L. N. 16, pp. 89-126), and in my
  critical essay on the sarcode body of the Rhizopoda (L. N. 19, p. 357,
  Taf. XXVI.).


210. _Secretion._--Under the name _secretions_, in the strict sense, all
the skeletal formations of the Radiolaria may be included. They may be
divided according to their chemical composition into three different
groups: pure silica in the SPUMELLARIA and NASSELLARIA, a silicate of
carbon in the PHÆODARIA, and acanthin in the ACANTHARIA (compare § 102). It
may indeed be assumed that these skeletons arise directly by a chemical
metamorphosis (silicification, acanthinosis, &c.) of the pseudopodia and
protoplasmic network; and this view seems especially justified in the case
of the Astroid skeleton of the ACANTHARIA (§ 114), the Spongoid skeleton of
the SPUMELLARIA (§ 126), the Plectoid skeleton of the NASSELLARIA (§ 125),
the Cannoid skeleton of the PHÆODARIA (§ 127), and several other types. On
closer investigation, however, it appears yet more probable that the
skeleton does not arise by direct chemical metamorphosis of the protoplasm,
but by secretion from it; for when the dissolved skeletal material (silica,
acanthin) passes from the fluid into the solid state, it does not appear as
imbedded in the plasma, but as deposited from it. However, it must be borne
in mind that a hard line of demarcation can scarcely, if at all, be drawn
between these two processes. In the ACANTHARIA the intracapsular sarcode is
the original organ of secretion of the skeleton; in the other three
legions, on the other hand, the extracapsulum performs this function (§§
106, 107). In addition to the skeleton, we may regard as secretions (or
excretions) the intracapsular crystals (§ 75) and concretions (§ 75A), and
perhaps certain pigment-bodies (§§ 74, 88); and further, the calymma (§ 82)
may be considered to be a gelatinous secretion of the central capsule, and
perhaps also the capsule-membrane, in so far as it represents only a
secondary excretory product of the unicellular organism.


211. _Adaptation._--The innumerable and very various adaptive phenomena
which we meet with in the morphology of the Radiolaria, and especially in
that of their skeleton, are like other phenomena of the same kind, to be
ultimately referred to altered nutritional relations. These may be caused
directly either by the influence of external conditions of existence
(nutrition, light, temperature, &c.), or by the proper activity of the
unicellular organism (use or disuse of its organs, &c.), or, finally, by
the combined action of both causes in the struggle for existence. In very
many cases the cause to which the origin of a particular form of Radiolaria
is due may be directly perceived or at least guessed at with considerable
probability; thus, for example, the lattice-shells {cxxxv}may be explained
as protective coverings, the radial spines as defensive weapons, and the
anchor-hooks and spathillæ as organs of prehension, which are of advantage
to their possessors in the struggle for existence; the regular arrangement
of the radial spines in the Radiolaria may also be explained on hydrostatic
grounds, it being advantageous that the body should be maintained in a
definite position of equilibrium, &c. The well-known laws of _direct_ or
_actual adaptation_, which we designate cumulative, correlative, divergent
adaptation, &c., here explain a multitude of morphological phenomena. The
connection is less distinct in the case of the laws of _indirect_ or
_potential adaptation_, although this must play as important a part in the
formation of the Radiolaria as in that of other organisms (compare on this
head my Generelle Morphologie, Bd. ii. pp. 202-222).


212. _Reproduction._--The most common form of reproduction in the
Radiolaria is the formation of spores in the central capsule, which in this
respect is to be regarded as a sporangium (§ 215). In many Radiolaria
(Polycyttaria and PHÆODARIA), however, there occurs in addition an increase
of the unicellular organism by simple division (§ 213); upon this the
formation of colonies in the social Radiolaria is dependent (§ 14).
Reproduction by gemmation is much less common, and has hitherto been
observed only in the Polycyttaria (§ 214). In this group alone there also
occur at certain times two different forms of swarm-spores which copulate,
and thus indicate the commencement of sexual reproduction (Alternation of
Generations, § 216). The general organ of reproduction is in all cases the
central capsule, whilst the extracapsulum never takes an active part in the
process.


213. _Cell-Division._--Increase by cell-division among the Radiolaria in
the early stage, before the formation of the skeleton, is widely
distributed (perhaps even general?); in the adults of this class it is
rather rare and limited to certain groups. It is most readily observed in
the Polycyttaria; the growth of the colonies in this social group depends
mainly (and in many species exclusively) upon repeated spontaneous division
of the central capsule; all the individuals of each colony (in so far as
this has not arisen by the accidental fusion of two or more colonies) are
descendants of a single central capsule, which has arisen from an asexual
swarm-spore (§ 215) or from the copulation of two sexual swarm-spores (§
216). Whilst the central capsules of the colonies continually increase by
division, their calymma remains a common gelatinous sheath. Among the
SPUMELLARIA reproduction by simple cell-division probably occurs also in
many monozootic #Collodaria#. Among the ACANTHARIA the peculiar group
Litholophida has perhaps arisen by the spontaneous division of
#Acanthonida# (see p. 734). Among the PHÆODARIA increase by cell-division
seems to occur commonly in many groups, as in the #Phæocystina#, which have
no skeleton (Phæodinida, Pl. 101, {cxxxvi}fig. 2), or only an incomplete
Beloid skeleton (Cannorrhaphida, Pl. 101, figs. 3, 6, and Aulacanthida, Pl.
104, figs. 1-3). The #Phæosphæria# also (Aulosphærida, Coelacanthida) and
the #Phæogromia# (Tuscarorida, Challengerida) appear sometimes to divide;
at all events, their central capsule often contains two nuclei. Of special
interest  is the spontaneous division of the #Phæoconchia#, especially the
Concharida (Pl. 124, fig. 6). In all monozootic Radiolaria, the nucleus
first divides by a median constriction into two equal halves (usually by
the mode of direct division); then the central capsule becomes constricted
in the middle (in the PHÆODARIA in the vertical main axis), and each
portion of the capsule retains its own nucleus. In the #Phæoconchia# each
half or daughter-cell corresponds to one valve of the shell, dorsal or
ventral, so that probably on subsequent separation each daughter-cell
retains one valve of the mother-cell, and forms a new one for itself by
regeneration (as in the Diatoms). In the polyzootic Radiolaria, which
already contain many small nuclei, but usually only a single central
oil-globule in each central capsule, the division of the latter is preceded
by that of the oil-globule. In many Polycyttaria the colony as a whole
multiplies by division.

  The increase of the central capsule by division was first described in
  1862 in my Monograph (L. N. 16, p. 146); since then R. Hertwig (L. N. 26,
  p. 24) and K. Brandt (L. N. 52, p. 144) have confirmed my statement. In
  the PHÆODARIA the division of the central capsule appears always to take
  place in the main axis; in the bilateral sometimes in the sagittal,
  sometimes in the frontal plane. In the Tripylea each daughter-cell seems
  to retain one parapyle and half the astropyle (compare the general
  description of the PHÆODARIA, Pl. 101, figs. 1-6, Pl. 104, figs. 1-3, and
  also Hertwig, L. N. 33, p. 100, Taf. x. figs. 2, 11). Regarding the
  spontaneous division of colonies of the Polycyttaria, see K. Brandt, L.
  N. 52, p. 142.


214. _Cell-Gemmation._--Reproduction by gemmation has hitherto been
observed only in the social Radiolaria, but in them it appears to be widely
distributed, and in very young colonies is perhaps almost universally
present. The gemmules or capsular buds (hitherto described as
"extracapsular bodies") are developed on the surface of young central
capsules before these had secreted a membrane. They grow usually in
considerable numbers, from the surface of the central capsule, which is
sometimes quite covered with them. Each bud usually contains a
raspberry-like bunch of shining fatty globules, and by means of reagents a
few larger or a considerable number of smaller nuclei may be recognised in
them; the naked protoplasmic body of the bud is not enclosed by any
membrane. As soon as the buds have reached a certain size they are
constricted off from the central capsule and separated from it, being
distributed in the meshes of the sarcoplegma by the currents in the
exoplasm. Afterwards each bud becomes developed into a complete central
capsule by surrounding itself with a membrane when it has attained a
definite size. From the special relations of the process of nuclear
formation, which take place in the multiplication of the {cxxxvii}social
central capsules by gemmation and by cell-division, it would appear that
the capsules produced by the former method afterwards produce anisospores,
whilst those in the latter way yield isospores (§ 216).

  The gemmules or capsular buds of the Polycyttaria were first accurately
  described by Richard Hertwig (L. N. 26, pp. 37-39), under the name
  "extracapsular bodies," and their significance rightly indicated; earlier
  observers had incidentally mentioned and figured them, but had not seen
  their origin from the central capsule. Quite recently Karl Brandt has
  given a very painstaking account of them in the different Polycyttarian
  genera (L. N. 52, pp. 179-198). In the Monocyttaria such a formation of
  buds has not yet been observed. The basal lobes of the central capsule,
  which occur in many NASSELLARIA, are not buds, but simple processes of
  the capsule, due to its protrusion through the collar pores of the
  cortinar septum (§ 55).


215. _Sporification._--Asexual reproduction by the formation of movable
flagellate spores has been hitherto observed only in a very small number of
genera; but since these belong to very different groups, and since the
comparative morphology of the capsule appears to be similar throughout as
regards the structure and development of its contents, it may be safely
assumed that this kind of reproduction occurs quite generally in the
Radiolaria. In all cases it is the contents of the central capsule, from
which the swarm-spores are formed, both nucleus and endoplasm taking an
equal share in the process; in all cases the spores produced are very
numerous, small, ovoid or reniform, and have one or two very long slender
flagella at one extremity (see §§ 141, 142). Since the whole contents of
the mature central capsule are used up in the formation of these flagellate
zoospores, it discharges the function of a sporangium. The division of the
simple primary nucleus into numerous small nuclei, which usually
(serotinous Radiolaria) takes place only shortly before sporification, but
sometimes (precocious Radiolaria, § 63) happens very early, is the
commencement of the often repeated process of nuclear division, which
terminates with the production of a very large number of small
spore-nuclei. The nucleolus often divides very peculiarly (§ 69, C). Each
spore nucleus becomes surrounded by a portion of endoplasm and usually
receives in addition one or more fatty granules, and sometimes also a small
crystal (hence the "crystal-spores"). The size of the flagellate zoospores
which emerge from the ruptured central capsule and swim freely in the water
by means of their flagellum, varies generally between 0.004 and 0.008 mm.
The extracapsulum is not directly concerned in the sporification, but
undergoes degeneration during the process and perishes at its conclusion.

  The first complete and detailed observations on the formation of spores
  in the Radiolaria were published by Cienkowski in 1871 and related to two
  genera of Polycyttaria, the skeletonless _Collozoum_ and the
  spherical-shelled _Collosphæra_ (L. N. 22, p. 372, Taf. xxix.). These
  were subsequently continued and supplemented by R. Hertwig (1876, L. N.
  26, pp. 26-42, and L. N. 33, p. 129), and a general summary of these
  results has been given by Bütschli (L. N. 41, pp. 449-455).
  {cxxxviii}Recently Karl Brandt has given a very detailed and fully
  illustrated account of the sporification of the Polycyttaria (L. N. 52,
  pp. 145-178). I have also had the opportunity during my sojourn in the
  Canary Islands (1866), in the Mediterranean at Corfu (1877), and
  Portofino (1880), as well as in Ceylon (1881), of observing the
  development of flagellate zoospores from the central capsule of
  individuals of all four legions: among the SPUMELLARIA in certain
  #Colloidea#, #Beloidea#, #Sphæroidea#, and #Discoidea#, among the
  ACANTHARIA in several #Acanthometra# and #Acanthophracta#, among the
  NASSELLARIA in individuals belonging to the #Stephoidea#, #Plectoidea#,
  and #Cyrtoidea#, and among the PHÆODARIA in one Castanellid. In most
  zoospores I could distinctly observe only a single long flagellum;
  sometimes, however, two or even three appeared to be present, but the
  determination of their number is very difficult.


216. _Alternation of Generations._--A peculiar form of reproduction, which
may be designated "alternation of generations," appears to occur generally
in the Polycyttaria, but has not yet been observed in the Monocyttaria. All
#Collozoida#, #Sphærozoida#, and Collosphærida which have hitherto been
carefully and completely examined with respect to their development, are
distinguished by the production of two different kinds of swarm-spores,
isospores and anisospores. The _Isospores_ (or monogonous spores)
correspond to the ordinary asexual zoospores of the Monocyttaria (§ 215);
they possess a homogeneous, doubly refracting nucleus of uniform
constitution and develop asexually, without copulation. The _Anisospores_
(or amphigonous spores), on the other hand, are sexually differentiated and
possess a heterogeneous, singly refracting nucleus of twofold constitution;
they may therefore be distinguished as female macrospores and male
microspores. The _Macrospores_ (or gynospores, comparable with the female
macrogonidia of many Cryptogams) are larger, less numerous, and possess
larger nuclei, which are less easily stained, and have a fine filiform
trabecular network. On the other hand the _Microspores_ (or _androspores_,
comparable with the male microgonidia) are much smaller and more numerous,
and are distinguished by their smaller nuclei, which have thicker tuberculæ
and become stained more intensely. The gynospores and androspores are
developed in the #Collozoida# and #Sphærozoida# in the same individual, but
not in the Collosphærida. It is very probable that these two forms of
anisospores copulate with each other after their exit from the central
capsule and thus produce a new cell by the simplest mode of sexual
reproduction. But, since the same Polycyttaria, which produce these
anisospores, at other times give rise to ordinary or asexual isospores, it
is further possible that these two forms of reproduction alternate with
each other, and that the Polycyttaria thus pass through a true alternation
of generations. This has not yet been observed in the Monocyttaria, and
hence these latter seem to bear to the Polycyttaria a relation similar to
that in which the sexless solitary Flagellata (Astasiea) stand to the
sexual social Flagellata (Volvocinea). In the two analogous cases the
sexual differentiation may be regarded as a consequence of the social life
in the gelatinous colonies.

  {cxxxix}The _sexual differentiation of the Polycyttaria_ was first
  discovered in 1875 by R. Hertwig, and accurately described in the case of
  _Collozoum inerme_ as occurring in addition to the formation of the
  ordinary crystal-spores (L. N. 26, p. 36); compare also the general
  discussion of Bütschli (L. N. 41, p. 52). Recently Karl Brandt has
  demonstrated the formation of both homogeneous isospores (crystal-spores)
  and heterogeneous anisospores (macro- and microspores) in seven different
  species of Polycyttaria, and has come to the conclusion that in all
  social Radiolaria there is a regular alternation between the former and
  latter generations. Compare his elaborate account of the colonial
  Radiolaria of the Gulf of Naples (L. N. 52, pp. 145-178).


217. _Inheritance._--Inheritance is to be regarded as the most important
accompaniment to the function of reproduction, and especially in the
present case, because the comparative morphology of the Radiolaria
furnishes abundant instances of the action of its different laws. The laws
of _conservative inheritance_ are illustrated by the comparative anatomy of
the larger groups; thus, in the four legions the characteristic
peculiarities of the central capsule are maintained unaltered in
consequence of continuous inheritance, although great varieties appear in
the skeleton in each legion. The individual parts of the skeleton furnish
by their development on the one hand and their degeneration on the other,
especially in the smaller groups, examples of _progressive inheritance_.
Thus in the SPUMELLARIA the constant formation of the primary lattice-shell
(a central medullary shell) and its ontogenetic relation to the secondary
one, which is developed concentrically round it, can only be explained
phylogenetically by conservative inheritance, whilst on the other hand the
characteristic differentiation of the axes in the various families of
SPUMELLARIA is to be explained by progressive inheritance. In the
ACANTHARIA the arrangement of the twenty radial spines (in accordance with
Müller's law, §§ 110, 172) was first acquired by a group of the most
archaic #Actinelida# (Adelacantha) through hydrostatic adaptation, and has
since been transmitted by inheritance to all the other families of the
legion (Icosacantha). The morphology of the NASSELLARIA is not less
interesting, because here several different heritable elements (the primary
sagittal ring and the basal tripod) combine in the most manifold ways in
the formation of the skeleton (compare §§ 123, 124, 182). The affinities of
the genera in the different families yield an astonishing variety of
interesting morphological phenomena, which can only be explained by
progressive inheritance. The same is true also of the PHÆODARIA. In this
legion the primary inheritance is especially manifested in the constant and
firm structure of the central capsule with its characteristic double wall
and astropyle, whilst the formation of the skeleton in this legion proceeds
in different directions by means of divergent adaptation. The morphology of
the Radiolaria thus proves itself a rich source of materials for the
physiological study of adaptation and inheritance.



{cxl}CHAPTER VIII.--ANIMAL FUNCTIONS.

(§§ 218-225.)

218. _Motion._--In addition to the internal movements which appear
generally in the unicellular Radiolaria and have already been mentioned as
plasmatic currents in treating of the circulation (§§ 207-209), two
different groups of external motor phenomena are to be observed in this
class: first, the _contraction_ of individual parts, which brings about
modifications of form (§ 220), and secondly, voluntary or reflex
_locomotion_ of the whole body (§ 220). These movements are partly due to
changes in form of undifferentiated plasmatic threads or sarcode filaments,
partly to the actual contraction of differentiated filaments which are
comparable to muscle fibrillæ, and must therefore be distinguished as
myophanes. In addition to this, endosmose and exosmose probably play an
important part in some of the locomotive phenomena, but nothing is yet
certainly known regarding these osmotic processes. We are at present
equally ignorant whether all the movements of the Radiolaria are simply
reflex (direct consequences of irritation) or whether they are in part
truly spontaneous.


219. _Suspension._--From direct observation of living Radiolaria, as well
as from deductive reasoning, based upon their morphology (and especially
their promorphology, §§ 17-50), the conclusion appears justified that all
Protista of this class in their normal condition float suspended in the
sea-water, either at the surface or at a definite depth. A necessary
condition of this hydrostatic suspension is that the specific gravity of
the Radiolarian organism must be equal to, or but slightly greater than
that of sea-water. The increase in specific gravity brought about by the
production of the siliceous skeleton, is compensated by the lighter fatty
globules, and partly perhaps by the calymma, especially when the latter
contains vacuoles or alveoles. The fluid or jelly contained in the latter
appears to be for the most part lighter than sea-water (containing no salt,
or only a very small quantity?). But if the specific gravity of the whole
body should be generally (or perhaps always) slightly greater than that of
sea-water, then the organism would be prevented from sinking, partly by the
increased friction, due to the radiating pseudopodia and the radial spines
usually present, and partly perhaps by active (if only feeble) movements of
the pseudopodia.


220. _Locomotion._--Active locomotion of the whole body, which is very
probably to be regarded as voluntary, occurs in the Radiolaria in three
different modes; (1) the vibratile movement of the flagellate swarm-spores;
(2) the swimming of the floating organisms; (3) the slow creeping of those
which rest accidentally upon the bottom. {cxli}The _vibratile_ movement of
the swarm-spores is the result of active sinuous oscillation of the single
or multiple flagellum, and is not essentially different from that of
ordinary flagellate Infusoria (see note A). Of the active swimming of
mature Radiolaria, only that form is known which is vertical in direction
and causes the sinking and rising in the sea-water. This is probably, for
the most part (perhaps exclusively), due to increase or diminution in the
specific gravity, which is perhaps brought about by the retraction or
protrusion of the pseudopodia; slow, oscillating, sinuous motions of these
organs have been directly observed to take place (though very slowly) in
suspended living Radiolaria. The most important hydrostatic organ is
probably the calymma, by the contraction of which the specific gravity is
increased, while it is diminished by its expansion; the contraction is
probably brought about by active contraction of the sarcodictyum, and is
connected with exosmosis, while the expansion is probably due to the
elasticity of the calymma and the inception of water by endosmosis. In the
#Acanthometra# (§ 96) the peculiar myophriscs appear to be charged with the
duty of distending the gelatinous envelope, and thus diminishing the
specific gravity; the latter increases again when the myophriscs are
relaxed, and the calymma contracts by virtue of its own elasticity (see
note B). The slow _creeping locomotion_ exhibited by Radiolaria on a glass
slide under the microscope, does not differ from that of the Thalamophora
(Monothalamia and Polythalamia), but can only occur normally when the
animal accidentally comes into contact with a solid surface or sinks to the
bottom of the sea. Whether this actually occurs periodically is not known
(see note C). The slow or gliding locomotion exhibited by creeping Monozoa
on a glass slide is due to muscle-like contractions of bundles of
pseudopodia, just as in the case of the social central capsules of Polyzoa,
which live together in the same coenobium and are able to move within their
common calymma sometimes centrifugally to its surface, sometimes towards
the centre where they aggregate into a roundish mass (see note D).

  A. Regarding the movement of the flagella in mature swarm-spores compare
  L. N. 22, p. 375; L. N. 26, pp. 31, 35; L. N. 41, p. 452, and L. N. 52,
  p. 170.

  B. On the active vertical swimming movements of mature Radiolaria,
  especially the cause of sinking and rising, see L. N. 16, p. 134; L. N.
  41, p. 443, and L. N. 52, pp. 97-102.

  C. On the active horizontal creeping movements of mature Radiolaria on a
  firm ground, compare L. N. 12, p. 10, and L. N. 16, pp. 132-134.

  D. Regarding the motion of social central capsules within the same
  coenobium and the changes thus brought about in the structure of the
  calymma, see L. N. 16, pp. 119-127, and L. N. 52, pp. 75-82.


221. _Contraction._--Motions, which are due to the contraction of
individual portions and cause changes in volume or form, have been partly
already spoken of under the head of locomotion (§ 220) and are partly
connected with other functions. Examples may be seen in the contraction of
the central capsule and of the calymma. A certain {cxlii}contraction of the
central capsule is probably brought about by the myophanes, which arise by
differentiation of the endoplasm and hence may assume different forms in
the four legions. In the SPUMELLARIA, where numerous radial fibrillæ run
from the central nucleus to the capsule membrane (§ 77), the endoplasm is
probably driven out evenly through all the pores of the capsule membrane by
their simultaneous contraction, and hence the volume of the capsule is
diminished in all directions.  The ACANTHARIA probably behave similarly,
but are different, inasmuch as the number of their contractile radial
fibrillæ is less, and special axial threads (§ 78) are already
differentiated. In the NASSELLARIA it is probable that owing to the
contraction of the divergent myophane fibrillæ in the podoconus the
vertical axis of the latter is shortened, the opercular rods of the
porochora are lifted, and the endoplasm driven out of its pores, so that
the volume of the monaxon central capsule is diminished (§ 79). In the
PHÆODARIA the same result is probably brought about by the contraction of
the cortical myophane fibrillæ, which run meridionally along the inside of
the capsule membrane from the apical to the basal pole of the vertical main
axis, where they are inserted into the periphery of the astropyle; since
the volume of the capsule is diminished by their contraction (their
spheroidal figure becoming more nearly spherical) the endoplasm will be
driven out through the proboscis of the astropyle. Whilst these
contractions of the central capsule are largely due to differentiated
muscle-like threads of endoplasm (myophanes), this appears to be but rarely
the case with the contractions of the extracapsulum (_e.g._, the myophriscs
of the #Acanthometra#, § 96). Most of the phenomena of contraction which
can be observed in the calymma and pseudopodia depend upon exoplasmatic
currents (§ 209).


222. _Protection._--Of the utmost importance, both for the physiology and
for the morphology of the Radiolaria are their manifold protective
functions, which we now consider under the heading "protection." From the
physiological point of view the consideration of the exposed situation in
which the delicate, free-swimming Radiolarian organism lives, and the
numerous dangers which beset it in the struggle for existence, would lead
_a priori_ to the expectation, that many special protective adaptations
would be developed by natural selection. On the other hand, morphological
experience shows us that this latter has been in action for immeasurable
periods, and has gradually produced an abundance of the most remarkable
protective modifications. Examples of these may be found in the formation
of the voluminous calymma, as a gelatinous protective covering for the
central capsule, and further, the formation of the capsule membrane itself,
which separates the generative contents of the central capsule from the
nutritive exoplasm. The phosphorescence of the central capsule, too (§
223), may be regarded as a useful protective arrangement; as also the
radiating of the numerous pseudopodia in all directions from the surface of
the calymma; for they are of great significance to the {cxliii}well-being
of the organism, both as sensory organs and as prehensile organs. By far
the most important and most varied means for the actual defence of the soft
body is to be seen in the endless modifications of the skeleton; first, in
the production of the enclosing lattice-shells and projecting radial
spines, but especially also in the very varied structure of the individual
parts of the skeleton, and in the special differentiation of the small
appendicular organs which grow out from it (hairs, thorns, spines, scales,
spathillæ, anchors, &c.). Finally "mimicry" possesses a considerable
significance among the different forms of adaptation which are to be
observed in this class.


223. _Phosphorescence._--Many Radiolarians shine in the dark, and their
phosphorescence presents the same phenomena as that of other luminous
marine organisms; it is increased by mechanical and chemical irritation, or
renewed if already extinguished. The light is sometimes greenish, sometimes
yellowish, and appears generally (if not always) to radiate from the
intracapsular fatty spheres (§ 73). Thus these latter unite several
functions, inasmuch as they serve, firstly, as reserve stores of nutriment,
secondly, as hydrostatic apparatus, and thirdly, as luminous organs for the
protection of the Radiolaria; probably the light acts by frightening other
animals, for the phosphorescent animals are provided with spines,
nettle-cells, poison glands or other defensive weapons. The production of
the light depends probably, as in other phosphorescent organisms, upon the
slow oxidation of the fat-globules, which combine with active oxygen in the
presence of alkalis. Phosphorescence is very likely widely distributed
among the Radiolaria.

  The shining of the Radiolaria in the dark has been noticed by the
  earliest observers of the class (see L. N. 1, p. 163, L. N. 16, p. 2, and
  L. N. 52, pp. 136-139). In the winter of 1859 I observed the production
  of light in the case of many monozootic and polyzootic Radiolaria, but
  inadvertently omitted to record the fact in my Monograph. I made more
  accurate observations in the winter of 1866 at Lanzerote in the Canary
  Islands, and convinced myself the the light emanates from the central
  capsule, and in particular from the fat-globules contained in it. In most
  Polycyttaria (both #Collosphærida# and #Sphærozoida#), when each central
  capsule contains a large central oil-globule the light radiates from it.
  In _Collozoum serpentinum_ (Pl. 3, figs. 2, 3) each cylindrical central
  capsule contains a row of luminous spherules like a string of beads. In
  _Alacorys friderici_ (Pl. 65, fig. 1) the four-lobed central capsule
  contains four shining points. Karl Brandt has recently made more detailed
  communication on this point (L. N. 52, p. 137).


224. _Sensation._--The general irritability which we ascribe to all
organisms, and as the basis of which we regard the protoplasm, remains at
an inferior stage of development in the Radiolaria. For although they are
subject to various stimuli, and certainly possess a power of
discrimination, special sensory organs are not differentiated; the
peripheral portions of the protoplasm, and especially the pseudopodia,
rather act both as organs of the different kinds of sensation and various
modes of motion. That different Radiolaria have attained different degrees
of development in this respect may be seen {cxliv}partly by direct
observation of the reaction of the living organism towards various stimuli,
and partly by the comparison of the different conditions of existence under
which Radiolarians exist, both in the most various depths of the ocean and
in all climatic zones (see note A). In general the Radiolaria seem to be
sensitive to the following stimuli; (1) pressure (see note B); (2)
temperature (see note C); (3) light (see note D); (4) chemical composition
of the sea-water (see note E). The reaction towards these stimuli,
corresponding to the sensation of pleasure or dislike which they call
forth, is shown in various forms of motion of the protoplasm, changes in
the currents in it, contraction of the central capsule, changes in the
size, position, and form of the pseudopodia, changes in the volume of the
calymma (by the evocation of water), &c. Among the sensory functions of the
Radiolaria must be especially mentioned their remarkably developed
perception of hydrostatic equilibrium (see note F), as well as their
perception of distances, so clearly shown in the production of equal
lattice-meshes and other regularly formed skeletal structures (see note G).

  A. I can add but little to the communication which I made twenty-four
  years ago regarding sensation in the Radiolaria (L. N. 16, pp. 128-131).
  The most important point would be the great difference in irritability
  which must obtain between the pelagic, zonarial and abyssal Radiolaria,
  which may be assumed from a consideration of their very different
  conditions of existence as regards pressure, light, warmth, nutrition,
  &c. It is natural to suppose that the numerous abyssal Radiolaria,
  discovered by the Challenger, which live at great depths (2000 to 4500
  fathoms) in complete darkness, in icy cold and under an enormous
  pressure, must have quite different sensations of pleasure from their
  pelagic relatives which live at the surface of the sea under an
  equatorial sun. Karl Brandt has recently added much to our knowledge
  regarding the special action of different vital conditions upon the
  various Polycyttaria and the degrees of their irritability (L. N. 52, pp.
  113-132).

  B. Regarding the sensation of pressure or sensation of touch of the
  Radiolaria and the various degrees of their mechanical irritability, see
  L. N. 16, p. 129; L. N. 41, p. 464.

  C. Regarding the sensation of warmth or temperature-sense and its
  dependence upon different climatic relations, see L. N. 16, p. 129; L. N.
  52, pp. 114-129.

  D. Regarding the sensation of light, compare L. N. 16, p. 128; L. N. 42,
  p. 304; L. N. 52, pp. 102-104, 114.

  E. Regarding the sense of taste of the Radiolaria or their peculiar
  sensitiveness towards the different chemical composition of the water,
  change in its salinity, presence of organic impurities, &c., see L. N.
  16, p. 130; L. N. 52, pp. 103, 113. This chemical irritability seems to
  be the most highly developed sense in the Radiolaria, even more so than
  their mechanical irritability.

  F. The perception of hydrostatic equilibrium among the Radiolaria is
  immediately visible from the position which their bodies, floating freely
  in the water, assume spontaneously, and from the symmetrical development
  of the skeleton, which by its gravitation necessitates a definite
  position. It may be assumed that the development of the various
  geometrical ground forms which correspond to a definite position of
  equilibrium, is the result of this particular kind of perception (compare
  §§ 40-45).

  {cxlv}G. The plastic perception of distance of the pseudopodia is shown
  by the symmetry with which the forms composing the regular skeletal
  structures (_e.g._, the ordinary lattice-spheres with regular hexagonal
  meshes, the radial spines with equidistant branches) are excreted from
  the exoplasm. Both this form of sensation and the one first mentioned
  (note F) have hitherto received scarcely any attention, but are deserving
  of a thorough physiological investigation.


225. _The Cell-Soul (Zellseele)._--The common central vital principle,
commonly called the "soul," which is considered to be the regulator of all
vital functions, appears in the Radiolaria as in other Protista in its
simplest form, as the cell-soul. By the continual activity of this central
"psyche" all vital functions are maintained in unbroken action, and in
uniform correlation. It is also probable that by it the stimulations which
the peripheral portions of the cell receive from the outer world are first
transmitted into true sensation, and that, on the other hand, the volition,
which alone calls forth spontaneous movements, proceeds from it. The
central capsule is most likely the sole organ of this cell-soul or central
psychic organ, and the active portion may be either the endoplasm or the
nucleus, or both. The central capsule may thus (apart from its function as
a sporangium, § 215) be regarded as a simple ganglion cell, physiologically
comparable to the nervous centre of the higher animals, whilst the exoplasm
(sarcomatrix and pseudopodia) are to be compared to the peripheral nervous
system and sense organs of the latter. The great simplicity of the
functions of the cell-soul which appear in the Radiolaria, and the intimate
connection of their different psychic activities, give to these unicellular
Protista a special significance for the comprehension of the monistic
elements of a natural psychology.

  Regarding the theory of the cell-soul as the only psychological theory
  which is able to explain naturally the true nature of the life of the
  soul in all organisms as well as in man, see my address on cell-souls and
  soul-cells ("Zellseelen und Seelenzellen") in Gesammelte populäre
  Vorträge aus dem Gebiete der Entwickelungslehre, Heft 1, p. 143; Bonn,
  1878.



{cxlvi}CHOROLOGICAL SECTION.


----


CHAPTER IX.--GEOGRAPHICAL DISTRIBUTION.

(§§ 226-240.)

226. _Universal Marine Distribution._--Radiolaria occur in all the seas of
the world, in all climatic zones and at all depths. Probably under normal
conditions they always float freely in the water, whether their usual
position be at the surface (pelagic), or at a certain depth (zonarial), or
near to the bottom of the sea (abyssal). This appears both from numerous
direct observations, as well as from conclusions which may be drawn from
their organisation (and especially their promorphology) regarding their
floating life (compare §§ 40-50, 219, 220). Hitherto no observation has
been recorded, which justifies the assumption that Radiolaria live anywhere
upon the bottom of the sea (on stones, Algæ, or other firm substances),
either sessile or creeping. They perform the latter action, however, when
they fall accidentally upon a firm basis or are accidentally placed upon
it, but they seem normally always to float freely in the water with
pseudopodia radiating in all directions. Active free-swimming movements are
only met with in the case of the flagellate zoospores (§ 142). The
development of Radiolaria in large masses is very remarkable (see note A),
and in many parts of the ocean is so great that they play an important part
in the economy of marine life, especially as food for other pelagic and
abyssal animals (see note B). Medium salinity of the water seems to be most
favourable to their development in masses, although it is not unknown in
seas of high and low salinity (see note C). There are no Radiolaria in
fresh water (see note D).

  A. The development of Radiolaria takes place in many parts of the ocean
  in astonishingly large masses on the surface, in different strata, and
  near the bottom. The #Collodaria# (and especially the Sphærozoida) often
  cover the surface of the sea in millions, and form a shining layer,
  phosphorescent in the dark like the _Noctilucæ_, as I observed in 1859 in
  the Strait of Messina, in 1866 at the Canaries, and in 1881 in the Indian
  Ocean. Similar masses of _Sphærozoum_ and _Acanthometron_ were seen by
  Johannes Müller on the French and Ligurian coasts (L. N. 12), and John
  Murray found another in the Gulf Stream, off the Færöe Islands, from the
  surface to a depth of 600 fathoms; considerable masses of large PHÆODARIA
  live there also.

  B. The alimentary canal of Medusæ, Salpæ, Crustacea, Pteropoda, and many
  other pelagic animals is a rich field for the discovery of Radiolaria,
  and many of the species hereinafter described are from such sources.
  Fossil coprolites too (_e.g._, those from the Jura) often contain many
  Polycystina.

  C. Some ACANTHARIA (#Acanthometra#) and PHÆODARIA (species of _Mesocena_
  and _Dictyocha_) {cxlvii}live in the Baltic; I found their skeletons in
  the alimentary canal of _Aurelia_, Ascidians and Copepods.

  D. The so-called "fresh-water Radiolaria," which have been described by
  Focke, Greeff, Grenacher and others, are all Heliozoa, without either
  central capsule or calymma.


227. _Local distribution._--As regards their local distribution and its
boundaries the Radiolaria show in general the same relations as other
pelagic animals. Since they are only to a very slight extent, if at all,
capable of active horizontal locomotion, the dispersion of the different
species from their point of development (or "centre of creation") is
dependent upon oceanic currents, the play of winds and waves and all the
accidental causes which influence the transport of pelagic animals in
general. These passive migrations are here, however, as always, of the
greatest significance, and bring about the wide distribution of individual
species in a far higher degree than any active wanderings could do. Any one
who has ever followed a stream of pelagic animals for hours and seen how
millions of creatures closely packed together are in a short time carried
along for miles by such a current, will be in no danger of underestimating
the enormous importance of marine currents in the passive migration of the
fauna of the sea. Such constant currents may, however, be recognised both
near the bottom of the sea and at various depths, as well as at the
surface, and are therefore of just as much significance for the abyssal and
zonarial as for the pelagic Radiolaria. It is easy to explain by this means
how it is that so many animals of this class (probably indeed the great
majority) have a wide range of distribution. The number of _cosmopolitan_
species which live in the Pacific, Atlantic and Indian Oceans is already
relatively large. In each of these three great ocean basins, too, many
species show a wide distribution. On the other hand, there are very many
species which are hitherto known only from one locality, and probably many
small local faunas exist, characterised by the special development of
particular groups. The observations which we at present possess are too
incomplete, and the rich material of the Challenger is too incompletely
worked out, to enable any definite conclusions to be drawn regarding the
local distribution of Radiolaria.

  The statements made in the systematic portion of this Report regarding
  the distribution of the Challenger Radiolaria are very incomplete. In
  most cases only one locality is mentioned, and that is the station (§
  240) in the preparations or bottom deposit from which I first found the
  species in question. Afterwards I often found the same species again in
  one or more additional stations (not seldom in numerous preparations both
  from the Pacific and Atlantic), without the possibility of adding them to
  the habitat recorded under the description. The necessary accurate
  determination and identification of the species (measuring the different
  dimensions, counting the pores, &c.), would have occupied too much time,
  and the writing of this extensive Report would have lasted not ten but
  twenty or thirty years.


228. _Horizontal Distribution._--From the extensive collections of the
Challenger and from the other collections which have furnished a welcome
supplement to them, it appears {cxlviii}that Radiolaria are distributed
throughout all seas without distinction of zones and physical conditions,
even though these latter may be the cause of differences in their
qualitative and quantitative development. In the case of the Radiolaria as
well as of many other classes of animals, the law holds good that the
richest development of forms and the greatest number of species occurs
between the tropics, whilst the frigid zones (both Arctic and Antarctic)
exhibit great masses of individuals, but relatively few genera and species
(see note A). In the Challenger collection the greatest abundance of
species of Radiolaria is exhibited by those preparations which were
collected at low latitudes in the immediate neighbourhood of the equator;
this is true both of the Atlantic (Stations 346 to 349) and of the Pacific
(Stations 266 to 274); in the former the richest of all is Station 347
(lat. 0° 15' S.), in the latter Station 271 (lat. 0° 33' S.) (see note B).
From the tropics the abundance of species seems to diminish regularly
towards the poles, and more rapidly in the northern than in the southern
hemisphere; the latter also appears, considered as a whole, to possess more
species than the former. A limit to the life of the Radiolaria towards the
poles has not yet been found; the expeditions towards the North Pole (see
note C), like those towards the South (see note D), have obtained
bottom-deposits and ice enclosures which contained Radiolaria; in some of
the most northerly and most southerly positions which were reached the
number of Radiolaria enclosed in the ice was relatively great.

  A. The greater abundance of Radiolaria in the tropical seas is probably
  to be explained by the more favourable conditions of existence, and in
  particular the larger quantity of nutritive material (especially of
  decayed animals) and not by the higher temperature of the surface, for at
  depths of from 2000 to 3000 fathoms where the abyssal Radiolaria live,
  the temperature is but little above the freezing point or even below it
  (compare the bottom temperatures in the list of Challenger Stations, §
  240).

  B. Station 271 of the Challenger Expedition, situated almost on the
  equator in the Mid Pacific (lat. 0° 33' S.), exceeds all other parts of
  the earth, hitherto known, in respect of its wealth in Radiolaria, and
  this is true of the pelagic as well as of the zonarial and abyssal forms.
  In the Station List the deposit at this point is stated to be
  "Globigerina ooze"; but after the calcareous matter has been removed by
  means of acid, the purest Radiolarian ooze remains, rich in varied and
  remarkable species. More than one hundred new species have been described
  from this Station alone.

  C. Regarding the Arctic Radiolaria compare the contributions of Ehrenberg
  (L. N. 24, pp. 138, 139, 195) and Brady on the English North Polar
  Expedition, 1875-76 (Ann. and Mag. Nat. Hist., 1878, vol. i. pp. 425,
  437).

  D. Regarding the Antarctic Radiolaria, compare § 230, note A, and
  Ehrenberg, Mikrogeologie (L. N. 6, Taf. xxxv., A.), also L. N. 24, pp.
  136-139.


229. _Fauna of the Pacific Ocean._--From the splendid discoveries of the
Challenger, and the supplementary observations obtained from other sources,
the Pacific seems to be the ocean basin which is richest both
quantitatively and qualitatively in Radiolarian life, {cxlix}excelling both
the Indian and Atlantic Oceans in this respect. It may be assumed with
great probability that by far the largest portion of the Pacific has a
depth of between 2000 and 3000 fathoms, and that its bottom is covered
either with Radiolarian ooze (§ 237) or with a red clay (§ 239), which
contains many SPUMELLARIA and NASSELLARIA, and has probably been derived
for a great part from broken down and metamorphosed Radiolarian ooze (see
note A). Pure Radiolarian ooze was found by the Challenger eastwards in the
Central Pacific (over a wide area between lat. 12° N. and 12° S., Stations
265 to 274), and also westwards in the latitude of the Philippines, twenty
degrees to the east of them (between lat. 5° N. and 15° N.). The great
abundance of Radiolaria present in the neighbourhood of the Philippines and
in the Sunda Sea was already known from other investigations (note B). The
red clay also, which covers a great part of the bottom of the North
Pacific, and which was obtained of very constant composition by the
Challenger between lat. 35° N. and 38° N., from Japan to the meridian of
Honolulu (from long. 144° E. to 156° W.), is so pre-eminently rich in
Radiolaria that it often approaches in composition the Radiolarian ooze,
and has probably been derived from it. The track of the Challenger through
the tropical and northern parts of the Pacific describes nearly three sides
of a rectangle, which includes about half of the enormous Pacific basin,
and from this as well as from other supplementary observations it may with
great probability be concluded that by far the largest part of the bed of
the Pacific (at least three-fourths) is covered either with Radiolarian
ooze or with red clay, which contains a larger or smaller amount of the
remains of Radiolaria. With this agrees also the important fact that the
numerous preparations of pelagic materials and collections of pelagic
animals, which were collected by the Challenger in the Pacific, almost
always indicate a corresponding amount of Radiolarian life on the surface.
This is true in particular also of the South Pacific, between lat. 33° S.
and 40° S. (from long. 133° W. to 73° W., Stations 287 to 301); the surface
of this southern region and the different bathymetrical zones were rich in
new and peculiar species of Radiolaria.

  A. Many specimens of bottom-deposits from the Pacific, which are entered
  in the Challenger lists either as "red clay" or "Globigerina ooze,"
  contain larger or smaller quantities of Radiolaria, and the number of
  different species of SPUMELLARIA and NASSELLARIA which they contain is
  often so great that the deposit might have been almost as appropriately
  termed "Radiolarian ooze," _e.g._, Stations 241 to 245, and 270, 271
  (compare §§ 236-239).

  B. Pacific Radiolarian ooze was first obtained by Lieutenant Brooke (May
  11, 1859) between the Philippines and Marianne Islands, from a depth of
  3300 fathoms (lat. 18° 3' N., long. 129° 11' E.). Ehrenberg, who first
  described it, found seventy-nine different species of Polycystina in it,
  and reported "that their quantity and the number of different forms
  increased with the depth" (Monatsber. d. k. preuss. Akad. d. Wiss.
  Berlin, 1860, pp. 466, 588, 766).


230. _Fauna of the Indian Ocean._--As regards its Radiolarian fauna the
Indian Ocean is the least known of the three great basins. Still the few
limited spots, regarding which {cl}investigations are forthcoming, indicate
a very rich development of Radiolarian life. Probably it approaches more
nearly the fauna of the Pacific than that of the Atlantic, both as regards
the abundance and the morphological characters of its species. The
researches of the Challenger are very limited and incomplete as regards the
Indian Ocean, for the expedition only just touched upon this great ocean
basin (2000 to 3000 fathoms deep) at its two extremities (westwards at the
Cape of Good Hope and eastwards at Tasmania), its course lying for the most
part south of lat. 45° S. and extending beyond lat. 65° S. (from Station
149 to 158, south of lat. 50° S.). It is true that this portion of the
South Indian Ocean was shown to contain Radiolaria everywhere, but these
were more plentiful in individuals than in species. Only from Station 156
to Station 159 (between lat. 62° and 47° S., and long. 95° and 130° E.) was
the bottom, which consisted partly of Diatom ooze and partly of Globigerina
ooze, richer in species (see note A). The gaps left by the Challenger in
the investigation of the Indian Ocean, have, however, been to some extent
filled from other sources. As early as 1859 the English "Cyclops"
expedition had shown that the bottom of the Indian Ocean to the east of
Zanzibar (lat. 9° 37' S., long. 61° 33' W.) is covered with pure
Radiolarian ooze (see note B). Also since the Tertiary rocks of the Nicobar
Islands are for the most part of the same composition, and since a great
abundance of Radiolaria has been shown to be present both in the east part
of the ocean, between the Cocos Islands and the Sunda Archipelago (see note
C), and in the northern part or Arabian Sea between Socotra and Ceylon (see
note D); it may be assumed with great probability that the greater part of
the basin of the Indian Ocean, like that of the Pacific, is covered either
with Radiolarian ooze or with the characteristic red clay. With this agrees
the richness of the surface of the Indian Ocean in Radiolaria of the most
various groups, which has been more extensively demonstrated.

  A. The Radiolarian fauna collected by the Challenger on the voyage from
  the Cape to Melbourne, shows in part, namely, from Station 156 to Station
  158, very peculiar and characteristic composition; in particular, the
  Diatom ooze of Station 157 passes over in great part into a Radiolarian
  ooze, mainly composed of #Sphærellaria#. This is worthy of a more
  thorough investigation than I was able, owing to lack of material and
  time, to give it.

  B. The remarkably pure Radiolarian ooze of Zanzibar, discovered by
  Ehrenberg in 1859, was the earliest known recent example of that deposit.
  It was brought up by Captain Pullen of the English man-of-war "Cyclops,"
  from a depth of 2200 fathoms, between Zanzibar and the Seychelles, and
  "under a magnifying power of 300 diameters, showed at the first glance a
  mass of almost pure Polycystina, such as no sample of a deep-sea deposit
  has hitherto shown. It is very noticeable that in the whole of this mass
  of living forms, no calcareous shells are to be seen" (Ehrenberg, L. N.
  24, pp. 148, 149).

  C. For the most important material from the Indian Ocean, I am indebted
  to Captain Heinrich Rabbe of Bremen, who during many voyages in the
  Indian Ocean, in his ship "Joseph Haydn," made numerous collections in
  different localities with the tow-net and the trawl, and admirably
  preserved the rich collections thus made. The greatest abundance of
  Radiolaria was found in those {cli}obtained to the east of Madagascar,
  and next in those from the neighbourhood of the Cocos Islands. I take
  this opportunity of expressing my thanks to Captain Rabbe for the
  liberality with which he placed all this valuable material at my
  disposal.

  D. On my voyage from Aden to Bombay, and thence to Ceylon (1881), and
  especially on my return journey from Ceylon, between the Maldive Islands
  and Socotra (1882), I carried on a number of experiments with a surface
  net, which yielded a rich fauna of pelagic animals, and among them many
  new species of Radiolaria, for observation. On several nights when the
  smooth surface of the Indian Ocean, unrippled by any wind, shone with the
  most lovely phosphorescent light, I drew up water from the surface with a
  bucket, and obtained a rich booty. A number of other new species of
  Radiolaria from very various parts of the Indian Ocean I obtained from
  the alimentary canal of pelagic animals, such as Medusæ, Salpæ,
  Crustacea, &c. Although the total number of Radiolaria known to me from
  the Indian Ocean is much less than from the Atlantic and Pacific, there
  are several new genera and numerous species among them, which show that a
  careful study of this fauna will be of wide interest.


231. _Fauna of the Atlantic Ocean._--The Atlantic Ocean in all parts, of
which the pelagic fauna has been examined, has shown the same constant
presence of Radiolaria, and in certain parts of its abyssal deposits a
larger or smaller quantity of different types belonging to this class; on
the whole, however, its Radiolarian fauna is inferior to that of the
Pacific, and probably also to that of the Indian Ocean, both in quantity
and quality. Pure Radiolarian ooze, such as is so extensively found on the
floor of the Pacific, and in certain places in that of the Indian Ocean,
has not yet been found in the Atlantic (see § 237). The red clay, too, of
the deep Atlantic does not seem to be so rich in Radiolaria as that of the
Pacific; nevertheless, the number of species peculiar to the Atlantic is
very large, and at certain points the abundance of species as well as of
individuals seems to be scarcely less than in the Pacific. This is
especially true of the eastern equatorial zone not far from Sierra Leone,
Stations 347 to 352 (see note A); also of the South Atlantic between Buenos
Ayres and Tristan da Cunha, Stations 324, 325, 331 to 333 (see note B);
and, lastly, in the North Atlantic in the Gulf Stream and near the Canary
Islands (see note C). The fauna of the latter agrees for the most part with
that of the Mediterranean (see note D). In addition to the material
collected by the Challenger, other deep-sea investigations have furnished
bottom-deposits from different parts of the ocean, which have proved very
rich in Radiolaria (see note E). Furthermore, since the island of Barbados
consists for the most part of fossil Radiolarian ooze, it is very probable
that at certain parts of the tropical Atlantic true Radiolarian ooze, like
that of the Pacific and Indian Oceans, will eventually be found in depths
between 2000 and 3000 fathoms, perhaps over a considerable area.

  A. The tropical zone of the eastern Atlantic seems to be especially rich
  in peculiar Radiolaria of different species. This is shown by numerous
  preparations from the surface, and from various depths (between lat. 3°
  S. and 11° N., and long. 14° W. to 18° W.), which were made towards the
  {clii}end of the cruise. Unfortunately no bottom-deposits were obtained
  from the most important stations (except Nos. 346 and 347, depths 2350
  and 2250 fathoms) in this region; at these the deposit was a Globigerina
  ooze containing numerous different species of Radiolaria.

  B. In the South Atlantic, between Buenos Ayres and Tristan da Cunha
  (between lat. 35° S. and 43° S., long. 8° W. and 57° W.) there appears to
  be a long stretch covered partly with Globigerina ooze (Stations 331 to
  334), or red clay (Stations 329, 330), partly with blue mud (Stations 318
  to 328), which contains not only large masses of individuals but numerous
  peculiar species of SPUMELLARIA and NASSELLARIA. The preparations from
  the surface-takings of this region are also rich in these, as well as in
  peculiar PHÆODARIA.

  C. The northern part of the Atlantic appears on the whole to be inferior
  to the tropical and southern portions as regards its richness in
  Radiolaria, and from the western half more especially, only few species
  are known. From my researches at Lanzerote in 1866-67, it appears that
  the pelagic fauna of the Canary Islands is very rich in them, as is also
  the Gulf Stream in the neighbourhood of the Færöe Channel, according to
  the investigations of John Murray (see his Report on the "Knight-Errant"
  Expedition, Proc. Roy. Soc. Edin., vol. xi., 1882).

  D. The Radiolaria of the Mediterranean are of special interest, because
  almost all our knowledge of these organisms in the living conditions and
  of their vital functions has been derived from investigations conducted
  on its shores. Johannes Müller laid the foundation of this knowledge by
  his investigations at Messina, and on the Ligurian and French coasts at
  Nice, Cette, and St. Tropez (L. N. 10). The many new Radiolaria which I
  described in my Monograph (L. N. 16, 1862), were for the most part taken
  at Messina, the place which possesses a richer pelagic fauna than any
  other, so far as is yet known, in the Mediterranean. Other new species I
  found afterwards at Villafranca near Nice, in 1864 (L. N. 19), at
  Portofino near Genoa (1880), at Corfu (1877), and at other points on the
  coast. In Messina also, Richard Hertwig collected the material for his
  valuable treatise on the Organisation of the Radiolaria (L. N. 33), after
  he had previously made investigations into their histology at Ajaccio in
  Corsica (L. N. 26). Lastly, at Naples, Cienkowski (L. N. 22) and Karl
  Brandt (L. N. 38, 39, 52) carried out their important investigations into
  the reproduction and symbiosis of the Radiolaria. With respect to the
  character of its Radiolaria, the Mediterranean fauna is to be regarded as
  a special province of the North Atlantic.

  E. Among the smaller contributions which have been made towards our
  knowledge of the Atlantic Radiolarian fauna, the communications of
  Ehrenberg on the deposits obtained in sounding for the Atlantic cable,
  and on the Mexican Gulf Stream near Florida, deserve special mention (L.
  N. 24, pp. 138, 139-145).


232. _Vertical Distribution._--The most important general result of the
discoveries of the Challenger, as regards the vertical or bathymetrical
distribution of the Radiolaria, is the interesting fact that numerous
species of this class are found living at the most various depths of the
sea, and that certain species are limited to particular bathymetrical
zones, _i.e._, are adapted to the conditions which obtain there. In this
respect three different Radiolarian faunas may be distinguished, which may
be shortly termed "pelagic," "zonarial," and "abyssal." The _pelagic_
Radiolaria swim at the surface, and when they sink (_e.g._, in a stormy
sea), only descend to a small depth, probably not more than from {cliii}20
to 30 fathoms (§ 233). The complicated conditions of existence created by
the keen struggle for existence at the surface of the sea, give rise to the
formation of very numerous pelagic species, especially of Porulosa
(SPUMELLARIA and ACANTHARIA). The _abyssal_ Radiolaria are very different
from those just mentioned; they live at the bottom of the deep-sea, not
resting upon nor attached to it, but probably floating at a little distance
above it, and are adapted to the conditions of existence which obtain there
(§ 235). Here the Osculosa (NASSELLARIA and PHÆODARIA) seem to predominate.
The _zonarial_ Radiolaria live floating at various depths between the
pelagic and abyssal species (§ 234). In their morphological characters they
gradually approach the pelagic forms upwards and the abyssal downwards.

  The views which have hitherto been held regarding the bathymetrical or
  vertical distribution of the Radiolaria have been entirely altered by the
  magnificent discoveries of the Challenger, and especially by the
  important observations of Sir Wyville Thomson (L. N. 31) and John Murray
  (L. N. 27). These two distinguished deep-sea explorers have, as a result
  of their wide experience, been convinced that Radiolaria exist at all
  depths of the ocean, and that there are large numbers of true deep-sea
  species which are never found at the surface of the sea nor at slight
  depths (L. N. 31, vol. i. pp. 236-238; L. N. 27, pp. 523, 525). The
  result of my ten years' work upon the Challenger Radiolaria, and the
  comparative study of more than a thousand mountings from all depths, has
  only been to confirm this opinion, and I am further persuaded that it
  will some day be possible by the aid of suitable nets (not yet invented)
  to distinguish different faunistic zones in the various depths of the
  sea. In this connection may be mentioned the specially interesting fact
  that the species of Radiolaria of one and the same family present in the
  different depths characteristic morphological distinctions, which
  obviously correspond to their different physiological relations in the
  struggle for existence. Owing to those extensive discoveries, the
  representation which I gave in my Monograph (1862, L. N. 16, pp. 172-196)
  of the vertical distribution of the Radiolaria, and of their life in the
  greatest depths of the sea, has been entirely changed. Compare also
  Bütschli (L. N. 41, p. 466).


233. _The Pelagic Fauna._--The surface of the open ocean seems everywhere,
at a certain distance from the coast at least, to be peopled by crowds of
living Radiolaria. In the tropical zone these pelagic crowds consist of
many different species, whilst in the frigid zones, on the other hand, they
are made up of many individuals belonging to but few species. Most of these
inhabitants of the surface may be regarded as truly pelagic species, which
either remain always at the surface or descend only very slightly below it.
Probably most Porulosa (both SPUMELLARIA and ACANTHARIA) belong to this
group; whilst but few Osculosa occur in it, and fewer PHÆODARIA than
NASSELLARIA. In general the pelagic Radiolaria are distinguished from the
abyssal by the more delicate and slender structure of their skeletons; the
pores of the lattice-shells are larger, the intervening trabeculæ thinner;
the armature of spines, spathillæ, anchors, &c., is more various and more
highly developed. Numerous forms are to be found among the pelagic
{cliv}Radiolaria which have either an incomplete skeleton or none at all.
When the pelagic forms leave the surface on account of unfavourable
weather, they appear only to sink to slight depths (probably not below 20
or 30 fathoms). Within the limits of the same family the size of the
pelagic species seems to be on an average greater than that of the related
abyssal forms.


234. _The Zonarial Fauna._--Between the pelagic fauna living at the surface
of the open sea and the abyssal, which floats immediately over the bottom,
there appears to be usually a middle fauna, which inhabits the different
bathymetrical zones of the intermediate water, and hence may be shortly
called the "zonarial" fauna.  The different species of Radiolaria which
inhabit these different strata in the same vertical column of water present
differences corresponding to those of the plants composing the several
zones of vegetation, which succeed each other at different heights on a
mountain; they correspond to the different conditions of existence which
are presented by the different strata of water, and to which they have
become adapted in the struggle for existence. The existence of such
bathymetrical zones has been shown by those important, if not numerous,
observations of the Challenger, in which the tow-net was used at different
depths at one and the same Station. In several cases the character of the
Radiolarian fauna at different depths presented characteristic differences.

  For the present, and until we are better acquainted with the characters
  of the Radiolarian fauna at different depths, we may distinguish
  provisionally the following _five bathymetrical zones_:--(1) The
  _pelagic_ zone, extending from the surface to a depth of about 25
  fathoms; (2) the _pellucid_ zone, extending from 25 to 150 fathoms, or as
  far as the influence of the sunlight makes itself felt; (3) the _obscure_
  zone, extending from 150 to 2000 fathoms, or from the depth at which
  sunlight disappears to that at which the influence of the water
  containing carbonic acid begins and the calcareous organisms vanish; (4)
  the _siliceous_ zone, extending from 2000 or 2500 to about 3000 fathoms,
  in which only siliceous not calcareous Rhizopoda are found, and in which
  the peculiar conditions of the lowest regions have not yet appeared; (5)
  the _abyssal_ zone, in which the accumulation of the oceanic deposits,
  and the influence of the bottom currents, create new conditions of
  existence. So far as our isolated and incomplete observations of the
  zonarial Radiolarian fauna extend, it appears that the subclass Porulosa
  (SPUMELLARIA and ACANTHARIA) predominates in the two upper zones, and as
  the depth increases is gradually replaced by the subclass Osculosa
  (NASSELLARIA and PHÆODARIA), so that the latter predominates in the two
  lowest zones. The obscure zone which lies in the middle is probably the
  poorest in species. In general, the morphological characters of the
  zonarial fauna appear to change gradually upwards into the delicate form
  of the pelagic and downwards into the robust constitution of the abyssal;
  so also the average size of the individuals (within the limits of the
  same family) appears to increase upwards and decrease downwards.


235. _The Abyssal Fauna._--The great majority of Radiolaria which have
hitherto been observed, and which are described in the systematic portion
of this Report, have been obtained from the bottom of the deep-sea, and
more than half of all the species have been {clv}derived from the pure
Radiolarian ooze, which forms the bed of the Central Pacific at depths of
from 2000 to 4000 fathoms (§ 237). Many of these abyssal forms were brought
up with the malacoma uninjured, and they show, both when mounted
immediately in balsam, and when preserved in alcohol, all the soft parts
almost as clearly as fresh preparations of pelagic Radiolaria. These
species are to be regarded as truly abyssal, _i.e._, as forms which live
floating only a little distance above the bottom of the deep-sea, having
become adapted to the peculiar conditions of life which obtain in the
lowest regions of the ocean. Probably the majority of the PHÆODARIA belong
to these abyssal Radiolaria, as well as a large number of NASSELLARIA, but
on the other hand, only a small number of ACANTHARIA and SPUMELLARIA are
found there. A character common to these abyssal forms, and rarely found in
those from the surface or from slight depths, is found in their small size
and their heavy massive skeletons, in which they strikingly resemble the
fossil Radiolaria of Barbados and the Nicobar Islands. The lattice-work of
the shell is coarser, its trabeculæ thicker and its pores smaller than in
pelagic species of the same group; also the apophyses (spines, spathillæ,
coronets, &c.), are much less developed than in the latter. From these true
abyssal Radiolaria must be carefully distinguished those species whose
empty skeletons, devoid of all soft parts, occur also in the Radiolarian
ooze of the deep-sea, but are clearly only the sunken remains of dead
forms, which have lived at the surface or in some of the upper zones.


236. _Deposits containing Radiolaria._--The richest collection of
Radiolaria is found in the deposits of ooze which form the bed of the
ocean. Although the pelagic material skimmed from the surface of the sea,
and the zonarial material taken by sinking the tow-net to various depths,
are always more or less rich in Radiolaria, still the number of species
thus obtained is, on the whole, much less than has hitherto been got merely
from deep-sea deposits. Of course the skeletons found in the mud of the
ocean-bed, may belong either to the abyssal species which live there (§
235), or to the zonarial (§ 234), or to the pelagic species (§ 233), for
the siliceous skeletons of these latter sink to the bottom after their
death. Almost all these remains found in the deposits belong to the
siliceous "Polycystina" (SPUMELLARIA and NASSELLARIA); PHÆODARIA occur but
sparingly, and ACANTHARIA are entirely wanting, for their acanthin skeleton
readily dissolves. The abundance of Radiolaria varies greatly according to
the composition and origin of the deposits. In general marine deposits may
be divided into two main divisions, terrigenous and abyssal, or, more
shortly, muds and oozes. The _terrigenous_ deposits (or muds) include all
those sediments which are made up for the most part of materials worn away
from the coasts of continents and islands, or brought down into the sea by
rivers. Their greatest extent from the coast is about 200 nautical miles.
They contain varying quantities of Radiolaria, but much fewer than those of
the next group. The _abyssal_ deposits (or oozes) usually commence at a
distance of from 100 to 200 nautical miles {clvi}from the coast. In general
they are characterised by great uniformity, corresponding to the constancy
of the conditions under which they are laid down; they may be divided into
three categories, the true Radiolarian ooze (§ 237), Globigerina ooze (§
238), and red clay (§ 239). Of these three most important deep-sea
formations the first is by far the richest in Radiolaria, although the
other two contain often very many siliceous shells.

  The marvellous discoveries of the Challenger have thrown upon the nature
  of marine deposits an entirely new light, which justifies most important
  conclusions regarding the geographical distribution and geological
  significance of the Radiolaria. Since Dr. John Murray and the Abbé Renard
  will treat fully of these interesting relations in a forthcoming volume
  of the Challenger series (Report on the Deep-Sea Deposits), it will be
  sufficient here to refer to their preliminary publication already
  published (Narrative of the Cruise of H.M.S. Challenger, 1885, vol. ii.
  part ii. pp. 915-926); see also the earlier communications by John Murray
  (1876, L. N. 27, pp. 518-537), and by Sir Wyville Thomson (The Atlantic,
  L. N. 31, vol. i. pp. 206-246). In the Narrative (_loc. cit._, p. 916)
  the following table of marine deposits is given:--

                       {Shore formations,       } Found in inland
                       {Blue mud,               }   seas and along the
                       {Green mud and sand,     }   shores of
                       {Red mud,                }   continents.
  Terrigenous deposits.{
                       {Volcanic mud and sand,  } Found around oceanic
                       {Coral mud and sand,     }   islands and along the
                       {Coralline mud and sand, }   shores of continents.

                       {Globigerina ooze,       } Found in the abysmal
                       {Pteropod ooze,          }   regions of the
  Abysmal deposits.    {Diatom ooze,            }   ocean basins.
                       {Radiolarian ooze,       }
                       {Red clay,               }

237. _Radiolarian Ooze._--By Radiolarian ooze, in the strict sense of the
term, are understood those oceanic deposits, the greater part of which
(often more than three-quarters) is composed of the siliceous skeletons of
this class. Such _pure_ Radiolarian ooze has only been found in limited
areas of the Pacific and Indian Oceans. It is most conspicuous in the
Central Pacific, between lat. 12° N. and 8° S., long. 148° W. to 152° W.,
the depth being everywhere between 2000 and 3000 fathoms (Stations 266 to
268 and 272 to 274). In the deepest of the Challenger soundings (Station
225, 4475 fathoms) the bottom is composed of pure Radiolarian ooze, as well
as at the next Station in the Western Tropical Pacific (Station 226, 2300
fathoms), the latitude varying from 12° N. to 15° N., and the longitude
from 142° E. to 144° E. In the Indian Ocean also, pure Radiolarian ooze was
found in the year 1859 between Zanzibar and the Seychelles, this being the
first known example of it (§ 230). On the other hand, it has not yet been
found in the bed of the Atlantic; but the Tertiary formations of Barbados
(Antilles, § 231) like those of the Nicobar Islands (Further India), are to
be regarded as pure Radiolarian {clvii}ooze in the fossil condition.
_Mixed_ Radiolarian ooze is the name given to those deposits in which the
Radiolaria exceed any of the other organic constituents, although they do
not make up half the total mass. To this category belong a large number of
the Challenger soundings which are entered in the Station list either as
red clay or Globigerina ooze. Such mixed Radiolarian ooze has been
discovered (A) in the North Pacific in an elongated area of red clay
extending from Station 241 to Station 245 (perhaps even from Station 238 to
Station 253), that is, at least, from long. 157° E. to 175° E., between
lat. 35° N. and 37° N.; (B) in the tropical Central Pacific in the
Globigerina ooze of Stations 270 and 271. The ooze from the latter station,
situated almost on the equator (lat. 0° 33' S., long. 151° 34' W.), is
specially remarkable, for it has yielded more new species of SPUMELLARIA
and NASSELLARIA than any other Station, not excluding even the neighbouring
Stations 268, 269, and 272. Probably such mixed Radiolarian ooze is very
widely distributed in the depths of the ocean, as, for example, in the
South Pacific (Stations 288, 289, 300, and 302), and in the Southern Ocean
(Stations 156 to 159); also in the South Atlantic (Stations 324, 325, 331,
332) and in the tropical Atlantic (Stations 348 to 352). When carefully
purified and decalcified by acids, Radiolarian ooze appears as a fine
shining white powder; in the raw state it is yellowish or reddish,
sometimes reddish-brown or dark brown in colour, according to the quantity
of oxides of iron, manganese, &c., which it contains. Calcareous skeletons
(especially the tests of pelagic Foraminifera) do not occur at all or only
in very minute quantities in _pure_ Radiolarian ooze from more than 2000
fathoms, whilst specimens of _mixed_ ooze often contain considerable
quantities of them.

  Pure Radiolarian ooze was first described by Dr. John Murray as regards
  its peculiar nature and composition under the name "Radiolarian ooze"
  (1876, L. N. 27, pp. 525, 526); compare also Sir Wyville Thomson (The
  Atlantic, L. N. 31, vol. i. pp. 231-238), and John Murray (Narr. Chall.
  Exp., L. N. 53, vol. i. pt. ii. pp. 920-926, pl. N. fig. 2). The
  different specimens of pure Radiolarian ooze obtained by the Challenger
  from the Pacific, and handed to me for investigation, are from depths of
  from 2250 fathoms to 4475 fathoms, and may be divided according to their
  composition into three different groups:--I. The Radiolarian ooze of the
  Western Tropical Pacific, Stations 225 and 226, from depths of 4475 and
  2300 fathoms (lat. 11° N. to 15° N., and long. 142° E. to 144° E.). II.
  The Radiolarian ooze of the northern half of the Central Pacific,
  Stations 265 to 269, from depths of 2550 to 2900 fathoms. III. The
  Radiolarian ooze of the southern half of the Central Pacific, Stations
  270 to 274, from depths of 2350 to 2925 fathoms. A fourth group would be
  constituted by the Radiolarian ooze from the Philippines, which was
  brought up by Brooke in 1860 near the Marianne Islands from 3300 fathoms,
  and described by Ehrenberg (Monatsber. d. k. preuss. Akad. d. Wiss.
  Berlin, 1860, p. 765). The Diatom ooze, too, found by the Challenger in
  the Antarctic regions (Stations 152 to 157) is in some parts so rich in
  Radiolaria that it passes over into true Radiolarian ooze. Regarding the
  Radiolarian ooze from Zanzibar, obtained by Captain Pullen in 1859 from
  2200 fathoms (§ 230), we have only the incomplete communications of
  Ehrenberg (L. N. 24, p. 147). A more accurate knowledge of these deposits
  from the Indian Ocean, and of {clviii}those which we may with probability
  expect from the tropical eastern Atlantic, will be sure to increase very
  widely our knowledge of the class.


238. _Globigerina Ooze._--Next to the Radiolarian ooze proper the
Globigerina ooze is the deposit which is richest in the remains of
Radiolaria. Often these are so abundant that it is doubtful to which
category the specimen should be referred (_e.g._, Stations 270 and 271, see
§ 237). In fact, the two pass without any sharp boundary into each other,
and both present transitions to the Diatom ooze. Next to red clay (§ 239),
Globigerina ooze is the most widely distributed of all sediments, and forms
a large part of the bed of the ocean at depths of 250 to 2900 fathoms
(especially between 1000 and 2000 fathoms). It covers extensive areas at
depths below 1800 fathoms, and in still deeper water is replaced by red
clay. It is a fine-grained white, grey, or yellowish powder, which
sometimes becomes coloured rose, red, or brown owing to the admixture of
oxides of iron and manganese. True Globigerina ooze consists for the most
part of the accumulated calcareous shells of pelagic Foraminifera,
principally _Globigerina_ and _Orbulina_, but also _Hastigerina_,
_Pulvinulina_, &c. It contains usually from 50 to 80 per cent. of calcium
carbonate, the extreme values being 40 and 95 per cent. After this has been
removed by acids, there remains a residue, which consists partly of the
siliceous shells of Radiolaria and Diatoms, and partly of mineral particles
identical with the volcanic elements of the red clay.

  Regarding the composition and significance of the Globigerina ooze, see
  John Murray (L. N. 27, pp. 523-525, and L. N. 53, vol. i. p. 919).
  Recently this author has separated from the Globigerina ooze (_sensu
  stricto_), the _Pteropod ooze_, distinguished from the former by the
  greater abundance of Pteropod shells and calcareous shells of larger
  pelagic organisms which it contains. It is found in moderate depths (at
  most 1500 fathoms), and contains fewer Radiolaria.


239. _Red Clay._--This is quantitatively the most important of all deep-sea
deposits, covering by far the greatest extent of the three great ocean
basins at depths greater than 2200 fathoms. It thus far surpasses in area
the other deposits, both Radiolaria and Globigerina oozes, and commonly
forms a still deeper layer beneath them. Probably these three deep-sea
deposits together cover about three-eighths of the whole surface of the
earth, that is, about as much as all the continents together, whilst only
two-eighths are covered by the terrigenous deposits. Red clay is
principally composed of silicate of alumina, mixed in various proportions
with other finely granular substances; its usual red colour, which
sometimes passes over into grey or brown, is more especially due to
admixture of oxides of iron and manganese. Calcareous matter is usually
entirely wanting, or present only in traces, whilst free silica is found in
very variable, often considerable quantities. The chief mass of the red
clay consists of volcanic ashes, pumice, fragments of lava, &c., whilst a
large part of it is generally composed of shells of Radiolaria or fragments
of {clix}them; in many places the number of well-preserved skeletons
contained in the red clay is very considerable, so that it passes over
gradually into the Radiolarian ooze (_e.g._, in the North Pacific, Stations
238 to 253, see § 237). Hence it may be supposed that a large part of the
red clay consists of decomposed Radiolarian ooze.

  The characteristic composition and fundamental significance of the red
  clay in the formation of the deep-sea bed were first made known by the
  discoveries of the Challenger (compare John Murray, 1876, L. N. 27, p.
  527, and Narr. Chall. Exp., L. N. 53, vol. i. pt. ii. pp. 920-926, pl. N;
  also Wyville Thomson, The Atlantic, L. N. 31, vol. i. pp. 226-229).  The
  mineral components of the red clay are for the most part of volcanic
  origin, due to the decomposition of pumice, lava, &c. Among the organic
  remains found in it, the siliceous skeletons of Radiolaria are by far the
  most important, and their number is often considerable. A large portion
  of the red clay appears to me to consist of broken down Radiolarian
  shells, in which a peculiar metamorphism probably has taken place. Sir
  Wyville Thomson was of opinion that a considerable proportion of it
  consisted of the remains of Globigerina ooze, the calcareous constituents
  of which had been removed by the carbon dioxide in the deep-sea water (L.
  N. 31, _loc. cit._). Among these remains, however, the siliceous
  skeletons of the Radiolaria play a significant and often the most
  important part. Furthermore, John Murray has called attention to the fact
  that in many deep-sea deposits yellow and red insoluble particles remain,
  which unmistakably present the form of Radiolarian shells (L. N. 27, p.
  513). At Station 303 he found "amorphous clayey matter, rounded yellow
  minerals, many Radiolaria-shaped;" at Station 302 there was sediment
  "consisting almost entirely of small rounded red mineral particles; many
  of these had the form of both Foraminifera and Radiolaria; and it seemed
  as if some substance had been deposited in and on these organisms."
  Similar transitions from well-preserved Radiolarian shells into amorphous
  mineral particles I have found in several other specimens of Challenger
  soundings, and consider them a further argument for the supposition that
  the Radiolaria often take an important share in the formation of the red
  clay.


240. _List of Stations at which Radiolaria were observed on the Challenger
Expedition._--The 168 Stations recorded below, in soundings or surface
preparations from which I found Radiolaria, belong to the most various
parts of the sea which the Challenger traversed during her voyage round the
world; they constitute about half of the (364) observing Stations contained
in the official list published in the Narrative of the Cruise (Narr. Chall.
Exp., vol. i. part ii. Appendix ii.).

  In addition to the particulars given in the list regarding the
  geographical position of the Station, depth, temperature, and composition
  of the bottom deposit, I have added the result of my investigations as
  regards the relative abundance of the Radiolaria in each. The five
  letters (A to E) denote the following degrees of frequency:--A, abundant
  Radiolaria (AI, pure Radiolarian ooze; AII, mixed Radiolarian ooze); B,
  very numerous Radiolaria (but not a predominating quantity); C, many
  Radiolaria (medium quantity); D, few Radiolaria; E, very few Radiolaria
  (as they occur almost always). In using these symbols regard has been had
  to abundance of the abyssal as well as of the zonarial and pelagic forms
  (§ 232); sometimes also the estimated number of Radiolaria has been
  inserted, based upon information given by John Murray in his Preliminary
  Report (L. N. 27), and in the Narrative of the Cruise (L. N. 53), as well
  as by Henry B. Brady in his Report on the {clx}Foraminifera (Zool. Chall.
  Exp., part xxii., 1884). From Stations 348 to 352 in the Eastern Tropical
  Atlantic no specimens of the bottom were obtained, but a rich pelagic
  Radiolarian fauna was demonstrated by numerous preparations from the
  surface. The depths are given in fathoms and the temperature in degrees
  Fahrenheit. In the column describing the nature of the bottom the
  following abbreviations are used:--

  rad. oz. = Radiolarian ooze (§ 237).
  gl. oz. = Globigerina ooze (§ 238).
  r. cl. = red clay (§ 239).
  pt. oz. = Pteropod ooze (see p. clviii).
  di. oz. = Diatom ooze (see p. clvii).
  bl. m. = blue mud,        } terrigenous deposits
  gr. m. = green mud,       }  (see p. clvi).
  volc. m. = volcanic mud,  }
  r. m. = red mud.

  +----------+-----------+--------+------------+-----------+--------------+
  |          |           |        |   Bottom   |           |   Relative   |
  |Challenger| Locality. |Depth in|Temperature,| Nature of | Abundance of |
  | Station. |           |Fathoms.|    ° F.    |  Bottom.  |  Radiolaria. |
  +----------+-----------+--------+------------+-----------+--------------+
  |          |           |        |            |           |              |
  |     1.   |  N. Atl.  |  1890  |    36.8    | gl. oz.   |  D few       |
  |     2.   |     "     |  1945  |    36.8    | gl. oz.   |  E very few  |
  |     5.   |     "     |  2740  |    37.0    | r. cl.    |  D few       |
  |     9.   |     "     |  3150  |    36.8    | r. cl.    |  E very few  |
  |    24.   |  Tr. Atl. |   390  |     ...    | pt. oz.   |  D few       |
  |          |           |        |            |           |              |
  |    32.   |  N. Atl.  |  2250  |    36.7    | gl. oz.   |  E very few  |
  |    45.   |     "     |  1240  |    37.2    | bl. m.    |  E     "     |
  |    50.   |     "     |  1250  |    38.0    | bl. m.    |  E     "     |
  |    64.   |     "     |  2700  |     ...    | r. cl.    |  D few       |
  |    76.   |     "     |   900  |    40.0    | pt. oz.   |  D  "        |
  |          |           |        |            |           |              |
  |    98.   |  Tr. Atl. |  1750  |    36.7    | gl. oz.   |  C many      |
  |   106.   |     "     |  1850  |    36.6    | gl. oz.   |  C   "       |
  |   108.   |     "     |  1900  |    36.8    | gl. oz.   |  C   "       |
  |   111.   |     "     |  2475  |    33.7    | gl. oz.   |  C   "       |
  |   120.   |     "     |   675  |     ...    | r. m.     |  D few       |
  |          |           |        |            |           |              |
  |   132.   |  S. Atl.  |  2050  |    35.0    | gl. oz.   |  C many      |
  |   134.   |     "     |  2025  |    36.0    | gl. oz.   |  C   "       |
  |   137.   |     "     |  2550  |    34.5    | r. cl.    |  D few       |
  |   138.   |     "     |  2650  |    35.1    | r. cl.    |  D  "        |
  |   143.   |  S. Ind.  |  1900  |    35.6    | gl. oz.   |  E very few  |
  |          |           |        |            |           |              |
  |   144.   |     "     |  1570  |    35.8    | gl. oz.   |  E     "     |
  |   145.   |     "     |   140  |     ...    | volc. s.  |  D few       |
  |   146.   |     "     |  1375  |    35.6    | gl. oz.   |  C many      |
  |   147.   |     "     |  1600  |    34.2    | di. oz.   |  C   "       |
  |   148.   |     "     |   210  |     ...   {| gravel, } |  D few       |
  |          |           |        |           {| shells  } |              |
  |          |           |        |            |           |              |
  |   149H.  |     "     |   127  |     ...    | volc. m.  |  D  "        |
  |   150.   |     "     |   150  |    35.2    | gravel    |  D  "        |
  |   151.   |     "     |    75  |     ...    | volc. m.  |  D  "        |
  |   152.   |     "     |  1260  |     ...    | di. oz.   |  C many      |
  |   153.   |     "     |  1675  |     ...    | bl. m.    |  C   "       |
  |          |           |        |            |           |              |
  |   154.   |     "     |  1800  |     ...    | bl. m.    |  C   "       |
  |   155.   |     "     |  1300  |     ...    | bl. m.    |  C   "       |
  |   156.   |     "     |  1975  |     ...    | di. oz.   |  B numerous  |
  |   157.   |     "     |  1950  |    32.1    | di. oz.   |  B     "     |
  |   158.   |     "     |  1800  |    33.5    | gl. oz.   |  B     "     |
  |          |           |        |            |           |              |
  |   159.   |     "     |  2150  |    34.5    | gl. oz.   |  B     "     |
  |   160.   |     "     |  2600  |    33.9    | r. cl.    |  C many      |
  |   162.   |     "     |    38  |     ...    | sand      |  E very few  |
  |   163.   |  S. Pac.  |  2200  |    34.5    | gr. m.    |  E     "     |
  |   164A.  |     "     |  1200  |     ...    | gr. m.    |  E     "     |
  |          |           |        |            |           |              |
  |   165.   |  S. Pac.  |  2600  |    34.5    | r. cl.    |  D few       |
  |   166.   |     "     |   275  |    50.8    | gl. oz.   |  D  "        |
  |   169.   |     "     |   700  |    40.0    | bl. m.    |  D  "        |
  |   175.   |  Tr. Pac. |  1350  |    36.0    | gl. oz.   |  E very few  |
  |   181.   |     "     |  2440  |    35.8    | r. cl.    |  E  "        |
  |          |           |        |            |           |              |
  |   193.   |     "     |  2800  |    38.0    | bl. m.    |  D few       |
  |   195.   |     "     |  1425  |    38.0    | bl. m.    |  C many      |
  |   197.   |     "     |  1200  |    35.9    | bl. m.    |  D few       |
  |   198.   |     "     |  2150  |    38.9    | bl. m.    |  C many      |
  |   200.   |     "     |   250  |     ...    | gr. m.    |  B numerous  |
  |          |           |        |            |           |              |
  |   201.   |     "     |    82  |     ...    | st. & gra.|  C many      |
  |   202.   |     "     |  2550  |    50.5    | bl. m.    |  B numerous  |
  |   205.   |     "     |  1050  |    37.0    | bl. m.    |  C many      |
  |   206.   |     "     |  2100  |    36.5    | bl. m.    |  B numerous  |
  |   211.   |     "     |  2225  |    50.5    | bl. m.    |  B     "     |
  |          |           |        |            |           |              |
  |   213.   |     "     |  2050  |    38.8    | bl. m.    |  C many      |
  |   214.   |     "     |   500  |    41.8    | bl. m.    |  C   "       |
  |   215.   |     "     |  2550  |    35.4    | r. cl.    |  C many      |
  |   216A   |     "     |  2000  |    35.4    | gl. oz.   |  B numerous  |
  |   217.   |     "     |  2000  |    35.2    | bl. m.    |  C many      |
  |          |           |        |            |           |              |
  |   218.   |     "     |  1070  |    36.4    | bl. m.    |  C   "       |
  |   220.   |     "     |  1100  |    36.2    | gl. oz.   |  C   "       |
  |   221.   |     "     |  2650  |    35.4    | r. cl.    |  B numerous  |
  |   222.   |     "     |  2450  |    35.2    | r. cl.    |  B     "     |
  |   223.   |     "     |  2325  |    35.5    | gl. oz.   |  B     "     |
  |          |           |        |            |           |              |
  |   224.   |     "     |  1850  |    35.4    | gl. oz.   |  B     "     |
  |   225.   |     "     |  4475  |    35.2    | rad. oz.  |  A very many |
  |   226.   |     "     |  2300  |    35.5    | rad. oz.  |  A     "     |
  |   230.   |  N. Pac.  |  2425  |    35.5    | r. cl.    |  C many      |
  |   231.   |     "     |  2250  |    35.2    | bl. m.    |  C   "       |
  |          |           |        |            |           |              |
  |   232.   |     "     |   345  |    41.1    | gr. m.    |  C   "       |
  |   234.   |     "     |  2675  |    35.8    | bl. m.    |  B numerous  |
  |   235.   |     "     |   565  |    38.1    | gr. m.    |  D few       |
  |   236.   |     "     |   775  |    37.6    | gr. m.    |  C many      |
  |   237.   |     "     |  1875  |    35.3    | bl. m.    |  C   "       |
  |          |           |        |            |           |              |
  |   238.   |     "     |  3950  |    35.0    | r. cl.    |  B numerous  |
  |   239.   |     "     |  3625  |    35.1    | r. cl.    |  B     "     |
  |   240.   |     "     |  2900  |    34.9    | r. cl.    |  B     "     |
  |   241.   |     "     |  2300  |    35.1    | r. cl.    |  A very many |
  |   242.   |     "     |  2575  |    35.1    | r. cl.    |  AII   "     |
  |          |           |        |            |           |              |
  |   243.   |     "     |  2800  |    35.0    | r. cl.    |  AII   "     |
  |   244.   |     "     |  2900  |    35.3    | r. cl.    |  AII   "     |
  |   245.   |     "     |  2775  |    34.9    | r. cl.    |  AII   "     |
  |   246.   |     "     |  2050  |    35.1    | gl. oz.   |  B numerous  |
  |   247.   |     "     |  2530  |    35.2    | r. cl.    |  C many      |
  |          |           |        |            |           |              |
  |   248.   |     "     |  2900  |    35.1    | r. cl.    |  C   "       |
  |   249.   |     "     |  3000  |    35.2    | r. cl.    |  B numerous  |
  |   250.   |     "     |  3050  |    35.0    | r. cl.    |  B     "     |
  |   251.   |     "     |  2950  |    35.1    | r. cl.    |  B     "     |
  |   252.   |     "     |  2740  |    35.3    | r. cl.    |  B     "     |
  |          |           |        |            |           |              |
  |   253.   |     "     |  3125  |    35.1    | r. cl.    |  B     "     |
  |   254.   |     "     |  3025  |    35.0    | r. cl.    |  C many      |
  |   255.   |     "     |  2850  |    35.0    | r. cl.    |  C   "       |
  |   256.   |     "     |  2950  |    35.2    | r. cl.    |  B numerous  |
  |   257.   |     "     |  2875  |    34.9    | r. cl.    |  C many      |
  |          |           |        |            |           |              |
  |   258.   |     "     |  2775  |    35.2    | r. cl.    |  C   "       |
  |   259.   |  Tr. Pac. |  2225  |    34.9    | r. cl.    |  C   "       |
  |   261.   |     "     |  2050  |    35.2    | volc. m.  |  C many      |
  |   262.   |     "     |  2875  |    35.2    | r. cl.    |  C   "       |
  |   263.   |     "     |  2650  |    35.1    | r. cl.    |  B numerous  |
  |          |           |        |            |           |              |
  |   264.   |     "     |  3000  |    35.2    | r. cl.    |  C many      |
  |   265.   |     "     |  2900  |    35.0    | r. cl.    |  A very many |
  |   266.   |     "     |  2750  |    35.1    | rad. oz.  |  A     "     |
  |   267.   |     "     |  2700  |    35.0    | rad. oz.  |  A     "     |
  |   268.   |     "     |  2900  |    34.8    | rad. oz.  |  A     "     |
  |          |           |        |            |           |              |
  |   269.   |     "     |  2550  |    35.2    | rad. oz.  |  A     "     |
  |   270.   |     "     |  2925  |    34.6    | gl. oz.   |  A     "     |
  |   271.   |     "     |  2425  |    35.0    | gl. oz.   |  A     "     |
  |   272.   |     "     |  2600  |    35.1    | rad. oz.  |  A     "     |
  |   273.   |     "     |  2350  |    34.5    | rad. oz.  |  A     "     |
  |          |           |        |            |           |              |
  |   274.   |     "     |  2750  |    35.1    | rad. oz.  |  A     "     |
  |   275.   |     "     |  2610  |    35.0    | r. cl.    |  B numerous  |
  |   276.   |     "     |  2350  |    35.1    | r. cl.    |  C many      |
  |   280.   |     "     |  1940  |    35.3    | gl. oz.   |  D few       |
  |   281.   |     "     |  2385  |    34.9    | r. cl.    |  C many      |
  |          |           |        |            |           |              |
  |   282.   |  S. Pac.  |  2450  |    35.1    | r. cl.    |  C   "       |
  |   283.   |     "     |  2075  |    35.4    | gl. oz.   |  D few       |
  |   284.   |     "     |  1985  |    35.1    | gl. oz.   |  C many      |
  |   285.   |     "     |  2375  |    35.0    | r. cl.    |  D few       |
  |   286.   |     "     |  2335  |    34.8    | r. cl.    |  D  "        |
  |          |           |        |            |           |              |
  |   287.   |     "     |  2400  |    34.7    | r. cl.    |  D  "        |
  |   288.   |     "     |  2600  |    34.8    | r. cl.    |  B numerous  |
  |   289.   |     "     |  2550  |    34.8    | r. cl.    |  B     "     |
  |   290.   |     "     |  2300  |    34.9    | r. cl.    |  C many      |
  |   291.   |     "     |  2250  |    34.6    | r. cl.    |  C   "       |
  |          |           |        |            |           |              |
  |   292.   |     "     |  1600  |    35.2    | gl. oz.   |  C   "       |
  |   293.   |     "     |  2025  |    34.4    | gl. oz.   |  C   "       |
  |   294.   |     "     |  2270  |    34.6    | r. cl.    |  D few       |
  |   295.   |     "     |  1500  |    35.3    | gl. oz.   |  C many      |
  |   296.   |     "     |  1825  |    35.3    | gl. oz.   |  D few       |
  |          |           |        |            |           |              |
  |   297.   |     "     |  1775  |    35.5    | gl. oz.   |  D  "        |
  |   298.   |     "     |  2225  |    35.6    | bl. m.    |  C many      |
  |   299.   |     "     |  2160  |    35.2    | bl. m.    |  C     "     |
  |   300.   |     "     |  1375  |    35.5    | gl. oz.   |  B numerous  |
  |   302.   |     "     |  1450  |    35.6    | gl. oz.   |  B     "     |
  |          |           |        |            |           |              |
  |   303.   |     "     |  1325  |    36.0    | bl. m.    |  D few       |
  |   304.   |     "     |    45  |     ...    | gr. m.    |  E very few  |
  |   318.   |  S. Atl.  |  2040  |    33.7    | bl. m.    |  C few       |
  |   319.   |     "     |  2425  |    32.7    | bl. m.    |  C  "        |
  |   323.   |     "     |  1900  |    33.1    | bl. m.    |  C  "        |
  |          |           |        |            |           |              |
  |   324.   |     "     |  2800  |    32.6    | bl. m.    |  B numerous  |
  |   325.   |     "     |  2650  |    32.7    | bl. m.    |  B     "     |
  |   326.   |     "     |  2775  |    32.7    | bl. m.    |  C many      |
  |   327.   |     "     |  2900  |    32.8    | bl. m.    |  C   "       |
  |   328.   |     "     |  2900  |    32.9    | bl. m.    |  B numerous  |
  |          |           |        |            |           |              |
  |   329.   |     "     |  2675  |    32.3    | r. cl.    |  C many      |
  |   330.   |     "     |  2440  |    32.7    | r. cl.    |  C   "       |
  |   331.   |     "     |  1715  |    35.4    | gl. oz.   |  B numerous  |
  |   332.   |     "     |  2200  |    34.0    | gl. oz.   |  B     "     |
  |   333.   |     "     |  2025  |    35.3    | gl. oz.   |  B     "     |
  |          |           |        |            |           |              |
  |   334.   |     "     |  1915  |    35.8    | gl. oz.   |  C many      |
  |   335.   |     "     |  1425  |    37.0    | pt. oz.   |  D few       |
  |   338.   |  Tr. Atl. |  1990  |    36.3    | gl. oz.   |  D few       |
  |   340.   |     "     |  1500  |    37.6    | pt. oz.   |  E very few  |
  |   341.   |     "     |  1475  |    38.2    | pt. oz.   |  E     "     |
  |          |           |        |            |           |              |
  |   342.   |     "     |  1445  |    37.5    | pt. oz.   |  D few       |
  |   343.   |     "     |   425  |    40.3    | volc. s.  |  E very few  |
  |   344.   |     "     |   420  |     ...    | volc. s.  |  E     "     |
  |   345.   |     "     |  2010  |    36.8    | gl. oz.   |  D few       |
  |   346.   |     "     |  2350  |    34.0    | gl. oz.   |  C many      |
  |          |           |        |            |           |              |
  |   347.   |     "     |  2250  |    36.2    | gl. oz.   |  B numerous  |
  |   348.   |     "     | (2450) |     ...    | (Pelag.)  |  B     "     |
  |   349.   |     "     |  ...   |     ...    | (Pelag.)  |  B     "     |
  |   350.   |     "     |  ...   |     ...    | (Pelag.)  |  B     "     |
  |   351.   |     "     |  ...   |     ...    | (Pelag.)  |  B     "     |
  |          |           |        |            |           |              |
  |   352.   |     "     |  ...   |     ...    | (Pelag.)  |  B     "     |
  |   353.   |  N. Atl.  |  2965  |    37.6    | r. cl.    |  C many      |
  |   354.   |     "     |  1675  |    37.8    | gl. oz.   |  D few       |
  +----------+-----------+--------+------------+-----------+--------------+

  +----------+--------+-----------------------+---------------------------+
  |          |        |                       |                           |
  |Challenger|  Date. |Latitude and Longitude.|        Nearest Land.      |
  | Station. |        |                       |                           |
  +----------+--------+-----------------------+---------------------------+
  |          |  1873. |                       |                           |
  |     1.   |Feb.  15|27° 24' N.,  16° 55' W.|S. of Tenerife.            |
  |     2.   | "    17|25° 52' N.,  19° 22' W.|S.W. of the Canary Islands.|
  |     5.   | "    21|24° 20' N.,  24° 28' W.|S.W. of the Canary Islands.|
  |     9.   | "    26|23° 23' N.,  35° 11' W.|    (Ocean).               |
  |    24.   |Mar.  25|18° 38' N.,  65°  5' W.|Culebra (Antilles).        |
  |          |        |                       |                           |
  |    32.   |April  3|31° 49' N.,  64° 55' W.|Bermuda.                   |
  |    45.   |May    3|38° 34' N.,  72° 10' W.|S. of New York.            |
  |    50.   | "    21|42°  8' N.,  63° 39' W.|S. of Halifax.             |
  |    64.   |June  20|35° 35' N.,  50° 27' W.|    (Ocean).               |
  |    76.   |July   3|38° 11' N.,  27°  9' W.|Azores.                    |
  |          |        |                       |                           |
  |    98.   |Aug.  14| 9° 21' N.,  18° 28' W.|W. of Sierra Leone.        |
  |   106.   | "    25| 1° 47' N.,  24° 26' W.|    (Ocean).               |
  |   108.   | "    27| 1° 10' N.,  28° 23' W.|    (Ocean).               |
  |   111.   | "    31| 1° 45' S.,  30° 58' W.|    (Ocean).               |
  |   120.   |Sept.  9| 8° 37' S.,  34° 28' W.|Pernambuco.                |
  |          |        |                       |                           |
  |   132.   |Oct.  10|35° 25' S.,  23° 40' W.|Tristan da Cunha.          |
  |   134.   | "    14|36° 12' S.,  12° 16' W.|Tristan da Cunha.          |
  |   137.   | "    23|35° 59' S.,   1° 34' E.|    (Ocean).               |
  |   138.   | "    25|36° 22' S.,   8° 12' E.|    (Ocean).               |
  |   143.   |Dec.  19|36° 48' S.,  19° 24' E.|Cape of Good Hope.         |
  |          |        |                       |                           |
  |   144.   | "    24|45° 57' S.,  34° 39' E.|    (Ocean).               |
  |   145.   | "    27|46° 43' S.,  38°  4' E.|Prince Edward Island.      |
  |   146.   | "    29|46° 46' S.,  45° 31' E.|    (Ocean).               |
  |   147.   | "    30|46° 16' S.,  48° 27' E.|W. of the Crozet Islands.  |
  |          |  1874. |                       |                           |
  |   148.   |Jan.   3|46° 47' S.,  51° 37' E.|E. of the Crozet Islands.  |
  |          |        |                       |                           |
  |   149H.  | "    29|48° 45' S.,  69° 14' E.|Kerguelen Island.          |
  |   150.   |Feb.   2|52°  4' S.,  71° 22' E.|N. of Heard Island.        |
  |   151.   | "     7|52° 59' S.,  73° 33' E.|Heard Island.              |
  |   152.   | "    11|60° 52' S.,  80° 20' E.|(Ocean).                   |
  |   153.   | "    14|65° 42' S.,  79° 49' E.|Antarctic Ice.             |
  |          |        |                       |                           |
  |   154.   | "    19|64° 37' S.,  85° 49' E.|Antarctic Ice.             |
  |   155.   | "    23|64° 18' S.,  94° 47' E.|Antarctic Ice.             |
  |   156.   | "    26|62° 26' S.,  95° 44' E.|    (Ocean).               |
  |   157.   |Mar.   3|53° 55' S., 108° 35' E.|    (Ocean).               |
  |   158.   | "     7|50°  1' S., 123°  4' E.|    (Ocean).               |
  |          |        |                       |                           |
  |   159.   | "    10|47° 25' S., 130° 22' E.|    (Ocean).               |
  |   160.   | "    13|42° 42' S., 134° 10' E.|    (Ocean).               |
  |   162.   |April  2|39° 10' S., 146° 37' E.|Bass Strait.               |
  |   163.   | "     4|36° 57' S., 150° 34' E.|Port Jackson.              |
  |   164A.  |June  13|34°  9' S., 151° 55' E.|W. of Sydney.              |
  |          |        |                       |                           |
  |   165.   | "    17|34° 50' S., 155° 28' E.|    (Ocean).               |
  |   166.   | "    23|38° 50' S., 169° 20' E.|W. of New Zealand.         |
  |   169.   |July  10|37° 34' S., 179° 22' E.|E. of New Zealand.         |
  |   175.   |Aug.  12|19°  2' S., 177° 10' E.|Fiji Islands.              |
  |   181.   | "    25|13° 50' S., 151° 49' E.|Louisiades.                |
  |          |        |                       |                           |
  |   193.   |Sept. 28| 5° 24' S., 130° 37' E.|Banda Sea.                 |
  |   195.   |Oct.   3| 4° 21' S., 129°  7' E.|Banda Sea.                 |
  |   197.   | "    14| 0° 41' N., 126° 37' E.|E. of Celebes.             |
  |   198.   | "    20| 2° 55' N., 124° 58' E.|N. of Celebes.             |
  |   200.   | "    23| 6° 47' N., 122° 28' E.|W. of Mindanao.            |
  |          |        |                       |                           |
  |   201.   | "    26| 7°  3' N., 121° 48' E.|W. of Mindanao.            |
  |   202.   | "    27| 8° 32' N., 121° 55' E.|W. of Mindanao.            |
  |   205.   |Nov.  13|16° 42' N., 119° 22' E.|W. of Luzon.               |
  |          |  1875. |                       |                           |
  |   206.   |Jan.   8|17° 54' N., 117° 14' E.|W. of Luzon.               |
  |   211.   | "    28| 8°  0' N., 121° 42' E.|W. of Mindanao.            |
  |          |        |                       |                           |
  |   213.   |Feb.   8| 5° 47' N., 124°  1' E.|S. of Mindanao.            |
  |   214.   | "    10| 4° 33' N., 127°  6' E.|N. of Gilolo.              |
  |   215.   | "    12| 4° 19' N., 130° 15' E.|N. of Gilolo.              |
  |   216A.  | "    16| 2° 56' N., 134° 11' E.|S. of Pelew Islands.       |
  |   217.   | "    22| 0° 39' S., 138° 55' E.|N. of New Guinea.          |
  |          |        |                       |                           |
  |   218.   |Mar.   1| 2° 33' S., 144°  4' E.|N. of New Guinea.          |
  |   220.   | "    11| 0° 42' S., 147°  0' E.|N. of New Guinea.          |
  |   221.   | "    13| 0° 40' N., 148° 41' E.|    (Ocean).               |
  |   222.   | "    16| 2° 15' N., 146° 16' E.|    (Ocean).               |
  |   223.   | "    19| 5° 31' N., 145° 13' E.|Carolines.                 |
  |          |        |                       |                           |
  |   224.   | "    21| 7° 45' N., 144° 20' E.|Carolines.                 |
  |   225.   | "    23|11° 24' N., 143° 16' E.|Ocean }                    |
  |   226.   | "    25|14° 44' N., 142° 13' E.|Ocean } North-West Pacific,|
  |   230.   |April  5|26° 29' N., 137° 57' E.|Ocean } between Carolines  |
  |   231.   | "     9|31°  8' N., 137°  8' E.|Ocean } and Japan.         |
  |          |        |                       |      }                    |
  |   232.   |May   12|35° 11' N., 139° 28' E.|Ocean }                    |
  |   234.   |June   3|32° 31' N., 135° 39' E.|S. of Japan.               |
  |   235.   | "     4|34°  7' N., 138°  0' E.|S. of Japan.               |
  |   236.   | "     5|34° 58' N., 139° 29' E.|S. of Japan.               |
  |   237.   | "    17|34° 37' N., 140° 32' E.|S. of Japan.               |
  |          |        |                       |                           |
  |   238.   | "    18|35° 18' N., 144°  8' E.|Ocean }                    |
  |   239.   | "    19|35° 18' N., 147°  9' E.|Ocean }                    |
  |   240.   | "    21|35° 20' N., 153° 39' E.|Ocean }                    |
  |   241.   | "    23|35° 41' N., 157° 42' E.|Ocean }                    |
  |   242.   | "    24|35° 29' N., 161° 52' E.|Ocean }                    |
  |          |        |                       |      }                    |
  |   243.   | "    26|35° 24' N., 166° 35' E.|Ocean } North Pacific,     |
  |   244.   | "    28|35° 22' N., 169° 53' E.|Ocean } between Japan and  |
  |   245.   | "    30|36° 23' N., 174° 31' E.|Ocean } San Francisco      |
  |   246.   |July   2|36° 10' N., 178°  0' E.|Ocean } (35°-38° N. lat.,  |
  |   247.   | "     3|35° 49' N., 179° 57' W.|Ocean } 144°-156° W. long.)|
  |          |        |                       |      }                    |
  |   248.   | "     5|37° 41' N., 177°  4' W.|Ocean }                    |
  |   249.   | "     7|37° 59' N., 171° 48' W.|Ocean }                    |
  |   250.   | "     9|37° 49' N., 166° 47' W.|Ocean }                    |
  |   251.   | "    10|37° 37' N., 163° 26' W.|Ocean }                    |
  |   252.   | "    12|37° 52' N., 160° 17' W.|Ocean }                    |
  |          |        |                       |      }                    |
  |   253.   | "    14|38°  9' N., 156° 25' W.|Ocean                      |
  |   254.   | "    17|35° 13' N., 154° 43' W.|Ocean }                    |
  |   255.   | "    19|32° 28' N., 154° 33' W.|Ocean } North Pacific      |
  |   256.   | "    21|30° 22' N., 154° 56' W.|Ocean } (35°-23° N. lat.,  |
  |   257.   | "    23|27° 33' N., 154° 55' W.|Ocean }154°-156° W. long.).|
  |          |        |                       |      }                    |
  |   258.   | "    24|26° 11' N., 155° 12' W.|Ocean }                    |
  |   259.   | "    26|23°  3' N., 156°  6' W.|Ocean }                    |
  |   261.   |Aug.  12|20° 18' N., 157° 14' W.|Sandwich Islands.          |
  |   262.   | "    20|19° 12' N., 154° 14' W.|Sandwich Islands.          |
  |   263.   | "    21|17° 33' N., 153° 36' W.|Ocean }                    |
  |          |        |                       |      }                    |
  |   264.   | "    23|14° 19' N., 152° 37' W.|Ocean }                    |
  |   265.   | "    25|12° 42' N., 152°  1' W.|Ocean }                    |
  |   266.   | "    26|11°  7' N., 152°  3' W.|Ocean } Tropical Central   |
  |   267.   | "    28| 9° 28' N., 150° 49' W.|Ocean } Pacific, between   |
  |   268.   | "    30| 7° 35' N., 149° 49' W.|Ocean } Sandwich and       |
  |          |        |                       |      }                    |
  |   269.   |Sept.  2| 5° 54' N., 147°  2' W.|Ocean } Paumotu            |
  |   270.   | "     4| 2° 34' N., 149°  9' W.|Ocean } (17° N. lat. to    |
  |   271.   | "     6| 0° 33' S., 151° 34' W.|Ocean } 11° S. lat.).      |
  |   272.   | "     8| 3° 48' S., 152° 56' W.|Ocean }                    |
  |   273.   | "     9| 5° 11' S., 152° 56' W.|Ocean }                    |
  |          |        |                       |      }                    |
  |   274.   | "    11| 7° 25' S., 152° 15' W.|Ocean }                    |
  |   275.   | "    14|11° 20' S., 150° 30' W.|Ocean }                    |
  |   276.   | "    16|13° 28' S., 149° 30' W.|Paumotu.                   |
  |   280.   |Oct.   4|18° 40' S., 149° 52' W.|S. of Tahiti.              |
  |   281.   | "     6|22° 21' S., 150° 17' W.|Tubuai Islands.            |
  |          |        |                       |                           |
  |   282.   | "     7|23° 46' S., 149° 59' W.|Tubuai Islands.            |
  |   283.   | "     9|26°  9' S., 145° 17' W.|N. of Oparo Island.        |
  |   284.   | "    11|28° 22' S., 141° 22' W.|S. of Oparo Island.        |
  |   285.   | "    14|32° 36' S., 137° 43' W.|Ocean }                    |
  |   286.   | "    16|33° 29' S., 133° 22' W.|Ocean }                    |
  |          |        |                       |                           |
  |   287.   | "    10|36° 32' S., 132° 52' W.|Ocean }                    |
  |   288.   | "    21|40°  3' S., 132° 58' W.|Ocean }                    |
  |   289.   | "    23|39° 41' S., 131° 23' W.|Ocean }                    |
  |   290.   | "    25|39° 16' S., 124°  7' W.|Ocean } Open South Pacific |
  |   291.   | "    27|39° 13' S., 118° 49' W.|Ocean } Ocean, between New |
  |          |        |                       |      } Zealand and        |
  |   292.   | "    29|38° 43' S., 112° 31' W.|Ocean } Valparaiso.        |
  |   293.   |Nov.   1|39°  4' S., 105°  5' W.|Ocean }                    |
  |   294.   | "     3|39° 22' S.,  98° 46' W.|Ocean }                    |
  |   295.   | "     5|38°  7' S.,  94°  4' W.|Ocean }                    |
  |   296.   | "     9|38°  6' S.,  88°  2' W.|Ocean }                    |
  |          |        |                       |      }                    |
  |   297.   | "    11|37° 29' S.,  83°  7' W.|Ocean }                    |
  |   298.   | "    17|34°  7' S.,  73° 56' W.|W. of Valparaiso.          |
  |   299.   |Dec.  14|33° 31' S.,  74° 43' W.|W. of Valparaiso.          |
  |   300.   | "    17|33° 42' S.,  78° 18' W.|N. of Juan Fernandez.      |
  |   302.   | "    28|42° 43' S.,  82° 11' W.|   (Ocean).                |
  |          |        |                       |                           |
  |   303.   | "    30|45° 31' S.,  78°  9' W.|W. of Patagonia.           |
  |   304.   | "    31|46° 53' S.,  75° 12' W.|W. of Patagonia.           |
  |          |  1876. |                       |                           |
  |   318.   |Feb.  11|42° 32' S.,  56° 29' W.|   (Ocean).                |
  |   319.   | "    12|41° 54' S.,  54° 48' W.|   (Ocean).                |
  |   323.   | "    28|35° 39' S.,  50° 47' W.|W. of Buenos Ayres.        |
  |          |        |                       |      }                    |
  |   324.   | "    29|36°  9' S.,  48° 22' W.|Ocean }                    |
  |   325.   |Mar.   2|36° 44' S.,  46° 16' W.|Ocean }                    |
  |   326.   | "     3|37°  3' S.,  44° 17' W.|Ocean } Open South Atlantic|
  |   327.   | "     4|36° 48' S.,  42° 45' W.|Ocean } Ocean, between     |
  |   328.   | "     6|37° 38' S.,  39° 36' W.|Ocean } Buenos Ayres and   |
  |          |        |                       |      }                    |
  |   329.   | "     7|37° 31' S.,  36°  7' W.|Ocean } Tristan da Cunha   |
  |   330.   | "     8|37° 45' S.,  33°  0' W.|Ocean } (35°-37° S. lat.,  |
  |   331.   | "     9|37° 47' S.,  30° 20' W.|Ocean } 21°-48° W. long.). |
  |   332.   | "    10|37° 29' S.,  27° 31' W.|Ocean }                    |
  |   333.   | "    13|35° 36' S.,  21° 12' W.|Ocean }                    |
  |          |        |                       |                           |
  |   334.   | "    14|35° 45' S.,  18° 31' W.|W. of Tristan da Cunha.    |
  |   335.   | "    16|32° 24' S.,  13°  5' W.|N. of Tristan da Cunha.    |
  |   338.   | "    21|21° 15' S.,  14°  2' W.|(Ocean).                   |
  |   340.   | "    24|14° 33' S.,  13° 42' W.|Ocean }                    |
  |   341.   | "    25|12° 16' S.,  13° 44' W.|Ocean } W. of St. Helena.  |
  |          |        |                       |                           |
  |   342.   | "    26| 9° 43' S.,  13° 51' W.|Ocean }                    |
  |   343.   | "    27| 8°  3' S.,  14° 27' W.|Ascension Island.          |
  |   344.   |April  3| 7° 54' S.,  14° 28' W.|Ascension Island.          |
  |   345.   | "     4| 5° 45' S.,  14° 25' W.|Ocean }                    |
  |   346.   | "     6| 2° 42' S.,  14° 41' W.|Ocean } Tropical Atlantic, |
  |          |        |                       |      } between Ascension  |
  |   347.   | "     7| 0° 15' S.,  14° 25' W.|Ocean } and Sierra Leone.  |
  |   348.   | "     9| 3° 10' N.,  14° 51' W.|Ocean }                    |
  |   349.   | "    10| 5° 28' N.,  14° 38' W.|Ocean }                    |
  |   350.   | "    11| 7° 33' N.,  15° 16' W.|W. of Sierra Leone.        |
  |   351.   | "    12| 9°  9' N.,  16° 41' W.|W. of Sierra Leone.        |
  |          |        |                       |                           |
  |   352.   | "    13|10° 55' N.,  17° 46' W.|W. of Sierra Leone.        |
  |   353.   |May    3|26° 21' N.,  33° 37' W.|W. of Canary Islands.      |
  |   354.   | "     6|32° 41' N.,  36°  6' W.|S. of Azores.              |
  +----------+--------+-----------------------+---------------------------+



{clxiv}CHAPTER X.--GEOGRAPHICAL DISTRIBUTION.

(§§ 241-250.)

241. _Historical Distribution._--Radiolaria are found fossil in all the
more important groups of the sedimentary rocks of the earth's crust. Whilst
a few years ago their well-preserved siliceous skeletons were only known in
considerable quantity from Cainozoic marls (§ 242), very many SPUMELLARIA
and NASSELLARIA have recently been found in Mesozoic and a few in Palæozoic
strata. By the aid of improved modern methods of investigation (especially
by the preparation of thin sections of very hard rocks) it has been shown
that many hard siliceous minerals, especially cryptocrystalline quartz,
contain numerous well-preserved Radiolaria, and sometimes are mainly
composed of closely compacted masses of such siliceous shells; of this kind
are many quartzites of the Jura (§ 243). These Jurassic quartzes
(Switzerland), as well as the Tertiary marls (Barbados) and clays (Nicobar
Islands), are to be regarded as "fossil Radiolarian ooze" (§ 237). Dense
masses of compressed SPUMELLARIA and NASSELLARIA form the principal part of
these rocks. Isolated or in smaller quantities, fossil Polycystina,
belonging to different families of SPUMELLARIA and NASSELLARIA, also occur
in in other rocks, and even in some of Palæozoic origin. Since specimens
have also been recently found both in Silurian and Cambrian strata, it may
be stated that as regards their historical distribution, Radiolaria occur
in all fossiliferous sedimentary deposits, from the oldest to those of the
present time.


242. _Cainozoic Radiolaria._--The great majority of fossil Radiolaria which
have hitherto been described, belong to the Cainozoic or Tertiary period,
and in fact, to its middle portion, the Miocene period. At this period the
richest and most important of all the Radiolarian formations were
deposited, such as the pure "Polycystine marl" of Barbados (see note A),
also that of Grotte in Sicily (see note B), and the clay of the Nicobar
Islands (see note C). Besides the above-mentioned deposits, which may be
designated "pure" fossil Radiolarian ooze, many deposits containing these
organisms have recently been discovered in widely separated parts of the
earth, partly of the nature of tripoli or marl, partly resembling clay.
Among these may be mentioned in the first place many coasts and islands of
the Mediterranean, both on the south coast of Europe (Sicily, Calabria,
Greece), and the north coast of Africa (from Oran to Tripoli). The
extensive layers of tripoli which are found in these Mediterranean Tertiary
mountains belong to the upper Miocene (Tortona stage), and consist partly
of marl rich in calcareous matter, and resembling chalk, partly passing
over into plastic clay or "Kieselguhr" (§ 246). The quantity of Radiolaria
contained varies, and is more conspicuous the fewer the calcareous shells
of Foraminifera present. Similar Tertiary Polycystine formations occur in
some parts of America (see note D); probably they have a very wide
distribution. In their general morphological characters, the Tertiary
SPUMELLARIA and NASSELLARIA {clxv}are related to those forms which are
found in the recent Radiolarian ooze of the depths of the Pacific,
especially to the species which are characteristic of the Challenger
Stations 225, 226, 265 and 268. Many living genera and families (_e.g._,
most #Larcoidea# and #Stephoidea#) have not yet been found in the Tertiary
formations.

  A. The famous Polycystine marl of Barbados in the Antilles, which Robert
  Schomburgk discovered forty years ago, belongs to the Miocene formation,
  and is the richest and best known of all the important Radiolarian
  deposits (see L. N. 16, pp. 5-8). After Ehrenberg had published in
  December 1846 the first preliminary communication regarding its
  composition out of masses of well-preserved Polycystina, he was able in
  the following year to describe no less than 282 species from it; he
  distributed these in 44 genera and 7 families (L. N. 4, 1847, p. 54). In
  the year 1854 Ehrenberg published figures of 33 species in his
  Mikrogeologie (L. N. 6,  Taf. xxxvi.); but it was only in 1873 that he
  published descriptions of 265 species (Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, Jan. 30, pp. 213-263). Finally there followed in 1875 his
  Fortsetzung der Mikrogeologischen Studien, mit specieller Rücksicht auf
  den Polycystinen-Mergel von Barbados (L. N. 25). On the thirty plates
  which accompany this the last work of Ehrenberg, 282 species are figured
  and named, of which 54 are SPUMELLARIA (13 #Sphæroidea#, 8 #Prunoidea#,
  33 #Discoidea#), and 228 NASSELLARIA (2 #Stephoidea#, 38 #Spyroidea#, and
  188 #Cyrtoidea#). The fourth section of this memoir contains a survey of
  the Polycystine formation of Barbados (pp. 106-115), and the fifth
  section the special description of a large specimen of rock from Mount
  Hillaby in Barbados (see also L. N. 28, p. 117, and L. N. 41, pp.
  476-478). The account given by Ehrenberg of the Polycystina of Barbados
  is in many respects very incomplete, and very far from exhausting this
  rich mine of remarkable forms. This may be readily seen from the
  twenty-five plates of figures of Polycystins in the Barbados Chalk
  Deposit published by Bury in 1862 (L. N. 17). The number of species here
  figured (140 to 142) is about half of those given by Ehrenberg; and there
  are among them numerous generic types, some of great interest, which were
  entirely overlooked by the latter; _e.g._ _Saturnalis_ (#Sphæroidea#),
  _Cannartidium_ (#Prunoidea#), _Tympanidium_ (#Stephoidea#),
  _Cinclopyramis_ (#Cyrtoidea#), &c. Finally, Ehrenberg always (until 1875)
  ignored Bury's atlas, which had been published thirteen years ago and was
  quite accessible to him. How different were the contents of the two works
  may easily be seen from the following abstract.

_Comparative View of the Species of Fossil Radiolaria from Barbados made
known by the figures of Bury in 1862 and of Ehrenberg in 1875._

  +-------------------+--------------------+--------+-----------+-------+
  |    Legion.        |            Order.  |  Bury. | Ehrenberg.| Total.|
  +-------------------+--------------------+--------+-----------+-------+
  |  I. Legion        |  { 1. Sphæroidea   |   16   |    13     |   29  |
  |     SPUMELLARIA   |  { 2. Prunoidea    |   10   |     8     |   18  |
  |     (PERIPYLEA).  |  { 3. Discoidea    |   37   |    33     |   70  |
  |                   |                    |        |           |       |
  | II. Legion        |  { 4. Stephoidea   |    5   |     2     |    7  |
  |     NASSELLARIA   |  { 5. Spyroidea    |   13   |    38     |   51  |
  |     (MONOPYLEA).  |  { 6. Cyrtoidea    |   60   |   188     |  248  |
  +-------------------+--------------------+--------+-----------+-------+
  |                               Total,   |  141   |   282     |  423  |
  +----------------------------------------+--------+-----------+-------+

  {clxvi}In 1882 Bütschli still further increased the number of known
  Radiolaria from Barbados both by figures and descriptions (L. N. 40), and
  gave in particular a very accurate morphological analysis of 12 new
  NASSELLARIA (3 #Stephoidea#, 3 #Spyroidea#, and 6 #Cyrtoidea#; L. N. 40,
  Taf. xxxii., xxxiii.). The number of the fossil species collected in the
  Barbados marl is, however, greater than would appear from the
  above-quoted communications. My respected friend, Dr. R. Teuscher, of
  Jena, has, at my request, made a large number (about a thousand) of very
  accurate drawings with the camera lucida of Polycystina from Barbados
  (see p. 1760). From these it appears that the variations in the structure
  of the shells, with respect to number, size, and form of the
  lattice-pores, of the spines, &c., is much greater than would be supposed
  from the figures of Ehrenberg and Bury. I have thus come to the
  conviction that the number of species from Barbados (using the word
  "species" in the sense understood by those authors) is not less than 400
  and probably more than 500. Descriptions of some particularly interesting
  new species from this series have been included in the systematic account
  of the Challenger Radiolaria. A complete critical investigation of the
  Radiolaria of Barbados, and especially an accurate comparison of these
  Cainozoic species with the Mesozoic forms from the Jura, on the one hand,
  and with recent types on the other, must be left to the future for its
  accomplishment (see § 246).

  B. The Cainozoic Polycystine tripoli or marl of the Mediterranean coast,
  which is probably always of Miocene origin, forms very extensive mountain
  ranges both in the south of Europe (Sicily, Calabria, Greece) and in the
  north of Africa (from Oran to Tripoli) (§ 246). Hitherto, however, only
  one locality has been thoroughly investigated, namely, Grotte in the
  province of Girgenti in Sicily (L. N. 35). In the accurate account which
  was given of it by Stöhr in 1880, 118 species were described, distributed
  in 40 genera (L. N. 35; pp. 72-84); of these 118 species 78 are quite
  new, 25 are identical with previously known fossils, and 29 identical
  with living forms. Among them are 73 SPUMELLARIA (28 #Sphæroidea#, 8
  #Prunoidea#, and 37 #Discoidea#), but only 40 NASSELLARIA (1
  #Stephoidea#, 6 #Spyroidea#, and 33 #Cyrtoidea#), and 5 PHÆODARIA
  (Dictyochida). The other parts of Sicily from which the same upper
  Miocene tripoli has been investigated (belonging to the Tortona stage)
  have proved less rich than Grotte. The best known of these places is
  Caltanisetta, since upon three genera discovered here (_Haliomma_,
  _Cornutella_, _Lithocampe_) the group Polycystina was founded by
  Ehrenberg in 1838 (see L. N. 16, p. 3). Afterwards 31 species were
  described from this locality, of which 23 were again found in Grotte. The
  richest deposit on the Mediterranean coast, however, appears to be at
  Oran. A small specimen of the Kieselguhr found there, which was recently
  sent to me by Professor Steinman, proved to be pure Radiolarian ooze,
  very similar to that now found in the Central Pacific, and contained many
  hitherto undescribed species; it is deserving of careful investigation
  and comparison.

  C. Regarding the Tertiary Radiolarian clay of the Nicobar Islands, see §
  247 and L. N. 25, pp. 116-120. Its fauna is incompletely known; probably
  it is of Miocene or Oligocene origin.

  D. Cainozoic tripoli, containing larger or smaller quantities of
  Radiolaria, appears to be rather widely distributed in America. Ehrenberg
  has described such from South America (polishing-slate from Morro di
  Mijellones, on the coast between Chili and Bolivia), and from North
  America (Richmond and Petersburg in Virginia, Piscataway in Maryland).
  Similar deposits are also found in the Bermuda Islands (L. N. 4, 1855-56;
  L. N. 6, Taf. 18; L. N. 16, pp. 3-9; L. N. 41, pp. 475-478, and L. N. 25,
  pp. 2-6).


{clxvii}243. _Mesozoic Radiolaria._--From the Mesozoic or Secondary period
numerous well-preserved Radiolaria have recently been described. They
belong for the most part to the Jurassic formation (see notes A, B, C),
whilst the more recent Chalk (see note D) and the older Trias (see note E)
have hitherto yielded but few species. All the main divisions of the Jura,
both the upper (Malm) and the middle (Dogger), and especially the lower
(Lias) appear in certain localities to be very rich in well-preserved
shells of fossil Polycystina. Most of these are aggregated together in
coprolites and quartzites (jasper, chert, flint, &c., § 248). The majority
are #Cyrtoidea#, the minority #Sphæroidea# and #Discoidea# in almost equal
proportions; a few #Beloidea# (_Sphærozoum_) and #Phæocystina# (Dictyocha)
are also found among them. The general morphological character of these
Jurassic Radiolaria is very different from that of the nearly related
Tertiary and living forms. In general, their siliceous shells are firmer
and more massive, usually also somewhat larger, but of simpler structure.
The manifold delicate appendages (spines, bristles, feet, wings, &c.) which
are so richly developed in the living SPUMELLARIA and NASSELLARIA, and are
also well shown in the Tertiary species, are entirely wanting in the
majority of the Jurassic Polycystina. The #Sphæroidea# and #Prunoidea# are
all simple spherical or ellipsoidal lattice-shells (Monosphærida);
concentric lattice-shells (Polysphærida) are entirely wanting. The
#Cyrtoidea# are, for the most part, devoid of radial processes or basal
feet (Eradiata); triradiate and multiradiate forms, such as are found
abundantly in the recent and Tertiary formations, are very rare. The large
number of many-jointed forms (Stichocyrtida) and of #Cyrtoidea# with
latticed basal opening is very striking.

  A. The most important work on the Jurassic Radiolaria, regarding which
  but little was known prior to the year 1885, is the valuable and in some
  respects very interesting Beiträge zur Kenntniss der fossilen Radiolarien
  aus Gesteinen des Jura, by Dr. Rüst of Freiburg i. B. (1885,
  Palæontographica, Bd. xxxi. 51 pp. with 12 plates). Unfortunately this
  important work was issued only when about half of the present Report was
  printed off, so that it was no longer possible to include the 234 species
  there described in its systematic part. I have therefore elsewhere given
  a list of the Jurassic Radiolaria, and at present only make the following
  remarks:--Of the 234 species described, the larger half (130) belong to
  the NASSELLARIA (#Cyrtoidea#), the smaller half (102) to the SPUMELLARIA
  (38 #Sphæroidea#, 14 #Prunoidea#, and 50 #Discoidea#). In addition, there
  are 2 PHÆODARIA depicted, and several spicules which are probably to be
  referred to the #Beloidea#. Among the 130 #Cyrtoidea# (of which 2 are
  described as #Botryodea#), there are 24 Monocyrtida, 14 Dicyrtida, 22
  Tricyrtida, and 70 Stichocyrtida. Just as striking as the predominant
  number of the last is the fact that there are only very few triradiate
  (9) and multiradiate (4) species found among these 130 #Cyrtoidea#, as
  also the large number of species with latticed basal opening;
  #Stephoidea# appear to be entirely wanting. The rich material of jasper,
  chert, flint, and coprolites in which Dr. Rüst found these Radiolaria, is
  derived for the most part from the Jurassic rocks of Germany (Hanover,
  South Bavaria), Tyrol, and Switzerland (compare § 248).

  {clxviii}B. Jurassic Radiolaria from Italy, also found in jasper, which
  are closely related to the forms from Germany and Switzerland described
  by Dr. Rüst, were made known so long ago as 1880 by Dante Pantanelli in
  his treatise I Diaspri della Toscana e i loro Fossili (Rome, 1880, 33 pp.
  60 figs.). Pantanelli believes, however, that this jasper is for the most
  part of Eocene origin; but from his description, and especially from the
  morphological character of the forms which he figures, it appears very
  probable "that these Tuscan jaspers from Galestro, like those of the
  Swiss conglomerates, are found in a secondary locality and belong to the
  Jurassic period" (Rüst, L. N. 51, p. 3). Unfortunately the figures of
  Pantanelli are so small and incomplete that a reliable determination of
  the species is hardly possible; for example, the lattice-work is only
  given in ten of the sixty figures. Among the 32 recorded species 15 are
  SPUMELLARIA (6 #Sphæroidea# and 9 #Discoidea#) and 17 NASSELLARIA (4
  #Stephoidea# and 13 #Cyrtoidea#); many of which seem to be identical with
  the forms more accurately described by Dr. Rüst (compare p. 1762).

  C. From the Lias of the Alps and more particularly "from the lower
  Liassic beds of the Schafberg near Salzburg," Dr. Emil von Dunikowski in
  1882 described 18 species of fossil Radiolaria (L. N. 44, pp. 22-34, Taf.
  iv.-vi.); most of these are #Sphæroidea# and #Discoidea# and appear to
  have been more or less altered by petrological changes; their spongy
  structure is probably secondary.

  D. Cretaceous Radiolaria have been hitherto described only in very small
  numbers; quite recently Dr. Rüst has found a larger number chiefly in
  flints from the English chalk, but they have not yet been published. In
  1876 Zittel described 6 very well-preserved species from the upper chalk
  of North Germany (L. N. 29, pp. 76-96, Taf. ii.); among them were 1
  #Sphæroidea#, 1 #Discoidea#, 1 Dictyocha, and 3 #Cyrtoidea#.

  E. Triassic Radiolaria have recently been discovered by Dr. Rüst in
  chert, but have not yet been described.


244. _Palæozoic Radiolaria._--The number of Radiolaria which are known from
the Palæozoic or Primary formations is much less than from either the
Mesozoic or Cainozoic periods. Here, however, the investigations of recent
times have yielded important information; a few species, at all events, of
Polycystina (mostly #Sphæroidea#) are now known from various Palæozoic
formations, and not only from the Permian ("Zechstein") and the
Coal-measures, but also from the older Devonian and Silurian systems. Even
in the still older Cambrian rocks a few fossil Radiolaria have been found.
All these Palæozoic Radiolaria are Polycystina of very simple form and
primitive structure, mostly simple SPUMELLARIA (latticed spheres,
ellipsoids, lenses, &c.), but partly also simple NASSELLARIA.

  The important discoveries which have recently been made by Dr. Rüst
  regarding the occurrence of Radiolaria in all the Palæozoic formations
  have not yet been published. From conversations with this estimable
  palæontologist I have learned, however, that he has pursued his fruitful
  investigation of the Mesozoic quartzites (§ 243), and has met with no
  less success in the case of similar Palæozoic structures. Although the
  number of species hitherto discovered is relatively small, the important
  conclusion appears to be warranted that they extend as far as the
  Silurian and Cambrian systems. All these very ancient SPUMELLARIA
  (#Sphæroidea#) and NASSELLARIA (#Cyrtoidea#) {clxix}exhibit very
  primitive structural relations. The occurrence of fossil Polycystina in
  the Carboniferous formation of England has been incidentally mentioned by
  W. J. Sollas:--"In the carboniferous beds of North Wales pseudomorphs of
  Radiolaria in calcite occur, along with minute quartz crystals" (Ann. and
  Mag. Nat. Hist., 1880, ser. 5, vol. vi. p. 439); and in the siliceous
  slate-beds of Saxony Rothpletz has shown the existence of a few
  #Sphæroidea# (Zeitschr. d. Deutsch. Geol. Gesellsch., 1800, p. 447).


245. _Abundance of Radiolaria in the Various Rocks._--The relative quantity
of well-preserved or at all events recognisable Radiolaria in the different
rocks is very variable. In this respect three different degrees may be
distinguished, which may be called shortly "pure, mixed, and poor"
Radiolarian formations. The _pure_ Radiolarian rocks consist for the
greater part (usually much more than half, sometimes even more than
three-quarters) of closely compacted often calcined masses of siliceous
Polycystine shells. To this category belong the pure Miocene Polycystine
marls of Barbados (§ 246), the Tertiary Polycystine clay of the Nicobar
Islands (§ 247), and the Polycystine quartz of the Jura (§ 248). All these
pure Radiolarian rocks may be regarded as fossil Radiolarian ooze (§ 237),
and are certainly of deep-sea origin, having probably been deposited at
depths greater than 2000 fathoms. Their palæontological character also is
in favour of this view, for the abyssal Osculosa (§ 235) are more abundant
and richer in species than the pelagic Porulosa (§ 233). The elevation of
this deep-sea layer above the surface of the sea appears to have taken
place but seldom; it has only been observed on a large scale at Barbados
and in the Nicobar Islands. The _mixed_ Radiolarian rocks are much more
common; they were probably deposited at much less depths, or perhaps are
not true deep-sea formations at all. The siliceous shells of Polycystina
always constitute less than half (sometimes less than one-tenth) of their
mass, and are less prominent than other siliceous remains (Diatoms), or
calcareous remains (Foraminifera), or in some cases than the mineral
constituents (pumice, &c.). To this group belong many of the
above-mentioned Tertiary marls and clays (especially the Mediterranean
Tripoli), also many flints, cherts, and other quartzites from Mesozoic
strata (especially from the Jura), and probably also some palæozoic
quartzites. The marine ooze from which they have originated may have been
deposited at very various, even at slight, depths of the ocean. Formations
_poor_ in Radiolaria, which contain only a few species of SPUMELLARIA and
NASSELLARIA mingled with other fossil remains and mineral particles, occur
in all formations and are probably very widely distributed. Further careful
examination of thin sections (especially of coprolites) will yield here a
rich harvest of new forms. Both the mixed and the pure Radiolarian
formations may be divided according to their petrographic characters into
three groups, which, however, are connected by intermediate varieties--(1)
soft, chalky marl (§ 246), (2) plastic clay (§ 247), and (3) hard, flinty
quartz (§ 248).


{clxx}246. _Radiolarian Marl._--Those soft, friable rocks, which contain a
large quantity of calcareous matter, but consist for the most part of the
shells of SPUMELLARIA and NASSELLARIA, are called Radiolarian or
Polycystine marl, often more correctly Polycystine tripoli; the best known
example of them is the chalky marl of Barbados in the Antilles (§ 242). The
Tertiary mountain system of this island, which in Mount Hillaby rises to a
height of 1147 feet and includes about 15,800 acres, consists almost
exclusively of these remarkable masses of rock. Most of it appears as a
soft, earthy, often chalky marl, with a considerable but variable amount of
calcareous matter. Those specimens, the greater half of which is composed
of well-preserved siliceous shells of Polycystina, and which contain little
lime, approach the tripoli and "Kieselguhr." Those specimens, however,
which contain the largest amount of calcareous matter resemble common
writing chalk in consistency, and consist for the most part of shells of
Foraminifera and their fragments; of these there are only few species but
large numbers of individuals, generally in small fragments with a fine
calcareous powder between them. They may be regarded as fossil Globigerina
ooze (§ 238). In a third group of specimens from Barbados the quantity of
fragments of pumice and other volcanic matters predominates; the amount of
clay is also very considerable; these deposits pass over partly into actual
clay partly into volcanic tuff. A fourth group exhibits relations to a
coarser often ferruginous material, and although the shells of Polycystina
are less abundant in it, still it may be shown to be composed largely of
fragments and metamorphosed remains of them. The colour of this deposit,
which in some places passes over into sandstone, in others into clay, is
usually rather dark, grey, brown, sometimes red and occasionally black
(bituminous). The Radiolarian marls of the first two groups, which
sometimes approach the white chalk, sometimes the Kieselguhr, are grey, or
even pure white (see note A). The same constitution is exhibited by the
yellowish or white, very light and friable Polycystine marls of Sicily,
which in Caltanisetta approach the chalk, and in Grotte the Kieselguhr. In
Greece (Ægina, Zante, &c.), on the other hand, they pass over into plastic
clay, and the same occurs in the Baden marl of the Vienna basin. In North
Africa, however, on the Mediterranean shores of which the Radiolarian marl
seems to be very widely distributed (from Tripoli to Oran), it sometimes
becomes changed into actual firm polishing slate, sometimes into
pulverulent Kieselguhr or tripoli (Terra tripolitana, see note B). Most of
these Radiolarian marls appear to date from the middle Tertiary (Miocene)
period, and to be deep-sea formations.

  A. The Polycystine marl of Barbados appears at different parts of the
  island to present greater variations in its petrographical and
  zoographical composition than would appear from Ehrenberg's description
  (1875, L. N. 25, pp. 106-116). Through the kindness of one of my former
  students, Dr. Dorner, to whom I take this opportunity of expressing my
  thanks for the favour, I received a large number of specimens of Barbados
  rock, taken from various parts of the island, and they exhibit very great
  variations in their external appearance, their chemical composition, and
  the {clxxi}Radiolaria which they contain. The white specimens resembling
  Kieselguhr contained approximately 60 to 70 per cent. by volume of
  Radiolarian shells, the yellowish marl 40 to 50 per cent., and the brown
  and black (bituminous) marl 10 to 20 per cent. or less. Two analyses of
  the first, which my friend Dr. W. Weber was good enough to carry out,
  yielded different results from those which are given by Ehrenberg on the
  basis of Rammelsberg's analyses (L. N. 25, p. 116). The results of both
  are here given for comparison.

  --------------------------------+--------------------------+-------------
       Ehrenberg-Rammelsberg      |         Weber I.         |  Weber II.
      (Fragment from Hillaby).    |  (Chalk-like Fragment).  |(Tripoli-like
                                  |                          |  Fragment).
  --------------------------------+--------------------------+-------------
  Silicate of alumina,      59.47 |Silica,              52.2 |        71.3
  Alumina and oxide of iron, 1.95 |Alumina (with traces      |
  Calcium carbonate,        34.31 |  of oxide of iron), 12.3 |        11.2
  Water,                     3.67 |Lime and magnesia,   31.9 |        14.8
                                  |Carbon dioxide,       3.2 |         2.7
                           ______ |                    _____ |       _____
        Total,              99.40 |      Total,         99.6 |       100.0
  --------------------------------+--------------------------+-------------

  For further comparison I here add the three different analyses of Miocene
  Tripoli-marls from Sicily, given by Stöhr on the authority of Fremy,
  Schwager, and Mottura (Tagebl. d. fünfzigsten Versamml. Deutsch. Naturf.
  u. Aertzte in München, 1877, p. 163).

  --------------------------+-------------+--------------+-------------
        Composition.        |Tripoli from | Tripoli from | Tripoli from
                            |   Licata    |    Grotte    | Caltanisetta
                            |  (Fremy).   |  (Schwager). |  (Mottura).
  --------------------------+-------------+--------------+-------------
  Silica,                   |   30.98     |    58.58     |      68.6
  Alumina,                  |   17.54     |    11.51     |    }
  Oxide of iron,            |    0.33     |     1.84     |    }  3.6
                            |             |              |
  Lime,       }             |   38.09     |  {  8.49     |    }
  Magnesia,   }             |             |  {  0.41     |    } 12.1
                            |             |              |
  Water and organic matter,}|             |  { 11.26     |    }
  Carbonic acid,           }|   13.06     |  {  7.12     |    }  15.2
                            +-------------+--------------+------------
                            |  100.00     |    99.21     |       99.5
  --------------------------+-------------+--------------+-------------

  B. The Radiolarian marl of the Mediterranean appears, judging by the
  accounts already published, to stretch along a considerable part of the
  coast in the earlier and middle Tertiary formations; thus it occurs of
  similar composition in widely separated localities, in Sicily, Calabria,
  Zante, and Greece; in North Africa from Tripoli to Oran and probably much
  farther. So long ago as 1854 Ehrenberg, in his Mikrogeologie (L. N. 6)
  gave a series of important, even if incomplete, communications regarding
  the "chalky white calcareous marl of Caltanisetta" (Taf. xxii.), the
  "Platten marl of Zante" (Taf. xx.), the "plastic clay of Ægina" (Taf
  xix.), and the "polishing slate of Oran" (Taf. xxi.). In 1880 Stöhr
  showed in his fundamental description of the Tripoli from {clxxii}Grotte
  in Sicily (L. N. 35) that its Radiolarian fauna is much richer than
  Ehrenberg supposed. The same is the case in the Tripoli of Caltanisetta,
  and also in the Baden marl of the Vienna basin. The richest deposit
  appears to be the pure Kieselguhr-like Tripoli from Oran; a small
  specimen, which was recently sent to me by Professor Steinmann of
  Freiburg, i. B., contained many hitherto undescribed species, and was at
  least as rich as the purest Barbados marl.


247. _Radiolarian Clays._--Among the Radiolarian or Polycystine clays we
include the firm, often plastic, formations, which contain a larger
proportion of Radiolaria than of other organic remains. The first of these
to be mentioned is the Cainozoic formation of the Nicobar Islands in
Further India, which rises to a height of 2000 feet above the level of the
sea, and consists for the most part of coloured masses of clay of varying
constitution; on Car Nicobar these are mostly grey or reddish, on the
Island of Camorta they are partly strongly ferruginous and red and yellow
(_e.g._ at Frederickshaven), partly white and light, like meerschaum
(_e.g._ at Mongkata). The latter varieties appear to pass over into pure
loose Polycystine marl like that of Barbados, the former into calcareous
sandstone. Although the Polycystine clays of the Nicobar Islands are as yet
only very incompletely known, it may be concluded with great probability
that they are true deep-sea formations and nearly allied to those recent
forms of red clay, which by their abundance in Radiolaria most nearly
approach the Radiolarian ooze, such for example as the red clay of the
North Pacific between Japan and the Sandwich Islands (Stations 241 to 245,
compare §§ 229 and 239). With this view agrees also the greater or less
quantity of pumice dust and other volcanic products. Probably Radiolarian
clays like those of the Nicobar Islands occur also in other Tertiary rocks;
part of the Barbados marl passes by gradually increasing content of clay
into such; and in this case also the amount of included pumice is often
considerable. Many mixed Radiolarian marls of the Mediterranean (_e.g._, of
Greece and Oran) also appear to pass over at certain points into
Radiolarian clay.

  The Radiolarian clays of the Nicobar Islands are unfortunately very
  incompletely known both as regards their geological nature and their
  palæontological composition. The communications of Rink (Die
  Nikobaren-Inseln, eine geographische Skizze, Kopenhagen, 1847) and of
  Ehrenberg (L. N. 6, p. 160 and L. N. 25, pp. 116 to 120) leave many
  important questions unanswered. The latter has only figured twenty-three
  species in his Mikrogeologie (L. N. 6, Taf. xxxvi.). In his tabular list
  of names (L. N. 25, p. 120) he only incompletely records thirty-nine
  species, although in 1850, immediately after the first examination of the
  Nicobar clay, he had distinguished "more than a hundred species, partly
  new, partly identical with those of Barbados" (L. N. 16, p. 8). I have
  unfortunately been unable in spite of many efforts, to obtain for
  investigation a specimen of Nicobar clay. The only microscopical
  preparation (from Ehrenberg's collection), which I was able to examine,
  contained several hitherto undescribed species. A thorough systematic
  examination of these important Radiolarian clays is a pressing necessity,
  especially as they seem to be markedly different from those of the
  Mediterranean (from Ægina, Zante, &c.).


{clxxiii}248. _Radiolarian Quartzes._--Under the name Radiolarian or
Polycystine quartzes are included those hard, siliceous rocks, which
consist for the most part of the closely compacted shells of SPUMELLARIA
and NASSELLARIA. To these "cryptocrystalline quartzes," or better,
quartzites, belong more especially the pure Radiolarian formations of the
Jura, which have been described as flint, chert, jasper, as well as other
cryptocrystalline quartzites. Most of the rocks of this nature hitherto
examined are from Germany (Hanover, South Bavaria), Hungary, Tyrol, and
Switzerland; others are known from Italy (Tuscany). They occur both in the
upper and middle, but especially in the lower Jurassic formation (also in
the lower layers of the Alpine Lias). A small part of them has been
examined in their primary situation (the red jaspers of Allgäu and Tyrol),
the greater part, however, only as loose rolled stones in secondary
situations (thus in Switzerland in the breccia of the Rigi, in the
conglomerate of the Uetli-Berg, and in many boulders of the Rhine, the
Limmat, the Reuss, and the Aar). The greatest abundance, however, of
Jurassic Radiolaria has been yielded by the silicified coprolites from the
Lias of Hanover. These "Radiolarian coprolites" are roundish or cylindrical
bodies, which may attain the size of a goose-egg; they probably originated
from Fish or Cephalopods, which had fed upon Crustacea, Pteropoda, and
similar pelagic organisms, whose stomachs were already full of Radiolarian
skeletons. Next to the coprolites the richest is the red jasper, whose
colour varies from bright to dark red; it constitutes a true "silicified
deep-sea Radiolarian ooze." The "_Aptychus_ beds" also of South Bavaria and
Tyrol are very rich, and have furnished about one-third of all the
Radiolaria known from the Jura; most of the species too are very well
preserved (compare § 243).

  Regarding the remarkable composition and manifold varieties of the
  Jurassic Radiolarian quartz, the very full treatise of Dr. Rüst may be
  consulted (L. N. 51). The very interesting Radiolarian coprolites, which
  that author has discovered in the lower and middle Jura of Hanover, occur
  in astonishing numbers in the iron mines at the village of Gross-Ilsede,
  four and a half miles south of the town of Peine. They constitute from 2
  to 5 per cent. by weight of the Liassic iron ore; of this latter, in the
  year 1883 alone, not less than two hundred and eighty million kilograms
  were excavated. It is very probable that the careful microscopic
  examination of thin sections of coprolites, as well as of flints, chert,
  jasper, and other quartzites, would yield a rich harvest of fossil
  Radiolaria in other formations also. In Italy Dante Pantanelli has
  discovered interesting Polycystine jaspers in Tuscany (L. N. 36, 45);
  these also appear to occur in the Jura (compare § 243, and L. N. 51, pp.
  3-10).


249. _Fossil Groups._--The preservation of Radiolaria in the fossil state
is, of course, primarily dependent on the composition of their skeleton.
Hence the ACANTHARIA, whose acanthin skeleton although firm is readily
soluble, are never found fossil. The same is true of the skeletons of the
PHÆODARIA, which consist of a silicate of carbon; here, however, a single
exception is found in the Dictyochida, a subfamily of the Cannorrhaphida,
the isolated parts of whose skeletons appear to consist of pure silica, and
{clxxiv}are often found fossil. Of the two other legions those families
which possess no skeleton are of course excluded; the Nassellida among the
NASSELLARIA, and the Thalassicollida and Collozoida among the SPUMELLARIA.
Thus of the 85 known families there remain scarcely 55 of which the
skeletons may be expected in the fossil state; and of these scarcely half
have been actually observed in this condition. Of the 20 orders of this
class enumerated in § 155, the following 9 may be, for palæontological and
geological purposes, completely excluded:--(A) The 4 orders of ACANTHARIA
(1, #Actinelida#; 2, #Acanthonida#; 3, #Sphærophracta#; 4, #Prunophracta#);
(B) 3 orders of PHÆODARIA (5, #Phæosphæria#; 6, #Phæogromia#; 7,
#Phæoconchia#); (C) 1 order of NASSELLARIA (8, #Nassoidea#); (D) 1 order of
SPUMELLARIA (9, #Colloidea#). From a geological point of view the following
6 orders, although occasionally found fossil, are of quite subordinate
importance:--(A) Among the SPUMELLARIA (10, #Beloidea#, and 11,
#Larcoidea#); (B) among the NASSELLARIA (12, #Plectoidea#; 13,
#Stephoidea#; 14, #Botryodea#); (C) among the PHÆODARIA (15, the
#Phæocystina#). On the other hand the following 5 orders, which are the
main constituents of Radiolarian rocks, are of pre-eminent geological
importance:--(A) Among the SPUMELLARIA (16, #Sphæroidea#; 17, #Prunoidea#;
18, #Discoidea#); (B) among the NASSELLARIA (19, #Spyroidea#, and 20,
#Cyrtoidea#). The numerical relation in which the different families of
these orders appear in the Radiolarian formations may be seen on consulting
§ 157.


250. _Fossil and Recent Species._--The fact that there are many Radiolaria
living at the present day, whose shells are found fossil in Tertiary rocks,
is of great phylogenetic and geological significance. This appeared to be
the case even from the older observations upon the Polycystina of the
Barbados marl (see note A), but more recent and extensive observations both
upon these and upon the Miocene Radiolaria of Sicily, have shown that the
number of these "living fossil" forms is much greater than was previously
supposed (see note B). Among the Miocene Radiolaria numerous species, both
of SPUMELLARIA (especially #Sphæroidea# and #Discoidea#) and of NASSELLARIA
(especially #Spyroidea# and #Cyrtoidea#) are not to be distinguished from
the corresponding still living forms (see notes C, D). On the other hand,
those genera, which are rich both in species and individuals (recent as
well as fossil), present continuous series of forms which lead gradually
and uninterruptedly from old Tertiary species to others still living, which
are specifically indistinguishable from them. These interesting
morphological facts are capable of direct phylogenetic application, and
furnish valuable proofs of the truth of the theory of descent.

  A. Ehrenberg, in his list of fossil Polycystina (L. N. 25, pp. 64-85,
  1875), records 325 species of which 26 are still living.

  {clxxv}B. Stöhr, in his list of Miocene Radiolaria from Grotte (L. N. 35,
  p. 84, 1880), records 118 species, of which 29 are still living.

  C. Teuscher, who at my request has made a large number of comparative
  measurements and drawings, both of fossil and living Radiolaria, comes to
  the conclusion that numerous SPUMELLARIA and NASSELLARIA from Barbados
  are to-day extant and unchanged in the Radiolarian ooze of the deep
  Pacific Ocean (compare § 242A, and p. 1760, Note).

  D. From the comparative investigations, which I have made during the last
  ten years into the recent deep-sea Radiolaria of the Challenger
  collection and the Miocene Polycystina of Barbados, it appears that about
  a quarter of the latter are identical with living species of the former.



{clxxvi}BIBLIOGRAPHICAL SECTION.


CHAPTER XI.--LITERATURE AND HISTORY.

251. _List of Publications from 1834 to 1884_:--

    _Note._--In the text the references to the following publications are
    indicated by the letters L. N.

  1. 1834. MEYEN, F., Palmellaria (Physematium, Sphærozoum), in Beiträge
  zur Zoologie, gesammelt auf einer Reise um die Erde. _Nova Acta Acad.
  Cæs. Leop.-Carol._, vol. xvi., Suppl., p. 160, Taf. xxviii. figs. 1-7.

  2. 1838. EHRENBERG, G., Polycystina (Lithocampe, Cornutella, Haliomma) in
  Ueber die Bildung der Kreidefelsen und des Kreidemergels durch
  unsichtbare Organismen. _Abhandl. d. k. Akad. d. Wiss. Berlin_, p. 117.

  3. 1839. EHRENBERG, G., Ueber noch jetzt lebende Thierarten der
  Kreidebildung (Haliomma radians). _Abhandl. d. k. Akad. d. Wiss. Berlin_,
  p. 154.

  4. 1844-1873. EHRENBERG, G., Vorläufige Mittheilungen über Beobachtungen
  von Polycystinen. _Monatsber. d. k. preuss. Akad. d. Wiss. Berlin_.
  Republished with illustrations in the Mikrogeologie (L. N. 6) and in the
  two treatises of 1872 (L. N. 24) and 1875 (L. N. 25). Compare the
  _Monatsberichte_ of 1844 (pp. 57, 182, 257), of 1846 (p. 382), of 1847
  (p. 40), of 1850 (p. 476), of 1854 (pp. 54, 205, 236), of 1855 (pp. 292,
  305), of 1856 (pp. 197, 425), of 1857 (pp. 142, 538), of 1858 (pp. 12,
  30), of 1859 (p. 569), of 1860 (pp. 765, 819), of 1861 (p. 222), of 1869
  (p. 253), of 1872 (pp. 300-321), of 1873 (pp. 214-263). Only one of these
  small papers is of permanent value, The First Systematic Arrangement of
  the Polycystina in 7 families, 44 genera, and 282 species (_Monatsber. d.
  k. preuss. Akad. d. Wiss. Berlin_, 1847, p. 54). Compare my Monograph
  (1862, L. N. 16), pp. 3-12, 214-219.

  5. 1851. HUXLEY, TH., Upon Thalassicolla, a new Zoophyte. _Ann. and Mag.
  Nat. Hist._, ser. 2, vol. viii. pp. 433-442, pl. xvi.

  6. 1854.  EHRENBERG, G., Mikrogeologie. Figures of numerous Polycystina
  on 8 plates; Taf. xviii. figs. 110, 111; Taf. xix. figs. 48-56, 60-62;
  Taf. xx. Nr. i., figs. 20-25, 42; Taf. xxi. figs. 51-56; Taf. xxii. figs.
  20-40; Taf. xxxv. A., Nr. xix. A. fig. 5; Taf. xxxv. B. figs. 16-23; Taf.
  xxxvi. figs. 1-33.

  7. 1855.  BAILEY, J. W., Notice of Microscopic Forms of the Sea of
  Kamtschatka. _Amer. Journ. Sci. and Arts_, vol. xxii. p. 1, pl. i.

  8. 1855. MÜLLER, JOHANNES, Ueber Sphærozoum und Thalassicolla.
  _Monatsber. d. k. preuss. Akad. d. Wiss. Berlin_, p. 229.

  9. 1855. MÜLLER, JOHANNES, Ueber die im Hafen von Messina beobachteten
  Polycystinen (Haliomma, Eucyrtidium, Dictyospyris, Podocyrtis).
  _Monatsber. d. k. preuss. Akad. d. Wiss. Berlin_, p. 671.

  10. 1856. MÜLLER, JOHANNES, Ueber die Thalassicollen, Polycystinen und
  Acanthometren des Mittelmeeres. _Monatsber. d. k. preuss. Akad. d. Wiss.
  Berlin_, p. 474.

  11. 1858. MÜLLER, JOHANNES, Erläuterung einiger bei St. Tropez am
  Mittelmeer beobachteter Polycystinen und Acanthometren. _Monatsber. d. k.
  preuss. Akad. d. Wiss. Berlin_, p. 154.

  12. 1858. MÜLLER, JOHANNES, Ueber die Thalassicollen, Polycystinen und
  Acanthometren des Mittelmeeres, _Abhandl. d. k. Akad. d. Wiss. Berlin_,
  pp. 1-62, Taf. i.-xi. (The fundamental treatise on the Radiolaria.)

  {clxxvii}13. 1858.  SCHNEIDER, ANTON, Ueber zwei neue Thalassicollen von
  Messina. _Archiv f. Anat. u. Physiol._, p. 38, Taf. iii. B, figs. 1-4.

  14. 1858. CLAPARÈDE et LACHMANN, Echinocystida (Plagiacantha et
  Acanthometra). Études sur les Infusoires et les Rhizopodes, p. 458, pl.
  xxii. figs. 8, 9; pl. xxiii. figs. 1-6.

  15. 1860. HAECKEL, ERNST, Ueber neue lebende Radiolarien des
  Mittelmeeres. _Monatsber. d. k. preuss. Akad. d. Wiss. Berlin_, pp. 794,
  835.

  16. 1862. HAECKEL, ERNST, Die Radiolarien (Rhizopoda radiaria). Eine
  Monographie. 572 pp. fol. with an Atlas of 35 Copperplates.

  17. 1862. BURY, Mrs., Polycystins, figures of remarkable forms in the
  Barbados Chalk Deposit. Ed. ii. By M. C. Cooke, 1868. 25 quarto plates,
  photographed from drawings by hand, containing many forms overlooked by
  Ehrenberg from Barbados.

  18. 1863 HARTING, PAUL, Bijdrage tot de Kennis der mikroskopische Fauna
  en Flora van de Banda-Zee (Diep-Zee-Polycystinen). _Verhandl. d. Kon.
  Akad. van. Wetensch. Amsterdam_, vol. ix. p. 30, pls. i.-iii.

  19. 1865. HAECKEL, ERNST, Ueber den Sarcode-Körper der Rhizopoden
  (Actinelius, Acanthodesmia, Cyrtidosphæra, &c.). _Zeitschr. f. wiss.
  Zool._, Bd. xv. p. 342, Taf. xxvi.

  20. 1867. SCHNEIDER, ANTON, Zur Kenntniss des Baues der Radiolarien
  (Thalassicolla). _Archiv f. Anat. u. Physiol._, 1867, p. 509.

  21. 1870. HAECKEL, ERNST, Beiträge zur Plastiden Theorie (Myxobrachia;
  Amylum in den gelben Zellen). _Jenaische Zeitschr. für Naturw._, Bd. v.
  p. 519-540, Taf. xviii.

  22. 1871. CIENKOWSKI, L., Ueber Schwärmer-Bildung bei Radiolarien.
  _Archiv f. mikrosk. Anat._, Bd. vii. p. 372-381, Taf. xxix.

  23. 1872. WAGNER, N., Myxobrachia Cienkowskii. _Bull. d. Acad. St.
  Petersburg_, vol. xvii. p. 140.

  24. 1872. EHRENBERG, GOTTFRIED, Mikrogeologische Studien über das
  kleinste Leben der Meeres-Tiefgründe aller Zonen und dessen geologischen
  Einfluss. _Abhandl. d. k. Akad. d. Wiss. Berlin_, 1872. Mit 12 Tafeln.
  (The Latin diagnoses of 113 new species here mentioned are given in the
  _Monatsberichte_ of April 25, 1872, pp. 300-321.)

  25. 1875. EHRENBERG, GOTTFRIED, Polycystinen-Mergel von Barbados
  (Fortsetzung der Mikrogeologischen Studien). _Abhandl. d. k. Akad. d.
  Wiss. Berlin_, 1875, 168 pag. mit 30 Tafeln. (The Latin diagnoses of 265
  species here recorded are given in Namensverzeichniss der fossilen
  Polycystinen von Barbados. _Monatsber. d. k. preuss. Akad. d. Wiss.
  Berlin_, Jan. 30, 1873, pp. 213-263.)

  26. 1876. HERTWIG, RICHARD, Zur Histologie der Radiolarien.
  Untersuchungen über den Bau und die Entwickelung der Sphærozoiden und
  Thalassicolliden. 91 pp. with 5 plates.

  27. 1876. MURRAY, JOHN, Challengerida. Preliminary Reports on Work done
  on board the Challenger. _Proc. Roy. Soc. Lond._, vol. xxiv. pp. 471-536,
  pl. xxiv.

  28. 1876. ZITTEL, KARL, Palæozoologie, Bd. i. pp. 114-126, figs. 46-56.

  29. 1876. ZITTEL, KARL, Ueber fossile Radiolarien der oberen Kreide.
  _Zeitschr. d. deutsch. geol. Gesellsch._, Bd. xxviii. pp. 75-96, Taf. ii.
  (with figures of six Cretaceous species).

  30. 1877. MIVART, ST. GEORGE, Notes touching recent researches on the
  Radiolaria. _Journ. Linn. Soc. Lond._ (Zool.), vol. xiv. pp. 136-186.
  (Historical sketch of previous literature.)

  31. 1877. WYVILLE THOMSON, The Voyage of the Challenger--The Atlantic,
  vol. i. pp. 231-237, figs. 51-54; vol. ii. pp. 340-343, figs. 58, 59, &c.

  32. 1878. HAECKEL, ERNST, Das Protistenreich, eine populäre Uebersicht
  über das Formengebiet der niedersten Lebewesen, pp. 101-104.

  33. 1879. HERTWIG, RICHARD, Der Organismus der Radiolarien. _Jenaische
  Denkschriften_, Bd. ii. Taf. vi.-xvi. pp. 129-277.

  34. 1879. HAECKEL, ERNST, Ueber die Phæodarien, eine neue Gruppe
  kieselschaliger mariner Rhizopoden. _Sitzungsb. med.-nat. Gesellsch.
  Jena_, December 12, 1879.

  35. 1880. STÖHR, EMIL, Die Radiolarien-Fauna der Tripoli von Grotte
  (Provinz Girgenti in Sicilien). _Palæontographica,_ Bd. xxvi. pp. 71-124,
  Taf. xvii.-xxiii. A preliminary communication regarding this fauna from
  the tripoli is given in _Tagebl. d. Naturf. Versamml. München_, 1877.

  {clxxviii}36. 1880. PANTANELLI, DANTE, I Diaspri della Toscana e i loro
  fossili. _Real. Accad. dei Lincei_, ser. 3, vol. vii. pp. 13-34, Tab. i.
  Radiolaria di Calabria. _Atti. Soc. Tosc._, p. 59.

  37. 1881. HAECKEL, ERNST, Prodromus Systematis Radiolarium, Entwurf eines
  Radiolarien-Systems auf Grund von Studien der Challenger-Radiolarien.
  _Jenaische Zeitschr. für Naturw._, Bd. xv. pp. 418-472.

  38. 1881. BRANDT, KARL, Untersuchungen an Radiolarien. _Monatsber. d. k.
  preuss. Akad. d. Wiss. Berlin_, (April 21), pp. 388-404, Taf. i.

  39. 1882. BRANDT, KARL, Ueber die morphologische und physiologische
  Bedeutung des Chlorophylls bei Thieren. I. Artikel. _Archiv f. Anat. u.
  Physiol._, pp. 125-151, Taf. i. II. Artikel. _Mittheil. a. d. Zool.
  Station zu Neapel_, Bd. iv. pp. 193-302, Taf. xix., xx.

  40. 1882. BÜTSCHLI, OTTO, Beiträge zur Kenntniss der
  Radiolarien-Skelette, insbesondere der der Cyrtida. _Zeitschr. f. wiss.
  Zool._, Bd. xxxvi. pp. 485-540, Taf. xxxi.-xxxiii.

  41. 1882. BÜTSCHLI, OTTO, Radiolaria. In Bronn's Klassen und Ordnungen
  des Thierreichs. Bd. i., Protozoa, pp. 332-478, Taf. xvii.-xxxii.

  42. 1882. GEDDES, PATRICK, Further Researches on Animals containing
  Chlorophyll. _Nature_, pp. 303-305.

  43. 1882. GEDDES, PATRICK, On the Nature and Functions of the "Yellow
  Cells" of Radiolarians and Coelenterates. _Proc. Roy. Soc. Edin._, p.
  377.

  44. 1882. DUNIKOWSKI, EMIL, Die Spongien, Radiolarien und Foraminiferen
  der Unter-Liassischen Schichten vom Schafberg bei Salzburg. _Denkschr. d.
  k. Akad. d. Wiss. Wien_, Bd. xlv. pp. 22-34. Taf. iv.-vi.

  45. 1882. PANTANELLI, DANTE, Fauna miocenica di Radiolari del Appennino
  settentrional. _Boll. Soc. Geol. Ital._

  46. 1883. HAECKEL, ERNST, Die Ordnungen der Radiolarien (Acantharia,
  Spumellaria, Nassellaria, Phæodaria). _Sitzungsb. med.-nat. Gesellsch.
  Jena_, February 16, 1883.

  47. 1883. HERTWIG, OSCAR, Die Symbiose oder das Genossenschaftsleben im
  Thierreich. 56. _Versamml. Deutscher Naturf. u. Aerzte_, Freiburg i/B.

  48. 1883. RÜST, WILHELM, Ueber das Vorkommen von Radiolarien-Resten in
  kryptokrystallinischen Quarzen aus dem Jura und in Koprolithen aus dem
  Lias. 56. _Versamml. Deutscher Naturf. u. Aerzte_, Freiburg i/B.

  49. 1884. CAR, LAZAR, Acanthometra hemicompressa (= Zygacantha
  semicompressa). _Zool. Anzeiger_, p. 94.

  50. 1884. HAECKEL, ERNST, Ueber die Geometrie der Radiolarien
  (Promorphologie). _Sitzungsb. med.-nat. Gesellsch. Jena_, November 22,
  1883.


251 A. _Supplementary List of Works Published in_ 1885:--

  51. 1885. D. RÜST, Beiträge zur Kenntniss der fossilen Radiolarien aus
  Gesteinen des Jura. 45 pp. 4to, and 20 plates. _Palæontographica_, Bd.
  xxxi. (oder iii. Folge, vii. Band).

  52. 1885. KARL BRANDT, Die koloniebildenden Radiolarien (Sphærozoeen) des
  Golfes von Neapel und der angrenzenden Meeres-Abschnitte. 276 pp. 4to,
  and 8 plates.

  53. 1885. JOHN MURRAY, Narrative of the Cruise of H.M.S. Challenger, with
  a general account of the scientific results of the Expedition. Vol i.
  First part, pp. 219-227, pl. A. Second part, pp. 915-926, pl. N. fig. 2.

  54. 1885. ERNST HAECKEL, System der Acantharien. _Sitzungsb. med.-nat.
  Gesellsch. Jena_, November 13.

    Since the printing of this Report began in 1884 and was far advanced in
    1885, it was impossible to include the important works of Rüst and
    Brandt (L. N. 51, 52) in the descriptive portion, so that they are only
    referred to in the Introduction.

251 B. _Phaulographic Appendix_:--

    A list of absolutely worthless literature, which contains either only
    long known facts or false statements, and may hence be entirely
    neglected with advantage. Compare § 252, and also L. N. 26, p. 9.

  55. 1865. WALLICH, G. C., On the structure and affinities of Polycystina.
  _Trans. Micr. Soc. Lond._, vol. xiii. pp. 57-84. (Compare L. N. 26, p.
  9.)

  {clxxix}56. 1879. WALLICH, G. C., Observations on the Thalassicollidæ.
  _Ann. and Mag. Nat. Hist._, ser. 4, vol. iii. p. 97.

  57. 1866. STUART, ALEXANDER, Ueber Coscinosphæra ciliosa, eine neue
  Radiolarie (= Globigerina echinoides!!). _Zeitschr. f. wiss. Zool._, Bd.
  xvi. p. 328, Taf. xviii. (Compare L. N. 26, p. 9.)

  58. 1870. STUART, ALEXANDER, Neapolitanische Studien. _Göttinger Nachr._,
  p. 99, and _Zeitschr. f. wiss. Zool._, Bd. xxii. p. 290 ("Blue Siliceous
  Crystals" in Collozoum inerme!).

  59. 1871. MACDONALD, JOHN DENIS, Remarks on the Structure of Polycystina
  (Astromma Yelvertoni = Euchitonia Mülleri). _Ann. and Mag. Nat. Hist._,
  ser. 4, vol. viii. p. 226.

  60. 1871. DOENITZ, W., Beobachtungen über Radiolarien. _Archiv f. Anat.
  u. Physiol._, 1871, p. 71, Taf. ii. (Compare L. N. 26, p. 7.)


252. _Progress of our Knowledge of the Radiolaria from_ 1862 _to_
1885.--The history of our scientific knowledge of the Radiolaria extends
over about half a century (from 1834 to 1885). A historical and critical
discussion of the works which appeared within the first twenty-eight years
of this period (from 1834 to 1862) is contained in the historical
introduction to my Monograph (L. N. 16, pp. 1-24); I shall therefore
give here only a brief survey of the investigations published during
the last twenty-three years (from 1862 to 1885). The most important
steps in our progress during this period we owe to the following
naturalists:--Cienkowski (1871), Ehrenberg (1872 and 1875), Richard Hertwig
(1876 and 1879), Karl Brandt (1881 and 1885), Bütschli (1882), and Rüst
(1885). To the valuable works of these authors must be added a number of
smaller contributions, which are recorded in the foregoing Bibliography.
Some communications from dilettanti, written with insufficient knowledge of
the subject, and hence of no value, are mentioned for the sake of
completeness in the "Phaulographic Appendix" (compare L. N. 55-60, also L.
N. 26, p. 9).

The first important advance in our knowledge of the organisation of the
Radiolaria, made after the publication of my Monograph (1862), was the
demonstration of the nature of the extracapsular "yellow cells." In the
year 1870 I showed that these yellow cells contain starch (L. N. 21, p.
519). I regarded them, as did all authors up to that time, as integral
parts of the Radiolarian organism, and hence considered this to be
multicellular; for no doubt was possible regarding the true cellular nature
of these remarkable, nucleated, yellow globules, which I had thoroughly
studied in 1862. It was first shown by Cienkowski in 1871 that the yellow
cells of the #Collodaria# remain unchanged even after the death of these
organisms, "that they continue to grow uninterruptedly, and eventually
multiply by division" (L. N. 22, pp. 378-380, Taf. xix. figs. 30-36).
Cienkowski concluded from these important observations that the yellow
cells are not integral parts of the Radiolarian body, but "parasitic
structures," independent, unicellular organisms, which live only as
parasites in the body of the Radiolaria (compare § 90).

This important recognition underwent ten years later a further development
and complete establishment by the extensive investigations of Karl Brandt
(L. N. 38, 39) {clxxx}and Patrick Geddes (L. N. 42, 43). This arrangement
was compared by Brandt to the remarkable symbiosis of the Algoid gonidia
and Fungoid hyphæ in the organisation of the Lichens, which had been
recently discovered, and since he recognised the independent nature of the
yellow cells, as unicellular Algæ, in all divisions of the Radiolaria, he
founded for them the genus _Zooxanthella_. Geddes named them _Philozoon_,
and showed experimentally that they give out oxygen under the influence of
sunlight (compare § 90). The great physiological importance of the yellow
cells in the metastasis of the Radiolaria, and, when they are developed in
large quantities, in the economy of marine organisms in general, has
recently been insisted upon by Brandt (see § 205 and L. N. 52, pp. 65-71,
86-94).

The proof that the yellow cells do not belong to the Radiolarian organism
itself, but only live parasitically in it, was a necessary preliminary to
the very important step which next took place in our knowledge of the
organisation of the Radiolaria. This step consisted in the demonstration
that the whole body of the Radiolaria, like that of all other Protista, is
only a single cell. It was Richard Hertwig who in two remarkable works (L.
N. 26, 33) firmly established this fundamental theorem of the unicellular
nature of the Radiolaria. In his treatise on the histology of the
Radiolaria (L. N. 26, 1876) he published complete investigations into the
structure and development of the Sphærozoida and Thalassicollida. Since he
made use of the modern methods of histological examination, and especially
of staining fluids, which he was the first to apply to the study of the
Radiolaria, he was able to show that no true cells (apart from the
parasitic yellow cells) are to be found in their bodies, but rather that
all their morphological components are to be regarded as differentiated
parts of a single true cell, and in particular that the central capsule
includes a genuine nucleus.

A wider foundation for this important discovery and its applicability to
all divisions of this extensive class, was given by Hertwig in a second
work on the organisation of the Radiolaria (L. N. 33, 1879). Among the
numerous discoveries by which this work enriched the natural history of the
Radiolaria must be specially mentioned the recognition of the fundamental
differences exhibited by the main divisions of the class in the structure
of their central capsule. Hertwig first observed that the capsular membrane
is double in the PHÆODARIA but single in the other Radiolaria (§ 56); the
former he named "TRIPYLEA" because he discovered in their capsular membrane
a large, peculiarly constructed main opening and two small accessory
openings. The NASSELLARIA, in which he found a single porous area at the
basal pole of the main axis, with a cone of pseudopodia rising from it, he
called on this account "MONOPYLEA"; whilst the other Radiolaria, whose
capsular membrane is perforated on all sides with fine pores, were termed
"PERIPYLEA." Besides the central capsule, Hertwig laid stress upon the
significance of the gelatinous envelope as a constant and important
constituent of the body. He also devoted attentive consideration to the
morphology of the skeleton, and on the basis of certain
{clxxxi}phylogenetic conclusions which he drew from it, he arrived at an
improved systematic arrangement in which he distinguished six orders:--(1)
#Thalassicollea#, (2) #Sphærozoea#, (3) #Peripylea#, (4) #Acanthometrea#,
(5) #Monopylea#, (6) #Tripylea#. The numerous isolated discoveries with
which Hertwig enriched the morphology of the Radiolaria, have been already
alluded to in the appropriate paragraphs in the anatomical portion of this
Introduction (see L. N. 42, pp. 340, 341).

The new and interesting group, which was thus erected into an order under
the name TRIPYLEA, I had already a year previously separated from the other
Radiolaria as "_Pansolenia_" in my Protistenreich (L. N. 32, p. 102).
Since, however, neither the three capsular openings of the TRIPYLEA nor the
skeletal tubes of the Pansolenia are present in all the families of this
extensive order, I substituted in 1879 the more suitable name PHÆODARIA,
which is applicable to all members of the group (L. N. 34). In the
preliminary memoir then published regarding the Phæodaria, a New Group of
Siliceous Marine Rhizopods, I distinguished four orders, ten families, and
thirty-eight genera. The great majority of these new forms (among which
were no less than 465 different species) were first discovered by the
deep-sea investigations of the Challenger. John Murray was the first who
called attention to the great abundance in the deep sea of these remarkable
Rhizopods, and to the constant presence of their peculiar, dark,
extracapsular pigment body (phæodium); even in 1876 he described a portion
of them as Challengerida (L. N. 27, p. 536; L. N. 53, p. 226). The earliest
observations on the PHÆODARIA were made at Messina in 1859, where I
examined five genera of this remarkable group alive (compare p. 1522 and L.
N. 16).

By the discovery that the PHÆODARIA, although differing in important
respects from the other Radiolaria, still conform to the definition of the
class, a new and extensive series of forms was added to this latter, and by
their closer investigation a fresh source of interesting morphological
problems was disclosed. In other groups, however, morphology was advanced
by comparative anatomical studies. In addition to the smaller contributions
of various authors, mentioned in the foregoing bibliography, I may
specially refer to the valuable Beiträge zur Kenntniss der
Radiolarien-Skelete, insbesondere der der Cyrtida by O. Bütschli (L. N. 40,
1882). On the basis of careful comparative anatomical studies,
investigations into the skeletal structure of a number of fossil
#Cyrtoidea# and critical application of the recently published researches
of Ehrenberg into the Polycystina of Barbados (L. N. 25), Bütschli
attempted to derive the complicated relations of the Monopylean skeletons
phylogenetically from a simple primitive form,--the primary sagittal ring.
Even if this attempt did not actually solve the very difficult
morphological problem in question, still the critical and synthetic mode in
which it was carried out deserves full recognition, and furnishes the proof
that the comparative anatomy of the skeleton in the Radiolaria not less
than in the Vertebrata, is a most interesting and fruitful field of
phylogenetic investigation. A {clxxxii}further demonstration of this was
furnished by Bütschli in the general account of the organisation of the
Radiolaria which he published in 1882 in Bronn's Klassen und Ordnungen des
Thierreichs (L. N. 41).

In our knowledge of the developmental history of these Protista the last
two decades have witnessed less progress than in their comparative anatomy.
The most important advance in this direction has been the proof that in all
the main groups of the class the contents of the central capsule are used
in the formation of swarm-spores. The movements of these zoospores in the
central capsule had indeed been observed by several previous authors in the
case of the SPUMELLARIA and ACANTHARIA (L. N. 10, 13, 16; compare also §
142, Note A). The origin of the flagellate spores from the contents of the
central capsule and their peculiar constitution were, however, first
described fully by Cienkowski in 1871 (L. N. 22, p. 372). Soon after this,
R. Hertwig discovered that in the social Radiolaria (Polycyttaria or
Sphærozoea) two different forms of zoospores are formed, one with, the
other without crystals, and that the latter are also divided into
macrospores and microspores (compare L. N. 26, and § 142). Recently this
sexual differentiation has been shown by Karl Brandt to exist in all the
groups of Sphærozoea, and its regular interchange with the formation of
crystal-spores has been interpreted as a true "alternation of generations"
(compare L. N. 52 and also § 216). The other forms of development also,
especially reproduction by cell-division (§ 213) and gemmation (§ 214),
have been elucidated by the recent investigations of the same author.

The palæontology of the Radiolaria has of late made important and
interesting advances. Until ten years ago fossil remains of this class were
known exclusively from the Tertiary period; almost the only source of our
information was to be found in the researches of Ehrenberg, commenced in
1838, continued in his Mikrogeologie in 1854, and concluded in his last
work (L. N. 25) published in 1875 (compare L. N. 16, pp. 3-9, 191-193). In
the year 1876 a number of Mesozoic Radiolaria from the chalk were described
by Zittel (L. N. 28), and afterwards others from the Jura by Dunikowski (L.
N. 44). That fossil Radiolaria occur in Mesozoic formations, especially in
the Jura, as well preserved and as abundantly as in the Tertiary rocks of
Barbados, was shown in 1883 by Rüst (L. N. 48). By the examination of
numerous thin sections he discovered that in all the main divisions of the
Jurassic formation (Lias, Dogger, Malm) there are distributed jaspers,
flints, cherts, and other quartzites, which consist largely of the
siliceous shells of Polycystina; the same is true also of many Coprolites
found in the Jura. The full account of these and the descriptions and
figures of 234 Jurassic species, distributed in 76 genera, are contained in
the Beiträge zur Kenntniss der fossilen Radiolarien aus Gesteinen des Jura
(L. N. 51, 1885). But even in the older rocks, the Trias, the Permian, and
Carboniferous systems, and even as far downwards as the Silurian and
Cambrian formations, Rüst has recently shown the existence of fossil
Radiolaria, {clxxxiii}and thus increased the known period of the
developmental history of the class by many millions of years (§ 244).

The great significance of the Radiolaria in geology and palæontology has
been brought into new light not only by these extensive discoveries, but
also by the important relations which have been shown to exist between the
Radiolarian rocks and the deep-sea deposits of the present day. In this
direction the wonderful discoveries of the Challenger, and especially the
investigation of the deep-sea deposits by Wyville Thomson (L. N. 31) and
John Murray (L. N. 27), have furnished us with new and valuable information
(compare §§ 236-239, and §§ 245-250). The Tertiary Polycystine formations
of Barbados and the Nicobar Islands, with which we have been acquainted for
the last forty years, as also the Mesozoic Radiolarian quartzes, which have
only recently been made known to us from the Jura, are ascertained to be
fossil representatives of the same deep-sea deposits which now occur in the
form of Radiolarian ooze (§ 237), and to some extent also of Globigerina
ooze and red clay (§§ 238, 239), on the bottom of the ocean, at depths of
from 2000 to 4500 fathoms.

These investigations into fossil Radiolaria and their comparison with
recent deep-sea forms have a further general significance, inasmuch as the
identity of many living and fossil species from the Tertiary formation has
been shown beyond all doubt. In this direction the numerous measurements
and accurate comparisons which I have made during the last ten years of the
abyssal forms in the Challenger collection, and of fossil species from
Barbados and Caltanisetta, have brought to light many important facts. In
this I had the able assistance of my friend, Dr. Reinhold Teuscher (compare
§ 250, and p. 1760). Further valuable contributions in this direction are
found in the careful observations and comparative measurements recently
published by Emil Stöhr (L. N. 35, 1880), regarding the Radiolarian fauna
of the Tripoli of Grotte in the province of Girgenti, Sicily. From these it
appears that the number of Miocene species which are still extant, is much
greater than would appear from the results of Ehrenberg.

Ehrenberg himself, towards the end of his long and laborious life,
collected the results of the systematic and palæontological researches,
which he had begun thirty-seven years previously (L. N. 16, pp. 3-12) into
the Polycystina, in two large works (L. N. 24, 25). The first treatise (L.
N. 24, 1872) contains the Mikrogeologische Studien über das Kleinste Leben
der Meeres-Tiefgründe aller Zonen und dessen geologischen Einfluss, with a
list of 279 Polycystina observed by him from the deep-sea, as well as
figures of 127 species. The second work (L. N. 25, 1875) contains the
Fortsetzung der Mikrogeologischen Studien, mit specieller Rücksicht auf den
Polycystinen-Mergel von Barbados; the list of fossil Polycystina observed
by him includes 325 species, of which 26 are still extant; 282 of them are
figured on the thirty plates accompanying the memoir. By means of these
numerous figures, as well as by the appended systematic and chorological
tables, Ehrenberg furnished a welcome {clxxxiv}supplement to the numerous
communications regarding the Polycystina, which he had made to the Berlin
Academy since 1838, and which he had published in his Mikrogeologie in
1854. It will always be the merit of this zealous and indefatigable
microscopist that he first called attention to the great wealth of forms
existing in this class; he separated systematically about 500 species, and
published drawings of about 400; in addition to which he was the first to
lay stress upon the great chorological and geological importance of the
Radiolaria.

With these systematic and descriptive, chorological and palæontological
works, however, which relate exclusively to the Polycystina, the merits of
the famous naturalist of Berlin are exhausted as regards this class of
animals. Of the organisation of the Radiolaria, Gottfried Ehrenberg
remained entirely ignorant up till his death in 1876. All that a number of
famous naturalists had observed during a quarter of a century as to the
structure and life-history of the Radiolaria, all the important discoveries
of Huxley (1851), Johannes Müller (1858), Claparède (1858), Cienkowski
(1871), and many others (L. N. 1-22), and all that I had published in my
Monograph (1862) on the basis of three years' study of their anatomy and
physiology--all this Ehrenberg ignored, or rather, he regarded it all as
worthless rubbish of science, as a chaos of devious errors, resting upon
incomplete observations and false conclusions. His strange "special
considerations regarding the Polycystina" (L. N. 24, pp. 339-346) and the
general "concluding remarks" (L. N. 25, pp. 146-147) leave no room for
doubt on this point. Ehrenberg indeed doubted to the last whether any
observer had seen living Radiolaria at all (L. N. 25, p. 108).

The invincible obstinacy with which Ehrenberg maintained his preconceived
opinion of the high organisation of the Radiolaria, and entirely ignored
the contrary observations of other naturalists, is explained by the
consistency with which he held to the end the "principle peculiar to
himself of the universally equal development of the animal kingdom" (L. N.
16, p. 7). From the complicated arrangement of their siliceous shells he
concluded that the animals inhabiting them must possess a structure
correspondingly complex, and nearly related to that of the Echinodermata
(Holothuria). Like all other animals the Radiolaria must possess systems of
organs for locomotion, sensation, nutrition, circulation, and reproduction.
Whilst Ehrenberg originally interpreted the Polycystina as siliceous
Infusoria polygastrica, and regarded them as compound Arcellina, he
afterwards classed them sometimes with the Echinodermata (Holothuria),
sometimes with the Bryozoa, sometimes with the Oscillaria (see L. N. 41, p.
336). Although a decided opponent of the cell-theory he called them
"multicellular animalcules" (Polycystina), interpreting the pores of the
siliceous shell as cells. To-day the opposite term (Monocystina) might be
adopted to express their unicellular organisation. It was a remarkable
irony of fate that in the self-same year (1838) in which Schwann of Berlin
made by his foundation of the cell theory the greatest advance in the whole
{clxxxv}of Biological Science, that Ehrenberg, all his life the most
zealous opponent of that theory, published his great work on the Infusoria,
and at the same time established the "family of multicellular animalcules
or Polycystina" (L. N. 16, p. 4).

The "short systematic survey of the genera of cellular animalcules" given
by Ehrenberg in 1875 (L. N. 25, p. 157), is only a new edition, increased
by sixteen genera, of his first systematic arrangement of the Polycystina
of 1847 (L. N. 4, p. 53). Since I have already given a full discussion of
this in my Monograph (L. N. 16, pp. 214-219), I need only here remark that
a correct understanding of his very inadequate generic diagnoses is only
possible by the aid of his figures. Relying upon these I have retained
almost all Ehrenberg's genera, although entirely new definitions of most of
them have been necessary.

The same is true also of the two orders which Ehrenberg distinguished in
his class of "Zellenthierchen." The first order is constituted by his
"Netzkörbchen" (Monodictya or NASSELLARIA) formerly known as "Polycystina
solitaria"; they include our #Cyrtoidea#, the greater part of Hertwig's
Monopylea. Ehrenberg's second order is the "Schaumsternchen" (Polydictya or
SPUMELLARIA), previously called "Polycystina composita"; they include the
Peripylea of Hertwig, as well as the Spyridina (our #Spyroidea#), which
belong properly to the NASSELLARIA. Although Ehrenberg's statements
regarding the organisation of both these orders were quite erroneous, and
his knowledge even of the structure of their shells very defective, I still
thought it advisable to retain his names for the groups, since they
constituted his one successful effort in the systematic treatment of the
Radiolaria (compare L. N. 41, p. 336).

The sketch of a systematic arrangement of the Radiolaria (L. N. 37), which
I published in 1881 on the basis of the study of the Challenger Radiolaria,
resembles, in respect of seven orders being distinguished, the new system
which R. Hertwig founded in 1879, in consequence of the variations which he
discovered in the structural relations of the central capsule (L. N. 33, p.
133). It differs, however, inasmuch as his Sphærozoea (my Polycyttaria) are
here divided into two orders, Symbelaria (#Collosphærida#) and Syncollaria
(#Sphærozoida#). In that sketch too I separated for the first time the two
subclasses Holotrypasta (Porulosa) and Merotrypasta (Osculosa). The fifteen
families established by Hertwig were then raised to twenty-four. The six
hundred and thirty genera, which I then distinguished, are still for the
most part retained, some, however, in a restricted sense, or with amended
definitions.

The differential characters of the orders and families of the Radiolaria,
given in the Prodromus in 1881, were amended in a further communication
which I gave in 1883 regarding the orders of the Radiolaria (L. N. 46, p.
17). There I reduced the seven orders to four, the structural relations of
the central capsule being precisely the same in the Polycyttaria and
#Collodaria# as in the #Peripylea#. The survey of the affinities of the
class was thus rendered much simpler and clearer, and the
{clxxxvi}hypothetical genealogical tree, which I then published, has been
still further carried out in Chapter VI. of the present Introduction (see
§§ 153-200).


253. _General Survey of the Growth of our Systematic Acquaintance with the
Radiolaria from 1834 to 1885._

  1834. MEYEN (L. N. 1) describes 2 genera and species of
  #Collodaria#:--_Sphærozoum fuscum_ and _Physematium atlanticum_.

  1838. EHRENBERG (L. N. 2) founds the family Polycystina upon 3 fossil
  genera (with 6 species):--_Lithocampe_, _Cornutella_, _Haliomma_.

  1847. EHRENBERG (L. N. 4) publishes his preliminary communications
  regarding the fossil Polycystina of Barbados and distinguishes 282
  species, distributed in 44 genera and 7 families. In the tabular view of
  the genera he distinguishes two orders:--I. #Solitaria#--(1)
  Halicalyptrina, (2) Lithochytrina, (3) Eucyrtidina; and II.
  #Composita#--(4) Spyridina, (5) Calodictya, (6) Haliommatina, (7)
  Lithocyclidina (compare L. N. 16, pp. 214-219).

  1851. HUXLEY (L. N. 5) gives the first accurate account of living
  Radiolaria, and describes 2 species of the genus _Thalassicolla_
  (_nucleata_ and _punctata_); under the latter are included 4 genera of
  #Sphærozoea#:--_Collozoum_, _Sphærozoum_, _Collosphæra_, _Siphonosphæra_
  (compare L. N. 16, pp. 12-14).

  1854. EHRENBERG (L. N. 6) publishes in his Mikrogeologie, figures of
  seventy-two species of fossil Polycystina (without descriptions).

  1855. JOHANNES MÜLLER (L. N. 8, p. 248) describes the first
  _Acanthometra_, and elucidates its affinity to Huxley's _Thalassicolla_
  and Ehrenberg's Polycystina.

  1858. JOHANNES MÜLLER (L. N. 12) establishes the new group Radiolaria as
  a special order of the Rhizopoda, and includes in it the Thalassicolla,
  Polycystina, and Acanthometra as closely related families. He opposes
  these radiate Rhizopoda to the Polythalamia, and describes 50 species
  observed by him living in the Mediterranean, these he arranges in 20
  genera, of which 10 are new. The figures are contained in eleven plates
  (see L. N. 16, pp. 22-24).

  1858. CLAPARÈDE (L. N. 14) describes the first #Plectoidean#
  (_Plagiacantha arachnoides_) and two species of _Acanthometra_, which he
  had observed living in Norway (see L. N. 16, p. 18).

  1860. EHRENBERG (L. N. 4) gives a short diagnosis of 22 new genera of
  Polycystina, based on the investigation of numerous deep-sea species
  brought up by Brooke from the depths of the Pacific Ocean. The number of
  his genera is thus increased to 66 (compare L. N. 16, pp. 10, 11).

  1862. ERNST HAECKEL (L. N. 16) embraces in his Monograph of the
  Radiolaria all the species hitherto known either by figures or
  descriptions, and arranges them in 15 families and 113 genera; of which
  latter 46 are new. The number of new species observed living amounts to
  144. In a "survey of the Radiolarian fauna of Messina" (p. 565) he
  records 72 genera and 169 species. Most of these are figured in the
  accompanying atlas of thirty-five plates.

  {clxxxvii}1862. BURY (L. N. 17) gives in an atlas of twenty-five plates,
  photographed from drawings, the figures of numerous fossil Polycystina of
  Barbados (without descriptions), of which many are new species overlooked
  by Ehrenberg (compare § 242, above).

  1872. EHRENBERG (L. N. 24) gives a list of names (without description) of
  all the Polycystina observed by him from the bottom of the sea, 279
  species, of which 127 are figured on twelve plates.

  1875. EHRENBERG (L. N. 25) gives a list of names of all the fossil
  Polycystina observed by him (from Barbados, the Nicobar Islands and
  Sicily), 326 species, of which 282 are figured (compare § 242 above). In
  a new "Systematic Survey of the Genera" the number of these is given as
  63. The 7 families are the same as given in 1847 (see above), as also the
  two orders (NASSELLARIA = Solitaria, SPUMELLARIA = Composita).

  1876. ZITTEL (L. N. 29) describes the first fossil Radiolaria from the
  chalk (6 species) and establishes the new Cyrtoid genus _Dictyomitra_.

  1876. JOHN MURRAY (L. N. 27) establishes the new family Challengerida,
  and figures 6 new generic types of PHÆODARIA.

  1879. RICHARD HERTWIG (L. N. 33) first describes the fundamental
  differences in the structure of the central capsule, and in accordance
  with them divides the Radiolaria into six orders:--(1) Thalassicollea,
  (2) Sphærozoea, (3) Peripylea, (4) Acanthometrea, (5) Monopylea, (6)
  Tripylea (p. 133). These are subdivided into 18 families, and their
  phylogenetic affinities discussed (p. 137). On the ten plates, several
  new species from Messina are figured, among them the types of several new
  genera (_Cystidium_, _Coelacantha_, _Echinosphæra_) (compare § 252).

  1879. ERNST HAECKEL (L. N. 34) founds the order PHÆODARIA as a "new group
  of marine siliceous Rhizopods," and distinguishes in it 4 suborders, 10
  families and 38 genera.

  1880. EMIL STÖHR (L. N. 35) describes the Miocene "Radiolarian fauna of
  the tripoli from Grotte in Sicily," 118 species, of which 78 are new;
  among them is the new genus _Ommatodiscus_, the type of a new family,
  Ommatodiscida. The new species are figured on seven plates.

  1880. DANTE PANTANELLI (L. N. 36) describes 30 species of fossil
  Polycystina from the jaspers of Tuscany, which he regarded as Eocene, but
  which were probably of Jurassic origin (compare § 243, note B, above).

  1881. ERNST HAECKEL (L. N. 37) publishes a "Sketch of a classification of
  the Radiolaria on the basis of the study of the Challenger Collection,"
  and distinguishes in his "conspectus ordinum" (p. 421) 2 subclasses and 7
  orders, and in the "prodromus systematis Radiolarium" (pp. 423-472) 24
  families with 630 genera, among which are more than 2000 new species.

  1882. BÜTSCHLI (L. N. 40) on the basis of studies of the fossil Monopylea
  of Barbados, investigates the "mutual relations of the Acanthodesmida,
  Zygocyrtida and Cyrtida," and gives a critical revision of the genera of
  these "Cricoidea;" a number of new species are described and figured
  (Tafs. xxxii., xxxiii.), and some new genera of Stichocyrtida established
  (_Lithostrobus_, _Lithomitra_, &c.).

  1882. DUNIKOWSKI (L. N. 44) describes 18 new fossil Polycystina from the
  lower lias of the Salzburg Alps, among them the types of 3 new genera
  (_Ellipsoxiphus_, _Triactinosphæra_, and _Spongocyrtis_).

  {clxxxviii}1883. ERNST HAECKEL (L. N. 46) revises the 4 orders and 32
  families of Radiolaria, and gives more accurate definitions of them, as
  well as of the 2 subclasses (I. _Holotrypasta_ = ACANTHARIA and
  SPUMELLARIA; II. _Merotrypasta_ = NASSELLARIA and PHÆODARIA).

  1885. D. RÜST (L. N. 51) describes 234 new species of fossil Radiolaria
  from the Jura, and illustrates them by twenty plates. Among them are 103
  SPUMELLARIA, 130 NASSELLARIA, and 1 PHÆODARIA; these are contained in 35
  genera, of which 20 belong to the Porulosa, and 15 to the Osculosa.


254. _Statistical Synopsis of the Twenty Orders_:--


  (a) Number of Families.
  (b) Number of Genera.
  (c) Number of Species.
  (d) Previously known Species.
  (e) New Species.
  (f) Fossil Species.
  (g) Pelagic Abundance.
  (h) Abyssal Abundance.
  (i) Figured on Plates

  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |     |     |      |     |      |     |     |     |    Figured on     |
  | (a) | (b) |  (c) | (d) |  (e) | (f) | (g) | (h) |      Plates.      |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  | I. Legion SPUMELLARIA (Porulosa peripylea)                          |
  +-----+---------------------------------------------------------------+
  |     | I. COLLODARIA (Spumellaria palliata)                          |
  +-----+-----+---------------------------------------------------------+
  |           | 1. Colloidea                                            |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  2  |   6 |   36 |   9 |   27 |   0 |  A  |  E  |   1, 3            |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 2. Beloidea                                             |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  2  |   8 |   56 |   9 |   47 |   0 |  A  |  D  |   2, 4            |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |     | II. SPHÆRELLARIA (Spumellaria loricata)                       |
  +-----+-----+---------------------------------------------------------+
  |           | 3. Sphæroidea                                           |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  6  | 107 |  660 | 105 |  555 |  66 |  A  |  B  |  { 5-8            |
  |     |     |      |     |      |     |     |     |  { 11-30          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 4. Prunoidea                                            |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  7  |  53 |  280 |  35 |  245 |  36 |  B  |  B  |  { 16, 17         |
  |     |     |      |     |      |     |     |     |  { 39, 40         |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 5. Discoidea                                            |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  6  |  91 |  503 | 126 |  376 | 102 |  B  |  A  |  { 31-38          |
  |     |     |      |     |      |     |     |     |  { 41-48          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 6. Larcoidea                                            |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  9  |  51 |  260 |   8 |  252 |   0 |  E  |  B  |  { 9, 10          |
  |     |     |      |     |      |     |     |     |  { 49, 50         |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  | II. Legion ACANTHARIA (Porulosa actipylea)                          |
  +-----+---------------------------------------------------------------+
  |     | III. ACANTHOMETRA (Acantharia palliata)                       |
  +-----+-----+---------------------------------------------------------+
  |           | 7. Actinelida                                           |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  3  |   6 |   22 |   6 |   16 |   0 |  E  |  E  | 129 (figs. 1-3)   |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 8. Acanthonida                                          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  3  |  21 |  138 |  50 |   88 |   0 |  A  |  C  | 130-132           |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |     | IV. ACANTHOPHRACTA (Acantharia loricata)                      |
  +-----+-----+---------------------------------------------------------+
  |           | 9. Sphærophracta                                        |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  3  |  27 |  149 |   9 |  140 |   0 |  B  |  B  | 133-138           |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 10. Prunophracta                                        |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  3  |  11 |   63 |   5 |   58 |   0 |  D  |  B  | 139, 140          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  | III. Legion NASSELLARIA (Osculosa monopylea)                        |
  +-----+---------------------------------------------------------------+
  |     | V. PLECTELLARIA (Nassellaria palliata)                        |
  +-----+-----+---------------------------------------------------------+
  |           | 11. Nassoidea                                           |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  1  |   2 |    5 |   1 |    4 |   0 |  E  |  E  |   91 (fig. 1)     |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 12. Plectoidea                                          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  2  |  17 |   61 |   5 |   56 |   0 |  D  |  C  |   91 (figs. 2-12) |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 13. Stephoidea                                          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  4  |  40 |  205 |  14 |  191 |  17 |  C  |  B  |  { 81, 82         |
  |     |     |      |     |      |     |     |     |  { 92-94          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |     | VI. CYRTELLARIA (Nassellaria loricata)                        |
  +-----+-----+---------------------------------------------------------+
  |           | 14. Spyroidea                                           |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  4  |  45 |  239 |  51 |  188 |  53 |  C  |  A  |    83-90          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 15. Botryodea                                           |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  3  |  10 |   55 |  15 |   40 |  10 |  E  |  C  |    96             |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 16. Cyrtoidea                                           |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  | 12  | 160 | 1122 | 328 |  794  |250 |  C  |  A  |    51-80          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  | IV. Legion PHÆODARIA (Osculosa cannopylea)                          |
  +-----+---------------------------------------------------------------+
  |     | VII. PHÆOCYSTINA (Phæodaria palliata)                         |
  +-----+-----+---------------------------------------------------------+
  |           | 17. Phæocystina                                         |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  3  |  15 |  112 |  30 |   82 |  24 |  C  |  B  |   101-105         |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |     | VIII. PHÆOCOSCINA (Phæodaria loricata)                        |
  +-----+-----+---------------------------------------------------------+
  |           | 18. Phæosphæria                                         |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  4  |  22 |  121 |   5 |  116 |   0 |  C  |  A  |   106-112         |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 19. Phæogromia                                          |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  5  |  27 |  159 |   5 |  154 |   0 |  C  |  A  |  { 99, 100        |
  |     |     |      |     |      |     |     |     |  { 113-120        |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |           | 20. Phæoconchia                                         |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  3  |  20 |   73 |   4 |   69 |   0 |  D  |  B  |   121-128         |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |                             Total,                                  |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+
  |  85 | 739 | 4318 | 810 | 3508 | 558 | ... | ... |   140             |
  +-----+-----+------+-----+------+-----+-----+-----+-------------------+

_Note._--In the tenth and eleventh columns the relative abundance of each
order at or near the surface and near the bottom is approximately indicated
by the letters A-E, which have the following significance:--A, abundant; B,
very numerous; C, many (medium quantity); D, few; E, very few.



{1}SYSTEMATIC PART.

----

CLASS RADIOLARIA.

  RADIOLARIA, Johannes Müller, 1858.
  RHIZOPODA RADIARIA, Johannes Müller, 1858.
  POLYCYSTINA (_pro parte_), Ehrenberg, 1838.
  ECHINOCYSTIDA, Claparède, 1858.
  RHIZOPODA CAPSULARIA, Haeckel, 1861.
  CYTOPHORA, Haeckel, 1862.

_Definition of the Class:_--#Rhizopoda with unicellular body, divided by a
porous membrane into an internal or intracapsular part (with nucleus), and
an external or extracapsular part (with calymma); propagating by
flagellated spores.#


The RADIOLARIA or CAPSULATE RHIZOPODA, first constituted by Johannes Müller
in the year 1858 as a separate group of the Rhizopoda, form a peculiar
class of the PROTISTA, or unicellular organisms. This class is exclusively
marine, and has in general the characteristic organisation of the
Rhizopoda, with the development of numerous _pseudopodia_ from the surface
of the cell; but it differs from all other Rhizopoda in the possession of a
peculiar _membrane_, dividing the cell-body into two different parts; the
_central capsule_ or the internal part with the _nucleus_, and the external
part or _extracapsulum_ with the _calymma_; propagation by flagellated
spores produced in the central capsule; the sarcode or the _protoplasm_ of
both parts communicates by fine _pores_, piercing the separating membrane,
which is called the _capsule-membrane_.

The _Central Capsule_ or the inner part of the Radiolarian body is
constantly composed of three essential parts, viz.:--

  1. _The Central Nucleus_ (a true cell-nucleus).

  2. _The Intracapsular Sarcode_ (endosarc) or surrounding internal
  protoplasm.

  3. _The Capsule Membrane_ or enveloping porous membrane.

{2}Besides these constant and essential elements, the central capsule
contains very commonly (but not constantly) some other enclosed structures,
viz.:--

  4. An internal or intracapsular skeleton.

  5. Intracapsular vacuoles or alveoli.

  6. Fat-granules or oil-globules.

  7. Crystals of different composition.

  8. Pigment-granules.

_The Extracapsulum_, or the outer part of the Radiolarian body is also
constantly composed of three essential elements,--

  1. _The Calymma_, or the thick extracapsular _jelly-veil_, completely
  enveloping the whole central capsule.

  2. _The Matrix_, or the maternal tissue of the external protoplasm,
  enveloping immediately the capsule-membrane as a thin continuous layer of
  _extracapsular sarcode_ (ectosarc).

  3. _The Pseudopodia_, or the very numerous thread-like filaments of
  protoplasm, which radiate from the matrix; whilst their inner part is
  enclosed in the calymma, their outer part floats freely in the sea-water.

Besides these three constant and essential elements, the extracapsulum
contains very commonly (but not constantly) some other enclosed structures,
viz.:--

  4. An external or extracapsular skeleton.

  5. Extracapsular vacuoles or alveoli.

  6. Fat-granules or oil-globules.

  7. Pigment-granules or a peculiar large body of dark extracapsular
  pigment, the "phæodium."

  8. "Xanthellæ" or "zooxanthellæ," peculiar yellow cells, which contain
  starch and are unicellular yellow Algæ, living as "Symbiontes" in true
  Symbiosis with a great many Radiolaria.

_The Nucleus_ of the Radiolaria is a large true simple cell-nucleus,
originally a solid spherical, roundish or longish body of nuclein. It is
placed either in the centre of the capsule (in most Peripylea) or
excentrically (in most other Radiolaria). Originally solid, the nucleus is
commonly differentiated later into an outer dense nuclear-membrane and an
inner softer or fluid content; either with one single nucleolus or with a
variable number of nucleoli. Originally always simple, the nucleus becomes
afterwards constantly divided into numerous small nuclei, each of which,
together with a part of the surrounding {3}protoplasm, forms a
vibratile-spore or "flagellate-spore." This division in the Acantharia and
in the social (or colonial) Peripylea begins very early, in all other
Radiolaria much later, immediately before propagation.

_The Endoplasm_ or "endosarc," or "intracapsular protoplasm" or "inner
sarcode," in all Radiolaria originally fills that space within the capsule,
which is not taken up by the nucleus. It seems to be employed mainly for
the purpose of propagation, becoming divided earlier or later into numerous
small particles, each of which surrounds a small particle of the nucleus
and forms together with it a flagellate-spore. Besides this the endoplasm
of the Radiolaria seems to have a great significance for the nutrition,
mainly for the interchange of materials. It becomes very often vacuolate or
alveolate, filled with smaller or larger spherical drops of fluid; it
produces very commonly smaller fat-granules or larger oil-globules, and
further pigment-granules of different colours, more rarely crystals and
other peculiar enclosed parts.

_The Membrane_ or "capsule-membrane" is the most typical and characteristic
part of the body of a Radiolarian, sufficient of itself to separate this
class from all other Rhizopoda. At the same time, by its different shape it
presents the best means for the systematic distinction of the four
subclasses or "legions" of the class. The membrane is composed of a special
organic matter (probably nearly related to chitin) and combines density
with elasticity to a high degree. Observed with a high power of the
microscope its margin (or section) appears commonly simple-edged, but often
in larger forms distinctly double-edged.

The legion PHÆODARIA is distinguished by a double membrane (the thinner
inner and thicker outer membranes being separated by an interval); in the
three other legions it is simple. The membrane completely separates the
intracapsular from the extracapsular body, both communicating only by
certain pores or openings in the membrane. With reference to this important
communication, the whole class can be divided into two subclasses,
Holotrypasta and Merotrypasta: the HOLOTRYPASTA contain the Peripylea and
Actipylea, in which the membrane is pierced by innumerable very small
pores; the MEROTRYPASTA consist of the Monopylea and the Cannopylea, in
which the membrane exhibits only one large main opening, distinguished in
the former by a peculiar "porous area," in the latter by an "osculum" or a
prolonged tubule.

_The Calymma_ or "jelly-veil" is the most characteristic part of the
extracapsular body in all Radiolaria; in the majority of the class it is
the most voluminous part of the whole body, being much more voluminous than
all the other parts taken together. The calymma is a structureless, clear,
and transparent jelly-envelope which always includes the whole central
capsule and often also the whole extracapsular skeleton. Owing to the high
degree of its consistence, this jelly-veil takes a very important part in
the formation of the extracapsular skeleton, furnishing the matrix for the
deposition of its tangential parts.

{4}_The Matrix_ or the "maternal tissue of the pseudopodia" is formed in
all Radiolaria by the thin layer of exoplasm or of extracapsular sarcode,
which immediately envelops the central capsule and is itself enclosed by
the calymma. This continuous sarcode-cover of the capsule communicates by
its pores or openings with the endoplasm or the intracapsular sarcode;
whilst from its outer surface arise the pseudopodia. The morphological
signification of the matrix is very small, but the physiological importance
is very great, for it seems to be the chief organ of many vital functions.

_The Pseudopodia_ or the very fine, long, thread-like filaments of exoplasm
arise in all Radiolaria in very great numbers from the surface of the
matrix, and exhibit in general the same characteristic shape as in the
other Rhizopoda. Their inner or proximal part is enclosed within the
jelly-veil or calymma, whilst their outer or distal part floats freely in
the sea-water. Their special motions and modifications exhibit considerable
variations in different groups, their tendency to ramify, anastomose, and
form networks being in some cases very small, in others very great. Also
the characteristic motion of granules in the pseudopodia is very different.
In general those most important exoplasmatic filaments serve as organs both
for the vegetative functions of nutrition, and for the animal functions of
motion and sensation.

_The class_ Radiolaria can be divided according to its varying structure
into four different legions or subclasses, the characters of which are the
following:--


I. PERIPYLEA OR SPUMELLARIA.

  Membrane of the central capsule simple, perforated by innumerable very
  fine pores. Fundamental form originally homaxon or spherical. Skeleton
  wanting or siliceous. No phæodium in the extracapsular calymma. The
  Peripylea comprise two orders:--

  A.  COLLODARIA (without lattice-shell).
  B.  SPHÆRELLARIA (with lattice-shell).

II.  ACTIPYLEA OR ACANTHARIA.

  Membrane of the central capsule simple, perforated by innumerable fine
  pores. Fundamental form originally homaxon or spherical. Skeleton
  acanthinic (not siliceous). No phæodium in the extracapsular calymma. The
  Actipylea consist of two orders:--

  A.  ACANTHOMETRA (without complete lattice-shell).
  B.  ACANTHOPHRACTA (with complete lattice-shell).


{5}III. MONOPYLEA OR NASSELLARIA.

  Membrane of the central capsule simple, perforated by a porous-area, or
  by one single large opening, divided into numerous very fine pores.
  Fundamental form originally monaxon or egg-shaped. Skeleton siliceous. No
  phæodium in the extracapsular calymma. The Monopylea comprise two
  orders:--

  A.  PLECTELLARIA (without complete lattice-shell).
  B.  CYRTELLARIA (with complete lattice-shell).

IV. CANNOPYLEA OR PHÆODARIA.

  Membrane of the central capsule double, perforated by one simple
  main-opening, prolonged into a tubulus, and besides this commonly by one
  or two (rarely more) small accessory openings. Fundamental form
  originally monaxon or egg-shaped. Skeleton siliceous. Constantly a
  peculiar dark pigment-body or "phæodium" in the extracapsular calymma.
  The Cannopylea comprise two orders:--

  A.  PHÆOCYSTINA (without lattice-shell).
  B.  PHÆOCOSCINA (with lattice-shell).

_Synopsis of the four Subclasses or Legions of Radiolaria._

  -------------------------------+-----------------------------------
         A. HOLOTRYPASTA.        |         B. MEROTRYPASTA.
                                 |
  Central capsule everywhere     |  Central capsule with one large
    perforated by innumerable    |    main-opening (with or without
    small pores.                 |    small accessory openings).
                                 |
  Fundamental form originally    |  Fundamental form originally
    homaxon (spherical or        |     monaxon (egg-shaped or
    derived from a sphere).      |     perhaps dipleural).
  --------------+----------------+-----------------+-----------------
        I.      |      II.       |      III.       |        IV.
                |                |                 |
   SPUMELLARIA. |  ACANTHARIA.   |  NASSELLARIA.   |    PHÆODARIA.
  (_Peripylea._)| (_Actipylea._) | (_Monopylea._)  |  (_Cannopylea._)
                |                |                 |
  Wall-pores of | Wall-pores of  | Main-opening of | Main-opening of
   the capsule  |  the capsule   |  the capsule    |  the capsule
   equally      | symmetrically  | with a porous   | with a short
   disposed.    |  disposed.     |  operculum.     |  tubule.
                |                |                 |
  Skeleton      | Skeleton       | Skeleton        | Skeleton
   siliceous    |  acanthinic    |  siliceous      |  siliceous
   or wanting.  |  (organic).    |  (rarely        |  (rarely
                |                |  wanting).      |  wanting).
                |                |                 |
  Calymma       | Calymma        | Calymma         | Calymma
   without      |  without       |  without        |  constantly
   phæodium.    |  phæodium.     |  phæodium.      |  with a
                |                |                 |  phæodium.
  --------------+----------------+-----------------+-----------------



{6}LEGION I. #SPUMELLARIA#,

VEL PERIPYLEA, VEL PERIPYLARIA (PLS. 1-50).

  _Spumellaria_ (_exclusis_ Spyridinis), Ehrenberg, 1875.
  _Peripylea_ (_inclusis_ Thalassicollis et Sphærozois), Hertwig, 1879.
  _Peripylaria_ (_inclusis_ Collodariis et Polycyttariis), Haeckel, 1881.

_Definition._--Radiolaria with simple membrane of the central capsule,
which is everywhere perforated by innumerable very fine pores.
Extracapsulum without phæodium. Skeleton wanting or siliceous. Fundamental
form originally spherical.

The legion SPUMELLARIA vel PERIPYLEA, in the extent here defined, was
constituted by me in 1883 in my paper on Die Ordnungen der Radiolarien.[2]
I propose to retain for this legion either the name SPUMELLARIA of
Ehrenberg (1875) or PERIPYLEA of Hertwig (1879), although both groups have
not quite the same extension. We exclude from the SPUMELLARIA the Spyridina
(united with them by Ehrenberg) and include the Collodaria. With the
Peripylea of Hertwig we unite his Thalassicollea and Sphærozoea. To avoid
any confusion it would perhaps be better to name this legion "Peripylaria."

The SPUMELLARIA agree with the ACANTHARIA in the structure of the simple
capsule-membrane, which is perforated by numerous small pores (but devoid
of the large main opening, which the NASSELLARIA and PHÆODARIA possess),
whence we unite both the former as Holotrypasta, both the latter as
Merotrypasta.

The difference between the two legions of Holotrypasta is determined by the
skeleton, which in the SPUMELLARIA is either siliceous or wanting, whilst
in the Acantharia it consists of the peculiar organic substance, acanthin.

The legion SPUMELLARIA is by far the largest and most important of the four
legions of Radiolaria, as well with respect to the number of different
forms, as to the enormous masses of individuals, which we encounter living
and fossil. We distinguish in this legion not less than thirty-two
different families, three hundred and sixteen genera, and more than
seventeen hundred species.

The classification of this large group requires for its better
comprehension a careful division into larger and smaller groups. We divide
it therefore first of all into two orders, #Collodaria# and #Sphærellaria#,
as proposed in the paper mentioned above.[3]

The #Collodaria# have no perfect latticed skeleton, and comprise two
suborders or sections: in the #Colloidea# the skeleton is entirely wanting,
in the #Beloidea# it is represented by a variable number of siliceous
needles or spicules, scattered in the calymma around the central capsule.

{7}The #Sphærellaria# differ from the #Collodaria# in the possession of a
perfect siliceous skeleton, which is originally a latticed spherical shell,
enveloping the central capsule. By modification of this fenestrated sphere
arises an enormous mass of different forms, which we dispose in
twenty-eight families, and these in four larger groups, suborders or
sections,--#Sphæroidea#, #Prunoidea#, #Discoidea#, and #Larcoidea#.

The #Sphæroidea#, the common ancestral group of the #Sphærellaria#, possess
a skeleton which is either a simple fenestrated sphere, or composed of two
or more concentric latticed spheres, which are united by radial beams; more
rarely it becomes more or less spongy.

The #Prunoidea# are derived from the #Sphæroidea# by prolongation of the
latticed sphere in one axis; the skeleton therefore becomes here
ellipsoidal or cylindrical (often with annular transversal constrictions).

The #Discoidea# on the contrary must be derived from the #Sphæroidea# by
shortening in one axis; here therefore the fenestrated shell becomes more
or less lenticular or iscoidal (often with radial spines or arms in the
equatorial plane, on the circular margin).

The #Larcoidea#, the fourth section, differ from the three foregoing
sections by the different growth of the shell in three different dimensions
of space; therefore here the fenestrated shell becomes "lentelliptical," or
a "triaxial ellipsoid," its length, breadth, and height being different.



_The Skeleton_ consists in all SPUMELLARIA either of pure _silica_ or of a
peculiar silicate. The siliceous bars and beams constituting it are
invariably _solid_, as also in the NASSELLARIA, never hollow, as in the
PHÆODARIA. Never is the skeleton composed of acanthin, as in all
ACANTHARIA. Whilst in the first order of SPUMELLARIA, #Collodaria#, the
form of the spicula, or the scattered needles, composing the skeleton, is
very simple, _never latticed_, in the second order, the #Sphærellaria#, it
is constantly latticed or fenestrated, often also spongy.

The geometrical fundamental form of the lattice-shell in the #Sphærellaria#
is originally spherical (homaxon), as preserved in all #Sphæroidea#; in the
#Prunoidea# and #Discoidea# it becomes monaxon, with one single axis
(prolonged in the former, shortened in the latter); in the #Larcoidea# it
becomes triaxon, by different growth in three principal axes, perpendicular
one to another. The further development of radial parts of the skeleton in
these three axes is very important for the "promorphology" of the
Radiolaria.

_The Malacoma_, or the whole soft body of the SPUMELLARIA as opposed to the
skeleton, exhibits some differences of structure in two different groups,
which were separated formerly (1862) as Monocyttaria and Polycyttaria,
corresponding to the "Radiolaria monozoa and polyzoa" of Johannes Müller
(1858).

The #Monocyttaria# (or the Spumellaria solitaria) live isolated as single
cells--like {8}all other Radiolaria--and are never aggregated in colonies;
the calymma includes one single central capsule, and this again one central
nucleus, which does not become divided until full maturity.

The #Polycyttaria# on the contrary (or the Spumellaria socialia) live
aggregated in large colonies; the calymma includes a variable number of
associated central capsules and each of these commonly one central
oil-globule, whilst the original simple nucleus commonly becomes very early
divided into numerous small nuclei.

_The Nucleus_ of the SPUMELLARIA is originally constantly _central_, placed
quite in the centre of the concentric capsule, and it retains this central
position in all Monocyttaria or solitary Peripylea; whereas in the
Polycyttaria--in consequence of its early division--its place is commonly
taken by a central oil-globule. Whilst the numerous nuclei of the latter
are very small, the single nucleus of the former is comparatively large,
extremely large (more than a millimeter in diameter) in some gigantic
#Collodaria#.

_The Endoplasm_ or the intracapsular sarcode exhibits in the greater number
of SPUMELLARIA a more or less distinct radial striation. It encloses a
great variety of different parts; vacuoles, oil-globules, pigment-granules,
crystals, &c.

_The Membrane_ of the capsule in all SPUMELLARIA is simple (never double as
in the _Phæodaria_) and everywhere equally perforated by innumerable small
pores; in the thick, double-edged membrane of many large #Collodaria# these
pores appear (in the optical section of the capsule-wall) as distinct fine
radial canals, very densely and regularly disposed.

_The Central Capsule_ in the SPUMELLARIA is originally a _geometrical
sphere_, and this simple globular form is preserved in all #Sphæroidea#,
and in the greatest part of #Colloidea# and #Beloidea#. By prolongation of
one axis the form becomes _ellipsoidal_ (or even cylindrical) in the
#Prunoidea#, and in some few forms of #Colloidea#. By shortening of one
axis it becomes _lenticular_ (or even discoidal) in the _Discoidea_, and in
some few forms of #Colloidea#. By unequal growth in three different axes,
perpendicular one to another, the capsule becomes _lentelliptical_ in all
#Larcoidea#. Very rarely the capsule assumes in the SPUMELLARIA a
polyhedral or irregular (sometimes even amoeboid) form, only in a few
#Colloidea#.

_The Calymma_, or the jelly-veil including the central capsule, is very
voluminous in many SPUMELLARIA of gigantic size, mainly in the large
#Colloidea#, and in all Polycyttaria or social Radiolaria. It includes here
a considerable number of large vacuoles or "alveoli." The calymma never
exhibits in this legion the dark voluminous phæodium, possessed by all
PHÆODARIA.

_Xanthellæ_ or "zooxanthellæ" are numerous in the calymma of most
SPUMELLARIA, but by no means constant; they are very variable in number and
size.

_The Matrix_, placed between the calymma and central capsule, is, in the
majority of the SPUMELLARIA, a rather thick layer of granular exoplasm.

_The Pseudopodia_ arising from it are very numerous, equally disposed over
the whole {9}surface, and are in general rather fluid, exhibiting a
considerable tendency to ramify, anastomose, and form networks. The
movement of granules is commonly lively. In the Polycyttaria all capsules
of one colony or "coenobium" are connected by the dense variable network of
anastomosing pseudopodia.

_Synopsis of the Orders and Suborders of_ SPUMELLARIA.

  I. COLLODARIA.       { Skeleton entirely wanting,       1. #Colloidea.#
  Skeleton wanting or  {
   quite imperfect,    { Skeleton represented by
   not latticed.       {  numerous scattered spicules,    2. #Beloidea.#

  II. SPHÆRELLARIA.    { Lattice-shell spherical or
                       {  composed of concentric spheres, 3. #Sphæroidea.#
  Skeleton a perfect   {
   shell of lattice    { Lattice-shell ellipsoidal or
   work, or spongy and {  prolonged in one axis,          4. #Prunoidea.#
   resembling          {
   wicker-work.        { Lattice-shell discoidal or
                       {  shortened in one axis,          5. #Discoidea.#
                       {
                       { Lattice-shell lentelliptical,
                       {  with different extent of growth
                       {  in three axes,                  6. #Larcoidea.#


----


Order I. COLLODARIA, Haeckel, 1881.

  _Collodaria_, Haeckel, Prodromus, 1881, p. 469.
  _Collida_ et _Sphærozoida_, Haeckel, 1862, Monogr. d. Radiol., pp. 246,
      522.

_Definition._--SPUMELLARIA without latticed shell.

The order #Collodaria#, the first order of Radiolaria, comprises all those
SPUMELLARIA in which the skeleton is either entirely wanting, or
represented by numerous single, solid, siliceous needles or spicules,
loosely scattered in the calymma around the central capsule. Never in this
order is there any trace of the latticed or fenestrated shell, which
characterises the second order, #Sphærellaria#. The skeleton exhibits no
trace of phylogenetic connection in the two orders.

In my monograph (1862) two families appertaining to this order are
described, the Collida (p. 244) and the Sphærozoida (p. 521). Both families
contain forms with and without a skeleton. Of the solitary or monozous
Collida the Thalassicollida are devoid of a skeleton, whilst the
Thalassosphærida are provided with a skeleton. Of the social or polyzous
Sphærozoida the Collozoida are without a skeleton, the Rhaphidozoida
provided with one. As the special form in both skeletophorous subfamilies
is exactly the same, I prefer now to associate them in the suborder
#Beloidea#, and to oppose them to the other two skeletonless subfamilies,
which are united under the name of #Colloidea#.

{10}_Synopsis of the four Families of Collodaria._

  Suborder I.         { Solitary cells, living
   COLLOIDEA.         {  as isolated individuals
                      { (_Colloidea monozoa_),       1. THALASSICOLLIDA.
  Skeleton entirely   {
    wanting.          { Associated cells, living
                      {  in colonies or coenobia
                      { (_Colloidea polyzoa_),       2. COLLOZOIDA.

  Suborder II.        { Solitary cells, living as
   BELOIDEA.          {  isolated individuals
                      {  (_Beloidea monozoa_),       3. THALASSOSPHÆRIDA.
  Skeleton composed   {
   of numerous        { Associated cells, living in
   needles or         {  colonies or coenobia
   spicula, scattered { (_Beloidea polyzoa_),        4. SPHÆROZOIDA.
   in the calymma.    {


----


Suborder I. COLLOIDEA, Haeckel.

_Definition._--SPUMELLARIA without skeleton.

The suborder #Colloidea# comprises all those SPUMELLARIA in which no
skeleton is developed. The whole body is therefore soft--a true
malacoma--and is composed only of two essential parts, the central capsule
and the enveloping extracapsulum. The suborder contains only two different
families, the solitary #Thalassicollida# (or Colloidea monozoa) and the
associated #Collozoida# (or Colloidea polyzoa). Both families are very
nearly allied, and differ only in one single essential character: the
solitary life of the former, the social union of the latter. It seems to be
merely in consequence of this difference that the cleavage of the nucleus
commonly takes place very late in the former, very early in the latter.

Therefore the full-grown Thalassicollida (till immediately before
propagation) commonly exhibit one single nucleus in the centre of the
capsule, whilst in the Collozoida the capsule is distended by numerous
small nuclei. In these latter the centre of the capsule usually contains
one large oil-globule, whilst in the former oil-globules are either
wanting, or scattered in large numbers in the endoplasm, or disposed in one
layer on the inside of the capsule membrane.

In the solitary Thalassicollida each capsule is enclosed in its own
peculiar spherical calymma, whilst in the associated Collozoida all
capsules of the colony are united in one common, very voluminous calymma.



Family I. #THALASSICOLLIDA#, Haeckel, 1862.

  _Thalassicollida_, Haeckel, 1862, Monogr. d. Radiol., p. 246.
  _Thalassicollida_, Haeckel, 1881, Prodromus, p. 469.

_Definition._--#Colloidea# solitaria.

The family Thalassicollida comprises all solitary SPUMELLARIA without a
skeleton. The oldest and best known form of this family is the genus
_Thalassicolla_, as restricted by {11}Johannes Müller.[4] The most common
representative of it, the cosmopolitan _Thalassicolla nucleata_, was first
described by Huxley in 1851. But as early as 1834 another large
Radiolarian, appertaining either to this or to a nearly allied family, had
been described by Meyen as _Physematium atlanticum_. A third genus was
detected by me in 1859 at Messina and figured under the name _Thalassolampe
margarodes_.[5] A very accurate histological description of these forms was
given in 1876 by Richard Hertwig.[6] The same author figured in his
Organismus in 1879 a very interesting simpler form under the name
_Thalassolampe primordialis_ (Taf. iii. fig. 5). Some similar forms had
already been observed by me, and are here united with it to form the first
genus _Actissa_.[7]

_Actissa_ is of the highest general interest as the most simple and typical
form of all Radiolaria, and as the common ancestral form, from which all
other forms of this large class may be derived. Its unicellular body
exhibits neither the extracapsular alveoli of _Thalassicolla_, nor the
intracapsular alveoli of _Thalassolampe_, and shows all essential
characters of the Radiolarian type in its most simple form (Pl. 1, figs. 1
to 1_c_). The simple cell-body is composed of a spherical central capsule
and a concentric, spherical, enveloping calymma, both separated by a thin
membrane which is perforated by innumerable pores. The capsule includes the
endoplasm and in the centre a simple spherical nucleus with nucleolus; at
the time of propagation this latter becomes cleft into numerous small
nuclei, each of which, together with a small piece of the surrounding
endoplasm, forms a flagellated zoospore (fig. 1_c_). The extracapsulum is
formed by the large, structureless, spherical calymma or concentric
jelly-veil enveloping the capsule, and by the thin granular matrix or the
layer of exoplasm which separates the calymma from the membrane. From this
matrix or maternal tissue arise innumerable very long and thin pseudopodia,
as simple radiating filaments, the proximal part of which is included in
the calymma, whilst the distal part floats freely in the sea-water (Pl. 1,
fig. 1).

The other Thalassicollida differ from their common ancestral form,
_Actissa_, mainly by the higher histological differentiation of the
unicellular body. Whilst in _Thalassicolla_ and _Thalassolampe_ the nucleus
remains a single sphere as in _Actissa_, it becomes branched or covered
with radial blind saccules in _Thalassopila_ and _Thalassophysa_; also the
intracapsular protoplasm develops here a great variety of peculiar
different corpuscles, as oil-globules, pigment-granules, concentric
concretions, crystals, &c. But the most striking peculiarity by which the
other Thalassicollida differ from _Actissa_ is the development of large
vesicular alveoli, either within or without the capsule; the unicellular
body reaches by this inflation the extraordinary size of 5 to 10 mm. or
more.

{12}_Synopsis of the Genera of Thalassicollida._

  A. Alveoli neither     { Nucleus spherical
   within nor without    {  (sometimes ellipsoidal),
   the central capsule.  {  not branched,             1. _Actissa_.

  B. Numerous large      { Nucleus spherical,         2. _Thalassolampe_.
   alveoli within the    {
   central capsule (not  { Nucleus branched or
   in the calymma).      {  covered with radial
                         {  sacs,                     3. _Thalassopila_.

  C. Numerous large      { Nucleus spherical,         4. _Thalassicolla_.
   alveoli without the   {
   central capsule,      { Nucleus branched, or
   within the jelly-veil { covered with radial
   or calymma.           { sacs,                      5. _Thalassophysa_.



Genus 1. _Actissa_,[8] n. gen.

_Definition._--#Thalassicollida# with simple spherical nucleus, without any
alveoli (either within or outside the central capsule).

The genus _Actissa_ is the most simple and typical form of all Radiolaria,
and may be regarded as the common ancestral form of the whole class. The
spherical body is composed of a simple spherical capsule and a concentric
spherical calymma or jelly-envelope. Neither the former nor the latter
contains alveoli. The central capsule possesses a strong membrane
perforated by small pores, and contains in the intracapsular sarcode
numerous small pellucid vacuoles, and in its middle a simple, concentric,
spherical nucleus (often with some nucleoli); sometimes also one or more
oil-globules. The extracapsularium forms a soft, voluminous, structureless
calymma or enveloping jelly-sphere, perforated by the numberless, fine
pseudopodia, which radiate outwards from the matrix or the thin granulated
sarcode-layer, surrounding the capsule. Often (but not constantly)
xanthellæ or yellow cells are scattered in it. _Actissa_ differs from the
following skeletonless genera in the absence of all alveoli; it has neither
intracapsular alveoli (like _Thalassolampe_) nor extracapsular alveoli
(like _Thalassicolla_). The first observed species of this genus is that
which I found in 1866 at the Canary Islands, _Actissa prototypus_; the
second is that which Hertwig accurately described in 1879, from the
Mediterranean (Messina), _Actissa primordialis_; the third I observed in
1881 at Ceylon, frequent and sporiparous, _Actissa princeps_. A fourth
species (_Actissa radiata_) exhibited a distinct radial segmentation of the
capsule-contents. These four species are quite spherical. Six other
species, occurring in different preparations from the Challenger, are
distinguished by modifications of the spherical capsule-form and may
represent three different subgenera (or, perhaps better,
genera?)--_Actiprunum_ ellipsoidal, _Actidiscus_ lenticular, _Actilarcus_
lentelliptical; perhaps these are the ancestral forms of the three
sections: #Prunoidea#, #Discoidea#, #Larcoidea#.



{13}Subgenus 1. _Procyttarium_, Haeckel, 1879.

  _Procyttarium_, Haeckel, Natürl. Schöpfungsgeschichte, ed. vii. p. 705.

_Definition._--Central capsule spherical.


1. _Actissa princeps_, n. sp. (Pl. 1, fig. 1).

Central capsule spherical, colourless or a little reddish, transparent,
with a thick double-edged membrane. Nucleus central, spherical, one-third
as broad as the central capsule, containing a single, central, glossy
nucleolus. Protoplasm finely granulated, without oil-globules, with
numerous clear spherical vacuoles of equal size and at equal distances; the
superficial layer of protoplasm (immediately below the membrane) radially
striated (fig. 1). In some older specimens the nucleus was divided into
numerous small nuclei (fig. 1_a_), which by further division gave the
nuclei of the flagellated spores (fig. 1_b_); each spore with a very thin
lateral flagellum (fig. 1_c_). Jelly-like calymma twice as broad as the
enclosed capsule, without xanthellæ or yellow cells, pierced by
innumerable, very thin and long, undivided pseudopodia, which arise from
the sarcode-matrix on the outside of the membrane (six to eight times
longer than shown in fig. 1).

_Dimensions._--Diameter of the central capsule 0.1 to 0.12, of the nucleus
0.03 to 0.04, of the jelly calymma 0.2 to 0.3.

_Habitat._--Indian Ocean, Ceylon, Belligemma, Haeckel, 1881; also in a
preparation from Station 271, Central Pacific, surface.


2. _Actissa primordialis_, Haeckel.

  _Thalassolampe primordialis_, R. Hertwig, 1879, Organismus der
  Radiolarien, p. 32, Taf. iii. fig. 5.

  _Procyttarium primordiale_, Haeckel, 1879, Natürl. Schöpf., ed. vii. p.
  705, Taf. xvi. fig. 1.

Central capsule spherical, dim-yellowish, with a thin, simple-edged but
compact membrane. Nucleus large, central (about half as broad), with one or
two dark nucleoli; on its side an excentric oil-globule, nearly of the same
size. Protoplasm between nucleus and membrane, in the younger specimens
finely granulated and radially striped; in the older specimens with
numerous hyaline globules (vacuoles). Jelly-envelope or calymma very
voluminous, ten to twelve times as broad as the central capsule,
structureless, containing numerous yellow bodies (xanthellæ?), pierced by
very numerous simple pseudopodia.

_Dimensions._--Diameter of the central capsule 0.11 to 0.18, of the nucleus
0.04 to 0.09, of the jelly-like calymma 1.2 to 1.5.

_Habitat._--Mediterranean, Messina, Hertwig, 1878, surface.


3. _Actissa prototypus_, n. sp.

Central capsule spherical, red-coloured, with a thick, double-edged
membrane. Nucleus central, spherical, half as large as the radius of the
capsule, containing a large number (forty to sixty) of small {14}dark
nucleoli. Protoplasm filled up with numerous small clear vacuoles, and
between them fine red pigment granules; on the inside of the membrane one
layer of dark oil-globules. Jelly-like calymma four times as broad as the
enclosed capsule, with very numerous small xanthellæ.

_Dimensions._--Diameter of the capsule 0.2, of the nucleus 0.05, of the
calymma 0.8.

_Habitat._--Atlantic, Canary Islands (Lanzerote, Haeckel), 1866; also at
Station 348, surface.


4. _Actissa radiata_, n. sp.

Central capsule spherical, dark, with a thick, double-edged membrane.
Nucleus central, spherical, half as large as the capsule, transparent.
Protoplasm divided into numerous cuneiform radial pieces which are
separated by clear intervals, and filled with very fine dark granules
(darker in the distal half). The equatorial optical section exhibits around
the circular clear nucleus a coronal of twenty-five such wedge-shaped
pieces (mother-cells of spores?) No oil-globules in the central capsule.
Jelly-like calymma one and a half times as broad as the enclosed capsule,
with numerous small xanthellæ.

_Dimensions._--Diameter of the capsule 0.15, of the nucleus 0.07, of the
calymma 0.24.

_Habitat._--North Pacific, Station 241, surface.



Subgenus 2. _Actiprunum_, Haeckel, 1882.

_Definition._--Central capsule ellipsoidal, with one prolonged axis.


5. _Actissa prunoides_, n. sp.

  _Actiprunum prunoideum_, Haeckel, 1882, Manuscript.

Central capsule ellipsoidal, colourless, with a thin, simple-edged
membrane. Proportion of its major axis to the minor 4 : 3. Nucleus
spherical, its diameter equal to one-third of the minor axis, in its centre
a large, dark, spherical nucleolus. Protoplasm clear, containing numerous
small vacuoles, separated by regular distances, and on the inside of the
capsule-membrane, numerous (forty to fifty) small oil-globules. Calymma (or
jelly-veil) ellipsoidal, with a thin sarcode-stratum on the outside of the
capsule; its diameter twice as large as that of the central capsule.

_Dimensions._--Major axis of the capsule 0.16, minor 0.12; diameter of the
nucleus 0.04; major axis of the calymma 0.32, minor 0.24.

_Habitat._--Central Pacific, Station 274, surface.


6. _Actissa ellipsoides_, n. sp.

  _Actiprunum ellipsoides_, Haeckel, 1882, Manuscript.

Central capsule ellipsoidal, red-coloured, with a thick, double-edged
membrane. Proportion of its major axis to the minor 5 : 3. Nucleus
ellipsoidal, one-third as large as the capsule, containing eight small dark
nucleoli.  Protoplasm dusky, filled with dark pink pigment-granules; in the
{15}major axis, on both poles of the nucleus-axis, two large oil-globules,
half as large as the nucleus. Calymma ellipsoidal, with numerous xanthellæ;
its diameter four times as large as that of the capsule.

_Dimensions._--Major axis of the capsule 0.2, minor 0.12; major axis of the
nucleus 0.07, minor 0.04; major axis of the calymma 0.8, minor 0.5.

_Habitat._--Mediterranean, Corfu, 1877, Haeckel, surface.



Subgenus 3. _Actidiscus_, Haeckel, 1882.

_Definition._--Central capsule lenticular, with one shortened axis.


7. _Actissa discoides_, n. sp.

  _Actidiscus discoides_, Haeckel, 1882, Manuscript.

Central capsule lenticular, red-coloured, about twice as broad as high,
with a thick, double-edged membrane. Nucleus spherical, one-third as broad
as the capsule, with one single, large central nucleolus. Protoplasm dusky,
filled with scarlet pigment; granules and small oil-globules between them.
Calymma lenticular, three times as broad as the capsule.

_Dimensions._--Major axis of the capsule 0.16, minor 0.08; diameter of the
nucleus 0.05; breadth of the calymma 0.5.

_Habitat._--North Pacific, Station 236, surface.


8. _Actissa lenticularis_, n. sp.

Central capsule lenticular, flattened, about three times as broad as high,
with a thin, simple-edged membrane. Nucleus lenticular, one-third as large
as the capsule, with ten small dark nucleoli. Protoplasm transparent,
colourless, filled with small vacuoles at regular distances; on the inside
of the membrane in the circular periphery of the lens twenty dark
oil-globules. Calymma lenticular, twice as broad as the capsule.

_Dimensions._--Major axis of the capsule 0.15, minor 0.05; breadth of the
nucleus 0.05, height 0.02; breadth of the calymma 0.03.

_Habitat._--East Pacific, Station 272, surface.


9. _Actissa phacoides_, n. sp.

  _Actidiscus phacoides_, Haeckel, 1882, Manuscript.

Central capsule lenticular, strongly flattened, about four times as broad
as high, with a thin, simple-edged membrane. Nucleus lenticular, one-fourth
as broad as the capsule, with numerous (twenty or more) small nucleoli.
Protoplasm filled with dark pigment-granules; on the inside of the membrane
in the circular periphery of the lens thirty-two dark oil-globules. Calymma
lenticular, three times as broad as the capsule.

{16}_Dimensions._--Major axis of the capsule 0.2, minor 0.05; breadth of
the nucleus 0.05, height 0.015; breadth of the calymma 0.6.

_Habitat._--Tropical Atlantic, Station 347, surface.



Subgenus 4. _Actilarcus_, Haeckel.

_Definition._--Central capsule lentelliptical, with three different axes.


10. _Actissa larcoides_, n. sp.

Central capsule lentelliptical; with three different axes, bearing the
proportion 4 : 3 : 2. Nucleus spherical; its diameter equal to the shortest
radius of the capsule. No nucleoli visible. Protoplasm transparent, with
small vacuoles; on the inside of the thin capsule-membrane numerous (fifty
to sixty) small oil-globules, regularly disposed. Calymma lentelliptical,
twice as large as the central capsule.

_Dimensions._--Major axis or length of the capsule 0.2, middle axis or
breadth 0.15, minor axis or height 0.1; diameter of the nucleus 0.05, of
the calymma 0.3-0.4.

_Habitat._--Central Pacific, Station 266, surface.



Genus 2. _Thalassolampe_,[9] Haeckel, 1862, Monogr. d. Radiol., p. 253.

_Definition._--#Thalassicollida# without extracapsular alveoles, but with
large roundish or globular alveoles within the central capsule, with a
simple spherical, not branched nucleus in the centre.

The genus _Thalassolampe_ is, next to _Actissa_, the most simple of all
Radiolaria, but differs from it by the large intracapsular alveoles. By
these the central capsule is inflated to an extraordinary size, which in
_Thalassolampe maxima_ exceeds that of most other Radiolaria. From the
nearly allied _Thalassopila_ it differs by the simple spherical nucleus,
from _Physematium_ by the absence of spicula. Of the two species of the
genus the first observed _Thalassolampe margarodes_, 1862, is
Mediterranean, the second, _Thalassolampe maxima_, 1882, is Indian.


1. _Thalassolampe margarodes_, Haeckel.

  _Thalassolampe margarodes_, Haeckel, 1862, Monogr. d. Radiol., p. 253,
  Taf. ii. figs. 4, 5.

  _Thalassolampe margarodes_, R. Hertwig, 1876, Histologie d. Radiol., p.
  68, Taf. iii. figs. 1-5.

Spherical body very soft and limpid, somewhat pearl-like opalescent,
yellowish or bluish. Central capsule with a very thin structureless
membrane, its diameter six to eight times as large as that of the central
spherical nucleus. Wall of the vesicular nucleus thick, perforated by fine
{17}pore-canals; on its inside often numerous oval nucleoli. In the movable
protoplasmic network between the large alveoles a considerable number of
large yellowish or orange oil-globules. Extracapsular jelly-envelope very
thin, contains small yellow bodies (zooxanthellæ). (Compare the accurate
description of this Mediterranean species in my monograph and in Hertwig's
work.) In the Canary Islands I found very often a large variety of it, of
double and triple the size, distinguished by the delicate orange colour of
the intracapsular oil-globules. This may be distinguished as _Thalassolampe
aurantiaca_.

_Dimensions._--Diameter of the whole jelly-sphere 2 to 4 mm., of the
central capsule 2 to 3 mm., of its nucleus 0.2 to 0.4 mm.

_Habitat._--Mediterranean, Messina, Haeckel, Hertwig; Canary Islands,
Lanzerote, Haeckel; surface.


2. _Thalassolampe maxima_, n. sp. (Pl. 1, fig. 2).

Spherical body quite pellucid, like a glass globule, colourless. Central
capsule with a moderately thick, but quite transparent, structureless
membrane, its diameter ten to twelve times as large as that of the central
spherical nucleus. Wall of the vesicular nucleus thick, perforated by fine
pore-canals; on its inside numerous small spherical nucleoli. No large
oil-globules in the movable protoplasmic network between the large
alveoles. Extracapsular jelly-envelope very thin, containing no yellow
bodies. This differs from the preceding nearly allied species in the want
of the intracapsular oil-globules and of the extracapsular yellow bodies.
It possesses the largest central capsule of all known Radiolaria. I found
them living and floating in water taken from the surface of the Indian
Ocean by a bucket.

_Dimensions._--Diameter of the whole jelly-body 12 to 15 mm., of the
central capsule 10 to 12 mm., of the nucleus 0.8 to 1.2 mm.

_Habitat._--Indian Ocean, near the Maldive Islands, Haeckel, 1882, surface.



Genus 3. _Thalassopila_,[10] Haeckel, 1881, Prodromus, p. 469.

_Definition._--Thalassicollida without extracapsular alveoles, but with
large roundish or globular alveoles within the central capsule, with a
papillate or branched nucleus in its centre.

The genus _Thalassopila_ has, like _Thalassolampe_, a voluminous foamy
central capsule, inflated by numerous large alveoles; but it differs in the
complicated form of the nucleus, which is like that of _Thalassophysa_, and
is either branched or occupied by conical or roundish papillæ.


1. _Thalassopila cladococcus_, n. sp. (Pl. 1, fig. 3).

Spherical body dark-spotted, with a thin yellowish jelly-envelope. Central
capsule with a thick and firm membrane, perforated by pores; its diameter
three times that of the central nucleus, {18}three-fourths that of the
whole jelly-sphere. Nucleus profusely branched or papillated, its spherical
surface covered with numerous (more than a hundred) finger-shaped obtuse
blind sacs, about as long as its radius. Protoplasm of the central capsule
forming a loose network between the large roundish alveoles, in the
cortical zone radially striped and containing one layer of large dark
oil-globules. These are regularly distributed on the inside of the
capsule-membrane and separated by intervals, twice as broad as its
diameter, giving to the capsule-surface a spotted appearance. Extracapsular
jelly-envelope thin, yellowish, with very numerous and small xanthellæ.

_Dimensions._--Diameter of the whole jelly-sphere 5 mm., of the central
capsule 4 mm., of the nucleus 1.3 mm.

_Habitat._--Antarctic Ocean, Station 154 (south of Kerguelen), surface.



Genus 4. _Thalassicolla_,[11] Huxley, 1851, Ann. and Mag. Nat. Hist., ser.
2, vol. viii. p. 433.

_Definition._--Thalassicollida without intracapsular alveoles, but with
large roundish or globular alveoles within the extracapsular calymma.
Nucleus in the centre of the capsule simple spherical, not branched.

The genus _Thalassicolla_ was proposed by Huxley in 1851, for a certain
number of different voluminous jelly-like Radiolaria, which he had observed
living during his voyage in the "Rattlesnake" through the tropical seas,
and of which he gives an excellent description--the first accurate
observations on living Radiolaria. Johannes Müller afterwards removed from
this genus the social genera _Sphærozoum_ and _Collosphæra_ (formerly
_Thalassicolla punctata_), and retained as type of the genus _Thalassicolla
nucleata_. In 1862 in my Monograph I added two other species,
_Thalassicolla pelagica_ and _Thalassicolla zanclea_, and later (1870)
_Thalassicolla sanguinolenta_. Now I think it better to separate the last
two species as a new genus, _Thalassophysa_, characterised by the papillate
or branched nucleus, and to retain in _Thalassicolla_ only those forms with
simple spherical nucleus. For both genera the extracapsular, voluminous,
spherical calymma or jelly-envelope, with numerous large alveoles, is
characteristic. The membrane of the central capsule in _Thalassicolla_ is
now structureless (subgenus _Thalassicollarium_, with three species), now
characterised by a peculiar structure, prominent ridges on the inside of
the membrane, which form a network with polygonal plates, resembling an
epithelium (Pl. 1, fig. 5_b_; subgenus _Thalassicollidium_, with four
species). Of the seven species here described, two are cosmopolitan, widely
distributed, and common; one is Mediterranean, one Atlantic, and three
Pacific.



Subgenus 1. _Thalassicollarium_, Haeckel.

_Definition._--Membrane of the central capsule structureless, only
perforated by innumerable very small radial pores.


{19}1. _Thalassicolla pellucida_, n. sp.

Spherical body very soft, transparent, clear and colourless, without any
pigment. Central capsule soft, hyaline, with a thin, structureless, not
areolated membrane. Diameter of the central capsule about three times that
of the nucleus, one-fourth to one-sixth that of the jelly-envelope. Nucleus
delicate, transparent, with one single central nucleolus, about one-third
its diameter. Protoplasm of the central capsule contains only small,
pellucid, densely packed globules (vacuoles?), no oil-globules.
Extracapsular body quite transparent, without pigment or oil-globules, only
composed of the large alveoles imbedded in the jelly-cover, and of the fine
protoplasmic network between them. No xanthellæ.

_Dimensions._--Diameter of the central capsule 0.8 to 1.2, of the nucleus
0.3 to 0.4, of the calymma 3 to 6 mm.

_Habitat._--Cosmopolitan, Canary Islands, Haeckel; Cape, Australia,
Pacific, Challenger; surface.


2. _Thalassicolla spumida_, n. sp.

Spherical body nearly transparent, yellowish, without dark pigment. Central
capsule pellucid, with a thick, structureless, not areolated membrane.
Diameter of the central capsule about twice that of the nucleus, one-sixth
to one-eighth that of the jelly-cover. Nucleus delicate, somewhat opaque,
with numerous small nucleoli. Protoplasm of the central capsule contains
small pellucid globules (vacuoles?), and immediately under its membrane (on
its inside) one single layer of large, dark, refractive oil-globules.
Extracapsular body very voluminous, foamy, with innumerable alveoles in the
jelly, and many xanthellæ between them.

_Dimensions._--Diameter of the central capsule 0.6 to 0.8, of the nucleus
0.3 to 0.4, of the calymma 3 to 5 mm.

_Habitat._--Atlantic, Canary Islands, Haeckel; Cape Verde Islands,
Challenger Station 350; Brazil, Rabbe; surface.


3. _Thalassicolla zanclea_, Haeckel.

  _Thalassicolla zanclea_, Haeckel, 1862, Monogr. d. Radiol., p. 252, Taf.
  ii. fig. 3.

Spherical body opaque, transparent only in the periphery, with colourless
central capsule, but with brown or black pigment-powder scattered
everywhere through the extracapsular alveolated jelly-cover. Central
capsule soft, transparent, colourless, with a thin structureless, not
areolated membrane. Diameter of the central capsule about one and a half
times that of the nucleus, one-half or one-third that of the jelly-cover.
Nucleus delicate, transparent, with a thin, finely punctated membrane, with
one or more nucleoli. Protoplasm of the central capsule contains only
small, pellucid, densely packed globules (vacuoles?), no oil-globules.
Extracapsular body very dark and opaque, with a great mass of brown or
blackish-brown pigment between the alveoles of the jelly-cover. Numerous
xanthellæ.

_Dimensions._--Diameter of the central capsule 0.1 to 0.12, of the nucleus
0.07 to 0.08, of the calymma 0.2 to 0.4.

_Habitat._--Mediterranean, Messina, Haeckel.



{20}Subgenus 2. _Thalassicollidium_, Haeckel.

_Definition._--Membrane of the central capsule areolated, with small
polygonal plates, resembling an epithelial cell-tissue, spotted by
innumerable fine radial pores.


4. _Thalassicolla australis_, n. sp.

Spherical body nearly transparent, without dark pigment. Central capsule
colourless, somewhat opaque, with a thick and firm, very elastic membrane,
areolated by polygonal, punctated figures resembling cells. Diameter of the
central capsule about three times that of the nucleus, one-third that of
the jelly-cover. Nucleus thin-walled, with many small nucleoli. Protoplasm
of the central capsule finely granulated, containing numerous hyaline
globules (vacuoles?) of different size, and in each of these one single
roundish, dark refringing corpuscle, concentrically lamellated like an
amylum grain. Extracapsular body without pigment or oil-globules, only
composed of the large alveoles imbedded in the jelly-cover, and of the fine
protoplasmic network between them. No xanthellæ.

_Dimensions._--Diameter of the central capsule 1 to 2, of its nucleus 0.3
to 0.4, of the nucleoli 0.12 to 0.16, of the hyaline globules in the
protoplasm of the capsule 0.02 to 0.05; calymma, 4 to 6 mm.

_Habitat._--South-west Pacific, east coast of Australia, New Zealand, &c.;
Challenger Stations 163, 171; surface.


5. _Thalassicolla nucleata_, Huxley.

  _Thalassicolla nucleata_, Huxley, 1851, Ann. and Mag. Nat. Hist., ser. 2,
  vol. viii. p. 435, pl. xvi. fig. 4.

  _Thalassicolla nucleata_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 28.

  _Thalassicolla coerulea_, Schneider, 1858, Archiv f. Anat. u. Physiol.,
  p. 40, Taf. iii. Bd. i. figs. 5-7.

  _Thalassicolla nucleata_, Haeckel, 1862, Monogr. d. Radiol., p. 249, Taf.
  iii. figs. 1-5.

  _Thalassicolla nucleata_, R. Hertwig, 1876, Histologie d. Radiol., p. 43,
  Taf. iii. figs. 61-5, Taf. iv., v.

  _Thalassicolla nucleata_, R. Hertwig, 1879, Organismus d. Radiol., p. 34.

Spherical body in the central part opaque, black or dark coloured, in the
periphery transparent, whitish, or yellowish. Central capsule rather
compact, yellowish, opaque, with a thick and firm, very elastic membrane,
areolated by polygonal, punctated figures resembling cells. Diameter of the
central capsule about twice as large as that of the nucleus, one-half to
one-fourth that of the jelly-cover. Nucleus with a very thick, finely
punctated membrane, containing a viscous fluid (when coagulated finely
granular), and sometimes one large, central, spherical, or ramified
nucleolus, sometimes a variable number of smaller roundish nucleoli.
Protoplasm of the central capsule containing many very variable corpuscles,
mostly pellucid (albuminous?) spherules, containing oil-globules, or
concentric amyloid concretions, or crystals, &c. Extracapsular body with
dark pigment-powder of variable colour (black, brown, violet, blue, &c.),
densely aggregated around the central capsule, more loosely dissipated
between the alveoles of the outer jelly-cover. Xanthellæ very numerous.

{21}_Dimensions._--Diameter of the central capsule 0.4 to 0.8, of the
nucleus 0.02 to 0.05, of the calymma 1 to 5 mm.

_Habitat._--Cosmopolitan; common in all warmer seas; Mediterranean,
Atlantic, Indian Ocean, Pacific, mainly between lat. 40° N. and lat. 40°
S.; surface.


6. _Thalassicolla maculata_, n. sp. (Pl. 1, fig. 4).

Spherical body in the central part opaque, black or dark coloured, in the
periphery semi-transparent, spotted. Central capsule compact, yellowish,
opaque, with a thick and firm, very elastic membrane, areolated by
polygonal, punctated figures resembling cells. Diameter of the central
capsule about twice that of the nucleus, one-third to one-fifth that of the
jelly-cover. Nucleus thin-walled, with one large spherical nucleolus.
Protoplasm of the central capsule contains innumerable very small, hyaline,
spherical vesicles of equal size (or vacuoles?), two to four times as broad
as the separating bridges of protoplasm. Extracapsular body with dark
pigment-powder of black or brown colour, densely accumulated around the
central capsule (in the matrix), loosely scattered between the alveoles of
the outer jelly-cover. The latter appears spotted by numerous large,
roundish lumps of protoplasm, scattered between the alveoles. No xanthellæ.

_Dimensions._--Diameter of the central capsule 0.3 to 0.6, of the nucleus
0.2 to 0.3, of the hyaline globules in the protoplasm of the capsule 0.02
to 0.03; calymma, 2 to 3 mm.

_Habitat._--South Pacific, Challenger Station 289.


7. _Thalassicolla melacapsa_, n. sp. (Pl. 1, fig. 5).

Spherical body in the central part opaque, black or dark coloured, in the
periphery semi-transparent, spotted. Central capsule compact, black, with a
thick and firm, very elastic membrane, areolated by polygonal, punctated
figures resembling cells. Diameter of the central capsule about twice that
of the nucleus, one-third or half that of the jelly-cover. Nucleus
thin-walled, transparent, containing very numerous and small nucleoli.
Protoplasm of the central capsule filled with small black pigment-granules,
quite intransparent, contains densely packed hyaline (albuminous?) globules
of equal size; every pellucid globule includes a smaller globule (one-third
or one-fourth its diameter), which appears to be composed of aggregated
oil-bubbles. Extracapsular body without pigment, contains between its
alveoles in the inner half numerous, dark refractive oil-globules, in the
outer half numerous amoeboid lumps of protoplasm, irregularly scattered. No
xanthellæ.

_Dimensions._--Diameter of the central capsule 2 to 2.5, of the nucleus 1
to 1.5, of the hyaline globules in the protoplasm of the capsule 0.03 to
0.04; calymma, 3 to 5 mm.

_Habitat._--South-east Pacific (near Valparaiso), Challenger Station 300,
surface.



Genus 5. _Thalassophysa_,[12] Haeckel, 1881, Prodromus, p. 470.

_Definition._--Thalassicollida without intracapsular alveoles, but with
large roundish or globular alveoles within the extracapsular calymma.
Nucleus in the centre of the capsule papillate or branched.

{22}The genus _Thalassophysa_ contains those species of Thalassicollida
formerly associated with _Thalassicolla_, which are distinguished by the
complicated, ramose, or papillate form of the large nucleus. All three
species here described are found in the Mediterranean and the Atlantic. To
this genus appertains also that strange form of Radiolaria which I
described in 1870 as _Myxobrachia_ (compare _Thalassophysa sanguinolenta_).


1. _Thalassophysa papillosa_, n. sp.

  _Thalassicolla papillosa_, Haeckel, 1867, Manuscript.

Spherical body transparent, colourless, or somewhat yellowish. Central
capsule soft, colourless, with a very thin but firm, elastic, structureless
membrane. Diameter of the central capsule about twice that of the nucleus,
one-fourth to one-sixth that of the jelly-envelope. Nucleus papillated, its
spherical surface covered with a great number (50 to 80) of conical or
finger-like protuberances or blind sacs, not longer than half its radius.
Protoplasm of the central capsule filled with very small and numerous
spherical vacuoles, without oil-globules. Extracapsular jelly-body, without
dark pigment, oil-globules, and large protoplasmic lumps, contains between
its alveoles very numerous xanthellæ.

_Dimensions._--Diameter of the whole jelly sphere 4 to 5 mm., of the
central capsule 0.8 to 1 mm., of its nucleus 0.4 to 0.5.

_Habitat._--Canary Islands, Lanzerote, common, Haeckel; Cape Verde Islands,
Challenger; surface.


2. _Thalassophysa sanguinolenta_, Haeckel.

  _Thalassicolla sanguinolenta_, Haeckel, 1870, Jenaische Zeitschr., Bd. v.
  p. 526, Taf. 18.

  _Thalassicolla sanguinolenta_, Haeckel, 1870, Biolog. Studien, i. p. 113,
  Taf. iv.

  _Thalassicolla sanguinolenta_, R. Hertwig, 1879, Organismus d. Radiol.,
  p. 37, Taf. iii. fig. 1.

  _Myxobrachia rhopalum_, Haeckel, 1870, Jenaische Zeitschr., Bd. v. p.
  519, Taf. 18 (et in Biol. Stud., _loc. cit._).

  _Myxobrachia pluteus_, Haeckel, 1870, Jenaische Zeitschr., Bd. v. p. 520,
  Taf. 18 (et in Biol. Stud., _loc. cit._).

Spherical body in the central part opaque, reddish, in the periphery
transparent, yellowish. Central capsule compact, white, red spotted, with a
thick elastic membrane, perforated by pores, but not areolated. Diameter of
the central capsule three times that of the nucleus, one-fifth to
one-eighth that of the jelly-envelope. Nucleus papillated, its spherical
surface covered with numerous (80 to 120) conical or finger-like
protuberances not longer than one-fourth or one-third of its radius. On the
inside of these blind sacs lie numerous small roundish nucleoli. Protoplasm
of the central capsule in the outer (cortical) zone (on the inside of the
membrane) radially striped, with one layer of very numerous red
oil-globules of equal size, producing its blood-spotted appearance; in the
inner (medullary) zone foamy, with numerous small spherical vacuoles.
Extracapsular jelly-body without dark pigment, contains between its
alveoles no large protoplasmic lumps (as in _Thalassophysa pelagica_), but
numerous small oil-globules and xanthellæ. This species sometimes amasses
in its jelly-envelope large accumulations of Coccoliths and Coccospheres,
{23}which are much heavier than the jelly-body, and produce arm-like
protuberances of it; this modified form, often of very regular and peculiar
appearance, I formerly described as _Myxobrachia_ (compare my Biolog.
Studien, _loc. cit._, and Hertwig, _loc. cit._, p. 37). Compare also
_Myxobrachia cienkowski_, Wagner, 1872, L. N. 23.

_Dimensions._--Diameter of the whole jelly-sphere 5 to 8 mm., of the
central capsule 1 to 1.2 mm., of its nucleus 0.3 to 0.4.

_Habitat._--Canary Islands, Lanzerote; common, Haeckel; Mediterranean,
Messina, Hertwig; surface.


3. _Thalassophysa pelagica_, Haeckel.

  _Thalassicolla pelagica_, Haeckel, 1862, Monogr. d. Radiol., p. 247, Taf.
  i.

  _Thalassicolla pelagica_, R. Hertwig, 1879, Organismus d. Radiol., p. 35,
  Taf. iii. fig. 4.

Spherical body in the central part opaque, yellowish, in the periphery
semi-transparent, spotted. Central capsule compact, yellowish-white, with a
thick and compact membrane, perforated by pores, but not areolated.
Diameter of the central capsule about twice that of the nucleus, one-half
to one-sixth that of the jelly-envelope. Nucleus papillated, its spherical
surface covered with numerous (20 to 60) conical, roundish, or finger-like
protuberances, not longer than its radius (commonly only one-half or
one-third as long). Enclosed in the semi-fluid substance of the nucleus are
very long and thin cylindrical nucleoli snake-like, contorted, and
penetrating into the protuberances of the nucleus. Protoplasm of the
central capsule in the outer (cortical) zone (on the inside of the
membrane) radially striped, with one layer of large oil-globules of
different sizes; in the inner (medullary) zone foamy, with numerous small
spherical vacuoles, mostly of equal size. Extracapsular jelly-body without
dark pigment, contains between its alveoles a large number of large
roundish or amoeboid lumps of protoplasm, and very numerous yellow cells or
xanthellæ (compare the detailed description in my Monograph, and in R.
Hertwig's work).

_Dimensions._--Diameter of the whole jelly-sphere 1 to 4 mm., of the
central capsule 0.5 to 0.6, of the nucleus 0.2 to 0.3.

_Habitat._--Mediterranean--Messina, Corfu, Nizza, Genoa, Haeckel; Messina,
R. Hertwig; surface.



Family II. #COLLOZOIDA#, Haeckel, 1862 (Pl. 3).

_Collozoida_, Haeckel, 1862, Monogr. d. Radiol., p. 522.

_Definition._--#Colloidea# socialia.

The family Collozoida comprises all associated or colony-building
Radiolaria without skeleton. We unite here all these skeletonless
Radiolarian colonies into one single genus _Collozoum_, constituted (1862)
in my Monograph (p. 522). The oldest known form of it was the _Collozoum
inerme_, described firstly by Johannes Müller (1856) as _Sphærozoum
inerme_. Two other species of the genus were figured (1862) in my Monograph
(p. 522, Tafn. xxxii., xxxv.). A most accurate description of its
histological structure and {24}development was given in 1876 by Richard
Hertwig in his Histologie der Radiolarien (pp. 12-42, Tafn. i., ii.). A
number of other very remarkable forms of _Collozoum_ have been observed by
me during the last few years, and partly figured in Pl. 3.

_Collozoum_, as the only representative of this family, is sufficiently
distinguished from all other Radiolaria by the definition "_Skeletonless
Radiolarian Colonies._" These occur floating on the surface of all warmer
seas, often in astonishing masses, and may be easily confounded, owing to
their external resemblance, with the jelly-like egg-masses of certain
Mollusca. _Collozoum_ is derived either from _Actissa_ or from
_Thalassicolla_, simply by multiplication of the unicellular body and by
reunion of the associated capsules in one common calymma or jelly-veil;
this is constantly alveolated, as in _Thalassicolla_. As in _Actissa_, the
form of the central capsule remains either spherical, or it becomes
ellipsoidal or discoidal, rarely polyhedral or amoeboid. In _Collozoum_ as
in all colonial Radiolaria, the original central nucleus commonly undergoes
cleavage very early into numerous small nuclei, whilst its place is usually
taken by a central oil-globule. This peculiarity may serve often (but not
constantly) for the distinction of isolated capsules of _Collozoum_ from
_Actissa_.



Genus 6. _Collozoum_,[13] Haeckel, 1862, Monogr. d. Radiol., p. 522.

_Definition._--Skeletonless colonies of Radiolaria.

The genus _Collozoum_, as already mentioned, is the only representative of
its family, and comprises all Radiolaria living associated in colonies, and
having no skeleton. Therefore _Collozoum_ possesses all the peculiarities
described above. Although the floating colonies of this genus occur in
enormous masses on the surface of all warmer seas, nevertheless the number
of different species in this genus is not great, and amounts only to
thirteen. If this number increase by further investigations, the subgenera
distinguished in the following description can be advanced to the range of
genera; in which case _Collodinium_ (or _Collozoum_ sensu restricto) will
be characterised by the spherical form of its central capsules,
_Colloprunum_ by the ellipsoidal form (Pl. 3, fig. 9), _Collophidium_ by
the cylindrical, very prolonged form (figs. 2, 3), _Collodiscus_ by the
lenticular or discoidal form, and _Collodastrum_ by the indefinite,
polyhedral, or amoeboid form (figs. 4, 5).


Subgenus 1. _Collodinium_, Haeckel.

_Definition._--Form of the central capsules spherical or subspherical,
never polyhedral, ellipsoidal, or cylindrical.


{25}1. _Collozoum inerme_, Haeckel (Pl. 3, figs. 10-12).

  _Collozoum inerme_, Haeckel, 1862, Monogr. d. Radiol., p. 522, Taf. xxxv.

  _Collozoum inerme_, Cienkowski, 1871, Archiv. f. mikrosk. Anat., vol.
  vii. p. 376, Taf. xxix. figs. 18-36.

  _Collozoum inerme_, R. Hertwig, 1876, Histologie der Radiol., p. 12, Taf.
  i., ii.

  _Collozoum inerme_, R. Hertwig, 1879, Organismus d. Radiol., p. 31, Taf.
  iii. fig. 12.

  _Sphærozoum inerme_, J. Müller, 1856, Monatsber. d. k. Akad. d. Wiss.
  Berlin, p. 478; Abhandl., p. 54.

  _Sphærozoum bicellulare_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 54, Taf. viii. fig. 5.

  _Thalassicolla punctata_, Huxley (_pro parte_), 1851, Ann. and Mag. Nat.
  Hist., ser. 2, vol. viii. p. 433.

Central capsules spherical, with thin, simple-edged membrane, with one
single oil-globule in the centre. (If the capsules multiply by division,
the spherical form becomes violin-shaped, constricted in the middle; and in
this condition the number of oil-globules increases; but in the ordinary
mature state the capsule of this species remains spherical, and its
oil-globule solitary. In quite young capsules the oil-globules are wanting;
Pl. 3, fig. 12.)

_Dimensions._--Diameter of the central capsules 0.04 to 0.16.

_Habitat._--Cosmopolitan, common in all warmer seas (Mediterranean,
Atlantic, Indian, and Pacific), surface.


2. _Collozoum nostochinum_, n. sp.

Central capsules spherical, very large, opaque, distended with red
pigment-granules and with very numerous (two hundred to three hundred)
small oil-globules. Membrane thick, double-edged.

_Dimensions._--Diameter of the central capsules 0.3 to 0.5.

_Habitat._--Indian Ocean, off Socotra, surface, Haeckel.


3. _Collozoum volvocinum_, n. sp.

Central capsules spherical, very large, opaque, containing a great number
(ten to thirty) of large oil-globules, and between them densely packed
masses of dark pigment. Membrane thick, double-edged. This species differs
from _Collozoum inerme_, mainly by the great size of the central capsules
(three to five times as big as in the former) and the great number of
oil-globules in them.

_Dimensions._--Diameter of the central capsules 0.2 to 0.3.

_Habitat._--Central Pacific, Station 272, surface.


Subgenus 2. _Colloprunum_, Haeckel.

_Definition._--Form of the central capsules ellipsoidal, with one prolonged
axis.


4. _Collozoum ovatum_, n. sp.

  _Colloprunum ovatum_, Haeckel, 1882, Manuscript.

Central capsules ovate or ellipsoidal, its longer diameter twice to three
times as large as the shorter. In the centre of every capsule one single
oil-globule.

{26}_Dimensions._--Length of the central capsules 0.2 to 0.3, breadth of
them 0.1 to 15.

_Habitat._--North Pacific, Station 244, surface.


5. _Collozoum ellipsoides_, n. sp. (Pl. 3, figs. 8, 9).

  _Colloprunum ellipsoides_, Haeckel, 1882, Manuscript.

Central capsules regularly ellipsoidal, very large; their longer diameter
once and a half to twice as large as the shorter. In every capsule fifty to
eighty oil-globules.

_Dimensions._--Length of the central capsules 0.3 to 4, breadth of them
0.2.

_Habitat._--North Atlantic, Færöe Channel (Gulf Stream), surface, John
Murray.


Subgenus 3. _Collophidium_, Haeckel.

_Definition._--Form of the central capsules cylindrical, often snake-like,
contorted, with one axis much prolonged, several times longer than the
transverse axis.


6. _Collozoum contortum_, n. sp.

  _Collophidium contortum_, Haeckel, 1882, Manuscript.

Central capsules cylindrical, three to four times as long as broad, C- or
S-like curved, transparent, without oil-globules.

_Dimensions._--Length of the central capsules 0.2 to 0.3, breadth 0.06 to
0.08.

_Habitat._--Tropical Atlantic, Station 347, surface.


7. _Collozoum serpentinum_, n. sp. (Pl. 3, figs. 1-3).

  _Collophidium serpentinum_, Haeckel, 1882, Manuscript.

Central capsules cylindrical, filiform, much elongated, ten to one hundred
times, sometimes two hundred to four hundred times as long as broad,
snake-shaped or worm-shaped, curved and contorted in the most irregular
manner, often spiral or twisted into a large nodule. Numerous oil-vesicles
constantly present, forming one series of globules in the axis of every
capsule; distance of the globules, one from another, and also from the
capsule-membrane, about equal to their diameter. (This interesting and very
curious form was very frequently observed living by me in the Canary
Islands, in January 1867; the jelly-colonies were commonly spherical, and
contained fifty to two hundred or more capsules of very different size and
form.)

_Dimensions._--Length of the central capsules 1 to 10, sometimes 20 to 40
mm.; average breadth 0.1 mm.

_Habitat._--Canary Islands, Lanzerote, Haeckel, surface.


{27}8. _Collozoum vermiforme_, n. sp. (Pl. 3, figs. 6, 7).

  _Collophidium vermiforme_, Haeckel, 1882, Manuscript.

Central capsules cylindrical, much elongated, five to ten times (sometimes
twenty to fifty times) as long as broad, snake-shaped or worm-shaped, very
irregularly curved and contorted. Numerous oil-globules constantly present,
forming in the axis of every capsule a double series of alternating
rose-coloured globules. (This species is nearly allied to the preceding;
but its capsules are thicker and shorter, and the oil-vesicles in them are
arranged not in a single, but in a double row.)

_Dimensions._--Length of the central capsules 0.6 to 1.2 mm., sometimes 3
to 6 mm.; breadth 0.12.

_Habitat._--Tropical Atlantic, near the west coast of Africa, Station 349,
Canary Islands, surface.


Subgenus 4. _Collodiscus_, Haeckel.

_Definition._--Form of the central capsules discoidal or lenticular, with
one shortened axis.


9. _Collozoum coeruleum_, Haeckel.

  _Collozoum coeruleum_, Haeckel, 1862, Monogr. d. Radiol., p. 523, Taf.
  xxxii. figs. 6-8.

  _Collodiscus coeruleus_, Haeckel, 1882, Manuscript.

Central capsule lenticular or discoidal, flattened, blue coloured, with one
single oil-globule in the centre. Protoplasm containing numerous crystals
and dark blue pigment-granules. Membrane very thick, double-edged. (Whilst
at Messina in 1859 I found this form not constantly discoidal, in 1867 in
the Canary Islands I observed it constantly lenticular.)

_Dimensions._--Breadth of the central capsules 0.1 to 0.15, height 0.04 to
0.08.

_Habitat._--Mediterranean (Messina), Atlantic (Canary Islands), surface.


10. _Collozoum discoideum_, n. sp.

  _Collodiscus discoideus_, Haeckel, 1882, Manuscript.

Central capsule discoidal, flattened, transparent, with a ring of twenty to
twenty-five oil-globules in its circular periphery (on the inside of the
thin membrane).

_Dimensions._--Breadth of the central capsules 0.2, height 0.05.

_Habitat._--South Pacific (Juan Fernandez), Station 300, surface.


Subgenus 5. _Collodastrum_, Haeckel.

_Definition._--Form of the central capsules irregular and indefinite,
variable, commonly polyhedral or polygonal, or amoeboid, often with
irregular, finger-like processes.


{28}11. _Collozoum pelagicum_, Haeckel.

  _Collozoum pelagicum_, Haeckel, 1862, Monogr. d. Radiol., p. 525, Taf.
  xxxii. figs. 4, 5.

  _Sphærozoum pelagicum_, Haeckel, 1860, Monatsber. d. k. Akad. d. Wiss.
  Berlin, 1860, p. 845.

Central capsules small, quite irregularly formed, roundish-polyhedral or
depressed-polygonal, transparent, without oil-globules. Often many
extracapsular oil-vesicles in the common jelly-body between the central
capsules. Membrane very thin and delicate.

_Dimensions._--Diameter of the central capsules 0.02 to 0.08.

_Habitat._--Mediterranean, Messina, Haeckel; Naples, Brandt; surface.


12. _Collozoum stellatum_, n. sp.

  _Collodastrum stellatum_, Haeckel, 1882, Manuscript.

Central capsules star-shaped, irregularly radiating, with a great number
(eight to twenty or more) of radial, short, conical, acute processes, very
variable in size and number. Membrane thin. In every capsule several (four
to eight) oil-globules.

_Dimensions._--Diameter of the central capsules 0.12 to 0.2.

_Habitat._--Central Pacific, Station 274, surface.


13. _Collozoum amoeboides_, n. sp. (Pl. 3, figs. 4, 5).

  _Collodastrum amoeboides_, Haeckel, 1882, Manuscript.

Central capsules amoebiform, of moderate size, quite irregularly formed,
with a variable number of finger-like, obtuse, irregular prolongations
(commonly three to six), very variable in size and form. Membrane thin. In
the centre of every capsule one single oil-globule.

_Dimensions._--Diameter of the central capsules 0.04 to 0.08.

_Habitat._--Indian Ocean, Ceylon, Haeckel; Madagascar, Rabbe; surface.


----


Suborder II. BELOIDEA, Haeckel.

_Definition._--SPUMELLARIA with an imperfect skeleton, composed of numerous
solid needles or spicula, scattered irregularly in the calymma.


The suborder #Beloidea# comprises all those SPUMELLARIA which possess an
imperfect or rudimentary skeleton, composed of a variable number of
isolated spicula scattered in the extracapsulum. The suborder contains only
two different families, the solitary Thalassosphærida (or Beloidea monozoa)
and the associated Sphærozoida (or Beloidea polyzoa). Both families are
very nearly allied, and differ only in one single character: the solitary
life of the former, the social union of the {29}latter. It seems to be
merely a consequence of this difference that the cleavage of the nucleus
commonly takes place very late in the former, very early in the latter.

Commonly, therefore, the full-grown Thalassosphærida (until immediately
before their propagation) exhibit one single nucleus in the centre of the
capsule, whilst in the Sphærozoida the capsule is distended with numerous
small nuclei. In these latter the centre of the capsule usually contains
one large oil-globule, whilst in the former oil-globules are either wanting
or scattered in large numbers in the endoplasm, or disposed in one layer on
the inside of the capsule membrane.

In the solitary Thalassosphærida each capsule is enclosed in its own
peculiar spherical calymma, whilst in the associated Sphærozoida all the
capsules of the colony are united into one common, very voluminous,
alveolated calymma.



Family III. #THALASSOSPHÆRIDA#, Haeckel, 1862, (Pl. 2).

_Thalassosphærida_, Monogr. d. Radiol., p. 255.

_Definition._--#Beloidea# solitaria.

The family Thalassosphærida comprises all solitary SPUMELLARIA with an
imperfect skeleton, composed of numerous solid needles or spicula,
scattered around the central capsule in the calymma. The structure of the
unicellular soft body is quite the same as in the Thalassicollida; it
differs from these only in the possession of the extracapsular skeleton.
All needles of this skeleton are solid siliceous spicula, never hollow, as
in the similar Cannorrhaphida among the PHÆODARIA. In the special structure
and form of the skeleton the Thalassosphærida agree perfectly with the
well-known, colony-building Sphærozoida; they differ from these only by
their hermit-like life and by some peculiarities derived from this solitary
development.

The oldest known form of this family is probably the first Radiolarian,
observed in the living state, described in 1834 by Meyen as _Physematium
atlanticum_ (see p. 35). A second form was figured in my Monograph (1862)
as _Thalassosphæra bifurca_ (p. 260, Taf. xii. fig. 1). A third form was
there described under the name _Thalassosphæra morum_; this remarkable form
was first observed by Johannes Müller, and figured under the name
_Thalassicolla morum_ (1858, Abhandl., p. 28, Taf. vii. figs. 1, 2). The
same form was afterwards observed living by myself in the Mediterranean, as
well as in the Atlantic, and in great numbers by the late Sir Wyville
Thomson in the Pacific. The latter gave a good figure of it with some
valuable remarks in his excellent work, The Atlantic (1877, vol. i. p. 233,
fig. 51). He called this peculiar Rhizopod _Calcaromma calcarea_, on
account of the very peculiar _calcareous_ bodies "looking in outline like
the rowels of spurs," which are accumulated in great quantity around the
central capsule, in the calymma. Further investigations have convinced me
that these peculiar stellate {30}bodies of carbonate of lime, for which we
propose the name "Calcastrella," are not parts of the skeleton produced by
the Radiolarian, but foreign bodies picked up by its extracapsular sarcode
(in the same way as the Coccoliths are picked up by _Thalassicolla
sanguinolenta = Myxobrachia!_). These Calcastrella occur also in the
calymma of some Discoidea and other Radiolaria; they are either unicellular
calcareous Algæ, or foreign bodies of other origin. The _Collodarium_,
however, described as _Thalassicolla morum_ and _Calcaromma calcarea_,
seems to be a simple _Actissa_, which has picked up a number of
Calcastrella.

The Challenger collection has yielded a number of other true
Thalassosphærida, which partly agree with _Thalassosphæra_ in the simple
structure of the unicellular body (resembling _Actissa_), and partly differ
from it in the development of alveoles, either within or without the
central capsule (similar to _Thalassolampe_ and _Thalassicolla_). The solid
siliceous spicula, which occur in great numbers scattered in the calymma,
agree perfectly in form with the spicula of the colony-building
Sphærozoida. A characteristic difference between the social and the
solitary #Beloidea# seems to be determined by the cleavage of the nucleus,
which takes place in the latter very late, in the former very early.
Therefore in the large central capsule of the mature solitary
Thalassosphærida, we commonly find one large nucleus in the centre, and a
number of oil-globules around it in the endosarc, or disposed in one layer
on the inside of the capsule-membrane (Pl. 2, figs. 2, 5); whereas in the
much smaller associated capsules of the Sphærozoida one large oil-globule
is placed commonly in the centre, and a great number of small nuclei
scattered in the endoplasm (compare above, p. 24).

_Synopsis of the Genera of Thalassosphærida._

  A. Alveoles neither within { Spicula simple,    7. _Thalassosphæra_.
   nor without the           {
   central capsule.          { Spicula branched,  8. _Thalassoxanthium_.

  B. Numerous large alveoles }
   within the central        } Spicula simple,    9. _Physematium_.
   capsule (not in the       }
   calymma).                 }

  C. Numerous large alveoles { Spicula simple,   10. _Thalassoplancta_.
   within the calymma (not   {
   in the central capsule).  { Spicula branched, 11. _Lampoxanthium_.


Genus 7. _Thalassosphæra_,[14] Haeckel, 1862, Monogr. d. Radiol., p. 259.

_Definition._--Thalassosphærida without alveoles, with simple, unbranched,
needle-shaped spicula in the calymma.

The genus _Thalassosphæra_ was founded by me in 1862 for those solitary
#Collodaria# in which the simple central capsule is surrounded by scattered
solid spicula. {31}I described these two different species, the new
_Thalassosphæra bifurca_ and the _Thalassosphæra morum_, which J. Müller
had formerly called _Thalassicolla morum_. This latter form is
characterised by peculiar _calcareous_ bodies "looking in outline like the
rowels of spurs, scattered irregularly in the gelatinous envelope," and was
therefore afterwards called "_Calcaromma calcarea_" by Sir Wyville
Thomson.[15] As already mentioned above, these calcareous rowels are
foreign bodies, picked up by an _Actissa_ (see p. 29). I here confine the
genus _Thalassosphæra_ to those solitary #Beloidea# in which the body
exhibits no alveoles, and the siliceous solid spicula in the calymma are
quite simple needles.


_Thalassosphæra belonium_, n. sp.

Spicula thin cylindrical rods, more or less curved, pointed at both ends,
with smooth surface (similar to the needles of _Rhaphidozoum italicum_).
Central capsule spherical, three times as large as the central nucleus,
without larger oil-globules.

_Dimensions._--Diameter of the central capsule 0.1 to 0.12, length of the
spicula 0.04 to 0.08.

_Habitat._--Central Pacific, Station 272, surface.


_Thalassosphæra rhaphidium_, n. sp.

Spicula thick cylindrical rods, more or less curved, pointed at both ends,
covered with numerous strong conical thorns, perpendicular to the axis.
Central capsule spherical, four times as broad as the central nucleus, with
twenty to thirty large oil-globules on the inside of the membrane.

_Dimensions._--Diameter of the central capsule 0.2, length of the spicula
0.12 to 0.16.

_Habitat._--Tropical Atlantic, Station 347, surface.


Genus 8. _Thalassoxanthium_,[16] Haeckel, 1881, Prodromus, p. 470.

_Definition._--Thalassosphærida without alveoles, with numerous branched or
compound spicula in the calymma.

The genus _Thalassoxanthium_ differs from the foregoing _Thalassosphæra_,
by the ramification of the spicula, and has therefore the same relation to
it as _Sphærozoum_ to _Belonozoum_. The soft unicellular body is as simple
as in _Actissa_, and exhibits alveoles neither in the capsule nor in the
calymma.


Subgenus 1. _Thalassoxanthella_, Haeckel.

_Definition._--Spicula not geminate, but simply radiate, consisting of
three, four, or more needles or shanks, radiating in different directions
from one and the same point; shanks now simple or needle-like, now furcate
or branched.


{32}1. _Thalassoxanthium triactinium_, n. sp.

Spicula all (or nearly all) triradiate, composed of three (or sometimes in
a few spicula four) needle-like shanks of equal length, diverging from one
common point. Shanks straight or somewhat curved, smooth, pointed. Central
capsule pellucid, twice as broad as its dark nucleus, without larger
oil-globules. Jelly-envelope very thin, with numerous xanthellæ.

_Dimensions._--Diameter of the central capsule 0.1, of its nucleus 0.05,
length of the spicule-shanks 0.6 to 0.8.

_Habitat._--Central Pacific, Station 266, surface.


2. _Thalassoxanthium triradiatum_, n. sp.

Spicula all (or nearly all) triradiate, composed of three (or sometimes in
a few spicula four) needle-like shanks of different length, diverging from
one common point. Shanks curved or bent, covered with small conical thorns.
Central capsule dark, three times as large as the nucleus, with numerous
large oil-globules. Jelly-envelope thick, without xanthellæ.

_Dimensions._--Diameter of the capsule 0.2, of the nucleus 0.07, length of
the spicule-shanks 0.1 to 0.15.

_Habitat._--South Pacific, Station 302, surface.


3. _Thalassoxanthium medusinum_, n. sp. (Pl. 2, fig. 5).

Spicula all (or nearly all) quadriradiate, irregular, composed of four (or
sometimes in a few spicula three) needle-like shanks (mostly of unequal
length), diverging from one common point. Shanks curved, pointed, thorny,
covered with small spinules. Central capsule dusky, twice to three times as
large as its dark central nucleus. On the inside of the membrane numerous
large oil-globules. Jelly-envelope thin, with numerous xanthellæ.

_Dimensions._--Diameter of the central capsule 0.45 to 0.5, of its nucleus
0.18 to 0.2.

_Habitat._--North Pacific, Station 244, surface.


4. _Thalassoxanthium hexactinium_, n. sp.

Spicula all (or nearly all) hexaradiate, composed of six (or sometimes in a
few spicula three) needle-like shanks, diverging in two opposite
hemispheres (three needles upwards, three needles downwards). Shanks
somewhat curved, pointed, smooth. Central capsule yellowish-brown, dark,
four times as broad as its dark central nucleus. Jelly-envelope thick
(about twice as broad as the capsule), with very numerous xanthellæ.

_Dimensions._--Diameter of the central capsule 0.3 to 0.4, of its nucleus
0.1 to 0.12.

_Habitat._--South Atlantic, Station 325, surface.


{33}5. _Thalassoxanthium cervicorne_, n. sp. (Pl. 2, figs. 3, 4).

Spicula all triradiate, trichotomously branched, with three equal shanks,
which diverge from one common point, and are again provided each with three
branches on the distal end. These nine branches are commonly once or twice
forked (each fork rarely provided with three ramules). The ramules are
thin, unequal, curved, or bent, and the ramification nearly resembles a
stag's horn. Central capsule transparent, without oil-globules, two to
three times as broad as the dark nucleus, which contains one single long
central nucleolus. Calymma thin, scarcely as thick as the radius of the
nucleus.

_Dimensions._--Diameter of the central capsule 0.2 to 0.25, of the nucleus
0.08 to 0.1, length of the spicula 0.05 to 0.15.

_Habitat._--Central Pacific, Stations 271, 274, surface.



Subgenus 2. _Thalassoxanthomma_, Haeckel.

_Definition._--Spicula all or partly geminate, consisting of one middle or
axial rod, from the two poles of which diverge two, three, or more shanks
in different directions. Shanks or needle-rays sometimes simple,
needle-like, sometimes bifurcated or branched.


6. _Thalassoxanthium furcatum_, n. sp.

Spicula all (or nearly all) geminate and simply forked, composed of a
simple axial rod and two simple, needle-like shanks on each end of it.
Shanks straight, pointed, smooth, somewhat shorter than the middle rod.
Central capsule yellowish, dark, three times as broad as its central dark
nucleus; besides this a single oil-globule, nearly of the same size.

_Dimensions._--Diameter of the central capsule 0.1, of its nucleus 0.03;
length of the axial rod of the spicula 0.04, of its shanks 0.03.

_Habitat._--Cape Verde Islands.


7. _Thalassoxanthium bifurcum_, Haeckel.

  _Thalassosphæra bifurca_, Haeckel, 1862, Monogr. d. Radiol., p. 260, Taf.
  xii. fig. 1.

  _Sphærozoum bifurcum_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, p. 845.

Spicula all geminate and double forked, composed of a simple axial rod and
two forked branches on each end; these branches are again forked, so that
each spiculum exhibits eight thin distal ends. All branches are thin,
slender and straight. Central capsule red, four times as broad as the
central nucleus, containing between the red pigment-granules numerous,
peculiar, violin-shaped bodies (fat-corpuscles?). Compare fig. 1, _loc.
cit._

_Dimensions._--Diameter of the central capsule 0.08, of the nucleus 0.02,
length of the spicula 0.05 to 0.08.

_Habitat._--Mediterranean (Messina), surface, Haeckel.


{34}8. _Thalassoxanthium ovodimare_, n. sp.

Spicula all geminate, composed of a simple, very short axial rod and three
diverging shanks or branches on each end of it; the shanks are very thin,
straight, or little curved, and eight to ten times as long as the axial
rod. The spicula are quite smooth, as in the similar _Sphærozoum ovodimare_
(in which, however, the axial rod is much longer). Central capsule
transparent, without oil-globules, twice as broad as the nucleus.

_Dimensions._--Diameter of the capsule 0.4, of the nucleus 0.2, length of
the spicula 0.1 to 0.2.

_Habitat._--Central Pacific, Station 273, surface.


9. _Thalassoxanthium punctatum_, n. sp.

Spicula all geminate-triradiate, composed of a simple middle rod and of
three diverging shanks on each end of it; the shanks are thorny with small
spinules and shorter than the axial rod, very similar to the common
_Sphærozoum punctatum_. Central capsule dark, with numerous (twenty to
thirty) oil-globules on the inside of the membrane, three times as broad as
the nucleus.

_Dimensions._--Diameter of the capsule 0.3, of the nucleus 0.1, length of
the spicula 0.05 to 0.2.

_Habitat._--Central Pacific, Station 274, surface.


10. _Thalassoxanthium octoceras_, n. sp. (Pl. 2, fig. 6).

Spicula all geminate-quadriradiate, composed of a simple short middle rod
and of four diverging shanks on each end of it; the shanks are quite
smooth, irregularly curved or bent, and four to eight times as long as the
middle rod. Central capsule dark, filled with pigment-granules, without
oil-globules, four times as large as the nucleus.

_Dimensions._--Diameter of the capsule 0.5, of the nucleus 0.12, length of
the spicula 0.2 to 0.4.

_Habitat._--Indian Ocean, Madagascar, Rabbe.


Genus 9. _Physematium_,[17] Meyen, 1834, Nova Acta Acad. Nat. Curios., vol.
xvi., Suppl., p. 286 (p. 162).

_Definition._--#Thalassosphærida# with large numerous alveoles within the
central capsule (not in the calymma), and with numerous simple,
needle-shaped spicula in the calymma.

The genus _Physematium_ is, together with the colony-forming _Sphærozoum_,
the first Radiolarian which was observed in the living state, described in
1834 by Meyen. It is most nearly allied to _Thalassolampe_, and has the
same large roundish alveoles within the central capsule, which reaches
therefore an extraordinary size, 5 to 10 mm. It {35}differs from the latter
by the possession of spicula in the calymma. The peculiar "centripetale
Zell-gruppen" on the inside of the capsule-membrane are probably due to
radial cleavages of the endoplasm; as also occurs in other #Collodaria#.


1. _Physematium mülleri_, Schneider.

  _Physematium mülleri_, Schneider, 1858, Archiv. f. Anat. u. Physiol., p.
  38, Taf. iii. B, figs. 1-5.

  _Physematium mülleri_, Haeckel, 1862, Monogr. d. Radiol., p. 256, Taf.
  iii. figs. 6-9.

Spherical body limpid, somewhat opalescent, sometimes a little yellowish or
brownish, rather soft. Central capsule with a thin, but firm, transparent
membrane, its diameter eight to ten times as large as that of the central
spherical nucleus. Membrane of the nucleus thick, porous, on its inside
with some nucleoli. In the protoplasmic network between the large
intracapsular alveoles, numerous large, pale, yellowish, or orange
oil-globules. On the inside of the membrane numerous conical bodies,
centripetally directed with the apex towards the centre; every conical body
("kegelförmige centripetale Zellgruppe") composed of three to nine
(commonly four or five) nucleated cells (mother-cells of the spores?); in
the axis of the cone there is often a yellowish, orange, or brown
oil-globule. Extracapsular jelly-envelope thin, with short pseudopodia.
Xanthellæ scarce or wanting. Spicula scattered in the jelly numerous,
small, simple needles, commonly C- or S-like curved, smooth.

_Dimensions._--Diameter of the whole jelly-sphere 3 to 6 mm., of the
central capsule 1 to 5 mm., of the nucleus 0.1 to 0.5, length of the
spicula 0.05 to 0.1.

_Habitat._--Mediterranean, Messina; Schneider, Haeckel; surface.


2. _Physematium atlanticum_, Meyen.

  _Physematium atlanticum_, Meyen, 1834, Nova Acta Acad. Nat. Curios., vol.
  xvi., Suppl., p. 286 (162), Taf. xxxviii. (xxviii.) figs. 1-3.

Spherical body opalescent, pearl-like, with a violet or purple lustre, very
soft. Central capsule with a strong, semi-transparent membrane, its
diameter six to eight times as large as that of the central spherical
nucleus. Membrane of the nucleus very thick, porous, on its inside with
many small nucleoli. In the protoplasmic network between the alveoles very
numerous, small, purple oil-globules. On the inside of the membrane a
continuous simple layer of small nuclei, enclosed in radially striped
protoplasm (mother-cells of the spores?). No centripetal conical bodies.
Extracapsular jelly-envelope very thin, with short pseudopodia. No
xanthellæ. Spicule scattered in the jelly numerous, small needles, straight
or slightly curved, thorny owing to numerous small vertical spinules. This
species and _Thalassolampe maxima_ (p. 17) possess the largest central
capsule.

_Dimensions._--Diameter of the whole jelly-sphere 8 to 12 mm., of the
central capsule 5 to 10 mm., of the nucleus 1 to 2 mm., length of the
spicula 0.1 to 0.3.

_Habitat._--Eastern Atlantic, between Canary Islands and Cape Verde
Islands, Meyen; Lanzerote, Haeckel.



{36}Genus 10. _Thalassoplancta_,[18] Haeckel, 1862, Monogr. d. Radiol., p.
261.

_Definition._--#Thalassosphærida# with numerous large alveoles in the
calymma (but not in the central capsule), and with numerous simple,
needle-shaped spicula around the central capsule.

The genus _Thalassoplancta_ was founded by me in 1862 for a Radiolarian
with simple hollow needles in the calymma, which was afterwards recognised
as a Phæodarium, belonging to _Cannorrhaphis_. We here retain this name for
a true Thalassosphærid, very similar to the latter, but distinguished by
the absence of the phæodium and the solid--not hollow--needle-shaped
spicula, which are scattered in the alveolated calymma. _Thalassoplancta_
can be regarded as the solitary form of the social _Belonozoum_.[19]


1. _Thalassoplancta longispicula_, n. sp.

Spicula long and thin, cylindrical, smooth, more or less bent, pointed at
both ends, similar to those of _Thalassoplancta cavispicula_. Central
capsule thin-walled, without oil-globules, four times as broad as the
nucleus, which encloses one single nucleolus.

_Dimensions._--Diameter of the capsule 0.6, of the nucleus 0.15, of the
calymma 4 mm.

_Habitat._--North Atlantic, Færöe Channel (Gulf Stream), John Murray.


2. _Thalassoplancta brevispicula_, n. sp. (Pl. 2, fig. 2).

  _Lampoxanthium brevispiculum_, Haeckel, 1882, Atlas.

Spicula short and thick, thorny, irregularly curved, pointed at both ends,
very numerous. In the observed specimen all spicula were aggregated in the
outer part of the voluminous calymma, whilst the inner alveolated part was
devoid of them. Central capsule thick walled, with a layer of large
oil-globules on its inner surface, twice as broad as the large nucleus
which contains numerous nucleoli.

_Dimensions._--Diameter of the central capsule 0.5, of the nucleus 0.2, of
the calymma 2.5.

_Habitat._--South Atlantic, Station 334, surface.


Genus 11. _Lampoxanthium_,[20] n. gen.

_Definition._--#Thalassosphærida# with numerous large alveoles in the
calymma (but not in the central capsule), and with numerous branched or
compound spicula in the calymma.

{37}The genus _Lampoxanthium_ differs from the foregoing,
_Thalassoplancta_, by the composite form of the spicula, which are not
simple needles, but radiate or geminate, or branched in different forms;
the former stands therefore in the same relation to the latter as the
social _Belonozoum_ to _Sphærozoum_. The spicula of some species of
_Lampoxanthium_ are identical with those of some species of _Sphærozoum_,
so that the latter may be derived from the former by forming colonies. The
large central capsule is enveloped by a very voluminous alveolated calymma,
and includes a large central nucleus with numerous nucleoli.


Subgenus 1. _Lampoxanthella_, Haeckel.

_Definition._--Spicula all (or nearly all) of one kind, radiate.


1. _Lampoxanthium tetractinium_, n. sp.

Spicula all (or nearly all) tetraradiate, with four thorny, straight,
pointed shanks, radiating from one common point. (Intermingled with these
are often some few, thorny, triradiate spicula.) On the inside of the
capsule a layer of large oil-globules as in _Thalassoplancta_, Pl. 2, fig.
2.

_Dimensions._--Diameter of the central capsule 0.2, of the nucleus 0.08, of
the calymma 0.8.

_Habitat._--South Pacific, Station 288, surface.


Subgenus 2. _Lampoxanthomma_, Haeckel.

_Definition._--Spicula all (or nearly all) of one kind, geminate-radiate,
with a simple middle rod and two to four diverging shanks on each end of
it.


2. _Lampoxanthium punctatum_, n. sp.

Spicula all geminate-triradiate, thorny, of the same form as in the common
_Sphærozoum punctatum_, of which this species is the large solitary
representative. The spicula are aggregated in a very condensed layer on the
surface of the large calymma.

_Dimensions._--Diameter of the capsule 0.8, of the nucleus 0.6, of the
calymma 2.0.

_Habitat._--North Pacific, Station 248, surface.


3. _Lampoxanthium octoceras_, n. sp.

Spicula all geminate-quadriradiate, with a very short simple middle rod and
four very long divergent shanks on both ends of it; the shanks are smooth,
five to ten times as long as the middle {38}rod, irregularly bent and
curved. (Differs from the similar _Thalassoxanthium octoceras_, Pl. 2, fig.
6, by slender, more curved shanks, and by the voluminous calymma, there
entirely wanting.)

_Dimensions._--Diameter of the capsule 0.5, of the nucleus 0.2, of the
calymma 3.0.

_Habitat._--South Atlantic, Station 331, surface.


Subgenus 3. _Lampoxanthura_, Haeckel.

_Definition._--Spicula of two or three different kinds, simple, radiate,
and geminate-radiate mixed.


4. _Lampoxanthium pandora_, n. sp. (Pl. 2, fig. 1).

Spicula mixed, of three different kinds--simple, radiate and
geminate-radiate; all three kinds partly smooth, partly thorny. The simple
needles short, thin spindle-shaped, often curved. The radiate spicula
commonly with three or four, rarely five or six, unequal rays, straight or
curved. The radiate-geminate spicula commonly with three, rarely four,
shanks on each end, often different on both ends of the middle rod. The
size, number, and form of the irregular spicula are here quite as variable
as in the social _Rhaphidozoum pandora_, of which it is the solitary
representative. The wall of the large central capsule is very thick, with
evident pore-canals, separated by a clear interval from the coagulated and
vacuolated endoplasm, which contains no oil-globules. Nucleus with numerous
nucleoli.

_Dimensions._--Diameter of the central capsule 0.5 to 0.6, of the nucleus
0.1 to 0.2, of the calymma 2 to 4 mm.

_Habitat._--North Pacific, Station 244, surface.



Family IV. #SPHÆROZOIDA#, Haeckel (Pl. 4).

_Sphærozoida_, Haeckel, 1862, Monogr. d. Radiol., p. 521.

_Definition._--#Beloidea# socialia.

The family #Sphærozoida# comprises all associated or colony-forming
Radiolaria, which are provided with an imperfect skeleton, composed of
numerous solid needles or spicula, scattered around the central capsule in
the calymma. The structure and form of this skeleton is quite the same as
in the preceding solitary Thalassosphærida, but on the other hand, the
structure and form of the colonies and of the included numerous central
capsules is the same as in the skeletonless Collozoida.

The oldest well-known form of Sphærozoida is the common cosmopolitan
_Sphærozoum punctatum_, probably first observed in 1834 by Meyen, and
called _Sphærozoum fuscum_, afterwards more accurately described by Huxley
in 1851.

{39}Other forms were afterwards described by Müller and by myself in
1862.[21] Further investigations have shown me that some species of this
family are among the most common Radiolaria, and occur in astonishing
numbers on the surface of all warmer seas. But the number of species is
comparatively small, and their distinction is very difficult, as all the
different forms are very variable and connected by intermediate forms--a
truly "_transformistic_" group.

The only character sufficient for the constitution of genera in this
transformistic group is found in the form and composition of the spicula;
the very variable form of the jelly-calymma and the enclosed central
capsule being without value for this purpose. But also the form of the
spicula is very variable, and not always constant. In some species the
particular form of the spicula is transmitted by constant heredity, whilst
in others it is very inconstant, even in one and the same individual.
(Compare the remarks on variability in the general introduction.)

As the number of various forms is rather great, it seems to be advisable to
distinguish the three following genera.

_Synopsis of the Genera of Sphærozoida._

  A. Spicula all of one kind, simple or needle-shaped,  12. _Belonozoum_.
  B. Spicula all of one kind, branched or radiate,
      or geminate,                                      13. _Sphærozoum_.
  C. Spicula of two more different kinds, partly
      simple, partly branched,                          14. _Rhaphidozoum_.


Genus 12. _Belonozoum_,[22] n. gen.

_Definition._--#Sphærozoida# with simple needle-shaped spicula, which are
neither radiate nor branched.

The genus _Belonozoum_ comprises the Sphærozoida with simple needle-shaped
spicula, and may be regarded as the colonial form of _Thalassosphæra_ or
_Thalassoplancta_, derived from these solitary #Beloidea# by multiplication
of the capsules and union in a common calymma.


1. _Belonozoum bacillosum_, n. sp.

  _Sphærozoum bacillosum_, Haeckel, 1881, Manuscript.

Spicula all simple rods, straight cylindrical, obtuse at both ends, quite
smooth. Central capsule pellucid, with one single central oil-globule.

_Dimensions._--Diameter of the central capsule 0.08 to 0.12, length of the
spicula 0.05 to 0.08.

_Habitat._--Central Pacific, Station 271, surface.


{40}2. _Belonozoum spinulosum_, Haeckel.

  _Sphærozoum spinulosum_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 54, Taf. viii. fig. 4.

  _Sphærozoum spinulosum_, Haeckel, 1862, Monogr. d. Radiol., p. 527, Taf.
  xxxiii. figs. 3, 4.

Spicula all simple rods, straight cylindrical, obtuse on both ends, thorny
with numerous small spines, placed vertically on the rods.

_Dimensions._--Diameter of the central capsule 0.08 to 0.1, length of the
spicula 0.05 to 0.2.

_Habitat._--Mediterranean, Nice, J. Müller; Messina, Haeckel; Naples,
Brandt; surface.


3. _Belonozoum italicum_, Haeckel.

  _Sphærozoum italicum_, Haeckel, 1862, Monogr. d. Radiol., p. 526, Taf.
  xxxiii. figs. 1, 2.

Spicula all simple rods, more or less curved or bent, pointed at both ends,
quite smooth. Central capsule with a variable number (commonly five to
twenty) of oil-globules.

_Dimensions._--Diameter of the central capsule 0.1 to 0.3, length of the
spicula 0.05 to 0.2.

_Habitat._--Mediterranean, Nice, Naples, Messina, Haeckel, surface.


4. _Belonozoum atlanticum_, n. sp.

  _Sphærozoum atlanticum_, Haeckel, 1881, Manuscript.

Spicula all together simple rods, more or less curved or bent, pointed at
both ends, thorny from numerous small spines, placed vertically on the
rods.

_Dimensions._--Diameter of the central capsule 0.1 to 0.2, length of the
spicula 0.07 to 0.15.

_Habitat._--Tropical Atlantic, Station 348, surface.


Genus 13. _Sphærozoum_,[23] Meyen, 1834, Nova Acta Acad. Nat. Curios., Bd.
xvi., Suppl., p. 287 (p. 163).

_Definition._--#Sphærozoida# with branched or radiate spicula of one kind.

The genus _Sphærozoum_, with _Physematium_ one of the two oldest
Radiolaria, observed in the living state, was founded 1834 by Meyen for one
of the social #Beloidea#, which was probably the common cosmopolitan
_Sphærozoum punctatum_, the true type of this genus. Johannes Müller
described a number of species, which were partly skeletonless
(_Collozoum_), partly armed with simple or with compound spicula. The
species with simple spicula we refer here to _Belonozoum_, the species with
two or more different kinds of spicula to _Rhaphidozoum_, while we unite in
_Sphærozoum_ all species with one kind of branched or compound spicula. The
two following species are incompletely known:--_Sphærozoum orientale_,
Dana, 1863, _Ann. and Mag. Nat. Hist._, vol. xii. p. 54. _Sphærozoum
sanderi_, Doenitz, 1871, L. N. 60, p. 71.


{41}Subgenus 1. _Sphærozonactis_, Haeckel.

_Definition._--Spicula radiate, not geminate, consisting of three, four, or
more needles or shanks, radiating in different directions from one common
central point.


1. _Sphærozoum triactinium_, n. sp.

Spicula all (or nearly all) triradiate, composed of three (or sometimes in
few spicula four) needle-like shanks, diverging from one common point.
Shanks straight or somewhat curved, smooth, pointed. Central capsules
spherical, with one central oil-vesicle. This species may be regarded as
the social form of _Thalassoxanthium triactinium_.

_Dimensions._--Diameter of the central capsules 0.1 to 0.12, length of the
spicula-shanks 0.05 to 0.1.

_Habitat._--South Pacific, Station 295, surface.


2. _Sphærozoum medusinum_, n. sp.

Spicula all (or nearly all) quadriradiate, composed of four (or sometimes
in few spicula three) needle-like shanks (mostly of unequal length),
diverging from one common point. Shanks slightly curved, pointed, thorny,
covered with small spinules. Central capsules ellipsoidal, containing
several (four to eight) oil-vesicles. This species may be regarded as the
social form of the solitary _Thalassoxanthium medusinum_ (Pl. 2, fig. 5).

_Dimensions._--Diameter of the central capsules 0.15 to 0.18, length of the
spicula-shanks 0.08 to 0.12.

_Habitat._--North Pacific, Station 236, surface.


3. _Sphærozoum hamatum_, n. sp.

Spicula all (or nearly all) quadriradiate, composed of four (or sometimes
in few spicula three) needle-like shanks, mostly of very different size,
diverging from one common point. Shanks strong, straight, curved, or
hook-like; thorny, covered with small spinules on the distal extremity.
Central capsules ellipsoidal, large, containing many (ten to twenty)
oil-globules. This large species is distinguished by the very irregular
form and size of the spicula.

_Dimensions._--Diameter of the central capsules 0.2 to 0.25, length of the
spicula-shanks 0.12 to 0.18.

_Habitat._--Central Pacific, Station 265, surface.


4. _Sphærozoum hexactinium_, n. sp.

Spicula all (or nearly all) hexaradiate, composed of six (or sometimes in
few spicula five or seven) needle-like shanks, mostly of equal size,
diverging from one common point in two opposite hemispheres (three needles
upwards, three needles downwards). Shanks somewhat curved, pointed,
{42}smooth. Central capsules spherical, small, with one central
oil-globule. This species may be regarded as the social form of
_Thalassoxanthium hexactinium_.

_Dimensions._--Diameter of the central capsule 0.06 to 0.08, length of the
spicula-shanks 0.05 to 0.06.

_Habitat._--North Atlantic, Færöe Channel (Gulf Stream), John Murray.



Subgenus 2. _Sphærozonoceras_, Haeckel.

_Definition._--Spicula all geminate-radiate, consisting of one middle rod,
which bears an equal and constant number of rays (two, three, or four) at
each end.


5. _Sphærozoum furcatum_, n. sp.

Spicula all (or nearly all) geminate and simply forked, composed of a
simple axial rod and two simple needle-like shanks on each end of it.
Shanks straight, pointed, smooth, commonly somewhat longer than the middle
rod.

_Dimensions._--Diameter of the central capsules 0.1 to 0.15, length of the
axial rod of the spicula 0.03, of its shanks 0.04 to 0.06.

_Habitat._--Tropical zone of the Atlantic, near Ascension Island, Station
344, surface.


6. _Sphærozoum furculosum_, n. sp.

Spicula all (or nearly all) geminate and simply forked, composed of a
simple axial rod and two simple needle-like shanks on each end of it.
Shanks curved or bent, pointed, thorny, with many small spinules, commonly
somewhat shorter than the middle rod.

_Dimensions._--Diameter of the central capsules 0.2 to 0.25, length of the
axial rod of the spicula 0.1, of its shanks 0.05 to 0.08.

_Habitat._--South Atlantic, near Tristan da Cunha, Station 334, surface.


7. _Sphærozoum ovodimare_, Haeckel.

  _Sphærozoum ovodimare_, Haeckel, 1862, Monogr. d. Radiol., p. 527, Taf.
  xxxiii. figs. 5, 6.

  _Sphærozoum punctatum_, var., Brandt, 1881, Monatsber. d. k. preuss.
  Akad. d. Wiss. Berlin, Taf. i. fig. 54.


Spicula all (or nearly all) geminate and triradiate, composed of a long
simple axial rod and three simple needle-like shanks on each end of it.
Shanks straight, pointed, smooth, commonly shorter than the middle rod.
(Often few furcate or four-rayed spicula are intermixed, or few spicula are
not smooth, but thorny.)

_Dimensions._--Diameter of the central capsules 0.05 to 0.2, length of the
middle rod of the spicula 0.02 to 0.06, of its shanks 0.01 to 0.04.

_Habitat._--Mediterranean, Naples, Messina, Haeckel; Atlantic, Canary
Islands, Cape Verde Islands, West Coast of Africa, Stations 351 to 354;
surface.


{43}8. _Sphærozoum trigeminum_, n. sp.

Spicula all (or nearly all) geminate-triradiate, composed of a short simple
axial middle rod and three simple needle-like shanks on each end of it.
Shanks curved or bent, very thin, smooth, commonly much longer than the
middle rod. (Often few quadriradiate or few thorny triradiate spicules are
interspersed among the others.)

_Dimensions._--Length of the middle rod of the spicula 0.02 to 0.04, of its
shanks 0.03 to 0.09.

_Habitat._--North Pacific, Stations 244 to 248, surface.


9. _Sphærozoum punctatum_, J. Müller.

  _Sphærozoum punctatum_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 54, Taf. viii. figs. 1, 2.

  _Sphærozoum punctatum_, Haeckel, 1862, Monogr. d. Radiol., p. 528, Taf.
  xxxiii. figs. 7-9.

  _Sphærozoum fuscum_, Meyen, 1834, Nova Acta Acad. Nat. Cur., vol. xvi.
  Taf. xxxviii. fig. 7.

  _Thalassicolla punctata_, Huxley, 1851, Ann. and Mag. Nat. Hist., ser. 2,
  vol. viii. p. 434, pl. xvi. figs. 1, 2, 3.

Spicula all (or nearly all) geminate-triradiate, composed of a long simple
axial middle rod and three simple needle-like shanks on each end of it.
Shanks straight, pointed, thorny, with many small spines, commonly somewhat
shorter than the middle rod. (Often few furcate or four-rayed spicula are
intermingled, or some of the spicula are smooth.) This cosmopolitan species
is extremely variable, and produces interesting transitional forms to many
other species of the genus. Compare also the general remarks on the genus,
and the chapter on "Transformation" in the general introduction.

_Dimensions._--Length of the middle rod of the spicula 0.02 to 0.06, of its
shanks 0.01 to 0.05.

_Habitat._--Cosmopolitan, common in nearly all warmer seas, Mediterranean,
Atlantic, Indian Ocean, Pacific; surface.


10. _Sphærozoum armatum_, n. sp. (Pl. 4, fig. 9).

Spicula all geminate-triradiate, with a stout and short middle rod and
three arborescent shanks on each end of it. Shanks longer than the middle
rod, very stout, straight, pine-shaped, with six to twelve irregular,
spinulated, lateral branches.

_Dimensions._--Diameter of the central capsules 0.04 to 0.08, length of the
middle rod of the spicula 0.02 to 0.03, of its shanks 0.05 to 0.08.

_Habitat._--North Pacific, Japan, Station 239, surface.


11. _Sphærozoum alveolatum_, n. sp. (Pl. 4, figs. 2, 3).

Spicula all together geminate-triradiate, with a simple stout middle rod
and three arborescent shanks on each end of it. Shanks more or less curved,
slender, pine-shaped, with four to eight short, thorny lateral branches. In
all coenobia of this remarkable species the central capsules are enclosed
in large thick-walled alveoles (of three times their breadth), and in each
alveole is placed besides {44}the capsule one single very large spiculum,
whilst the others are much smaller (fig. 3). All the alveolated capsules
are placed in one single stratum on the surface of the jelly-like spherical
coenobium, comparable to the blastoderm-cells of a blastula.

_Dimensions._--Diameter of the central capsules 0.08 to 0.1, of the
alveoles 0.2 to 0.4, length of the spicula 0.1 to 0.3.

_Habitat._--South Pacific (Juan Fernandez), Station 300, surface.


12. _Sphærozoum verticillatum_, n. sp. (Pl. 4, fig. 7).

Spicula all geminate-triradiate, with a short simple middle rod and three
much longer arborescent shanks on each end of it. Shanks straight, slender,
pine-shaped, each in the distal half with three to four elegant verticils
of thorny lateral branches.

_Dimensions._--Diameter of the capsules 0.1 to 0.12, middle rod of the
spicula 0.03 to 0.05, shanks 0.1 to 0.15.

_Habitat._--Indian Ocean, Ceylon, Haeckel; Madagascar, Rabbe; surface.


13. _Sphærozoum octoceras_, n. sp.

Spicula all geminate-quadriradiate, with a short simple middle rod and four
diverging shanks on each end of it. Shanks smooth, irregularly curved or
bent, three to six times as long as the middle rod. It may be regarded as
the social form of _Thalassoxanthium octoceras_ (Pl. 2, fig. 6).

_Dimensions._--Diameter of the capsules 0.12 to 0.16, middle rod of the
spicula 0.02, shanks 0.01.

_Habitat._--Australia, south coast, Faber; Station 163, surface.


14. _Sphærozoum quadrigeminum_, n. sp.

Spicula all geminate-quadriradiate, with a long thick middle rod and four
shorter diverging shanks on each end of it. Shanks straight, thorny.

_Dimensions._--Diameter of the capsules 0.06 to 0.08, length of the spicula
0.05 to 0.15.

_Habitat._--North Atlantic, Azores, Station 354, surface.


15. _Sphærozoum araucaria_, n. sp.

Spicula all geminate-quadriradiate, with stout straight middle rod and four
longer diverging shanks on each end of it. Shanks arborescent, with six to
twelve thorny lateral branches.

_Dimensions._--Diameter of the capsules 0.1 to 0.15, length of the spicula
0.05 to 0.1.

_Habitat._--South Atlantic, coast of Brazil, Rabbe; surface.


16. _Sphærozoum arborescens_, n. sp. (Pl. 4, fig. 8).

Spicula all geminate-quadriradiate, with a stout straight middle rod and
four longer diverging shanks on each end of it. Shanks arborescent,
pine-shaped, with four to six verticils of lateral branches, which again
are ramified and thorny.

{45}_Dimensions._--Diameter of the capsules 0.16 to 0.18, length of the
spicula 0.1 to 0.2.

_Habitat._--South Atlantic (Tristan da Cunha), Station 332, surface.



Subgenus 3. _Sphærozonura_, Haeckel.

_Definition._--Spicula all geminate-radiate, but with a different and
variable number of shanks on each end of the middle rod.


17. _Sphærozoum stellatum_, n. sp.

Spicula all geminate-radiate, with a strong middle rod and a variable
number of shorter radiating shanks on the two ends of it. Shanks straight,
nearly conical, smooth; for the most part three or four shanks on each end,
but sometimes also five or six; very often this number is unequal on the
two ends.

_Dimensions._--Diameter of the central capsules 0.1 to 0.2, length of the
spicula 0.05 to 0.15.

_Habitat._--Central Pacific, Station 270, surface.


18. _Sphærozoum geminatum_, n. sp. (Pl. 4, fig. 4).

Spicula all geminate-radiate, with a strong middle rod and a variable
number of longer radiant shanks on each end of it. Shanks straight,
conical, in the distal half thorny; commonly either three or four shanks on
each end of the middle rod, often also three on one end, four on the other
end; rarely five or six rays on one end.

_Dimensions._--Diameter of the capsules 0.15 to 0.2, length of the spicula
0.05 to 0.1.

_Habitat._--Indian Ocean, Ceylon, Haeckel; surface.


19. _Sphærozoum circumtextum_, n. sp.

Spicula all geminate-radiate, with a very variable number of rays (two to
six) on each end of the thin middle rod. All spicula very thin and
delicate, smooth, with curved or bent shanks, densely covering the central
capsule like a cobweb. The number of rays on each end is usually different,
generally four or five, often also two or three, rarely six.

_Dimensions._--Diameter of the capsule 0.1 to 0.2, length of the spicula
0.04 to 0.12.

_Habitat._--Southeast part of the Indian Ocean, Station 160, surface.


20. _Sphærozoum variabile_, n. sp. (Pl. 4, fig. 5).

Spicula all geminate-radiate, with a short middle rod and a variable number
of shanks on each end of it. Shanks four to eight times as long as the
middle rod, curved or bent, in the distal half thorny; their number is
commonly different on the two ends of it, three or five, often also four or
six, rarely two; their size and form very variable.

{46}_Dimensions._--Diameter of the capsules 0.1 to 0.3, length of the
spicula 0.1 to 0.2.

_Habitat._--North Pacific, Station 248, surface.



Genus 14. _Rhaphidozoum_,[24] Haeckel, 1862, Monogr. d. Radiol., p. 529.

_Definition._--Sphærozoida with two or more different kinds of spicula; one
kind simple, needle-shaped; the other kinds compound, radiate, or branched.

The genus _Rhaphidozoum_ differs from _Sphærozoum_ by the composition of
the skeleton of two or more different kinds of spicula, and has therefore
the same relation to it as the solitary _Lampoxanthura_ to
_Lampoxanthella_.

In some species nearly all the different forms, which characterise the
numerous species of #Beloidea#, may be united in one and the same
individual.



Subgenus 1. _Rhaphidonactis_, Haeckel.

_Definition._--Spicula of two different kinds; one kind simple,
needle-shaped, the other radiate (composed of three, four, or more shanks,
diverging from one common point).


1. _Rhaphidozoum pelagicum_, n. sp.

Spicula of two different kinds; one kind simple thin needles, a little
curved or bent, the other kind triradiate, with three thin, curved shanks.
Both kinds smooth, without thorns. Resembles a combination of _Belonozoum
italicum_ and _Sphærozoum triactinium_.

_Dimensions._--Diameter of the central capsules 0.1 to 0.12, length of the
spicula 0.05 to 0.15.

_Habitat._--Central Pacific, Station 267, surface.


2. _Rhaphidozoum pacificum_, n. sp.

Spicula of two different kinds; one kind simple needles, stout and
straight, pointed at both ends, the other kind triradiate, with three
straight and stout shanks. Both kinds thorny.

_Dimensions._--Diameter of the central capsule 0.06 to 0.08, length of the
spicula 0.05 to 0.1.

_Habitat._--Central Pacific, Station 271, surface.


3. _Rhaphidozoum acuferum_, Haeckel.

  _Rhaphidozoum acuferum_, Haeckel, 1862, Monogr. d. Radiol., p. 529, Taf.
  xxxii. figs. 9-11.

  _Sphærozoum acuferum_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 54, Taf. viii. fig. 3.

  _Thalassicolla acufera_, J. Müller, 1855, Monatsber. d. k. preuss. Akad.
  d. Wiss. Berlin, p. 237.

Spicula of two different kinds, simple needles and quadriradiate; both
strong, thorny, covered with small spinules. Simple needles mostly curved,
C-shaped. Four shanks of the quadriradiate {47}spicula now straight, now
curved, commonly of very different size. (Often one single quadriradiate
spiculum is distinguished by its extraordinary size.) For the detailed
description of this species compare my Monograph (_loc. cit._).

_Dimensions._--Diameter of the central capsules 0.05 to 0.35, length of the
simple needles 0.05 to 0.25, shanks of the quadriradiate spicula 0.05 to
0.15.

_Habitat._--Mediterranean, Messina, Naples, Nice.


4. _Rhaphidozoum arachnoides_, n. sp.

Spicula of two different kinds; one kind simple, needle-like, the other
quadriradiate; both very thin and slender, smooth, without spicules. Simple
needles curved, C-shaped. Four shanks of the quadriradiate spicula also
curved, commonly of nearly equal size. The numerous thread-like spicula of
this species are so densely packed around the central capsule, that they
extend all around its surface like the network round a balloon.

_Dimensions._--Diameter of the central capsules 0.12 to 0.15, length of the
simple needles 0.1 to 0.12, shanks of the quadriradiate spicula 0.06 to
0.08.

_Habitat._--Tropical Atlantic, Station 345, surface.


5. _Rhaphidozoum asperum_, n. sp.

Spicula of two different kinds; one kind simple, needle-shaped, stout, and
straight, the other kind hexaradiate; its six shanks about half as long as
the former, conical. Both kinds very thorny, covered with short conical
spinules.

_Dimensions._--Diameter of the capsules 0.06 to 0.08, length of the simple
needles 0.05 to 0.07, shanks of the hexaradiate spicula 0.03 to 0.04.

_Habitat._--South Pacific, Station 288, surface.



Subgenus 2. _Rhaphidoceras_, Haeckel.

_Definition._--Spicula of two different kinds; one kind simple,
needle-shaped, the other kind geminate-radiate, with rays on both poles of
a middle rod.


6. _Rhaphidozoum neapolitanum_, Haeckel.

  _Sphærozoum neapolitanum_, C. Brandt, 1881, Monatsber. d. k. preuss.
  Akad. d. Wiss. Berlin, p. 390, Taf. i. figs. 14, 16-18.

Spicula mixed, of two different kinds; simple needles and geminate-forked.
Simple rods, like those of _Belonozoum italicum_, more or less curved,
pointed at both ends, smooth (sometimes a little thorny at both ends).
Geminate spicula simply forked, like those of _Sphærozoum furcatum_,
composed of a short, simple, axial rod, and two simple, smooth, straight
shanks on each end of it, commonly somewhat longer than the middle rod.
This species, which I have observed myself in Spezzia in great quantity, is
quite as variable as all the other species of the genus, and has not more
claim to specific rights than the others. Commonly the simple needles are
much more numerous {48}than the geminate-forked, but sometimes the contrary
is the case. On their variability compare the general remarks on the genus,
and the chapter on "Transformation" in the general introduction.

_Dimensions._--Length of the simple spicula 0.05 to 0.1, of the middle rod
of the forked spicule 0.05 to 0.08, of their shanks 0.01 to 0.03.

_Habitat._--Mediterranean, Naples, Spezzia, surface.


7. _Rhaphidozoum patagonicum_, n. sp.

Spicula mixed, of two different kinds, simple needles and
geminate-triradiate. Simple rods, like those of _Belonozoum spinulosum_,
straight, thorny, pointed at both ends. Geminate spicula double-triradiate,
like those of _Sphærozoum punctatum_, composed of a simple, short, axial
rod and three simple pointed shanks on each end of it. Shanks straight,
thorny, with many small spinules, commonly somewhat longer than the middle
rod. (Often some of the spicula of both kinds are smooth, not thorny, or
not straight, but a little curved, or a few forked or four-radiated
geminate spicula are mingled with the others.)

_Dimensions._--Diameter of the central capsules 0.08 to 0.2, length of the
simple spicula 0.1 to 0.15, of the geminate 0.08 to 0.16.

_Habitat._--South Pacific, west coast of Patagonia, Station 302, surface.


8. _Rhaphidozoum ascensionis_, n. sp.

Spicula mixed, of two different kinds, simple needles and
geminate-triradiate; both kinds thin, smooth, without spinules. Simple
needles somewhat curved, C- or S-shaped. Geminate spicula
double-triradiate, composed of a simple, short, straight axial rod and
three slender curved shanks on each end of it. Shanks two to four times
longer than the middle rod. (Sometimes few simple hexaradiate and geminate
tetraradiate spicula are mingled.)

_Dimensions._--Diameter of the central capsules 0.12 to 0.15, length of the
simple spicula 0.1, of the double-triradiate 0.05 to 0.2.

_Habitat._--South Atlantic, off Ascension Island, Station 342, surface.


9. _Rhaphidozoum capense_, n. sp.

Spicula of two different kinds; one kind simple, needle-shaped, straight,
pointed at both ends, the other kind geminate-quadriradiate, with a stout
short middle rod and four longer bent shanks on each end of it. Both kinds
smooth.

_Dimensions._--Diameter of the capsules 0.2 to 0.25, length of the simple
needles 0.01 to 0.3, of the geminate spicula 0.05 to 0.15.

_Habitat._--Cape of Good Hope (Agulhas), Station 142, surface.


10. _Rhaphidozoum australe_, n. sp.

Spicula of two different kinds; one kind simple, needle-shaped, curved,
thin; the other kind geminate, with a variable number of shanks on both
ends of the shorter middle rod, often {49}different on the two poles of it.
The prevalent number of rays on each end is three or four, often also two
or five, rarely six. All spicula smooth, more or less bent.

_Dimensions._--Diameter of the capsules 0.1 to 0.2, length of the spicula
0.05 to 0.15.

_Habitat._--South West Pacific, Station 165, surface.



Subgenus 3. _Rhaphidonura_, Haeckel.

_Definition._--Spicula of three different kinds: one kind simple,
needle-shaped; the second kind radiate, with three to six shanks radiating
from a common central point; the third kind geminate-radiate, with rays on
both poles of a middle rod.


11. _Rhaphidozoum polymorphum_, n. sp.

Spicula of three different kinds; simple needles, radiate, and geminate
mixed. The simple needles straight and stout. The radiate spicula commonly
with three or six, rarely four or five, rays. The geminate-radiate spicula
prevalent, with three or four, rarely two or five, shanks on each end of
the middle rod. Number very variable. All shanks straight and smooth.

_Dimensions._--Diameter of the capsule 0.1 to 0.2, length of the spicula
0.05 to 0.15.

_Habitat._--South Pacific, Station 295, surface.


12. _Rhaphidozoum pandora_, n. sp. (Pl. 4, fig. 6).

Spicula of three different kinds; simple needles, radiate and geminate
mixed. The simple needles thin spindle-shaped, often curved. The radiate
spicula commonly with three or four, rarely five or six, curved rays. The
geminate-radiate spicula commonly with three or four, rarely two or five,
shanks on each end, often different on the two ends of the middle rod.
Number and form very variable. All or most of the shanks more or less bent
and thorny.

_Dimensions._--Diameter of the capsule 0.1 to 0.3, length of the spicula
0.05 to 0.2.

_Habitat._--South Atlantic (near Ascension Island), Station 343, surface.


----


Order II. SPHÆRELLARIA, Haeckel, 1881.

  _Sphærellaria_, Haeckel, 1881, Prodromus, p. 421.
  _Sphæridea_ vel _Peripylea_, Hertwig, 1879, Organismus der Radiol., p.
      133.

_Definition._--SPUMELLARIA with latticed or spongy shell.

The order #Sphærellaria#, the second order of Radiolaria, comprises all
those SPUMELLARIA in which the skeleton is a latticed or fenestrated, often
more or less spongy, siliceous shell. Originally this shell is a simple
extracapsular lattice-sphere, in which the central capsule is included;
from this simple ancestral form an enormous {50}mass of different and often
very complicated forms is derived; this order is by far the largest, and in
morphological respects the most important and most interesting, of all
Radiolaria. It contains not less than twenty-eight different families,
three hundred and five genera, and more than sixteen hundred species.

In my Monograph (1862) seven families appertaining to this group are
described--the Ethmosphærida, Cladococcida, Ommatida, Spongurida, Discida,
Lithelida, and Collosphærida. The astonishing increase of this group by the
detection of a large series of new and interesting forms, and particularly
of important connecting forms between very different branches of it, now
enables me to give a much better arrangement. I discern now four suborders
or sections of #Sphærellaria#, according to the different geometrical form
of the central capsule and of the latticed shell enveloping it. The first
of these, and the common ancestral group of the whole order, is the
#Sphæroidea#, with spherical capsule; in the #Prunoidea# it becomes
ellipsoidal or cylindrical by prolongation of one axis; in the #Discoidea#
lenticular or discoidal by shortening of one axis; in the #Larcoidea#
lentelliptical, or triaxon-ellipsoid, by different growth of the capsule in
three different "dimensive axes."

_Synopsis of the Four Suborders of_ #Sphærellaria#.

  Central capsule    { Shell a simple sphere or a
   spherical.        {  system of concentric spheres,  1. #Sphæroidea#.

  Central capsule    { Shell a simple ellipsoid or a
   ellipsoidal or    {  cylinder with annular
   cylindrical.      {  transverse constrictions,      2. #Prunoidea#.

  Central capsule
   lenticular or     { Shell a biconvex lens or a
   discoidal.        {  flat disk,                     3. #Discoidea#.

  Central capsule
   lentelliptical or { Shell a triaxon-ellipsoid, with
   triaxon.          {  three different axes,          4. #Larcoidea#.


----


Suborder I. SPHÆROIDEA, Haeckel.

  _Sphæroida_, _Sphæridea_, _Sphærida_, Haeckel, 1878, Protistenreich, p.
      103.
  _Sphæridea_, R. Hertwig, 1879, Organismus der Radiol., p. 39.

_Definition._--SPUMELLARIA with spherical central capsule (very rarely
somewhat modified, or allomorphous); with spherical fenestrated siliceous
shell (often an endospherical polyhedron, very rarely of more modified,
subspherical form or allomorphous). Growth of the shell in the three
dimensive axes equal.

The suborder #Sphæroidea#, the first and most important of the four of the
#Sphærellaria#, comprises those SPUMELLARIA in which the original
geometrical {51}spherical form is quite constantly preserved in the central
capsule, and commonly also in the fenestrated shell enveloping the latter,
although in many forms the sphere is more or less modified; very frequently
it is an "endospherical polyhedron," _i.e._, a polyhedron all the angles
(or the nodes of the network) of which lie upon the surface of a
geometrical sphere; more rarely the spherical form is more or less modified
and irregular. In the great majority of #Sphæroidea# there is no external
indication of the three dimensive axes; but in many forms they are
indicated by the regular position of certain external radial spines or
internal radial beams. However, in no case are those three axes expressed
in the form of the shell itself and of the enclosed spherical central
capsule; this is the main character by which the #Sphæroidea# differ from
the following sections:--#Prunoidea#, #Discoidea#, #Larcoidea#, all three
of which arise from them.

The section #Sphæroidea#, in the sense here restricted, was founded by me
in my Protistenreich (1878, p. 103) and adopted by Hertwig (1879) in his
Organismus der Radiolarien (p. 39). The different groups appertaining to
this large section were characterised more accurately in my Prodromus
(1881, pp. 448-456); there I gave the characters of six subfamilies with
thirty tribes, containing ninety-three genera. Formerly, in my Monograph
(1862), the #Sphæroidea# were disposed in five different
families:--Ethmosphærida, Cladococcida, Ommatida, Spongosphærida,
Collosphærida. At that time I could not separate them sufficiently from
some ACANTHARIA and PHÆODARIA, which have a similar spherical
lattice-shell.

As the number of different genera and species in the #Sphæroidea# is much
greater than in all other sections of SPUMELLARIA, many forms were already
described by former authors. In the oldest system of Ehrenberg (1847, _loc.
cit._, p. 53) they represent one part of his Haliommatina (with four
genera, _Haliomma_, _Chilomma_, _Stylosphæra_, _Spongosphæra_). Most
species, however, of these genera are #Discoidea#. Also in the latest
system of Ehrenberg (1875, _loc. cit._, p. 157) his Haliommatina are a
confused conglomeration of different SPUMELLARIA (#Sphæroidea#,
#Discoidea#, and #Prunoidea#).

The section #Sphæroidea# is the largest division of #Sphærellaria#,
comprising not less than one hundred and seven genera and six hundred and
fifty species. This enormous number (easily to be augmented by further
investigations) requires a careful disposition in different families and
subfamilies. For this disposition two different principles only can be
employed: firstly, the number and disposition of the _radial spines_;
secondly, the number of the _concentric latticed spheres_, which are
connected by radial beams. I give here the preference to the first
principle, whilst in my Prodromus (1881) I had preferred the second. The
question, which of the two principles is more important for the
classification of #Sphæroidea#, is very difficult to answer; probably in
many cases the former, in many the latter is more important for their
phylogeny.

{52}Regarding the number of the concentric shells which compose the
latticed carapace of the #Sphæroidea#, we can distinguish six families,
viz.:--

     I. Monosphærida (with one single shell).
    II. Dyosphærida (with two concentric shells).
   III. Triosphærida (with three concentric shells).
    IV. Tetrasphærida (with four concentric shells).
     V. Polysphærida (with five or more concentric shells).
    VI. Spongosphærida (with spongy shells).

On the other hand, regarding the number of the radial spines and their
regular disposition on the shell-surface, we can distinguish five families,
viz.:--

     I. Liosphærida (without radial spines).
    II. Stylosphærida (with two radial spines, opposite in one axis).
   III. Staurosphærida (with four radial spines, opposite in pairs in two
      axes, perpendicular one to another).
    IV. Cubosphærida (with six radial spines, opposite in pairs in the
      three dimensive axes).
     V. Astrosphærida (with numerous--eight, twelve, twenty, or
      more--radial spines, often more than a hundred).

All five latter groups contain representatives of all six former groups;
therefore we get together not less than thirty different subfamilies of
#Sphæroidea#, already enumerated in my Prodromus, 1881, p. 449. I repeat
them here to give a better survey of the system there employed.

  +------------------+----------------+---------------+---------------+
  |  Families and    |  LIOSPHÆRIDA   |STYLOSPHÆRIDA  |STAUROSPHÆRIDA |
  | Subfamilies of   |  (anacantha).  | (diacantha).  |(tetracantha). |
  |   SPHÆROIDEA.    |                |               |               |
  +------------------+----------------+---------------+---------------+
  | _Monosphærida._  |Ethmosphærida.  |Xiphostylida.  |Staurostylida. |
  |   (One single    |                |               |               |
  |      shell.)     |                |               |               |
  |                  |                |               |               |
  |  _Dyosphærida._  |Carposphærida.  |Sphærostylida. |Staurolonchida.|
  | (Two concentric  |                |               |               |
  |     shells.)     |                |               |               |
  |                  |                |               |               |
  | _Triosphærida._  |Thecosphærida.  |Amphistylida.  |Stauracontida. |
  |(Three concentric |                |               |               |
  |     shells.)     |                |               |               |
  |                  |                |               |               |
  |_Tetrasphærida._  |Cromyosphærida. |Cromyostylida. |Staurocromyida.|
  |(Four concentric  |                |               |               |
  |     shells.)     |                |               |               |
  |                  |                |               |               |
  | _Polysphærida._  |Caryosphærida.  |Caryostylida.  |Staurocaryida. |
  |  (Five or more   |                |               |               |
  |    concentric    |                |               |               |
  |     shells.)     |                |               |               |
  |                  |                |               |               |
  |_Spongosphærida._ |Plegmosphærida. |Spongostylida. |Staurodorida.  |
  |(Spongy shells.)  |                |               |               |
  +------------------+----------------+---------------+---------------+

  +------------------+-------------+---------------+
  |  Families and    |CUBOSPHÆRIDA |ASTROSPHÆRIDA  |
  | Subfamilies of   |(hexacantha).|(polyacantha). |
  |   SPHÆROIDEA.    |             |               |
  +------------------+-------------+---------------+
  | _Monosphærida._  |Hexastylida. |Coscinommida.  |
  |   (One single    |             |               |
  |      shell.)     |             |               |
  |                  |             |               |
  |  _Dyosphærida._  |Hexalonchida.|Haliommida.    |
  | (Two concentric  |             |               |
  |     shells.)     |             |               |
  |                  |             |               |
  | _Triosphærida._  |Hexacontida. |Actinommida.   |
  |(Three concentric |             |               |
  |     shells.)     |             |               |
  |                  |             |               |
  |_Tetrasphærida._  |Hexacromyida.|Cromyommida.   |
  |(Four concentric  |             |               |
  |     shells.)     |             |               |
  |                  |             |               |
  | _Polysphærida._  |Hexacaryida. |Arachnommida.  |
  |  (Five or more   |             |               |
  |    concentric    |             |               |
  |     shells.)     |             |               |
  |                  |             |               |
  |_Spongosphærida._ |Hexadorida.  |Spongiommida.  |
  |(Spongy shells.)  |             |               |
  +------------------+-------------+---------------+

{53}The #Monosphærida# comprise all those #Sphæroidea# in which the
carapace is represented only by one single lattice-shell. Originally this
shell is probably everywhere an extracapsular or "cortical shell," which is
developed on the outside of the jelly-veil enveloping the central capsule,
and serves as a protective carapace for these soft enclosed parts. But with
the progress of growth the central capsule becomes larger than the
including shell, and sends out through its pores club-shaped prolongations
or cæcal-sacs (Pl. 11, figs. 1, 5; Pl. 19, figs. 2, 3, 5; Pl. 20, fig.
1_a_; Pl. 27, fig. 3). These protruded sacs may fuse together again outside
the shell and form a spherical bladder, now enveloping the smaller shell;
the latter now becomes an intracapsular or "medullary shell."

As #Pliosphærida# (or _Sphæroidea concentrica_) we can oppose to the simple
Monosphærida all other #Sphæroidea#, the lattice-shell of which is composed
of two or more concentric shells, connected by radial beams. Probably all
Pliosphærida (or at least the greater part of them) arise from the
Monosphærida by centrifugal growth; two or more radial spines are developed
from the surface of the simple lattice-sphere, and are united together by
communicating lateral branches, developed at equal distances from the
centre; and this same process may be repeated, two, three, four, or more
times. In this way originate the characteristic systems of concentric
spheres, all united by piercing radial beams which arise from the surface
of the innermost sphere (not from its centre). Regarding this mode of
growth, we can distinguish the innermost as "original" or "primary" shell,
and all subsequent ones as "apposed" or "secondary" shells; if the number
of concentric shells amount to three or more, commonly both innermost
shells lie within the central capsule and are medullary shells, whilst all
others lie outside it and are therefore cortical shells. This difference
can be commonly recognised also in the isolated shell, without its central
capsule; the distance between the cortical and the medullary shells being
commonly much larger than the distance between the two medullary shells.

The #Dyosphærida#, or the #Sphæroidea# with two concentric shells, are the
most numerous among the Pliosphærida. Commonly in this group the inner or
primary shell lies within the central capsule as a true "medullary shell,"
whilst the outer lies outside it as a "cortical shell"; therefore the
radial beams, connecting both, pierce the wall of the capsule. But in
several forms, mainly in the peculiar group of Diplosphærida, both
concentric shells remain outside the central capsule, and both are
therefore "cortical shells."

The #Triosphærida#, or the #Sphæroidea# with three concentric shells, are
also very rich in different forms, though not so numerous by far as the
Dyosphærida. Commonly in the Triosphærida both inner shells lie within the
central capsule as "medullary shells," whilst the third lies outside it as
a "cortical shell"; therefore the central capsule remains intermediate in
size between the outer and the middle shell. But in some genera (_e.g._,
_Rhodosphæra_) both outer shells are cortical and only the {54}innermost is
a medullary shell. In this case the size of the capsule remains
intermediate between the inner and the middle shell.

The #Tetrasphærida#, or the #Sphæroidea# with four concentric shells, are
in general not frequent, and not rich in different forms. In most of the
observed species two inner shells are medullary, two outer cortical shells,
the former within, the latter without, the central capsule; and the wall of
the capsule, pierced by the connecting radial beams, lies between the two
middle shells. But there are some Tetrasphærida in which all four shells
seem to be external or cortical shells.

The #Polysphærida#, or the #Sphæroidea# with five or more concentric
shells, seem of course to offer the greatest possibility for the
development of very different forms; but in reality this group is the
poorest and smallest of all; and only one part of it, the Arachnosphærida,
is rather common. In this peculiar division the shell is composed of five
to ten or more, very delicate, cobweb-like concentric shells, which are
connected by radial beams; all are cortical shells, and lie outside the
central capsule. Much more rare are those Polysphærida, in which both
innermost shells, as true medullary shells, lie within the central capsule,
all others being outside it. The total number of concentric shells in this
group is commonly between five and ten, rarely more.

The #Spongosphærida# are distinguished from all other #Sphæroidea# by the
spongy structure of the spherical shell, which is composed wholly or
partially of an irregular spongy framework. The relation of this group to
the other groups of #Sphæroidea# is probably rather complicated, for in
some Spongosphærida the whole shell is composed of massive spongy
reticulation, whilst in others it contains a spherical central cavity, and
in a third group this cavity is filled up by one or two concentric
lattice-shells, connected by radial beams. Many of these Spongosphærida are
very common, and of considerable size.

The #Collosphærida# form a peculiar separate group of #Sphæroidea#,
distinguished from all others by their social life or aggregation in
colonies (coenobia). They represent the only group of #Sphærellaria# in
which this association of numerous individual capsules or cells is
realised. The shell is almost constantly simple, without regularly disposed
radial spines; therefore they may be called "social Monosphærida," or
better "polyzoic Ethmosphærida." Only in one small group (Clathrosphærida)
the shell, enveloping every central capsule, is double or surrounded by an
external mantle; these may be compared to the Diplosphærida (or better to a
part of the Carposphærida, _Liosphæra_, p. 76). In most of the
Collosphærida the lattice-shell is more or less irregular in form and
structure.


_The Lattice Work_ of the fenestrated shells is in the #Sphæroidea# of the
greatest variability, and its innumerable modifications serve mainly for
the distinction of species. In general we can distinguish as the most
important modifications a _regular_ network (with equal size, form, and
distance of the pores or meshes) and an _irregular_ network (with
{55}differences in the size, form, or distance of the meshes or pores). In
both groups the pores may be either angular or round; so that there may
exist together four different main forms of network--(A) regular lattice
with equal hexagonal pores; (B) regular lattice with equal circular pores;
(C) irregular lattice with unequal polygonal pores; (D) irregular lattice
with unequal roundish pores. Besides these modifications, the pores may be
prolonged into tubules which are directed radially towards the outside
(rarely towards the inside) of the sphere. In other cases they are
surrounded by elevated or honeycomb-like frames.

_The Radial Spines_ exhibit in the #Sphæroidea# the greatest variety in
form, size, disposition, &c., and their numerous modifications serve mainly
for the distinction of genera, their peculiar formation and size also for
the distinction of species. In general we may distinguish as the most
important modifications primary and secondary spines. The primary spines or
"main spines" are commonly direct outward prolongations of the internal
radial beams, connecting the concentric shells. The secondary or
"by-spines" arise only from the surface of the lattice-shell, without
reference to the internal beams. The by-spines are commonly smaller, and
much more numerous than the main spines. Regarding the form, the radial
spines are either roundish (cylindrical or conical, often also club-shaped,
rarely spindle-shaped) or angular (commonly three-sided, prismatic or
pyramidal). The spines are constantly solid, never hollow; the "internal
canals," described by some authors, are only microscopic views of the
transparent edges. In many cases the spines are branched or forked. The
most important difference in the variable shape of the spines is their
regular or irregular number and disposition, which afford characters for
the distinction of our five families.

_The Three Dimensive Axes_--or the three diameters of the sphere,
perpendicular one to another--are in the great majority of the #Sphæroidea#
significant in the promorphological consideration of the body, and are
indicated either by the position of the external radial spines, or at least
of the internal radial beams, connecting the concentric spheres. Commonly
two radial spines are placed opposite in each axis. The most perfect group
in this respect seems to be that of the Cubosphærida, in which the three
axes are represented by three pairs of spines. Next come the
Staurosphærida, in which two axes in cross-form are exhibited by two pairs
of spines. The most simple group are the Stylosphærida, in which only one
pair of spines is developed, indicating one single axis. These three
families form together a continuous natural series,--the #Sphæroidea# with
real dimensive axes,--and exhibit at the same time relations to the three
other suborders of #Sphærellaria#, the #Larcoidea#, #Discoidea#, and
#Prunoidea# respectively. At both ends of this series stand two other
families, on one side the Liosphærida, without any radial spines on the
surface of the sphere, on the other side the Astrosphærida, in which the
radial spines are developed in great and variable numbers, at least eight
to twelve, commonly twenty to forty, often more than a hundred or even a
thousand.

{56}The #Liosphærida# comprise all those #Sphæroidea# in which the surface
of the shell is smooth, without radial spines (Pls. 12, 20). The simplest
of these are the Ethmosphærida, with one single lattice-shell, enveloping
the spherical central capsule. _Cenosphæra_, the most simple form of the
Ethmosphærida, may be regarded as the common ancestral form of all
#Sphæroidea#, in an ontogenetical as well as in a phylogenetical and
morphological sense. From this simple lattice sphere all other #Sphæroidea#
can be derived either by radial or by tangential growth. If the radial
beams, arising from the surface of the simple fenestrated sphere, become
connected (at equal distances from the centre) by tangential beams, we get
the compound shells of the "Liosphærida concentrica" (with two, three,
four, or more concentric spheres). The radial beams connecting these
exhibit in many Liosphærida the same regular disposition and number as the
external radial spines in the Astrosphærida. Perhaps these forms in a
"natural system" would be better united (_e.g._, Liosphærida with twelve or
twenty internal radial beams, and Astrosphærida with twelve or twenty
external radial spines); but in many cases (mainly for higher numbers) the
certain determination of their number and disposition is very difficult or
quite impossible.

The #Cubosphærida# (Pls. 21-25) represent the large and very important
family of #Sphæroidea#, in which all three dimensive axes are equally
distinguished by pairs of spines, corresponding to three axes of a cube or
of a regular octahedron, agreeing therefore also with the three axes of the
cubic or regular crystalline system. In the majority of the Cubosphærida
the six radial spines are accurately opposite each other in pairs in three
axes, perpendicular one to another, and commonly they are of equal size and
form; but in some genera the three pairs of spines become differentiated,
whilst both spines of each pair remain equal. Either one pair is larger
than the two others (which are equal), corresponding to the axes of the
quadratic crystalline system; or all three pairs are different
(corresponding to the three unequal axes of the rhombic crystalline
system); the former nearer to the #Discoidea#, the latter to the
#Larcoidea#. We may suppose with some probability, that the Cubosphærida
are for the most part the common ancestral group of those #Sphæroidea#, in
which a certain number of radial spines or beams is disposed in a regular
order; the Staurosphærida may be derived from them by loss of one pair of
spines, the Stylosphærida by loss of two pairs of spines, and most
Astrosphærida by multiplying the radial spines, six to fourteen or more
secondary spines being added to the six primary "dimensive spines."
However, in many Astrosphærida (_e.g._, in those with eight spines,
_Centrocubus_, _Octodendron_, &c.) the regular geometrical disposition of
the radial spines seems to follow another mathematical order, quite
independent of the Cubosphærida.

The #Staurosphærida# (Pl. 15) are distinguished by the possession of four
radial spines, opposite in pairs in two axes, perpendicular one to another.
This rectangular cross determines a certain plane, the "equatorial plane,"
and this brings the Staurosphærida near {57}to the #Discoidea#, mainly to
those which also bear on the periphery of the circular equatorial plane
four crossed spines (such as _Staurodisculus_, _Stethostaurus_,
_Staurodictya_, &c.). But in these cruciform #Discoidea# the shell and the
enclosed central capsule are discoidal or lenticular, whilst in the
Staurosphærida they remain spherical. Commonly the cross is quite regular,
with four right angles and four equal beams; but often also it becomes more
or less irregular. In some genera one pair of equal opposite spines is
larger than the other pair. These forms represent the three different axes
of the rhombic crystal system, whilst the common regular Staurosphærida
represent those of the quadratic crystal system. The latter can be derived
from the Cubosphærida (representing the regular crystal system) by
reduction of one axis and loss of its pair of spines. In general the number
of species (and particularly of the individuals) is much smaller in the
Staurosphærida than in all other families of #Sphæroidea#.

The #Stylosphærida# (Pls. 13-17) can be derived from the Cubosphærida by
reduction of two dimensive axes and loss of two pairs of spines. Therefore,
here one pair of spines only is developed, opposite in one single axis.
This "monaxonial" form brings the Stylosphærida very near to the
ellipsoidal #Prunoidea# (mainly to many two-spined forms of Ellipsida and
Druppulida); but they differ from these by the spherical (not ellipsoidal)
form of the central capsule and of the enclosing lattice-shell. In the
greater part of the Stylosphærida both spines are of equal size and form,
accurately opposite in the "main axis." But in many forms both spines
become unequal in size or form, often very different. More rarely they are
not accurately opposed, but placed in two different axes, intersecting at a
small variable angle. The small group of Saturnalida presents a very
remarkable and peculiar structure, in which both spines (at equal distances
from the centre) are united by a circular or elliptical ring (Pl. 13, figs.
15, 16; Pl. 16, figs. 16, 17).

The #Astrosphærida# are distinguished from the other #Sphæroidea# by the
great and variable number of their external radial spines (Pls. 11, 18-20,
26-30). Commonly this number amounts to from twelve to twenty, rarely to
only eight to ten, very often to thirty-two to forty or more; in many
species more than one hundred are present. As already mentioned above, it
would be important to distinguish between primary spines (as outer
prolongations of the inner radial beams) and secondary spines (developed
from the surface of the shell), but in many cases this distinction is
difficult or impossible. More practical is the distinction between larger
"main spines" and smaller "by-spines." The size and form of the radial
spines is extremely variable. Much more important is their number and
disposition. In general we can here distinguish the following different
cases:--(A) radial spines are developed from all the nodal points of the
network on the shell surface; (B) the number of the spines is smaller than
that of the nodal points, but they are irregularly scattered; (C) the
radial spines exhibit a limited number and a certain regular disposition.
In this latter case the following modes of distribution seem to be the most
important:--(_a_) eight spines placed in the four diagonal axes of the
{58}regular cube (Pl. 18, figs. 1-3); (_b_) twelve spines (placed in the
corner axes of the regular icosahedron); (_c_) fourteen spines (six placed
in the three dimensive axes of the regular octahedron, eight in the centres
of its eight faces); (_d_) twenty spines (placed either in the same order
as in many #Larcoidea# and ACANTHARIA [?], or in the twenty corners of the
regular dodecahedron); (_e_) thirty-two spines (twelve placed in the twelve
corners of the regular icosahedron, twenty in the centre of its triangular
faces). Besides these most important and quite geometrical modes of
disposition there also seem to occur in the Astrosphærida the following
subregular (or symmetrical?) modes: 9, 10, 16, 18, 24, 40, 60, 80. But it
is very difficult to give a correct account of these modes. In every case
this manifold and regular disposition of the radial spines is of the
highest interest for the study of general "Promorphology."


_The Central Capsule_ is in all #Sphæroidea# (without any exception) a
perfect sphere in the geometrical sense, even in those forms in which the
enclosing lattice-shell is more or less irregular (_i.e._, many
Collosphærida). This is the most important character, which separates the
#Sphæroidea# from all other #Sphærellaria#. For in the #Prunoidea# the
capsule is ellipsoidal, with one prolonged axis; in the #Discoidea#
lenticular, with one shortened axis; in the #Larcoidea# lentelliptical,
with three different dimensive axes. The central capsule is originally
always enclosed by the lattice-shell; but in many cases with increasing
growth this relation becomes inverted; the capsule sending out many
club-shaped blind sacs through the meshes of the lattice-shell, and these
melting together outside the latter, a new membrane is formed, enclosing a
"medullary shell."

_The Nucleus_ of the cell exhibits a very different shape in the solitary
and the social #Sphæroidea#. In the solitary or monozoic #Sphæroidea# the
centre of the central capsule is occupied by a large spherical concentric
nucleus, with or without nucleoli; also this nucleus is originally always
within the innermost lattice-shell, but with increasing size may overgrow
and enclose it. A short time before the formation of the vibratile spores
the central nucleus becomes resolved into many small nuclei. In the social
or polyzoic #Sphæroidea#--the Collosphærida--commonly the simple central
nucleus very early (a long time before the formation of the spores) is
divided into a great number of small nuclei, whilst the centre of the
capsule becomes filled with a large oil-globule. Therefore we find the same
difference between the solitary and social forms in the #Sphæroidea# as in
the #Colloidea#. Here also the calymma, or the jelly-mantle, enveloping the
central capsule, is in the social forms very large and voluminous,
differentiated into alveoles, whilst in the solitary forms it is much
smaller, without alveoles.

{59}_Synopsis of the Families of_ #Sphæroidea#.

                 { A. Liosphærida     { Spherical shell
                 {  monozoa.          {  commonly
                 {  Single cells      {  quite regular,
                 {  (each with shell) {  simple, or
  Surface of     {  living solitary.  {  composed of
   the spherical {                    {  two or more
   shell smooth, {                    {  concentric
   rough, or     {                    {  spheres,       5. LIOSPHÆRIDA.
   thorny, but   {
   not armed     { B. Liosphærida     { Spherical shell
   with radial   {  polyzoa.          {  commonly
   spines.       {  Aggregated cells  {  more or less
                 {  (each with        {  irregular,
                 {  shell) living     {  simple (rarely
                 {  in colonies.      {  composed of
                 {                    {  two concentric
                 {                    {  spheres),      6. COLLOSPHÆRIDA.

  Surface of     { Two radial main-spines, opposite in
   the spherical {  one axis of the shell               7. STYLOSPHÆRIDA.
   shell armed   {
   with two,     { Four radial main-spines, opposite in
   four, or six  {  pairs in two dimensive axes,
   radial main   {  perpendicular one to another,       8. STAUROSPHÆRIDA.
   spines,       {
   opposite in   { Six radial main-spines, opposite in
   pairs in one, {  pairs in three dimensive
   two, or three {  axes (perpendicular one to
   dimensive     {  another),                           9. CUBOSPHÆRIDA.
   axes (always  {
   solitary).    {

  Surface of the spherical shell covered with numerous
   (commonly irregularly disposed) radial spines,
   often also twelve to twenty, more or less regularly
   disposed,                                           10. ASTROSPHÆRIDA.



Family V. #LIOSPHÆRIDA#, Haeckel, 1881.

_Liosphærida_, Haeckel, 1881, Prodromus, p. 449.

_Definition._--#Sphæroidea# without radial spines on the surface of the
spherical shell; living solitary (not associated in colonies).

The family #Liosphærida# comprises all those solitary #Sphæroidea# in which
the surface of the spherical shell is not armed with radial spines. Nearly
the half of this large group is formed by the Ethmosphærida, in which the
carapace is a quite simple, spherical lattice-shell; this subfamily is
probably the common ancestral group from which all other #Sphæroidea#, or
even all #Sphærellaria#, can be derived in a phylogenetical as well as in a
morphological sense. The central capsule in this first subfamily is
constantly enclosed by the fenestrated shell, and separated from it by the
jelly-veil. The shell is therefore an extracapsular or medullary shell.

To these simple Ethmosphærida all other subfamilies can be opposed as
"Liosphærida concentrica," as their carapace is composed of two or more
concentric lattice-shells; two in the Carposphærida, three in the
Thecosphærida, four in the Cromyosphærida, five or more in the
Caryosphærida. In all these four subfamilies the concentric shells are
simple (not spongy) fenestrated shells. In a sixth subfamily, in the
Plegmosphærida, the shell is wholly or partially composed of spongy
wicker-work, with or without a latticed medullary shell in the centre.

The internal radial beams, in the "Liosphærida composita" connecting the
concentric spheres, exhibit in their number and disposition similar
important differences, such as the external radial spines in the
Astrosphærida. The following eight {60}different cases of regular
disposition were observed:--(A) two opposite beams in one axis; (B) four
beams, opposite in pairs in two axes perpendicular one to another; (C) six
beams, opposite in pairs in the three dimensive axes; (D) eight beams,
opposite in pairs in the four diagonals of the regular cube; (E) twelve
beams corresponding to the twelve axes of the regular icosahedron; (F)
fourteen beams quite regularly disposed (six corresponding to the three
axes of the regular octahedron, eight to the central points of its faces);
(G) twenty beams (probably corresponding to the twenty corners of a regular
dodecahedron); (H) thirty-two beams, regularly disposed. Rarely the number
of the radial beams is intermediate between these eight cases, and rarely
it is higher; then commonly the disposition is irregular. The regularity of
their disposition in the great majority of cases is very remarkable and
evident.

_Synopsis of the Genera of Liosphærida._

  -------------------------------------------------------------------------
  I. Subfamily Ethmosphærida.
     (Shell one single latticed sphere.)
  -------------------------------------------------------------------------
                     {Shell cavity
                     { simple,          15. _Cenosphæra_.
  Pores of the       {
   shell  simple,    {Shell cavity
   not prolonged     { with radial
   into free tubuli. { beams united
                     { in the
                     { centre,          16. _Stigmosphæra_.

  Pores prolonged    {Tubuli external,
   into free         { centrifugal,     17. _Ethmosphæra_.
   conical or        {
   cylindrical       {Tubuli internal,
   tubuli.           { centripetal,     18. _Sethosphæra_.
  -------------------------------------------------------------------------
  II. Subfamily Carposphærida.
      (Two concentric spheres.)
  -------------------------------------------------------------------------
  One shell medullary (intracapsular),
   the other cortical (extracapsular),  19. _Carposphæra_.

  Both shells cortical
   (near together),                     20. _Liosphæra_.
  -------------------------------------------------------------------------
  III. Subfamily Thecosphærida.
       (Three concentric spheres.)
  -------------------------------------------------------------------------
  Two shells medullary
   (intracapsular), one shell
   cortical (extracapsular),            21. _Thecosphæra_.

  One shell medullary (intracapsular),
   two shells cortical
  (extracapsular),                      22. _Rhodosphæra_.
  -------------------------------------------------------------------------
  IV. Subfamily Cromyosphærida.
      (Four concentric spheres.)
  -------------------------------------------------------------------------
  Two inner medullary shells
   (intracapsular), and two outer
   cortical shells (extracapsular),     23. _Cromyosphæra_.
  -------------------------------------------------------------------------
  V. Subfamily Caryosphærida.
     (Five or more concentric spheres.)
  -------------------------------------------------------------------------
  Two inner medullary shells, and
   three  or more outer cortical
   shells,                              24. _Caryosphæra_.
  -------------------------------------------------------------------------
  VI. Subfamily Plegmosphærida.
      (Spherical shell wholly or partially of spongy structure.)
  -------------------------------------------------------------------------
  Spongy sphere      {Sphere solid,     25. _Styptosphæra_.
   without latticed  {
   medullary shell   {Sphere with a
   in the centre.    { central cavity,  26. _Plegmosphæra_.

  Spongy sphere with {One single
   one or two        { medullary shell, 27. _Spongoplegma_.
   latticed          {
   medullary shells  {Two concentric
   in the centre.    { medullary
                     { shells,          28. _Spongodictyon_.



{61}Subfamily ETHMOSPHÆRIDA,[25] Haeckel, 1862, Monogr. d. Radiol., p. 348
(_sensu restricto_).

_Definition._--#Liosphærida# with one single spherical lattice-shell;
living solitary, not aggregated in colonies.


Genus 15. _Cenosphæra_,[26] Ehrenberg, 1854, Monatsber. d. k. preuss. Akad.
d. Wiss. Berlin, p. 237.

_Definition._--#Liosphærida# with one single latticed sphere, with simple
shell-pores (not prolonged into free tubuli) and with simple shell-cavity
(without internal radial beams).

The genus _Cenosphæra_ is the most simple form of all SPHÆROIDEA, and may
be regarded as the common ancestral form of this order. The siliceous
latticed shell, in which the central capsule is enclosed, represents a
simple regular sphere, with simple cavity. The pores of the shell-wall are
simple, not prolonged into radial tubuli (as in _Ethmosphæra_ and
_Sethosphæra_). According to the different form of the pores, the numerous
species of this genus can be disposed in four different subgenera. Some
species may be easily confounded with isolated shells of the corresponding
social _Collosphæra_; but in this latter the spherical shell-form is
commonly more or less irregular, in _Cenosphæra_ quite regular.



Subgenus 1. _Phormosphæra_, Haeckel, 1881, Prodromus, p. 448.

_Definition._--Pores of the shell regular or subregular, hexagonal or
circular, with hexagonal frames or lobes; all nearly of equal size and
form.


1. _Cenosphæra primordialis_, n. sp.

Shell very thin walled, smooth. Pores hexagonal, regular, or subregular;
twelve to fifteen on the half meridian of the shell; bars between them
extremely delicate (only visible when three hundred or four hundred times
enlarged). Diameter of the shell nine to ten times that of the meshes. This
species is remarkable for the extreme delicacy of the arachnoidal network
of the simple spherical shell; it may be regarded as the common ancestral
form of all #Sphæroidea#. The shell equals that of _Heliosphæra tenuissima_
(figured in my Monograph, 1862, pl. ix. fig. 2), but differs from it by the
smooth surface and the absence of all spines or thorns. I observed this
species living in the Indian Ocean, near Ceylon, in 1882; the spherical
diameter of the central capsule is about one-third of that of the shell;
the contents of the central capsule are colourless {62}and transparent,
except the central dark globular nucleus. The same shells also occur in
some mounted preparations of surface organisms from the Challenger.

_Dimensions._--Diameter of the shell 0.12, of the pores 0.012.

_Habitat._--Indian Ocean, Ceylon, Haeckel; Central Pacific, Stations 266,
271, surface.


2. _Cenosphæra inermis_, Haeckel.

  _Heliosphæra inermis_, Haeckel, 1862, Monogr. d. Radiol., p. 351, Taf.
  ix. fig. 1.

Surface of the thin-walled shell smooth. Pores regular, hexagonal, twelve
to fifteen times as broad as the bars, seven to nine on the quadrant.

_Dimensions._--Diameter of the shell 0.08 to 0.12, pores 0.012 to 0.015,
bars 0.001.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific,
surface.


3. _Cenosphæra hexagonalis_, n. sp.

Surface of the thick-walled shell smooth. Pores regular, hexagonal, five to
six times as broad as the bars, six to eight on the quadrant.

_Dimensions._--Diameter of the shell 0.1 to 0.15, pores 0.01 to 0.012, bars
0.002.

_Habitat._--Central Pacific, Stations 265 to 274, at various depths.


4. _Cenosphæra mellifica_, n. sp. (Pl. 12, fig. 9).

Surface of the thick-walled shell smooth. Pores regular, circular, with
thin hexagonal frames, four times as broad as the bars, six to eight on the
quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.12, bars 0.003.

_Habitat._--South Pacific, Station 288, surface.


5. _Cenosphæra favosa_, n. sp. (Pl. 12, fig. 10).

Surface of the thick-walled shell rough. Pores regular, circular, with thin
hexagonal frames, three times as broad as the bars, ten to twelve on the
quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.09, bars 0.003.

_Habitat._--North Atlantic, Færöe Channel (Gulf Stream), John Murray,
surface.


6. _Cenosphæra vesparia_, n. sp. (Pl. 12, fig. 11).

Surface of the thick-walled shell smooth.  Pores regular, circular, with
thick hexagonal frames, twice as broad as the bars, ten to twelve on the
quadrant.

_Dimensions._--Diameter of the shell 0.25, pores 0.016, bars 0.008.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms, and surface.


{63}7. _Cenosphæra bombus_, n. sp.

Shell thick walled, rough. Pores regular, circular, with thin hexagonal
frames, of the same breadth as the bars, twenty to twenty-two on the
quadrant.

_Dimensions._--Diameter of the shell 0.3, pores and bars 0.005.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.


8. _Cenosphæra melecta_, n. sp.

Shell thick walled, papillate. Pores regular, circular, double-edged, with
thick hexagonal frames, of the same breadth as the bars; a short conical
papilla in the corner of each hexagon; fourteen to sixteen pores on the
quadrant.

_Dimensions._--Diameter of the shell 0.2, pores and bars 0.008.

_Habitat._--Fossil in Barbados.


9. _Cenosphæra anthophora_, n. sp.

Shell thick walled, papillate. Pores regular, circular, with an elegant
six-lobed frame and a coronal of six short papillæ; the latter alternating
with the six lobes (quite as in Pl. 28, fig. 1_b_). Pores twice as broad as
the bars, ten to twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.13, pores 0.01, bars 0.005.

_Habitat._--Central Pacific, Station 271, surface.


10. _Cenosphæra rosetta_, n. sp.

Shell thin walled, smooth. Pores regular, circular, with an elegant
six-lobed outer opening, without papillæ. Pores of the same breadth as the
bars, six to eight on the quadrant.

_Dimensions._--Diameter of the shell 0.1, pores and bars 0.006.

_Habitat._--South Atlantic, Station 323, depth 1900 fathoms.



Subgenus 2. _Circosphæra_, Haeckel.

_Definition._--Pores of the spherical shell regular or subregular,
circular, without hexagonal frames or lobes, all nearly of equal size and
form.


11. _Cenosphæra porophæna_, Ehrenberg.

  _Cenosphæra porophæna_, Ehrenberg, 1858, Monatsber. d. k. preuss. Akad.
  d. Wiss. Berlin, p. 31.

Shell thin walled, smooth. Pores regular, circular, six to eight times as
broad as the bars, five to six on the quadrant.

_Dimensions._--Diameter of the shell 0.1, pores 0.012, bars 0.002.

_Habitat._--Mediterranean (Crete, depth 1100 fathoms; Corfu, surface).


{64}12. _Cenosphæra setosa_, Ehrenberg.

  _Cenosphæra setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 287, Taf. vii. fig. 1.

Shell thin walled, covered with very short and numerous bristles. Pores
regular, circular, five to six times as broad as the bars, six to eight on
the quadrant.

_Dimensions._--Diameter of the shell 0.17, pores 0.2, bars 0.03.

_Habitat._--West Tropical Pacific, 3300 fathoms; Philippine Sea, Station
200, depth 250 fathoms.


13. _Cenosphæra plutonis_, Ehrenberg.

  _Cenosphæra plutonis_, Ehrenberg, 1854, Mikrogeol., Taf. xxxv. B, B. iv.
  fig. 20.

Shell thin walled, covered with short conical papillæ. Pores regular,
circular, twice as broad as the bars, eight to nine on the quadrant.

_Dimensions._--Diameter of the shell 0.09, pores 0.006, bars 0.003.

_Habitat._--North Atlantic, Station 353, depth 2965 fathoms.


14. _Cenosphæra proserpinæ_, n. sp.

Shell thin walled, smooth. Pores regular, circular, four times as broad as
the bars, five to six on the quadrant.

_Dimensions._--Diameter of the shell 0.08, pores 0.008, bars 0.002.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.


15. _Cenosphæra eridani_, n. sp.

Shell thin walled, smooth. Pores regular, circular, three times as broad as
the bars, eleven to twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.16, pores 0.01, bars 0.003.

_Habitat._--South Pacific, Station 295, depth 1500 fathoms.


16. _Cenosphæra lethe_, n. sp.

Shell thick walled, smooth. Pores regular, circular, double-edged, five
times as broad as the bars, sixteen to eighteen on the quadrant.

_Dimensions._--Diameter of the shell 0.25, pores 0.01, bars 0.002.

_Habitat._--North Atlantic, Station 64, depth 2700 fathoms.


17. _Cenosphæra elysia_, n. sp. (Pl. 12, fig. 8).

Shell thick walled, rough. Pores regular, circular, double-edged, twice as
broad as the bars, twelve to fourteen on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.01, bars 0.005.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.


{65}18. _Cenosphæra nirwana_, n. sp.

Shell thick walled, smooth. Pores regular, circular, twice as broad as the
bars, twenty-four to twenty-five on the quadrant.

_Dimensions._--Diameter of the shell 0.25, pores 0.004, bars 0.002.

_Habitat._--Indian Ocean, Belligemma, Ceylon, surface; Haeckel.


19. _Cenosphæra maxima_, n. sp.

Shell thick walled, smooth. Pores regular, circular, twice as broad as the
bars, thirty to thirty-three on the quadrant.

_Dimensions._--Diameter of the shell 0.3 to 0.4, pores 0.012, bars 0.006.

_Habitat._--West Tropical Pacific, Station 225, depth 4475; also fossil in
Barbados.


20. _Cenosphæra compacta_, n. sp. (Pl. 12, fig. 7).

Shell very thick walled, rough (its wall one-fourth to one-third as thick
as the radius). Pores subregular, circular, of the same breadth as the
bars, seven to eight on the quadrant.

_Dimensions._--Diameter of the shell 0.15, pores and bars 0.012.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.

_Cenosphæra radiata_, Zittel, 1876 (L. N. 29, p. 84, Taf. ii. figs. 7, 8),
a fossil Cretaceous species, is closely allied to _Cenosphæra compacta_.


21. _Cenosphæra crassa_, n. sp.

Shell very thick walled, rough (its wall nearly half as thick as the
radius). Pores tubular, double-edged, regular, circular, ten times as broad
as the thin united bars, twelve to fourteen on the quadrant.

_Dimensions._--Diameter of the shell 0.14, pores 0.01, bars 0.001.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.


22. _Cenosphæra solida_, n. sp.

Shell very thick walled, covered with innumerable short bristles (its wall
one-third as thick as the radius). Pores regular, circular, four times as
broad as the bars, tubular, eight to ten on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.02, bars 0.005.

_Habitat._--Antarctic Ocean, Station 157, depth 1950 fathoms.



Subgenus 3. _Cyrtidosphæra_, Haeckel, 1862, Monogr. d. Radiol., p. 348.

_Definition._--Pores of the spherical shell irregularly polygonal, of
unequal size or form, sometimes roundish with polygonal frames.


{66}23. _Cenosphæra reticulata_, Haeckel.

  _Cyrtidosphæra reticulata_, Haeckel, 1862, Monogr. d. Radiol., p. 349,
  Taf. xi. fig. 2.

Shell very thin walled, smooth. Pores irregular, polygonal, two to eight
times as broad as the bars, fifteen to twenty on the quadrant (groups of
four to eight smaller meshes are scattered on the surface, and separated by
reticular rows of larger meshes).

_Dimensions._--Diameter of the shell 0.16, pores 0.004 to 0.016, bars
0.002.

_Habitat._--Mediterranean (Messina), surface.


24. _Cenosphæra tenerrima_, n. sp.

Shell extremely thin walled, smooth, like a cobweb. Pores very irregular
and small, polygonal with thread-like bars, thirty to forty on the
quadrant.

_Dimensions._--Diameter of the shell 0.25, pores 0.002 to 0.008, bars under
0.001.

_Habitat._--Central Pacific, Station 271, surface.


25. _Cenosphæra polygonalis_, n. sp.

Shell thin walled, smooth, with irregular, polygonal pores, three to four
times as broad as the bars, eight to ten on the quadrant.

_Dimensions._--Diameter of the shell 0.2, pores 0.012 to 0.02, bars 0.005.

_Habitat._--North Pacific, Station 236, surface.


26. _Cenosphæra papillata_, n. sp.

Shell thick walled, covered with short conical papillæ. Pores irregular,
polygonal, three to five times as broad as the bars, fourteen to sixteen on
the quadrant.

_Dimensions._--Diameter of the shell 0.12, pores 0.004 to 0.007, bars
0.0015.

_Habitat._--South Atlantic, Station 325, surface.


27. _Cenosphæra cristata_, n. sp.

Shell thick walled, rough. Pores irregular, roundish, surrounded by
polygonal crested frames two to three times as broad as the bars, eight to
twelve on the quadrant.

_Dimensions._--Diameter of the shell 0.16, pores 0.006 to 0.01, bars 0.003.

_Habitat._--North Pacific, Station 254, surface.


28. _Cenosphæra perforata_, n. sp. (Pl. 26, fig. 10).

  _Ceriosphæra perforata_, Haeckel, 1881, Prodromus et Atlas, _loc. cit._

Shell thick walled, rough. Pores irregular, roundish, surrounded by high
polygonal funnel-shaped frames, which are solid in the inner half,
perforated by numerous very small pores in the {67}outer half,
sieve-shaped. Pores one to three times as broad as the bars, of very
different size, four to six on the quadrant.

_Dimensions._--Diameter of the shell 0.15, pores 0.01 to 0.02, bars 0.005
to 0.01.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.


29. _Cenosphæra coronata_, n. sp. (Pl. 26, fig. 11).

Shell thick walled, rough. Pores irregular, roundish, surrounded by high
polygonal frames bearing on their sharp crest a series of small papillæ, so
that each pore is surrounded by a coronal of such spinules. Pores four to
eight times as broad as the bars, four to five on the quadrant.

_Dimensions._--Diameter of the shell 0.15, pores 0.01 to 0.03, bars 0.002
to 0.008.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.



Subgenus 4. _Porosphæra_, Haeckel.

_Definition._--Pores of the spherical shell irregular, roundish, without
polygonal frames, of unequal size or form.


30. _Cenosphæra antiqua_, Haeckel.

  _Cenosphæra plutonis_, var., Dunikowski, 1882, Denkschr. d. k. Akad. d.
  Wiss. Wien, Bd. xlv. p. 25, Taf. iv. figs. 47, 48.

  _Cenosphæra plutonis_, var., Stöhr, 1880, Palæontogr. xxvi. p. 85, Taf.
  i. fig. 1.

Shell thin walled, smooth. Pores irregular, roundish, two to eight times as
broad as the bars, ten to fifteen on the quadrant.

_Dimensions._--Diameter of the shell 0.15 to 0.2, pores 0.007 to 0.015,
bars 0.002 to 0.008.

_Habitat._--Fossil in the Jurassic, Cretaceous, and Tertiary formations;
living in the depths of the Atlantic and Pacific; Station 332, depth 2200
fathoms; Station 225, depth 4475 fathoms, &c.


31. _Cenosphæra gigantea_, n. sp.

Shell thick walled, smooth. Pores irregular, roundish, two to five times as
broad as the bars, thirty to forty on the quadrant.

_Dimensions._--Diameter of the shell 0.4 to 0.5, pores 0.004 to 0.01, bars
0.002.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; also fossil
in Barbados.


32. _Cenosphæra marginata_, n. sp.

Shell very thick walled, smooth. Pores irregular, roundish, double-edged,
three to eight times as broad as the bars, six to eight on the quadrant.

{68}_Dimensions._--Diameter of the shell 0.12, pores 0.01 to 0.03, bars
0.004.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.


33. _Cenosphæra aspera_, Stöhr.

  _Cenosphæra aspera_, Stöhr, 1880, Palæontogr. Bd. xxvi. p. 85, Taf. i.
  fig. 2.

Shell thick walled, rough, covered with short conical papillæ. Pores
irregular, roundish, of about the same breadth as the bars, eight to twelve
on the quadrant.

_Dimensions._--Diameter of the shell 0.17, pores and bars 0.01 to 0.04.

_Habitat._--Fossil in Tertiary rocks of Sicily; Grotte, Stöhr.


34. _Cenosphæra hirsuta_, Ehrenberg.

  _Cenosphæra hirsuta_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.,
  Berlin, p. 287, Taf. x. fig. 18.

Shell thin walled, rough, covered with innumerable very short bristles.
Pores very irregular, roundish, of about the same breadth as the bars.

_Dimensions._--Diameter of the shell 0.11, pores and bars 0.002 to 0.012.

_Habitat._--Indian Ocean, Zanzibar, Pullen; depth 2200 fathoms.



Genus 16. _Stigmosphæra_,[27] Haeckel, n. gen.

_Definition._--#Liosphærida# with one single latticed sphere, with simple
shell-pores (not prolonged into free tubuli); in the central point of the
spherical shell-cavity are united a number of radial beams, which become
forked and inserted into the inner surface of the shell by their distal
ends.

The genus _Stigmosphæra_ differs from _Cenosphæra_ (and from all other
Monosphærida) by internal radial beams, which are united in the centre of
the simple spherical shell; these beams are branched, and the distal ends
of the branches inserted on the internal surface of the shell. I have
observed only two, nearly identical specimens of this genus, both with
regular, hexagonal pores and thin bars; the beams were implanted in the
corners of the hexagons. In one specimen the surface was covered with short
radial bristles, whilst these in the other specimen were prolonged into
radial spines (like _Acanthosphæra_). Possibly this peculiar genus is
derived from _Carposphæra_, by reduction and loss of a central medullary
shell.


_Stigmosphæra actinocentra_, n. sp.

Shell very thin walled, rough, with regular circular, hexagonally framed
pores, six times as broad as the bars, eight to ten on the quadrant; in the
corner of each hexagon a small bristle. In {69}the central point of the
shell are united about twelve (?) thin and straight radial beams, which are
forked, with dichotomous branches; the distal ends of the branches are
inserted in the corners of the hexagons on the inside of the shell.

_Dimensions._--Diameter of the shell 0.15, pores 0.02, bars 0.003.

_Habitat._--Central Pacific, Station 271, surface.



Genus 17. _Ethmosphæra_,[28] Haeckel, 1862, Monogr. d. Radiol., p. 349.

_Definition._--#Liosphærida# with one single latticed sphere, with simple
shell-cavity; with shell-pores which are prolonged on the outside in
centrifugal, conical, or cylindrical tubuli.

The genus _Ethmosphæra_ differs from the simple _Cenosphæra_, its ancestral
form, by the peculiar formation of the shell-pores; in all observed species
of the genus these are quite regular, of nearly equal size and form; their
base in the spherical shell-face is hexagonal, but on the outside prolonged
into centrifugal, external, radial tubuli, which are either conical or
cylindrical (in the latter case both openings of the tubes being equal, in
the former the outer opening being smaller than the inner). The solitary
_Ethmosphæra_ corresponds to the social _Siphonosphæra_; but in the former
the formation of the shell and of its tubuli is quite regular, in the
latter more or less irregular.



Subgenus 1. _Ethmosphærella_, Haeckel.

_Definition._--Tubuli conical, their outer opening smaller than the inner.


1. _Ethmosphæra siphonophora_, Haeckel.

  _Ethmosphæra siphonophora_, Haeckel, 1862, Monogr. d. Radiol., p. 350,
  Taf. xi. fig. 1.

Tubuli conical, their outer opening half as broad as the inner and three
times as broad as their height. Five to six pores on the quadrant. Diameter
of the outer pores one and a half times as large as their distance from
each other.

_Dimensions._--Diameter of the shell 0.1, outer pores 0.01, their distance
0.007.

_Habitat._--Mediterranean (Messina), surface, Haeckel.


2. _Ethmosphæra conosiphonia_, n. sp. (Pl. 12, figs. 5, 5_a_).

Tubuli conical, their outer opening two thirds as broad as the inner, and
scarcely broader than their height. Ten to twelve pores on the quadrant.
Diameter of the outer pores twice as large as their distance from each
other.

_Dimensions._--Diameter of the shell 0.17, outer pores 0.01, their distance
0.005.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.


{70}3. _Ethmosphæra polysiphonia_, n. sp. (Pl. 12, fig. 6).

Tubuli conical, their outer opening three-fourths as broad as the inner and
three times as broad as their height. Sixteen to eighteen pores on the
quadrant. Diameter of the outer pores three times as large as their
distance apart.

_Dimensions._--Diameter of the shell 0.2, outer pores 0.008, their distance
0.003.

_Habitat._--West Tropical Pacific, Station 225, depth 4475 fathoms; also
fossil in Barbados and in Sicily.



Subgenus 2. _Ethmosphæromma_, Haeckel.

_Definition._--Tubuli cylindrical, their outer opening about as large as
the inner.


4. _Ethmosphæra stenosiphonia_, n. sp.

Tubuli cylindrical, short, quite contiguous, so that their diameter is six
times as large as their distance apart, but about equal to their height.
Nine to ten pores on the quadrant.

_Dimensions._--Diameter of the shell 0.14, outer pores 0.012, their
distance 0.002.

_Habitat._--Central Pacific, Station 271, surface.


5. _Ethmosphæra pachysiphonia_, n. sp.

Tubuli cylindrical, twice as long as broad, very thick-walled, and nearly
contiguous, so that their diameter is five times as large as their distance
apart. The thickness of their wall is equal to their lumen. Twelve to
fourteen pores on the quadrant.

_Dimensions._--Diameter of the shell 0.16, outer pores 0.01, their distance
0.002.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.


6. _Ethmosphæra leptosiphonia_, n. sp.

Tubuli cylindrical, short, about as long as broad, very thin-walled and
fragile, separated by wide distances, which are three times as large as
their diameter. Six to seven pores on the quadrant. (Very similar to
_Siphonosphæra cyathina_, Pl. 6, fig. 10, but quite regular, all tubuli
retaining the same size and distance.)

_Dimensions._--Diameter of the shell 0.12, outer pores 0.01, their distance
0.03.

_Habitat._--North Atlantic, Færöe Channel, John Murray; surface.


7. _Ethmosphæra macrosiphonia_, n. sp.

Tubuli cylindrical, very elongated, four times as long as broad; their
bases separated by distances which are equal to their breadth. Eight to ten
tubuli on the quadrant. (The tubes are similar to those of _Siphonosphæra
serpula_, Pl. 6, fig. 6, but quite regular, straight, not curved, all of
the same size and at equal distances apart.)

{71}_Dimensions._--Diameter of the shell 0.1, length of the tubes 0.04,
breadth 0.01, basal distance 0.01.

_Habitat._--Indian Ocean, Cocos Islands, surface, Rabbe.



Genus 18. _Sethosphæra_,[29] Hæckel, 1881, Prodromus, p. 452 (_sensu
emendato_).

_Definition._--#Liosphærida# with one single latticed sphere, with simple
shell-cavity; with shell-pores, which are prolonged on the inside into
centripetal, conical, or cylindrical tubuli.

The genus _Sethosphæra_ differs from its ancestral form, _Cenosphæra_, by
the production of internal, centripetal, radial tubuli on the inside of the
shell (the contrary of the preceding genus _Ethmosphæra_). It corresponds
therefore to the social _Pharyngosphæra_; but in the latter the formation
of the shell and its tubes is more or less irregular, whilst in the former
each regular pore is prolonged into a regular tubule.


1. _Sethosphæra entosiphonia_, n. sp.

Shell with smooth surface and regular circular pores, separated by
hexagonal frames, twice as broad as the bars. Six to eight on the quadrant.
Each pore is prolonged on the inside of the shell in a short conical
centripetal tube, twice as long as its diameter.

_Dimensions._--Diameter of the shell 0.15, outer pores 0.008, bars 0.004,
length of the tubuli 0.015.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.


2. _Sethosphæra entosolenia_, n. sp.

Shell with smooth surface and regular circular pores, without hexagonal
frames, of about the same breadth as the bars. Ten to twelve on the
quadrant. Each pore is prolonged on the inside of the shell into a thin
cylindrical centripetal tube, three times as long as its diameter.

_Dimensions._--Diameter of the shell 0.2, outer pores and bars 0.006,
length of the tubuli 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.



Subfamily CARPOSPHÆRIDA,[30] Haeckel, 1881, Prodromus, p. 449.

_Definition._--#Liosphærida# with two concentric spherical lattice-shells,
which are united by radial beams.


_Carposphæra_,[31] Haeckel, 1881, Prodromus, p. 451.

_Definition._--Liosphærida with one medullary (intracapsular) and one
cortical (extracapsular) shell, both connected by radial beams piercing the
central capsule.

{72}The genus _Carposphæra_ comprises a large number of double-shelled
#Sphæroidea#, formerly united with _Haliomma_, but different from this
genus by the absence of radial spines. The shell is composed of two
concentric latticed spheres, the inner of which (or the medullary shell) is
situated within the central capsule, the other (or the cortical shell)
outside it. Both shells are connected by radial beams which pierce the wall
of the central capsule. The distance between the shells is at least as
large as (commonly much larger than) the radius of the inner shell, whilst
in the following genus, _Liosphæra_, that distance is much smaller than
this radius.



Subgenus 1. _Melittosphæra_, Haeckel, 1881, Prodromus, p. 451.

_Definition._--Pores of the cortical shell regular, hexagonal (or circular,
with hexagonal frames or lobes), all of nearly equal size and form.


1. _Carposphæra capillacea_, n. sp.

Cortical shell very delicate, four times as broad as the similarly
constructed medullary shell, with regular hexagonal meshes (twenty to
twenty-five on the quadrant) and very thin thread-like bars. Both shells
connected by twenty (?) very thin radial beams. (Similar to _Heliosoma
radians_, Pl. 28, fig. 3, 3_a_, but with smooth surface, without any radial
spines.)

_Dimensions._--Diameter of the outer shell 0.2, inner 0.05, pores 0.01,
bars below 0.001.

_Habitat._--Central Pacific, Station 274, surface.


2. _Carposphæra cubaxonia_, n. sp.

Cortical shell smooth, three times as broad as the medullary shell, with
regular hexagonal pores, four times as broad as the bars. Eight to ten
pores on the quadrant. Medullary shell with regular circular pores, twice
as broad as the bars. Both shells connected by six radial beams, which are
three-sided prismatical, opposite in pairs in the three dimensive axes.

_Dimensions._--Diameter of the outer shell 0.15, inner 0.05; outer pores
0.01, inner 0.005.

_Habitat._--South Pacific, Station 291, surface.


3. _Carposphæra infundibulum_, Haeckel.

  _Haliomma infundibuliforme_, Stöhr, 1880, Palæontogr. Bd. xxvi. p. 87,
  Taf. i. fig. 6.

Cortical shell very thick-walled, two and a half times as broad as the
medullary shell, with rough surface and regular hexagonal, funnel-shaped
pores, of about the same breadth as the bars. Five to six on the quadrant.

_Dimensions._--Diameter of the outer shell 0.1, inner 0.04, outer pores and
bars 0.01.

_Habitat._--North Atlantic, Station 354; fossil in Tertiary rocks (Barbados
and Sicily).


{73}4. _Carposphæra melissa_, n. sp.

Cortical shell thick walled, four times as broad as the medullary shell,
with regular circular, hexagonally framed pores, three times as broad as
the bars. Eight to ten pores on the quadrant. Medullary shell with simple
circular pores.

_Dimensions._--Diameter of the outer shell 0.16, inner 0.04, outer pores
0.012, bars 0.004.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.


5. _Carposphæra melitomma_, n. sp. (Pl. 20, fig. 4).

  _Melitomma melittosphæra_, Haeckel, 1881; Prodromus et Atlas, _loc. cit._

Cortical shell thick walled, with thorny surface, two and a half times as
broad as the medullary shell. Its pores regular, circular, twice as broad
as the bars, elegantly six-lobed, separated by crested hexagonal frames; in
each hexagon-corner a short conical papilla (alternating with a lobe).
Eight to ten pores on the quadrant. Medullary shell with small simple
circular pores.

_Dimensions._--Diameter of the outer shell 0.17, inner 0.07, outer pores
0.01, bars 0.005, inner pores 0.005.

_Habitat._--Central Pacific, Stations 266 to 274, in various depths.



Subgenus 2. _Cerasosphæra_, Haeckel, 1881, Prodromus, p. 451.

_Definition._--Pores of the cortical shell regular, circular, without
hexagonal frames, all of nearly equal size and form.


6. _Carposphæra cerasus_, n. sp.

Cortical shell thin walled, smooth, twice as broad as the medullary shell;
both with regular circular pores, six times as broad as the bars. Twelve to
fifteen pores on the quadrant. Outer pores twice as large as the inner.

_Dimensions._--Diameter of the outer shell 0.24, inner 0.12; outer pores
0.016, inner 0.008.

_Habitat._--Central Pacific, Station 271, surface.


7. _Carposphæra apiculata_, Haeckel.

  ? _Haliomma apiculatum_, Ehrenberg, 1872; Monatsber. d. k. preuss. Akad.
  d. Wiss. Berlin, p. 313.

Cortical shell thin-walled, covered with numerous short conical thorns,
three times as broad as the medullary shell. Pores regular, circular, four
times as broad as the bars. Six to eight pores on the quadrant.

_Dimensions._--Diameter of the outer shell 0.15, inner 0.05, outer pores
0.012, bars 0.03.

_Habitat._--North Pacific, California, depth 2000 fathoms; Station 254,
depth 3025 fathoms.


{74}8. _Carposphæra entactinia_, Haeckel.

  _Haliomma entactinia_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 74, Taf. xxvi. fig. 4.

Cortical shell thick walled, rough, twice as broad as the medullary shell;
both shells with regular circular pores, twice as broad as the bars. Six to
eight pores on the quadrant. Outer pores half as broad as the inner. Both
shells connected by very numerous (twenty-four to forty-eight or more)
radial beams.

_Dimensions._--Diameter of the outer shell 0.12, inner 0.06, outer pores
0.008, bars 0.004, inner pores 0.004.

_Habitat._--Cosmopolitan; Atlantic and Pacific, in various depths; fossil
in Barbados and Sicily.


9. _Carposphæra modesta_, Haeckel.

  _Haliomma modestum_, Stöhr, 1880, Palæontogr. Bd. xxvi. p. 86, Taf. i.
  fig. 5.

Cortical shell thick walled, rough, three times as broad as the medullary
shell, with regular circular pores of the same breadth as the bars. Eight
to twelve pores on the quadrant. (Very common, like the preceding species,
and connected with it by numerous intermediate forms.)

_Dimensions._--Diameter of the outer shell 0.12 to 0.2, inner 0.04 to 0.07,
pores and bars 0.006 to 0.008.

_Habitat._--Atlantic and Pacific, from many Stations and at various depths;
fossil in Barbados and Sicily.


10. _Carposphæra belladonna_, n. sp.

Cortical shell thick walled, smooth, five times as broad as the medullary
shell, with regular circular pores of the same breadth as the bars. Twenty
to twenty-two pores on the quadrant.

_Dimensions._--Diameter of the outer shell 0.3, inner 0.06, outer pores and
bars 0.004.

_Habitat._--North Atlantic, Færöe Channel, John Murray.


11. _Carposphæra areca_, n. sp.

Cortical shell very thick walled, rough, twice as broad as the medullary
shell, with regular circular pores half as broad as the bars. Eight to ten
pores on the quadrant.

_Dimensions._--Diameter of the outer shell 0.12, inner 0.06, outer pores
0.03, bars 0.006.

_Habitat._--Indian Ocean, Ceylon, Haeckel, surface.



Subgenus 3. _Prunosphæra_, Haeckel, 1881, Prodromus, p. 451.

_Definition._--Pores of the cortical shell irregular polygonal, of unequal
size or dissimilar form.


12. _Carposphæra prunulum_, n. sp.

Cortical shell thin walled, smooth, four times as broad as the medullary
shell, with large irregular polygonal pores, four to eight times as broad
as the bars.  Connecting beams between them numerous.

{75}_Dimensions._--Diameter of the outer shell 0.24, inner 0.06, outer
pores 0.008 to 0.016, bars 0.002.

_Habitat._--South Atlantic, Station 325, surface.


13. _Carposphæra corypha_, n. sp.

Cortical shell thin walled, rough, three times as broad as the medullary
shell, with irregular polygonal pores, three to six times as broad as the
bars. Connecting beams between the two shells twenty, regularly disposed.

_Dimensions._--Diameter of the outer shell 0.15, inner 0.05, outer pores
0.01 to 0.02, bars 0.003.

_Habitat._--South Pacific, Station 300, surface.


14. _Carposphæra borassus_, n. sp.

Cortical shell thick walled, smooth, three times as broad as the medullary
shell, with irregular polygonal pores, two to four times as broad as the
bars. Connecting beams between the two shells six, opposite by pairs in the
three dimensive axes. (Similar to _Hexalonche aristarchi_, Pl. 22, fig. 3,
but without external radial spines.)

_Dimensions._--Diameter of the outer shell 0.12, inner 0.04, outer pores
0.01 to 0.02, bars 0.005.

_Habitat._--Central Pacific, Station 268, surface.



Subgenus 4. _Phoenicosphæra_, Haeckel.

_Definition._--Pores of the cortical shell irregular roundish, of unequal
size or form.


15. _Carposphæra nobilis_, Haeckel.

  _Haliomma nobile_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, p. 268; Abhandl., 1875, Taf.  xxvii. fig. 6.

Cortical shell thin walled, rough, twice as broad as the medullary shell,
with irregular roundish pores, two to four times as broad as the bars.

_Dimensions._--Diameter of the outer shell 0.1, inner 0.05, outer pores
0.01 to 0.02, bars 0.006.

_Habitat._--Cosmopolitan; Atlantic, Indian, Pacific, at various depths;
fossil in Jurassic, Cretaceous, and Tertiary rocks.


16. _Carposphæra micrococcus_, n. sp.

Cortical shell thin walled, rough, seven times as broad as the medullary
shell, with irregular roundish pores, three to six times as broad as the
bars.

_Dimensions._--Diameter of the outer shell 0.2, inner 0.03, outer pores
0.012 to 0.025, bars 0.004.

_Habitat._--South Atlantic, Station 330, surface.


{76}17. _Carposphæra maxima_, n. sp.

Cortical shell thin walled, smooth, five times as broad as the medullary
shell, with irregular roundish pores, of about the same breadth as the
bars.

_Dimensions._--Diameter of the outer shell 0.4, inner 0.08, pores and bars
0.004 to 0.008.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.


18. _Carposphæra nodosa_, n. sp. (Pl. 28, figs. 2, 2_a_).

  _Anthomma nodosum_, Haeckel, 1879, Atlas, _loc. cit._

Cortical shell thick walled, covered with forty to fifty scattered
pyramidal nodules, two and a half times as broad as the medullary shell,
connected with it by very numerous thin radial beams. Outer and inner pores
irregular roundish or polygonal, two to three times as broad as the bars.
(This species in consequence of the cortical nodules may represent a
peculiar genus, analogous to _Conosphæra_, called _Anthomma_.)

_Dimensions._--Diameter of the outer shell 0.13, inner 0.05, inner and
outer pores 0.008 to 0.012, bars 0.004.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.



Genus 20. _Liosphæra_,[32] Haeckel, 1881, Prodromus, p. 449.

_Definition._--#Liosphærida# with two cortical (extracapsular) shells
(without a medullary or intracapsular shell).

The genus _Liosphæra_ agrees with the preceding _Carposphæra_ in the
possession of two concentric latticed spheres; but whilst in the latter
genus the inner sphere is a medullary one (intracapsular), the outer a
cortical shell (extracapsular), both connected by radial beams piercing the
capsule-wall, here in _Liosphæra_ the central capsule lies freely within
the inner lattice shell and is not pierced by radial beams. Therefore both
shells are here cortical shells, both separated by a distance, which is
constantly much smaller than the radius of the inner shell; whereas in
_Carposphæra_ this distance is at least as large as that radius (commonly
much larger). In _Carposphæra_ the number of pores in both shells is never
the same; in several species of _Liosphæra_ this number is the same, each
outer regular hexagonal pore exactly corresponding to an inner; the six
corners of each connected by six short radial beams.



Subgenus 1. _Melitomma_, Haeckel.

_Definition._--Pores of both shells regular, in each shell all of nearly
equal size and form.


1. _Liosphæra hexagonia_, n. sp. (Pl. 20, fig. 3).

Both shells with the same number of pores, exactly corresponding, about ten
on the quadrant. {77}All pores regular, or subregular, hexagonal; the outer
twice as broad as the inner. Outer bars very thin, thread-like; inner bars
thick, one-third as broad as the pores. Surface smooth. Both shells
connected by numerous radial beams, their distance one-third as large as
the radius of the inner shell.

_Dimensions._--Diameter of the outer shell 0.16, inner 0.12, distance of
both 0.02; outer pores 0.014, inner pores 0.007.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.


2. _Liosphæra rhodococcus_, n. sp.

Both shells with the same number of pores, exactly corresponding, about
twelve on the quadrant. All pores regular or subregular; the inner
circular, with elegant six-lobed frames, twice as broad as the bars; the
outer hexagonal, with very thin thread-like bars. All corners of the outer
and inner hexagons connected by thin, bristle-shaped radial beams. (Similar
to _Haliomma rhodococcus_, Pl. 19, fig. 6; but with smooth surface and
regular hexagonal pores of the outer shell.)

_Dimensions._--Diameter of the outer shell 0.2, inner 0.16, distance of
both 0.02; outer pores 0.03, inner 0.01.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.


3. _Liosphæra porulosa_, n. sp.

Both shells with regular hexagonal pores; their number in the outer shell
seven times as great as in the inner. Pores of the stout inner shell large,
three times as broad as the bars, about eight on the quadrant. From each
hexagon-corner arises one bristle-shaped radial beam; their distal ends are
united by threads (three from each), forming the large meshes of the
delicate outer shell. Each of these is divided by very thin threads into
seven small circular porules, one central and six around it.

_Dimensions._--Diameter of the outer shell 0.25, inner 0.2, distance of
both 0.025; outer pores 0.04, their porules 0.012, inner pores 0.15.

_Habitat._--Indian Ocean, Sunda Strait, Rabbe; surface.



Subgenus 2. _Craspedomma_, Haeckel.

_Definition._--Pores of both shells irregular, in each shell differing
either in form or size.


4. _Liosphæra peridromium_, n. sp.

Both shells with the same number of large, polygonal, very irregular pores,
exactly corresponding (about eight to ten on the quadrant); both with a
very delicate thin framework. From the thread-like bars of the inner, very
large and thin-walled, sphere arise perpendicularly innumerable short
bristles of equal length, which are united at equal distances by tangential
thread-like bars, parallel to the former, composing the outer shell. Each
mesh is, therefore, surrounded by a delicate ballister or rail.

{78}_Dimensions._--Diameter of the outer shell 0.42, inner 0.4, distance of
both 0.01; diameter of the meshes 0.02 to 0.06.

_Habitat._--North Pacific, Station 250, surface.


5. _Liosphæra polypora_, n. sp. (Pl. 20, fig. 2).

Both shells with small irregular roundish pores, of about the same size as
the bars between them; twenty to thirty on the quadrant. The pores of the
outer shell somewhat smaller, therefore much more numerous than the pores
of the inner shell. Distance between the two shells about one-third as
great as the radius of the inner. Both shells connected by numerous thin
radial beams. Surface smooth or a little rough.

_Dimensions._--Diameter of the outer shell 0.18, inner 0.14, distance of
both 0.02; pores and bars 0.003 to 0.005.

_Habitat._--West Tropical Pacific, Station 225, depth 4475.



Subfamily THECOSPHÆRIDA,[33] Haeckel, 1881, Prodromus, pp. 449, 452.

_Definition._--#Liosphærida# with three concentric spherical
lattice-shells, which are united by radial beams.



Genus 21. _Thecosphæra_,[34] Haeckel, 1881, Prodromus, p. 452.

_Definition._--#Liosphærida# with two medullary (intracapsular) shells and
one cortical (extracapsular) shell.

The genus _Thecosphæra_ comprises a large number of triple-shelled
#Sphæroidea#, formerly united with _Actinomma_, but different from this
genus in the absence of radial spines. The latticed shell is composed of
three concentric spheres, two of which lie within the central capsule
(medullary shells), and one outside (cortical shell). This latter is
connected with the former by radial beams piercing the wall of the central
capsule. From the following _Rhodosphæra_ (with one medullary and two
cortical shells) _Carposphæra_ differs also by the distance of the three
shells. In the former the distance between the two outer shells is much
smaller, in the latter much larger, than the distance between the inner
shells.



Subgenus 1. _Thecosphærantha_, Haeckel.

_Definition._--Pores of the cortical shell regular, hexagonal, or circular,
with hexagonal frames or lobes, all of nearly equal size and form.


{79}1. _Thecosphæra triplodictyon_, n. sp.

Cortical shell thin walled, smooth, with regular, hexagonal pores, four
times as broad as the bars. Radial proportion of the three spheres =
1 : 2 : 8. Both medullary shells with regular circular pores, twice as
broad as the bars, the inner half as broad as the outer. All three shells
connected by six thin radial beams, opposite in pairs in the three
dimensive axes.

_Dimensions._--Diameter of the outer shell 0.2, middle 0.05, inner 0.025;
cortical pores 0.012, bars 0.003.

_Habitat._--Central Pacific, Station 271, surface.


2. _Thecosphæra phænaxonia_, n. sp.

Cortical shell thick walled, rough, with regular, circular, hexagonally
framed pores, twice as broad as the bars. Radial proportion of the three
spheres = 1 : 2 : 6. Both medullary shells with regular hexagonal pores and
thin bars. All three shells connected by six prismatic radial beams,
opposite in pairs in the three dimensive axes. (Shell similar to
_Hexacontium sceptrum_, Pl. 24, fig. 1, 1_a_, but without external spines.)

_Dimensions._--Diameter of the outer shell 0.12, middle 0.04, inner 0.02;
cortical pores 0.01, bars 0.005.

_Habitat._--North Pacific, Station 253, surface.


3. _Thecosphæra favosa_, n. sp.

Cortical shell thick walled, thorny, with regular, circular, hexagonally
framed pores, of the same breadth as the bars. Radial proportion of the
three spheres = 1 : 3 : 10. Both medullary shells with regular circular
pores, connected with the former by twelve short prismatic, regularly
disposed radial beams.

_Dimensions._--Diameter of the outer shell 0.2, middle 0.06, inner 0.02;
cortical pores and bars 0.008.

_Habitat._--Central Pacific, Station 268, surface; also fossil in Barbados.


4. _Thecosphæra floribunda_, n. sp.

Cortical shell thick walled, smooth, with regular, elegantly six-lobed
pores, three times as broad as the bars. Radial proportion of the three
spheres = 1 : 2 : 4. Both medullary shells with simple regular circular
pores, connected with the former by six dimensive radial beams. (Similar to
_Hexacontium floridum_, Pl. 24, fig. 4, but without external spines.)

_Dimensions._--Diameter of the outer shell 0.12, middle 0.06, inner 0.03;
cortical pores 0.01, bars 0.0033.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.



{80}Subgenus 2. _Thecosphærella_, Haeckel.

_Definition._--Pores of the cortical shell regular, circular, without
hexagonal frames or lobes, all of nearly equal size and form.


5. _Thecosphæra inermis_, Haeckel.

  _Actinomma inerme_, Haeckel, 1862, Monogr. d. Radiol., p. 440, Taf. xxiv.
  fig. 5.

  _Haliomma inerme_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d. Wiss.
  Berlin, p. 815.

Cortical shell thin walled, rough, with regular circular pores, twice as
broad as the bars. Radial proportion of the three spheres and of their
circular regular pores = 1 : 2 : 4. All three spheres connected by twelve
regularly disposed radial beams.

_Dimensions._--Diameter of the outer shell 0.1, middle 0.05, inner 0.025;
cortical pores 0.006, bars 0.003.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific, at many
Stations and at various depths.


6. _Thecosphæra æquorea_, Haeckel.

  _Haliomma æquorea_, Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, p. 83; Mikrogeol., 1854, Taf. xxii. fig. 35.

  _Actinomma æquorea_, Haeckel, 1862, Monogr. d. Radiol., p. 443.

Cortical shell thick walled, smooth, with regular circular pores of the
same breadth as the bars. Radial proportion of the three spheres and of
their regular pores = 1 : 2 : 6 or = 1 : 3 : 9; they are connected by six
radial beams, opposite by pairs in the three dimensive axes.

_Dimensions._--Diameter of the outer shell 0.08 to 0.12, middle 0.03 to
0.04, inner 0.09 to 0.12; cortical pores and bars about 0.006.

_Habitat._--Mediterranean, Corfu, surface; fossil in Greece and Sicily.


7. _Thecosphæra medusa_, Haeckel.

  _Haliomma medusa_, Ehrenberg, 1838, Abhandl. d. k. Akad. d. Wiss. Berlin,
  p. 130; Mikrogeol., 1854, Taf. xxii. figs. 33, 34.

  _Actinomma medusa_, Haeckel, 1862, Monogr. d. Radiol., p. 444.

  _Actinomma medusa_, Stöhr, 1880, Palæontogr., Bd. xxvi. p. 90, Taf. ii.
  fig. 3.

Cortical shell thick walled, rough or thorny, with regular circular pores
of the same breadth as the bars. Radial proportion of the three spheres =
1 : 2 : 4 (or 1 : 2.5 : 6); they are connected by four radial beams,
crossed by pairs in two diameters, perpendicular one to another.

_Dimensions._--Diameter of the outer shell 0.08 to 0.12, middle 0.04 to
0.06, inner 0.02 to 0.025; cortical pores and bars in average 0.005.

_Habitat._--Fossil in Tertiary rocks of Barbados and the Mediterranean.


{81}8. _Thecosphæra entactinia_, n. sp.

Cortical shell thick walled, smooth, with regular circular pores of the
same breadth as the bars. Radial proportion of the three spheres =
1 : 3 : 12; they are connected by very numerous (forty to fifty, or more)
thin radial beams.

_Dimensions._--Diameter of the outer shell 0.24, middle 0.06, inner 0.02;
cortical pores and bars 0.008.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.


9. _Thecosphæra micropora_, n. sp.

Cortical shell thin walled, smooth, with very small and numerous, regular,
circular pores, half as broad as the bars. Radial proportion of the three
shells = 1 : 2 : 5; they are connected by twenty regularly disposed radial
beams.

_Dimensions._--Diameter of the outer shell 0.2, middle 0.08, inner 0.04;
cortical pores 0.002, bars 0.004.

_Habitat._--South Pacific, Station 288, surface.



Subgenus 3. _Thecosphærina_, Haeckel.

_Definition._--Pores of the cortical shell irregular polygonal, of unequal
size or dissimilar form.


10. _Thecosphæra capillacea_, n. sp.

Cortical shell thin walled, smooth, with irregular polygonal pores, three
to six times as broad as the bars. Both medullary shells with similar, but
smaller, pores. Radial proportion of the three spheres = 1 : 3 : 8; they
are connected by very numerous (sixty to eighty or more) thin radial beams.
 (Similar to _Actinomma capillaceum_, Pl. 29, fig. 6, but without external
spines.)

_Dimensions._--Diameter of the outer shell 0.2, middle 0.075, inner 0.025;
cortical pores 0.006 to 0.012, bars 0.002.

_Habitat._--North Pacific, Station 250, surface.


11. _Thecosphæra diplococcus_, n. sp.

Cortical shell thick walled, rough, with large irregular polygonal pores,
two to three times as broad as the bars. Both medullary shells with small
regular circular pores. Radial proportion of the three spheres = 1 : 2 : 6;
they are connected by twenty (?) stout radial beams.

_Dimensions._--Diameter of the outer shell 0.12, middle 0.04, inner 0.02;
cortical pores 0.008 to 0.012, bars 0.004.

_Habitat._--South Atlantic, Station 330, surface.



Subgenus 4. _Thecosphæromma_, Haeckel.

_Definition._--Pores of the cortical shell irregular, roundish, of unequal
size or dissimilar form.


{82}12. _Thecosphæra dodecactis_, n. sp.

Cortical shell thin walled, smooth, with large irregular roundish pores,
two to eight times as broad as the bars. Both medullary shells with regular
circular pores, twice as broad as the bars. Radial proportion of the three
spheres = 1 : 2 : 5; they are connected by twelve regularly disposed stout
radial beams.

_Dimensions._--Diameter of the outer shell 0.2, middle 0.08, inner 0.04;
cortical pores 0.004 to 0.016, bars 0.002.

_Habitat._--Central Pacific, Station 263, depth 2650 fathoms.


13. _Thecosphæra icosactis_, n. sp.

Cortical shell thin walled, with small irregular roundish pores, two to
four times as broad as the bars. Both medullary shells with similar but
smaller pores. Radial proportion of the three spheres = 1 : 3 : 8; they are
connected by twenty thin radial beams.

_Dimensions._--Diameter of the outer shell 0.32, middle 0.12, inner 0.04;
cortical pores 0.005 to 0.012, bars 0.003.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.


14. _Thecosphæra maxima_, n. sp.

Cortical shell thin walled, with small irregular roundish pores, two to six
times as broad as the bars. Both medullary shells with similar, but
smaller, pores. Radial proportion of the three spheres = 1 : 3 : 9; they
are connected by numerous (forty to sixty or more) thin radial beams.

_Dimensions._--Diameter of the outer shell 0.45, middle 0.15, inner 0.05;
cortical pores 0.008 to 0.024, bars 0.004.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.



Genus 22. _Rhodosphæra_,[35] Haeckel, 1881, Prodromus, p. 452.

_Definition._--#Liosphærida# with one medullary (intracapsular) shell and
two cortical (extracapsular) shells.

The genus _Rhodosphæra_ differs from the preceding _Thecosphæra_ in the
same manner in which, among the Dyosphærida, _Liosphæra_ differs from
_Carposphæra_. The cortical shell is double, composed of two not far
distant shells, lying outside the central capsule. The distance between the
shells is much smaller than the radius of the inner shell. This is
connected by radial beams (piercing the central capsule) with the small
central medullary shell.



Subgenus 1. _Rhodosphærella_, Haeckel.

_Definition._--Pores of both cortical shells regular, in each shell all of
nearly equal size and form.


{83}1. _Rhodosphæra hexagonia_, n. sp.

Both cortical shells with the same number of regular hexagonal pores; the
inner four times as broad as the bars, and half as broad as the outer
pores, which are separated by thread-like bars. Medullary shell only
one-fourth as broad as the inner cortical shell, with regular hexagonal
pores of half the size. (Differs from the similar _Liosphæra hexagonia_,
Pl. 20, fig. 3, by the possession of a medullary shell.)

_Dimensions._--Diameter of the outer shell 0.2, middle 0.16, inner 0.04;
outer pores 0.013, middle 0.008, inner 0.004.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.


2. _Rhodosphæra melitomma_, n. sp.

Both cortical shells with the same number of regular pores; the inner
regular, circular, twice as broad as the bars, with elegant hexagonal
frames and six roundish lobes alternating with the six radial spines which
arise from the hexagon-corners; these short conical spines are connected at
the distal end (at equal distances from the centre) by delicate threads
(three from each spine), which form the delicate external shell. Medullary
shell one-third as broad as the inner cortical shell, with small, simple,
regular circular pores. (If in _Carposphæra melitomma_, Pl. 20, fig. 4, the
distal ends of the spines became united by a cobweb-like outer shell, this
species would be formed.)

_Dimensions._--Diameter of the outer shell 0.22, middle 0.18, inner 0.06;
outer pores 0.025, middle 0.0125, inner 0.005.

_Habitat._--Central Pacific, Station 270, depth 2925 fathoms.



Subgenus 2. _Rhodosphæromma_, Haeckel.

_Definition._--Pores of both cortical shells irregular, in each shell of
unequal size or dissimilar form.


3. _Rhodosphæra palliata_, n. sp.

Both cortical shells with an unequal number of irregular roundish pores;
the outer pores somewhat smaller and much more numerous than the inner
pores; the bars between the latter are thicker. Medullary shell about one
quarter as broad as the inner cortical shell, with regular circular pores.

_Dimensions._--Diameter of the outer shell 0.4, middle 0.36, inner 0.08;
outer pores on an average 0.008, middle 0.012, inner 0.004.

_Habitat._--Fossil in Barbados.


4. _Rhodosphæra pentaphylla_, n. sp.

Both cortical shells with unequal number of irregular roundish pores; the
inner pores large, three to four times as broad as the bars; to each inner
pore corresponds a group of five smaller {84}outer pores, like the five
petals of a flower. Medullary shell half as broad as the inner cortical
shell, with regular circular pores.

_Dimensions._--Diameter of the outer shell 0.25, middle 0.2, inner 0.1;
outer pores on an average 0.006, middle 0.012, inner 0.004.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.



Subfamily CROMYOSPHÆRIDA,[36] Haeckel, 1881, Prodromus, pp. 449, 453.

_Definition._--#Liosphærida# with four concentric spherical latticed
shells, united by radial beams.



Genus 23. _Cromyosphæra_,[37] Haeckel, 1881, Prodromus, p. 453.

_Definition._--#Liosphærida# with two intracapsular (medullary) shells and
two extracapsular (cortical) shells; the former united with the latter by
radial beams piercing the wall of the central capsule.

The genus _Cromyosphæra_ is the only known genus of Cromyosphærida, or of
such #Sphæroidea#, the smooth shell of which is composed of two medullary
and two cortical shells. There may possibly be other Cromyosphærida, in
which the shell is composed of one simple medullary and three cortical
shells, or only of four extra-capsular cortical shells; but such have not
as yet been observed. _Caryosphæra polysphærica_, Bütschli, 1882 (L. N. 41,
Taf. xxiii. fig. 12) is probably a _Cromyosphæra_ (fossil in Barbados).


1. _Cromyosphæra quadruplex_, n. sp. (Pl. 30, fig. 9).

Radial proportion of the four spheres = 1 : 2 : 4 : 5. Outer cortical shell
smooth, with large regular hexagonal pores, ten times as broad as the bars;
inner cortical shell with irregular polygonal pores, five times as broad as
the bars. Both medullary shells with regular circular pores of the same
breadth as the bars.

_Dimensions._--Diameter of the four spheres--(A) 0.16, (B) 0.12, (C) 0.06,
(D) 0.03.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.


2. _Cromyosphæra rosetta_, n. sp.

Radial proportion of the four spheres = 1 : 2 : 8 : 10. Outer cortical
shell smooth, with regular hexagonal pores and very thin bars; inner
cortical shell with the same number of exactly corresponding, regular
circular, hexagonally framed pores, twice as broad as the bars; the corners
of the outer and inner hexagons united by radial bristles. Both medullary
shells with regular circular pores, twice as broad as the bars.

_Dimensions._--Diameter of the four spheres--(A) 0.2, (B) 0.16, (C) 0.04,
(D) 0.02.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.


{85}3. _Cromyosphæra bigemina_, n. sp.

Radial proportion of the four spheres = 1 : 2 : 7 : 8. Outer cortical shell
smooth, with regular hexagonal pores and very thin bars; inner cortical
shell with the same number of exactly corresponding, regular circular
pores. Both medullary shells with regular circular pores of the same
breadth as the bars. (Somewhat similar to _Hexacromyon elegans_, Pl. 24,
fig. 9, also with six inner radial beams, but without external radial
spines.)

_Dimensions._--Diameter of the four spheres--(A) 0.2, (B) 0.17, (C) 0.05,
(D) 0.025.

_Habitat._--North Pacific, Station 241, depth 2300 fathoms.


4. _Cromyosphæra cepa_, n. sp.

Radial proportion of the four spheres = 1 : 2 : 4 : 5. All four shells of
the same structure, thick-walled, with regular circular pores, two to four
times as broad as the bars; the size of the pores increases gradually from
the inner to the outer shell. Surface thorny. Distance between the second
and third shells twice as great as that between the others.

_Dimensions._--Diameter of the four spheres--(A) 0.125, (B) 0.1, (C) 0.05,
(D) 0.025.

_Habitat._--Fossil in Barbados.


5. _Cromyosphæra scorodonium_, n. sp.

Radial proportion of the four spheres = 1 : 2 : 3 : 4. All four shells of
the same structure, thin-walled, with irregular roundish pores, two to four
times as broad as the bars; the size of the pores increasing gradually from
the inner to the outer shell. Surface smooth. Distance between each two
shells equal to the diameter of the innermost.

_Dimensions._--Diameter of the four spheres--(A) 0.12, (B) 0.09, (C) 0.06,
(D) 0.03.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; also fossil
in Barbados.


6. _Cromyosphæra antarctica_, n. sp..

Radial proportion of the four spheres = 1 : 2 : 5 : 7. Both cortical shells
with irregular polygonal roundish pores; the outermost with thinner bars
and rough surface, the inner with thicker bars. Both medullary shells with
irregular roundish pores.

_Dimensions._--Diameter of the four spheres--(A) 0.18, (B) 0.12, (C) 0.05,
(D) 0.025.

_Habitat._--Antarctic Ocean; in very large number, together with
_Rhizosphæra antarctica_, in the diatomaceous ooze of Station 157 (3rd
March 1874); depth 1950 fathoms.



Subfamily CARYOSPHÆRIDA,[38] Haeckel, 1881, Prodromus, pp. 449, 454.

_Definition._--#Liosphærida# with numerous (five or more) concentric
spherical latticed shells, united by radial beams.



{86}Genus 24. _Caryosphæra_,[39] Haeckel, 1881, Prodromus, p. 454.

_Definition._--#Liosphærida# with two intracapsular (medullary) shells and
three or more extracapsular (cortical) shells; the former united with the
latter by radial beams piercing the wall of the central capsule.

The genus _Caryosphæra_, the only observed form of this subfamily,
comprises those #Liosphærida# in which the shell is composed of two
medullary and three or more cortical shells. Such forms (without radial
spines) are very rare; I observed only two species, one with five, the
other with six shells. They are derived from _Cromyosphæra_ by further
apposition of outer cortical shells.


1. _Caryosphæra pentalepas_, n. sp.

Shell composed of five concentric spheres, with radial proportion =
1 : 2 : 8 : 10 : 12. Both medullary shells with regular circular pores,
twice as broad as the bars. First cortical shell with regular, circular,
hexagonally framed pores, three times as broad as the bars; second cortical
shell with regular hexagonal pores, four times as broad as the bars; third
(outermost) cortical shell with regular hexagonal pores and very thin
thread-like bars. Surface smooth.

_Dimensions._--Diameter of the five shells--(A) 0.02, (B) 0.04, (C) 0.16,
(D) 0.2, (E) 0.24.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.


2. _Caryosphæra hexalepas_, n. sp.

Shell composed of six concentric spheres, with the radial proportion =
1 : 2 : 4 : 5 : 6 : 8. All six shells with regular circular pores, two to
four times as broad as the bars, with increasing size from the centrum
against the smooth surface.

_Dimensions._--Diameter of the six shells--(A) 0.025, (B) 0.05, (C) 0.1,
(D) 0.13, (E) 0.16, (F) 0.2.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms; also fossil
in Barbados.



Subfamily PLEGMOSPHÆRIDA,[40] Haeckel, 1881, Prodromus, p. 455.

_Definition._--#Liosphærida# with spongy spherical shell, with or without
latticed medullary shell in the centre.



Genus 25. _Styptosphæra_,[41] Haeckel, 1881, Prodromus, p. 455.

_Definition._--#Liosphærida# forming a solid sphere of spongy framework,
without enclosed medullary shell, and without central cavity.

{87}The genus _Styptosphæra_ presents a spherical shell with smooth or
rough surface (without radial spines), the whole mass of which is composed
of looser or denser spongy wicker-work.


1. _Styptosphæra spumacea_, n. sp.

Spongy framework of the solid sphere loose, with large polygonal meshes of
slightly different size, ten to twenty times as broad as the bars.
Structure of the whole spongy sphere the same. Central capsule filled with
crystals. Surface smooth.

_Dimensions._--Diameter of the sphere 0.32, of the central capsule 0.26,
meshes 0.01 to 0.02, bars 0.001.

_Habitat._--North Pacific, Station 236, surface.


2. _Styptosphæra spongiacea_, n. sp.

Spongy framework in the central part of the solid sphere much more compact
than in the peripheral part, becoming gradually looser towards the rough
surface. Meshes in the centre three to five times, in the periphery fifteen
to twenty times as broad as the bent bars.

_Dimensions._--Diameter of the sphere 0.45, inner meshes 0.006 to 0.01,
outer meshes 0.03 to 0.04, bars 0.002.

_Habitat._--Central Pacific, Station 271, surface.


3. _Styptosphæra stupacea_, n. sp.

Spongy framework of the solid sphere rather compact, everywhere of the same
structure, with roundish, nearly equal meshes, six to eight times as broad
as the bars. Surface rough with prominent thorns.

_Dimensions._--Diameter of the sphere 0.22, meshes 0.01 to 0.012, bars
0.0015.

_Habitat._--South Pacific, Station 291, surface.



Genus 26. _Plegmosphæra_, Haeckel,[42] 1881, Prodromus, p. 455.

_Definition._--#Liosphærida# forming a hollow sphere of spongy framework,
without a medullary shell in the central cavity.

The genus _Plegmosphæra_ develops a large hollow sphere, the wall of which
is composed of looser or denser spongy wicker-work. On the inner as well as
on the outer face of the spongy shell-wall may be present a simple
lattice-sphere from which the threads of the framework arise; but in some
species these lattice-plates are quite absent.



{88}Subgenus 1. _Plegmosphærantha_, Haeckel.

_Definition._--Inside and outside of the spongy shell-wall smooth, closed
by a lattice-plate with polygonal meshes.


1. _Plegmosphæra maxima_, n. sp.

Radius of the spherical shell-cavity eight to ten times as great as the
thickness of the thin spongy wall. Inside and outside of the wall smooth,
closed by a lattice-plate with irregular polygonal meshes. Only three or
four meshes in the thickness of the wall.

_Dimensions._--Diameter of the spongy sphere 0.8 to 1.0 mm., of its inner
cavity 0.7 to 0.8, meshes 0.01 to 0.02, bars 0.002 to 0.003, central
capsule 0.5 to 0.6, nucleus 0.1 to 0.15.

_Habitat._--Central Pacific, Station 271, surface.


2. _Plegmosphæra coelopila_, n. sp.

Radius of the spherical shell-cavity eight to ten times as great as the
thickness of the spongy wall. Inside and outside of the wall closed by a
smooth lattice-plate with irregular polygonal meshes, five to ten times as
broad as the bars.

_Dimensions._--Diameter of the shell 0.32, of its cavity 0.26, meshes 0.01
to 0.02, bars 0.002.

_Habitat._--North Atlantic, Færöe Channel, Gulf Stream, John Murray.


3. _Plegmosphæra pachypila_, n. sp.

Radius of the spherical shell-cavity about equal to the thickness of the
spongy wall. Inside and outside of the wall closed by a smooth
lattice-plate with irregular polygonal meshes, three to six times as broad
as the bars.

_Dimensions._--Diameter of the shell 0.24, of its cavity 0.12.

_Habitat._--North Pacific, Station 250, surface.



Subgenus 2. _Plegmosphærella_, Haeckel.

_Definition._--Inside of the spongy shell-wall closed by a smooth
lattice-plate, outside rough, spongy, with prominent thorns.


4. _Plegmosphæra entodictyon_, n. sp.

Radius of the spherical shell-cavity half as great as the thickness of the
spongy wall. Inside of the wall closed by a smooth lattice-plate, outside
rough, spongy.

_Dimensions._--Diameter of the shell 0.24, of its cavity 0.08.

_Habitat._--South Pacific, Station 300, surface.


{89}5. _Plegmosphæra leptodictyon_, n. sp.

Radius of the spongy shell-cavity six times as great as the thickness of
the spongy wall. Inside of the wall closed by a smooth lattice-plate,
outside rough spongy.

_Dimensions._--Diameter of the shell 0.44, of its cavity 0.36.

_Habitat._--Central Pacific, Station 266, surface.



Subgenus 3. _Plegmosphæromma_, Haeckel.

_Definition._--Inside of the spongy shell-wall rough spongy, without
lattice-plate, outside closed by a smooth lattice-plate.


6. _Plegmosphæra exodictyon_, n. sp. (Pl. 18, fig. 8).

Radius of the spongy shell-cavity only one-fourth as great as the thickness
of the spongy shell-wall. Outside of the wall closed by a smooth
lattice-plate, inside rough, spongy.

_Dimensions._--Diameter of the shell 0.4, of its cavity 0.08.

_Habitat._--South Atlantic, Station 325, surface.



Subgenus 4. _Plegmosphærusa_, Haeckel.

_Definition._--Inside and outside of the spongy shell-wall rough, with
spongy or spiny surface, without lattice-plate.


7. _Plegmosphæra leptoplegma_, n. sp.

Radius of the spherical shell-cavity half as great as the thickness of the
loose spongy shell-wall. Inside and outside of the wall rough spongy, not
closed by a lattice-plate. Meshes ten to twenty times as broad as the bars.

_Dimensions._--Diameter of the shell 0.3, of its cavity 0.088.

_Habitat._--North Atlantic, Station 253, surface.


8. _Plegmosphæra pachyplegma_, n. sp.

Radius of the spherical shell-cavity about equal to the thickness of the
dark and dense spongy shell-wall. Inside and outside of the wall rough
spongy, not closed by a lattice-plate. Meshes three to five times as broad
as the bars.

_Dimensions._--Diameter of the shell 0.2, of its cavity 0.1.

_Habitat._--Central Pacific, Station 270, surface.



Genus 27. _Spongoplegma_,[43] Haeckel, 1881, Prodromus, p. 455.

_Definition._--#Liosphærida# forming a sphere of spongy framework, which
encloses in the centre one single latticed medullary shell.

{90}The genus _Spongoplegma_ may be regarded as a _Carposphæra_, in which
the simple latticed cortical shell is represented by an irregular spongy
framework, immediately enclosing the simple latticed medullary shell.


1. _Spongoplegma antarcticum_, n. sp.

Cortical shell with loose spongy framework and rough surface, four to six
times as broad as the enclosed simple medullary shell. Pores of the latter
regular circular, twice as broad as the bars. From its surface arise
numerous (forty to fifty or more) short radial beams, which become forked
and compose, by communication of lateral branches, the spongy cortical
shell.

_Dimensions._--Diameter of the spongy cortical shell 0.2 to 0.3 of the
latticed medullary shell 0.05 to 0.06.

_Habitat._--Antarctic Ocean, in large number, together with _Cromyosphæra
antarctica_; in the Diatom ooze of Station 157 (depth 1950 fathoms).



Genus 28. _Spongodictyon_,[44] Haeckel, 1862, Monogr. d. Radiol., p. 459.

_Definition._--#Liosphærida# forming a sphere of spongy framework, which
encloses in the centre a double latticed concentric medullary shell.

The genus _Spongodictyon_ can be regarded as a _Thecosphæra_, in which the
simple latticed cortical shell is represented by an irregular spongy
framework, which immediately encloses the double latticed medullary shell.
Sometimes this latter appears triple, the inner surface of the spongy
cortical shell forming a smooth spherical lattice-plate, separated by an
interval from the double medullary shell.



Subgenus 1. _Dictyoplegma_, Haeckel, 1862, Monogr. d. Radiol, p. 458.

_Definition._--Spongy cortical shell enveloping immediately the double
medullary shell.


1. _Spongodictyon spongiosum_, Haeckel.

  _Dictyosoma spongiosum_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 31, Taf. ii. figs. 9-11.

  _Dictyoplegma spongiosum_, Haeckel, 1862, Monogr. d. Radiol., p. 458.

Spongy framework of the cortical shell loose, with large, polygonal
roundish meshes, on an average as large as the double medullary shell,
which is immediately enveloped by it. Both concentric medullary shells with
subregular roundish pores, twice as broad as the bars.

_Dimensions._--Diameter of the cortical shell 0.2 to 0.3 or more; of the
outer medullary shell 0.03, inner 0.01.

_Habitat._--Mediterranean (French south coast, surface), J. Müller.


{91}2. _Spongodictyon cavernosum_, n. sp.

Spongy framework of the cortical shell rather compact in the inner part,
which immediately envelops the double medullary shell; very loose, with
large caverns in the outer part, caverns of the surface larger than the
medullary shell. Both medullary shells with regular circular pores, three
times as broad as the bars.

_Dimensions._--Diameter of the cortical shell 0.3 to 0.4, outer medullary
shell 0.1, inner 0.03.

_Habitat._--Tropical Atlantic, Station 338, surface.



Subgenus 2. _Spongodictyoma_, Haeckel.

_Definition._--Spongy cortical shell on the inner surface with a smooth
lattice-plate (or third medullary shell), which is connected by radial
beams with the inner double medullary shell.


3. _Spongodictyon trigonizon_, Haeckel.

  _Spongodictyon trigonizon_, Haeckel, 1862, Monogr. d. Radiol., p. 459,
  Taf. xxvi. figs. 4-6.

  _Dictyosoma trigonizon_, Haeckel, 1860, Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, p. 841.

Spongy framework of the cortical shell very loose, with very large, for the
most part triangular meshes, which are two to six times as large as the
enclosed double medullary shell. From the surface of the latter arise
numerous radial beams, which are connected by a spherical lattice-plate,
forming the smooth inner surface of the spongy sphere (or a third medullary
shell). The structure of the framework reminds one of the PHÆODARIUM
_Sagena_ (Pl. 108). Pores of both medullary shells regular circular, twice
as broad as the bars.

_Dimensions._--Diameter of the cortical shell 0.5 to 1.15, outer medullary
0.05, inner 0.035.

_Habitat._--Mediterranean, Messina, surface.


4. _Spongodictyon arcadophoron_, n. sp.

Spongy framework of the cortical shell in the inner part very loose, in the
outer part more compact; outer meshes scarcely as large as the inner
medullary shell (or only half as large), inner meshes two to four times as
large. From the surface of the double medullary shell arise numerous radial
beams, which are forked at equal distances from the centre; the fork
branches are curved and united together by dichotomous branches, like
elegant arcades; and these arcades form together the large polygonal meshes
on the inside of the cortical shell (or a third medullary shell). Both
medullary shells with regular circular pores, of the same breadth as the
bars.

_Dimensions._--Diameter of the cortical shell 0.2, outer medullary shell
0.04, inner 0.02.

_Habitat._--Tropical Atlantic, Station 349, surface.



{92}Family VI. #COLLOSPHÆRIDA#, J. Müller[45] (Pls. 5-8).

_Definition._--#Sphæroidea# living associated in colonies, united by an
alveolar jelly-body, and connected by the network of anastomosing
pseudopodia.

The family #Collosphærida# comprises all polyzous or social #Sphæroidea#,
and constitutes the only polyzoic group among the SPHÆRELLARIA. This group
was first constituted by J. Müller as "_Radiolaria polyzoa_ with
shells."[46] Formerly following his authority, in my Monograph I had
separated them from the other #Sphæroidea# and united them with the social
Collodaria (Sphærozoida).[47] Also R. Hertwig in his Organismus der
Radiolarien[48] united them with his Sphærozoea. In my Prodromus[49] I had
retained this isolated position. But a further careful study has convinced
me that this isolation is not truly natural, and that the Collosphærida are
only "social Ethmosphærida" which have arisen from this solitary subfamily
by adaptation to colonial life. There are some forms of Collosphærida which
are nearly identical with some forms of Ethmosphærida, only differing from
the latter by their association in colonies; and in some forms of both
groups it is quite impossible to decide whether the isolated shells
appertain to one or to the other family.

The isolated shell of the Collosphærida is almost constantly (with few
exceptions) a simple extracapsular lattice-shell, as in the Monosphærida;
only the small group of Clathrosphærida (with the genera _Clathrosphæra_
and _Xanthiosphæra_) exhibit an exception, the simple lattice-shell being
overgrown by an external mantle or veil of very thin, cobweb-like,
irregular lattice-work (Pl. 8, figs. 6-11). Therefore these Clathrosphærida
bear to the Acrosphærida (or the common simple Collosphærida) a relation
similar to that which _Liosphæra_ (p. 76) bears to _Cenosphæra_; both
shells are extracapsular "cortical shells" at a very short distance apart.
In the Collosphærida true concentric medullary shells never occur; the
central capsule always lies quite freely in the simple or double cortical
shell, separated from it by a jelly-veil.

Although a well marked difference in the simple lattice-shell of the social
Collosphærida and the solitary Ethmosphærida does not exist, nevertheless
in most cases the two shells can be distinguished by a practiced observer.
The simple fenestrated shells of the monozoic Ethmosphærida are commonly
quite regular spheres in a mathematical sense, or regular "endospherical
polyhedra"; whereas in the Collosphærida they are commonly more or less
irregular, often to an extraordinary degree (Pls. 5-8). Some species of
Collosphærida, however, also possess quite regular spherical shells.
Another difference is often shown in the lattice-work of the shells, which
in the Collosphærida is nearly always very irregular, and exhibits a
peculiar tendency to the {93}production of radial, conical, or cylindrical
tubules. These occur as well on the inside as on the outside of the shell,
and the tubules are now more conical, now more cylindrical; their wall
either solid or pierced by pores (Pls. 5-8). The tubules are commonly very
irregular in form, size, and disposition; distinguished, however, by a
number of hereditary peculiarities, which are sufficient for the
distinction of genera. Similar tubules occur also in some genera of
solitary Ethmosphærida (_Coscinomma_, _Ethmosphæra_, _Conosphæra_, &c., Pl.
12); but the tubules are here much more regular and not so highly
developed.

Besides the tubules of the fenestrated shells, in some genera of
Collosphærida the surface is armed with irregular thorns, rarely with more
regular radial spines. But these spines obtain constantly the character of
accessory by-spines, and remain short and thin. In this family typical
radial spines never occur in a regular and characteristic disposition,
corresponding to dimensive axes, as is the case in nearly all solitary
#Sphæroidea#, only excepting the Liosphærida. Commonly these spines or
thorns serve as protective arms for the shell-meshes, surrounding them
often in the form of coronels. Often the lattice-plate of the irregular
roundish shell is tubercular, elevated into irregular protuberances,
bearing on the top a short spine or thorn (Pl. 8).

The _Central Capsule_ of the Collosphærida is always a regular sphere, as
in all other #Sphæroidea#; it is constantly placed within the
lattice-shell, and commonly much smaller than it, separated from it by a
thick jelly-veil. A remarkable difference from the solitary #Sphæroidea# is
shown in the early division of the nucleus. Commonly the central capsule of
the Collosphærida contains in its centre a large oil-globule, surrounded by
very numerous small nuclei. R. Hertwig estimated this difference as so
important, that he separated the social "Sphærozoea" and the solitary
"Peripylea" as two different orders. As already shown above (p. 7, 24), we
cannot support this separation, and are now convinced that this difference
in the development of the spores--just as in the #Collodaria#--is the
consequence of an adaptation to social life.

The common jelly-body, in which the numerous central capsules and their
enveloping shells are united, exhibits in the Collosphærida quite the same
characters as in the other social Radiolaria, the Collozoida and
Sphærozoida. The jelly-body is very voluminous, commonly spherical, often
cylindrical, of considerable size; constantly containing numerous large
alveoles. Often each shell is enclosed in a separate alveole with rather
solid wall (Pl. 6, fig. 2). Sometimes in the dead colonies all shells are
united in the central part of the jelly-body, whilst its peripheral part is
composed of a stratum of large alveoles (Pl. 8, fig. 11); at other times no
alveoles are visible (Pl. 7, fig. 11). In many living colonies I found a
very large spherical alveole with thick wall in the centre of the spherical
colony, surrounded by many strata of delicate thin-walled alveoles (Pl. 5,
fig. 1).  In this case often the inner younger capsules were naked,
{94}without shells, the outer only surrounded by shells. Already in my
Monograph I had described the same peculiar formation.[50]

_Synopsis of the Genera of Collosphærida._

  -------------------------------------------------------------------------
  I. Subfamily Acrosphærida. (Lattice-shell simple, without an external
     mantle of network.)
  -------------------------------------------------------------------------
                {Inside        {Inside smooth,   29. _Collosphæra_.
  Outside of    {  without     {
    the shell   {  tubuli.     {Inside spiny,    30. _Tribonosphæra_.
    smooth,     {
    without     {              {Tubuli
    spines or   {Inside with   {  imperforated,  31. _Pharyngosphæra_.
    tubuli.     {  centripetal {
                {  tubuli.     {Tubuli
                {              {  fenestrated,   32. _Buccinosphæra_.

                               {Spines
                               {  irregularly
                               {  scattered on
                               {  the surface,   33. _Acrosphæra_.
                               {
  Outside of the shell armed   {Each larger
    with solid spines, but     {  pore with one
    with hollow tubuli.        {  single spine,  34. _Odontosphæra_.
                               {
                               {Each larger
                               {  pore with
                               {  a coronal of
                               {  spines,        35. _Choenicosphæra_.

                               {Mouth of the
                               {  tubuli
                               {  truncated,
                               {  smooth,        36. _Siphonosphæra_.
                               {
  Outside of    {Tubuli        {Mouth with
    the shell   {  simple, not {  one single
    with        {  branched.   {  large tooth,   37. _Mazosphæra_.
    irregular   {              {
    radial      {              {Mouth with a
    tubuli,     {              {  coronal of
    the wall of {              {  teeth,         38. _Trypanosphæra_.
    which is    {
    solid, not  {Tubuli irregularly branched,
    fenestrated.{  each with two to four or
                {  more openings,                39. _Caminosphæra_.

                               {Mouth of the
                               {  tubuli
                               {  truncated,
                               {  smooth,        40. _Solenosphæra_.
  Outside of the shell with    {
    irregular radial tubuli,   {Mouth with one
    open on both ends,         {  single large
    with fenestrated wall.     {  tooth,         41. _Otosphæra_.
                               {
                               {Mouth with a
                               {  coronal of
                               {  teeth,         42. _Coronosphæra_.
  -------------------------------------------------------------------------
  II. Subfamily Clathrosphærida. (Lattice-shell double, with an external
      mantle of network.)
  -------------------------------------------------------------------------
  Surface of the outer shell smooth,            43. _Clathrosphæra_.

  Surface of the outer shell thorny,            44. _Xanthiosphæra_.



Subfamily ACROSPHÆRIDA, Haeckel, 1881, Prodromus, p. 471.

_Definition._--#Collosphærida# with one simple lattice-shell around every
central capsule of the coenobium.



{95}Genus 29. _Collosphæra_,[51] J. Müller, 1855.

_Definition._--#Collosphærida# with simple shells, smooth on the inside and
on the outside, without any spines or tubuli.

The genus _Collosphæra_ is the most simple form of all Collosphærida, and
must be regarded as the common ancestral form of this family. As the
lattice-shell is quite a simple sphere, without any spines, tubules, or
other peculiar productions, it agrees perfectly with _Cenosphæra_, and
represents the social or polyzoid aggregate of this solitary or monozoid
genus. Therefore a certain distinction between the isolated shells of the
two genera is often very difficult or even impossible; but commonly this
distinction is possible owing to the circumstance, that in the majority of
the _Collosphæræ_ the shell is more or less irregular roundish or
polyhedral, not quite spherical, as in _Cenosphæra_. _Dermatosphæra_,
Ehrenberg, is a _Collosphæra_ with small pores (compare L. N. 16, p. 533).



Subgenus 1. _Eucollosphæra_, Haeckel.

_Definition._--Shell a regular or subregular sphere.


1. _Collosphæra primordialis_, n. sp.

Shell a regular sphere, with very delicate and regular network of hexagonal
meshes. Six to eight meshes in the half meridian of the shell. Diameter of
the meshes ten to fifteen times as broad as the thin bars between them. Can
be regarded as social form of _Cenosphæra primordialis_.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.008.

_Habitat._--Central Pacific, Stations 271 to 274, surface.


2. _Collosphæra regularis_, n. sp.

Shell a regular sphere, with a perfectly regular network of circular
meshes, all of the same size. Ten to twelve meshes in the half meridian of
the shell. Diameter of the meshes the same as that of the bars between
them.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.005 to
0.006.

_Habitat._--Indian Ocean, Madagascar, surface, Rabbe.


3. _Collosphæra globularis_, n. sp.

Shell a regular sphere, with subregular network of circular meshes of
different sizes; few large pores between many smaller pores. Ten to twenty
meshes in the half meridian of the shell. Diameter of the meshes from half
to twice as broad as that of the bars.

{96}_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.002 to
0.008, breadth of the bars 0.004 to 0.008.

_Habitat._--Tropical and subtropical zone of both hemispheres, widely
distributed; Canaries, Azores, Cape Verde Islands, Guinea Coast, Brazil
Coast, Indian Ocean, Madagascar, Ceylon, surface.



Subgenus 2. _Dyscollosphæra_, Haeckel.

_Definition._--Shell not a regular sphere, but irregular roundish, in all
degrees of variation between subspherical and polyhedral or quite irregular
forms.


4. _Collosphæra huxleyi_, J. Müller.

  _Collosphæra huxleyi_, J. Müller, 1855, Abhandl. d. k. Akad. d. Wiss.
  Berlin, pp. 55-59, Taf. viii. figs. 6-9.

  _Collosphæra huxleyi_, Haeckel, 1862, Monogr. d. Radiol., p. 534, Taf.
  xxxiv.

  _Collosphæra huxleyi_, Cienkowski, 1871, Archiv f. mikrosk. Anat., Bd.
  vii. p. 374, Taf. xxix. figs. 1-6.

  _Collosphæra ligurina_, J. Müller, 1856, Monatsber. d. k. Akad. d. Wiss.
  Berlin, p. 481.

  _Thalassicolla punctata_, var., Huxley, 1851, Ann. and Mag. Nat. Hist.,
  ser. 2, vol. viii. p. 434, pl. xvi. fig. 6.

Shell subspherical, somewhat irregular, sometimes with more or less
superficial impressions, with irregular network of roundish meshes. Eight
to sixteen meshes in the half meridian of the shell, one to three times as
broad as their bars. Very variable, with direct transition-forms to other
species of this genus, especially to _Collosphæra globularis_, _Collosphæra
tuberosa_, _Collosphæra pyriformis_, and _Collosphæra polyedra_.

_Dimensions._--Diameter of the shell 0.1 to 0.16, of the pores 0.004 to
0.012, of the bridges 0.003 to 0.006.

_Habitat._--Cosmopolitan; common in the greater part of the warmer seas,
surface.


5. _Collosphæra polygona_, n. sp. (Pl. 5, fig. 13).

  _Collosphæra huxleyi_ var., Haeckel, 1862, Monogr. d. Radiol., Taf.
  xxxiv. fig. 5.

Shell irregular polygonal, with very delicate, irregular network of
polygonal meshes, four to twelve times as broad as the bars.  Ten to twenty
pores on the half meridian of the shell.

_Dimensions._--Diameter of the shell 0.1 to 0.2, of the pores 0.012 to
0.004, of the bars 0.001 to 0.002.

_Habitat._--Mediterranean, Atlantic, surface; Stations 348 to 354.


6. _Collosphæra pyriformis_, Haeckel, n. sp.

Shell irregular, rounded, ovate or pear-shaped, with irregular network of
rounded or nearly polygonal meshes. Ten to twenty meshes in the half
meridian of the shell, one to three times as broad as the bars. Commonly
one large opening (two to three times as broad as the largest {97}meshes)
on the thinner end of the ovate shell (corresponding to the insertion of a
pear-stalk); sometimes two or three such large openings.

_Dimensions._--Diameter of the shell 0.1 to 0.15, of the pores 0.008 to
0.016, of the bridges 0.004 to 0.008.

_Habitat._--Tropical zone--Cape Verde Islands, Ceylon; Central Pacific,
Stations 266 to 272, 348 to 352, &c.


7. _Collosphæra polyedra_, n. sp.

  _Trisolenia zanguebarica_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 301, Taf. x. fig. 11.

Shell irregular, polyhedral, with even or somewhat vaulted sides, and
obtuse ridges between them. Network more or less irregular, with small
rounded meshes, quite as broad or twice as broad as their bars. Besides
these small pores constantly some large round openings (commonly three to
six), situated on the corners of the polyhedral shell, four to six times as
large as the pores. Often an acute tooth on the edge of each large opening.
Transition-form between _Collosphæra_ and _Solenosphæra_ or _Odontosphæra_.

_Dimensions._--Diameter of the shell 0.1 to 0.15, of the pores 0.004 to
0.008, of their bridges 0.004, of the large openings 0.24 to 0.032.

_Habitat._--Tropical zone of the Pacific and the Indian Ocean; Stations 266
to 272, surface.


8. _Collosphæra tuberosa_, n. sp.

  _Collosphæra huxleyi_, var., Haeckel, 1862, Monogr. d. Radiol., Taf.
  xxxiv. figs. 3, 9.

Shell very irregular, between subspherical and polyhedral in form, but
always with irregular impressions, boils or bosses, and between these
different rounded prominent tubercles and ridges. Network irregular,
strong, with rounded, subcircular or nearly polygonal meshes. Ten to thirty
pores in the half meridian of the shell. Diameter of the meshes half to
four times as broad as that of the thick bars.

_Dimensions._--Diameter of the shell very variable in the same coenobium,
0.05 to 0.2, of the pores 0.002 to 0.008, breadth of the bridges 0.004 to
0.006.

_Habitat._--Cosmopolitan, common in all warmer seas, surface.


9. _Collosphæra irregularis_, n. sp.

  _Collosphæra huxleyi_, var., Haeckel, 1862, Monogr. d. Radiol., Taf.
  xxxiv. fig. 8.

Shell quite irregular, knotty or bulbous, with irregular impressions, and
prominent knobs or bulbs between them. Network thin, fragile, quite
irregular, with polygonal meshes of most unequal size and form. Five to
twenty pores in the half meridian of the shell. Diameter of the meshes two
to ten times as broad as that of the thin bars.

_Dimensions._--Diameter of the shell very variable in the same coenobium,
0.04 to 0.24, of the pores 0.005 to 0.05, of the bridges 0.002 to 0.004.

_Habitat._--Mediterranean, Atlantic, not common; Stations 348, 352, &c.,
surface.



{98}Genus 30. _Tribonosphæra_,[52] Haeckel, 1881, Prodromus, p. 471.

_Definition._--#Collosphærida# with simple shells, on the inside with
radial centripetal beams.

The genus _Tribonosphæra_ differs from _Collosphæra_ by a very peculiar and
rare character, the development of centripetal radial sticks on the
internal face of the shell; these beams are not united in the centrum, but
finish freely in a certain distance from it.


1. _Tribonosphæra centripetalis_, n. sp. (Pl. 5, fig. 12).

Shell roundish or subspherical, with numerous small circular or roundish
pores, about twice as broad as the bars. Twenty to thirty pores on the half
meridian of the shell. Outside of the shell smooth, inside a variable
number (ten to twenty) of thin, radial, centripetal sticks or spines,
one-third or one-half as long as the radius of the shell. (In the central
capsule many very large crystals, resting after the destruction of the
capsule.)

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.003 to
0.005, of the bridges 0.001 to 0.002; length of the inner centripetal
sticks 0.02 to 0.03.

_Habitat._--Central Pacific, Station 271, surface.



Genus 31. _Pharyngosphæra_,[53] n. gen.

_Definition._--#Collosphærida# with simple shells, having on the inside
radial centripetal tubes, the walls of which are solid.

The genus _Pharyngosphæra_ differs from _Collosphæra_ by the development of
radial tubules on the inside of the shell, which are directed centripetally
towards its centre. The wall of the tubule is solid, not latticed as in the
following genus.


1. _Pharyngosphæra stomodæa_, n. sp. (Pl. 5, fig. 10).

Shell irregular polyhedral, with ten to fifteen polygonal faces and rounded
edges. Pores very small, circular, irregularly scattered, smaller than the
bars. Twelve to fifteen pores on the half meridian of the shell. On the
inside of every shell-face one short, nearly cylindrical, centripetal
tubule, twice as long as broad, and about one-third as long as the shell
radius. Outer umbilical mouth of the tubules somewhat wider than the inner
truncated mouth.

_Dimensions._--Diameter of the shell 0.11 to 0.12, of the pores 0.003 to
0.005, of the bars 0.01 to 0.02; length of the inner tubuli 0.02, breadth
of them 0.01.

_Habitat._--South Pacific, Station 288, depth 2600 fathoms.



{99}Genus 32. _Buccinosphæra_,[54] n. gen.

_Definition._--#Collosphærida# with simple shells, having on the inside
radial centripetal tubes, the walls of which are fenestrated.

The genus _Buccinosphæra_ exhibits, on the inner surface of the shell,
radial centripetal tubules similar to those of the foregoing
_Pharyngosphæra_; but the walls of these tubes are here latticed, not
solid; they represent therefore true invaginations of the whole shell-wall.


1. _Buccinosphæra invaginata_, n. sp. (Pl. 5, fig. 11).

Shell irregular roundish or nearly polyhedral, with a variable number of
umbilical depressions, which are prolonged on the inside into cylindrical
or somewhat conical, centripetal, fenestrated tubes, about one-third as
long as the shell radius. Inner mouth of the tubes narrower, scarcely half
as broad as the outer mouth, about equal to one-fourth the shell radius,
truncated. Pores of the tubes and of the shell small, roundish, irregular
in size and distribution, about as broad as the bars. Twenty-five to thirty
pores in the half meridian of the shell. In all observed specimens the
spherical central capsule (half as broad as the shell) contained a large
number of crystals.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.001 to
0.003, of the bars 0.002 to 0.003; length of the tubuli 0.02; outer mouth
0.026, inner mouth 0.013; crystals in the central capsule 0.002 to 0.004,
sometimes 0.008.

_Habitat._--Philippine Islands (Samboangan), Station 213, surface.


2. _Buccinosphæra tubaria_, n. sp.

Shell irregular polyhedral with rounded edges, with a variable number of
umbilical depressions, which are prolonged on the inside into large, nearly
cylindrical, centripetal, fenestrated tubes, half as long as the shell
radius. In the middle the tubes are somewhat constricted and narrower.
Inner mouth of the tubes dilated, nearly as broad as the outer mouth, about
equal to one-half the shell-radius, truncated. Pores of the tubes and of
the shell large, roundish polygonal, irregular in size and distribution,
three to four times as broad as the bars. Fifteen to twenty pores in the
half meridian of the shell.

_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.008 to
0.012, of the bars 0.002 to 0.004; length of the tubuli 0.03; outer mouth
0.04, inner mouth 0.03.

_Habitat._--North coast of New Guinea, Station 217, surface.



Genus 33. _Acrosphæra_,[55] Haeckel, 1881, Prodromus, p. 471.

_Definition._--#Collosphærida# with simple shells, the outer surface of
which is covered with radial, irregularly scattered spines.

{100}The genus _Acrosphæra_ differs from its ancestral genus _Collosphæra_
by the development of spines on the outer surface of the shell. These are
either short, straight, radial spines, or oblique and often curved; their
base is often inflated; they are irregularly scattered on the whole surface
between the pores.


1. _Acrosphæra erinacea_, n. sp.

Shell a regular sphere, everywhere covered with small, very numerous,
straight radial spines, regularly scattered between the pores. In the half
meridian of the shell ten to twelve circular pores, all of the same form
and size, double as broad as the bars. Spines bristle-shaped, very thin,
solid, about as long as the diameter of the pores.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.008 to
0.012; length of the spines 0.01.

_Habitat._--Tropical zone of the Atlantic, coast of Brazil, Rabbe, surface.


2. _Acrosphæra echinoides_, n. sp. (Pl 8, fig. 1).

Shell a regular sphere, covered with numerous, straight, radial spines,
irregularly scattered over the whole surface. In the half meridian of the
shell twenty to thirty irregular roundish pores of variable size, one to
four times as broad as the bars. Spines conical, strong, quite radial, at
the top of small conical elevations, which are perforated by from three to
six pores.

_Dimensions._--Diameter of the shell 0.12 to 0.15, of the pores 0.002 to
0.008; length of the spines 0.015, of their basal zones 0.01.

_Habitat._--South-east corner of the Pacific, Valparaiso, Station 298,
surface.


3. _Acrosphæra setosa_, Haeckel.

  _Polysolenia setosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 299, Taf. viii. fig. 10.

Shell a regular sphere, covered with numerous bristle-shaped radial spines,
irregularly scattered between the pores. In the half meridian of the shell
two to four very large circular pores (equal to one-third the radius), and
between them numerous very small, point-like pores.

_Dimensions._--Diameter of the shell 0.05 to 0.08, of the large pores 0.01,
of the small 0.001; length of the spines 0.01 to 0.02.

_Habitat._--West Tropical Pacific, Philippine Sea, Station 206, depth 2100
fathoms.


4. _Acrosphæra spinosa_, Haeckel.

  _Collosphæra spinosa_, Haeckel, 1862, Monogr. d. Radiol., p. 536, Taf.
  xxxiv. figs. 12, 13.

  _Collosphæra spinosa_, Cienkowsky, 1871, Archiv f. mikrosk. Anat., vii.
  p. 374, Taf. xxix. figs. 7-17.

Shell a regular or subregular sphere, covered with numerous, obliquely
standing spines, irregularly scattered over the surface. In the half
meridian of the shell fifteen to twenty irregular {101}roundish pores of
very different form and size, one to four times as broad as their bars.
Spines conical, irregularly diverging and curved, their hollow base
perforated by several pores, not longer than the diameter of the largest
pores.

_Dimensions._--Diameter of the shell 0.1 to 0.2, of the pores 0.001 to
0.04; length of the spines 0.01 to 0.02.

_Habitat._--Mediterranean, Messina; Canary Islands, Haeckel.


5. _Acrosphæra collina_, n. sp. (Pl. 8, fig. 2).

Shell quite irregular, polyhedrical, hilly, with a variable number (eight
to sixteen) of large conical hill-like prominences; every cone or hill
about as high as broad, perforated by the same pores as the shell, on its
top bearing a larger irregular roundish pore, and on its edge one single
bristle-like spine, not larger than the diameter of this pore, obliquely
inserted. In the half meridian of the shell twenty to thirty irregular
roundish pores of very different size, one to six times as broad as the
bars. A very characteristic species, closely resembling the following
_Odontosphæra_.

_Dimensions._--Diameter of the shell 0.15 to 0.25, of the pores 0.005 to
0.02; length of the spines 0.01 to 0.02, height of the hills from which
they rise 0.03 to 0.04.

_Habitat._--North coast of New Guinea, Station 218, surface.


6. _Acrosphæra inflata_, n. sp. (Pl. 5, fig. 7).

  _Mazosphæra inflata_, Haeckel, 1879, Atlas, _loc. cit._

Shell more or less irregular, polyhedral, hilly, with a variable number
(six to twelve) of large pyramidal, hill-like prominences; every hill about
as high as broad, on the top a strong conical, radial, or obliquely
inserted spine, inflated, with three to six very large polygonal meshes,
much larger than the other pores between the hills, which are also
polygonal, two to six times as broad as the bars. Ten to fifteen pores on
the half meridian.

_Dimensions._--Diameter of the shell 0.1 to 0.14, of the largest pores
0.05, of the smallest 0.005; length of the spines 0.02 to 0.03.

_Habitat._--North Atlantic, Station 64, surface.



Genus 34. _Odontosphæra_,[56] n. gen.

_Definition._--#Collosphærida# with simple shells, the outside of which
bears single scattered spines, one single spine on the margin of each
larger pore.

The genus _Odontosphæra_ is distinguished from the foregoing _Acrosphæra_
by the peculiar disposition of the spines, which are not scattered on the
outside of the shell between the pores, but so disposed that each larger
pore is protected by one single spine, obliquely placed over it.


{102}1. _Odontosphæra monodon_, n. sp. (Pl. 5, fig. 5).

Shell spherical or subspherical, with very small and numerous circular
pores, much smaller than the bars. Twelve to fifteen pores on the half
meridian of the shell. Between them a variable number of larger roundish
apertures (mostly twelve to sixteen) irregularly scattered, one-fourth to
one-fifth as broad as the shell radius. On the margin of every larger
aperture a single (rarely two or three) sharp conical tooth, about as long
as the diameter of the aperture, and obliquely laid over them.

_Dimensions._--Diameter of the shell 0.1 to 0.13, of the pores 0.001 to
0.003, of the bars 0.01 to 0.02, of the larger apertures 0.01 to 0.02.

_Habitat._--Sunda Archipelago, Station 192, surface.


2. _Odontosphæra cyrtodon_, n. sp. (Pl. 5, fig. 6).

Shell spherical or subspherical, with numerous roundish pores of very
irregular size and distribution, mostly larger than the bars. Ten to twelve
pores on the half meridian of the shell. Between them a variable number
(mostly six to nine) of large roundish pores, about half as broad as the
shell radius, armed on one side of the margin with one single large tooth,
about as long as the diameter of the aperture, hook-like, curved, and
obliquely laid over them.

_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.01 to
0.02, of the bars 0.003 to 0.006, of the larger apertures 0.03 to 0.04.

_Habitat._--Indian Ocean, near the Cocos Islands, Rabbe, surface.



Genus 35. _Choenicosphæra_,[57] n. gen.

_Definition._--#Collosphærida# with simple shells, armed on the outside
with radial spines, forming elegant coronals around the larger pores.

The genus _Choenicosphæra_ is characterised by the peculiar disposition of
its radial spines, which form protective coronals around the larger pores,
or even around all pores of the shell.



Subgenus 1. _Choenicosphærula_.

_Definition._--A coronal of spines around every pore of the shell.


1. _Choenicosphæra murrayana_, n. sp. (Pl. 8, fig. 4).

Shell spherical, with large circular or roundish pores of unequal size, two
to four times as broad as the bars. Ten to twelve pores in the half
meridian of the shell. Margin of every pore {103}with a coronal of six to
nine short and acute spines, not longer than the half diameter of the pore.
No spines between the pores.

_Dimensions._--Diameter of the shell 0.16 to 0.2, of the pores 0.02 to
0.03; length of the spines 0.008 to 0.012.

_Habitat._--Færöe Channel (Gulf Stream), common. Expedition of H.M.S.
"Triton," John Murray.


2. _Choenicosphæra flosculenta_, n. sp.

Shell spherical, with large circular or roundish pores of different size,
three to six times as broad as the bars. Six to eight pores in the half
meridian of the shell. Margin of every pore somewhat prominent, with a
coronal of ten to twenty parallel acute spines of different length, the
largest somewhat longer than the diameter of the pore. No spines between
the pores.

_Dimensions._--Diameter of the shell 0.12 to 0.15, of the pores 0.02 to
0.04; length of the spines 0.02 to 0.05.

_Habitat._--Central Pacific, Station 272, depth 2600 fathoms.



Subgenus 2. _Choenicosphærium_.

_Definition._--A coronal of spines only around the larger pores, not around
the smaller.


3. _Choenicosphæra nassiterna_, n. sp. (Pl. 8, fig. 3).

Shell spherical, with circular or roundish pores of very different size.
The smaller pores very numerous, without coronal of spines, roundish, about
as broad as the bridges. Twenty to thirty pores in the half meridian of the
shell. Between them, irregularly scattered, a small number (eight to
twelve) of very large circular pores, one-third to one-half as broad as the
radius of the shell, armed with a coronal of six to nine parallel,
straight, acute spines, about half as long as the radius of the shell.

_Dimensions._--Diameter of the shell 0.1 to 0.13, of the smaller pores
0.002 to 0.004, of the larger armed pores 0.02 to 0.03; length of the
spines 0.03 to 0.04.

_Habitat._--Philippine Islands, Mindanao, Station 213, depth 2050 fathoms.


4. _Choenicosphæra flammabunda_, n. sp. (Pl. 8, fig. 5).

Shell spherical, with circular or roundish pores of very different size.
The smaller pores very numerous and unequal, very irregularly scattered,
hardly one-fourth to one-half as broad as the bridges between them. Twelve
to twenty-four pores in the half meridian of the shell. Between them,
irregularly scattered, a variable number (ten to twenty) of very large
circular pores, about one-fourth as broad as the radius of the shell. The
margin of these large pores is armed with a very irregular coronal of four
to twelve unequal, curved acute spines, partly simple, partly branched like
{104}a deer-horn, one-fourth to one-half as long as the radius of the
shell. Some other small spines irregularly scattered over the shell.

_Dimensions._--Diameter of the shell 0.12 to 0.16, of the smaller pores
0.001 to 0.004, of the larger armed pores 0.016 to 0.024; length of the
spines 0.02 to 0.04.

_Habitat._--Central area of the Tropical Pacific, Stations 266 to 272,
depth 2425 to 2925 fathoms.



Genus 36. _Siphonosphæra_,[58] J. Müller, 1858, Abhandl. d. k. Akad. d.
Wiss. Berlin, p. 59.

_Definition._--#Collosphærida# with simple shells, the pores of which are
prolonged into external simple radial tubuli with solid wall; outer mouth
of the tubuli truncated, smooth.

The genus _Siphonosphæra_ is, next to _Collosphæra_, the most common of all
Collosphærida, and rich in different species; all agreeing in the tubular
prolongation of the pores, and corresponding therefore to _Ethmosphæra_
among the simple Liosphærida.



Subgenus 1. _Holosiphonia_, Haeckel.

_Definition._--All the pores or apertures of the shell prolonged into
tubules.


1. _Siphonosphæra pansiphonia_, n. sp.

Shell a regular sphere, everywhere occupied by short, regular cylindrical
tubes, all of the same size and form. Length of the tubules equal to their
breadth and to the intervals between them. Ten to twelve tubules in the
half meridian of the shell. This most regular species is nearly allied to
_Collosphæra regularis_, and may be derived from it by tubular prolongation
of all the regular pores.

_Dimensions._--Diameter of the shell 0.1 to 0.12, length and breadth of the
tubules 0.005 to 0.006.

_Habitat._--Indian Ocean, Sunda Strait, Rabbe, surface.


2. _Siphonosphæra marginata_, n. sp.

Shell a regular or subregular sphere, occupied by numerous short
cylindrical tubules of different sizes. Six to eight tubules in the half
meridian of the shell. Diameter of the tubules about equal to their
distance apart, but two to four times as large as their length.

_Dimensions._--Diameter of the shell 0.1 to 14; length of the tubules 0.004
to 0.006, breadth of the tubules and the intervals 0.01 to 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.


{105}3. _Siphonosphæra tubulosa_, J. Müller (Pl. 6, fig. 4).

  _Siphonosphæra tubulosa_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 59.

  _Siphonosphæra tubulosa_, Haeckel, 1862, Monogr. d. Radiol., p. 532.

  _Collosphæra tubulosa_, J. Müller, 1858, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 59.

  _Thalassicolla punctata_, var., Huxley, 1851, Ann. and Mag. Nat. Hist.,
  ser. 2, vol. viii. p. 435, pl. xvi. fig. 5.

Shell subspherical or roundish, somewhat irregular, occupied by a small
number (five to ten) of short cylindrical tubules, irregularly scattered at
great distances; intervals between the tubules very large, two to four
times as broad as the length of the tubules, which is equal to their
breadth and about one-fifth or one-sixth of the shell diameter. Only two or
three tubules in the half meridian of the shell.

_Dimensions._--Diameter of the shell 0.12 to 0.15, length and breadth of
the tubules 0.02 to 0.03.

_Habitat._--Equatorial zone of the Pacific, Stations 225, 265, 268,
surface.


4. _Siphonosphæra cyathina_, n. sp. (Pl. 6, fig. 10).

Shell a regular sphere, everywhere occupied by short cup-like tubules of
somewhat different size. In the half meridian of the shell about ten to
twelve tubules, nearly cylindrical, but constricted in the middle. Inner
and outer aperture of the tubule of the same size; their diameter equal to
their length and distance.

_Dimensions._--Diameter of the shell 0.1 to 0.12, length and breadth of the
tubules 0.005 to 0.01.

_Habitat._--West coast of Tropical Africa, Stations 348 to 352, surface.


5. _Siphonosphæra patinaria_, n. sp. (Pl. 6, figs. 7, 8).

Shell a regular or subregular sphere, occupied by numerous broad cup-like
tubules of very different sizes. In the half meridian of the shell about
six to eight tubules, very flat, circular or subcircular, much constricted
in the middle. Diameter of the inner aperture larger than that of the
middle stricture, smaller than that of the outer aperture of the tubule;
outer diameter two to four times as great as their length.

_Dimensions._--Diameter of the shell 0.1 to 0.15, of the pores 0.01 to
0.04; length of the tubules 0.01, breadth 0.02 to 0.04.

_Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms.


6. _Siphonosphæra infundibulum_, n. sp.

Shell subspherical or irregular rounded, occupied by a small number (six to
twelve) of large funnel-like tubules of very different size, scattered
irregularly at great distances. Intervals between the tubules larger than
their length, which surpasses the radius of the shell. Outer opening of the
funnels three to four times as broad as the inner.

_Dimensions._--Diameter of the shell 0.15; length of the tubules 0.05 to
0.09.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.


{106}7. _Siphonosphæra conifera_, n. sp. (Pl. 6, fig. 9).

Shell subspherical, everywhere occupied by irregular conical tubules, the
length of which nearly reaches the shell radius. Inner aperture of the
cones two to three times as large as the outer. Four to five tubules in the
half meridian of the shell. Distances between the bases of the cones small
and irregular.

_Dimensions._--Diameter of the shell 0.06 to 0.08, length of the tubules
0.03 to 0.04; inner aperture of the cones 0.01 to 0.02, outer aperture
0.008 to 0.01.

_Habitat._--Indian Ocean, Cocos Islands, Rabbe, surface.


8. _Siphonosphæra fragilis_, n. sp.

Shell quite irregular roundish or nearly ovate, very thin and fragile,
everywhere occupied by irregular, short, and broad cylindrical or conical
tubes. Six to ten tubes in the half meridian of the shell. Diameter of the
tubules about one-eighth that of the shell, three to four times as large as
the length of the tubules, and the distance apart of their bases.

_Dimensions._--Diameter of the shell 0.16 to 0.24, of the tubules 0.02 to
0.03; length of the tubules 0.006 to 0.008, distance of them 0.005 to
0.009.

_Habitat._--East coast of Australia, Sydney, Faber; Station 165, surface.



Subgenus 2. _Merosiphonia_, Haeckel.

_Definition._--Only part of the shell apertures prolonged in tubules, the
others simple.


9. _Siphonosphæra socialis_, n. sp. (Pl. 6, figs. 1, 2).

Shell a regular or subregular sphere, bearing only a small number (one to
four, commonly two to three) of short and broad cylindrical tubules,
irregularly scattered. Between them many small circular or subcircular
pores of different sizes, double as broad as their bars. Eight to ten pores
in the half meridian of the shell. Tubules three to six times as broad as
the pores, about as long as broad, now quite cylindrical, now somewhat
dilated at the outer opening. (Although the shells and cells of this common
species are among the smallest, their colonies are among the largest, often
containing more than one hundred social individuals, often enclosed in
alveoles.)

_Dimensions._--Diameter of the shell 0.04 to 0.05, of the pores 0.002 to
0.004, of the tubules 0.015 to 0.02; length of them about the same.

_Habitat._--Tropical and subtropical part of the Eastern Atlantic, Cape
Verde Islands, Canaries, very common, Haeckel; Stations 338 to 353,
surface.


10. _Siphonosphæra polysiphonia_, n. sp.

Shell a regular or subregular sphere, bearing twelve to sixteen circular
pores in its half meridian. Nearly one half the pores simple, very small;
the other half prolonged into short cylindrical tubules, {107}half as long
as broad, two to four times as broad as the pores and their intervals. This
species is nearly related to the foregoing, which it represents in the
western tropical part of the Atlantic, but differs constantly in the double
size of the shell and the much larger number of the tubules.

_Dimensions._--Diameter of the shell 0.06 to 0.09, of the pores 0.002 to
0.004, of the tubules 0.01 to 0.012; their length 0.006 to 0.008, surface.

_Habitat._--Tropical and subtropical part of the Western Atlantic, coast of
Brazil, &c., Rabbe.


11. _Siphonosphæra macrosiphonia_, n. sp.

Shell a regular sphere, with numerous very small pores of equal size and
distribution. Twelve to sixteen pores in its half meridian. Bars (between
the pores) three to four times as broad as their diameter. Only a small
number (two to four) of very long cylindrical tubes, irregularly scattered,
nearly as long or somewhat longer than the shell diameter; now quite
straight, now somewhat curved. Diameter of the cylinders four to six times
as large as that of the pores.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.002 to
0.004, of the tubules 0.015 to 0.018; length of the tubules 0.08 to 0.16.

_Habitat._--Central Tropical Pacific, Station 266 to 272, surface.


12. _Siphonosphæra serpula_, n. sp. (Pl. 6, fig. 6).

Shell a regular sphere, with numerous very small pores of equal size and
distribution. Eight to ten pores in its half meridian; bars between them
three to four times as broad as their diameter. Only a small number (six to
eight) of very long and snake-like, contorted, cylindrical tubes,
irregularly scattered. The shape of the latter is very much like that of
the calcareous tubes of some species of _Serpula_; they are nearly as long
as, or longer than, the shell diameter, and four to six times as broad as
the pores.

_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.003 to
0.005, of the tubules 0.02 to 0.022; length of the tubules 0.1 to 0.2.

_Habitat._--North Eastern Pacific, Station 252 to 262, Sandwich Islands,
Haltermann.


13. _Siphonosphæra chonophora_, n. sp. (Pl. 6, fig. 5).

Shell a regular or subregular sphere, with numerous very small pores of
equal size and distribution, ten to twelve in its half meridian. Bars
between the pores four to six times their diameter. Only a small number
(two to six) of very large funnel-like tubules, irregularly scattered. The
inner half of these tubules is a short cylindrical tube, of the same
thickness as the shell, three to four times as broad as the pores; the
outer half is an irregular funnel, suddenly expanded, with siliceous walls
of the utmost tenuity and fragility, often irregularly folded and
contorted, like a decayed flower-calyx, often half as large as the shell.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.003 to
0.005, inner half of the tubules 0.015 to 0.02, outer funnel-like half 0.05
to 0.08.

_Habitat._--South Pacific, Stations 285 to 295, surface.


{108}14. _Siphonosphæra pipetta_, n. sp. (Pl. 6, fig. 3).

Shell more or less irregularly roundish or subspherical, occupied in part
by very small pores, in part by very large cylindrical tubules, inflated in
the middle. Number, form, and size of the tubes very irregular; commonly
there are five to ten, half as long or as long as the shell radius; their
inner and outer aperture about half as broad as their inflated middle part;
three to nine times as broad as the pores. A very irregular and variable
species.

_Dimensions._--Diameter of the shell 0.1 to 0.15, of the pores 0.001 to
0.005, of the tubules 0.015 to 0.03; length of the tubules 0.03 to 0.08.

_Habitat._--North Pacific, Stations 242 to 253, surface.



Genus 37. _Mazosphæra_,[59] Ehrenberg, 1860.

  _Mazosphæra_, Ehrenberg, 1860, Monatsber. d. k. preuss. Akad. d. Wiss.
  Berlin, p. 833.

_Definition._--#Collosphærida# with simple shells, the pores of which are
prolonged into external simple radial tubuli with solid wall; outer mouth
of each tubulus armed with a single tooth.

The genus _Mazosphæra_ is intermediate between _Siphonosphæra_ and
_Odontosphæra_, agreeing with the former in the tubular prolongation of the
pores, with the latter in the possession of a single large protective tooth
on the outer opening.


1. _Mazosphæra hippotis_, n. sp. (Pl. 5, fig. 8).

Shell spherical, with circular pores of irregular size and distribution,
scarcely half as broad as the bars; fifteen to twenty on the half meridian
of the shell. Between them, irregularly distributed, a variable number (ten
to fifteen) of short cylindrical radial tubules, about twice as long as
broad, and half as long as the shell radius. Mouth of the tubuli obliquely
truncated, having on one side a strong acute tooth.

_Dimensions._--Diameter of the shell 0.11 to 0.12, of the pores 0.002 to
0.004, of the bridges 0.006 to 0.009; length of the tubuli 0.03, breadth of
them 0.01 to 0.015.

_Habitat._--North Pacific, Station 253, depth 3125 fathoms.


2. _Mazosphæra lagotis_, n. sp. (Pl. 5, fig. 9).

Shell spherical, with circular pores of irregular size and distribution,
about as broad as the bars; twelve to sixteen on the half meridian. Between
them, irregularly distributed, a variable number (eight to twelve) of long,
cylindrical, curved tubules, three to six times as long as broad, and about
as long as the shell radius; their external mouth lateral, obliquely
truncated, ovate, having on one side a strong conical tooth.

{109}_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.002
to 0.01; length of the tubuli 0.05 to 0.07.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.


3. _Mazosphæra lævis_, Ehrenberg.

  _Mazosphæra lævis_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 297, Taf. vii. fig. 7.

Shell spherical, with very small pores, scarcely one-fourth as broad as the
bars. Fifteen to twenty pores on the half meridian of the shell. Between
them, irregularly distributed, a variable number (fifteen to twenty) of
short conical tubules, about as long as broad, only one-fifth to one-sixth
as long as the shell radius. Mouth of the tubuli truncated, with an obtuse
short tooth on one side.

_Dimensions._--Diameter of the shell 0.08 to 0.09, of the pores 0.001 to
0.002, of the bridges 0.005 to 0.008; length of the tubuli 0.01 to 0.02,
breadth of them the same.

_Habitat._--Philippine Islands (depth 3300 fathoms), Ehrenberg; Station
206, depth 2100 fathoms; Station 225, depth 4575 fathoms.


4. _Mazosphæra apicata_, Ehrenberg.

  _Mazosphæra apicata_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, p. 316.

Shell spherical, without small pores, only with a variable number (ten to
twenty) of short conical tubules, twice as long as broad, and half as long
as the shell radius. Mouths of the tubuli obliquely truncated, with a
strong acute tooth on one side. (This species differs from the two
preceding by the want of the small pores between the tubules.)

_Dimensions._--Diameter of the shell 0.08 to 0.1, of the tubules 0.01.

_Habitat._--Philippine Islands (depth 3300 fathoms), Ehrenberg; north coast
of New Guinea, depth 2000 fathoms; Station 217.



Genus 38. _Trypanosphæra_,[60] n. gen.

_Definition._--#Collosphærida# with simple shells, the pores of which are
prolonged into external simple radial tubuli with solid walls; outer mouth
of each tubulus armed with a coronal of spines.

The genus _Trypanosphæra_ is intermediate between _Siphonosphæra_ and
_Choenicosphæra_ agreeing with the former in the tubular prolongation of
the pores, with the latter in the possession of a coronal of teeth on their
outer opening.



Subgenus 1. _Trypanosphærula_, Haeckel.

_Definition._--All pores of the shell prolonged into short coronated
tubules.


{110}1. _Trypanosphæra trepanata_, n. sp. (Pl. 5, fig. 4).

Shell regular spherical, with regular circular pores of nearly equal size,
at unequal distances, one to four times as broad as the bars. Eight to ten
pores on the half meridian. All the pores prolonged into short cylindrical
tubuli about as long as broad, armed on the external mouth with an elegant
coronal of twenty to thirty straight bristle-shaped, parallel teeth.

_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.015 to
0.02; length of the tubuli 0.02.

_Habitat._--Central Pacific, Station 268, depth 2900 fathoms.


2. _Trypanosphæra dentata_, n. sp.

Shell regular spherical, with regular circular pores of equal size, but at
very different distances. Only three to four pores on the half meridian.
All the pores prolonged into irregular curved, cylindrical tubuli, about as
long as the shell radius, with a coronal of ten to twelve short conical
teeth on the distal end.

_Dimensions._--Diameter of the shell 0.08 to 0.09; length of the tubuli
0.04, breadth 0.02.

_Habitat._--Central Pacific, Station 274, depth 2750 fathoms.



Subgenus 2. _Trypanosphærium_, Haeckel.

_Definition._--Only part of the shell-pores prolonged into coronated
tubules.


3. _Trypanosphæra coronata_, n. sp. (Pl. 5, fig. 3).

Shell regular spherical, with irregular roundish pores of very different
sizes. On the half meridian four to six large and twelve to sixteen very
small pores. About half of the large pores prolonged into short cylindrical
tubuli, the outer mouth of each being armed with an elegant coronal of ten
to twenty thin irregular teeth.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the large pores 0.01
to 0.02, of the small pores 0.001; length of the tubuli 0.012.

_Habitat._--North Pacific, Station 241, depth 2300 fathoms.


4. _Trypanosphæra terebrata_, n. sp.

Shell irregular roundish, with unequal, small, roundish pores. Sixteen to
twenty pores on the half meridian. Six to eight larger pores are prolonged
into curved cylindrical tubuli, about as long as the shell radius, with a
coronal of ten to twelve strong conical straight teeth on the distal end.

_Dimensions._--Diameter of the shell 0.15, of the pores 0.001 to 0.003;
length of the tubuli 0.08, breadth 0.02.

_Habitat._--West Tropical Pacific, Station 225, depth 4575 fathoms.


{111}5. _Trypanosphæra transformata_, n. sp. (Pl. 5, figs. 1, 2).

Shell quite irregular, of very variable, roundish, or polyhedral form, with
small irregular roundish pores, two to four times as broad as the bars. Ten
to thirty on the half meridian. The different form of the shell depends
upon the variable number of tubuli, which arise at irregular distances from
the shell; commonly three to four, often also five to six, more rarely one
or two. The tubuli are now more conical, now more cylindrical, about as
long as the shell radius, at other times scarcely one-half or one-third as
long, with a coronal of ten to twenty more or less curved teeth on the
narrower distal mouth. All the different forms are to be found in one and
the same colony, as shown in fig. 1. This coenobium, which I observed
living in Ceylon, exhibited the same peculiar formation as I figured in
_Collosphæra huxleyi_ in my Monograph 1862 (Taf. xxxiv. fig. 1). In the
centre of the jelly-sphere lies a large globular alveole, surrounded by
numerous small, young central capsules without shell; whilst in the surface
lies one layer of older capsules, enclosed in shells. Some of the younger
capsules exhibit self-division.

_Dimensions._--Diameter of the shells 0.08 to 0.12, pores 0.002 to 0.006;
length and breadth of the tubuli 0.03 to 0.05.

_Habitat._--Indian Ocean, Belligemma, Ceylon, surface.



Genus 39. _Caminosphæra_,[61] n. gen.

_Definition._--#Collosphærida# with simple shells, the pores of which are
prolonged into external branched radial tubuli with solid wall.

The genus _Caminosphæra_ differs from _Siphonosphæra_ (and from all other
Collosphærida) in the ramification of the tubuli, which arise from the
pores; the walls of the tubuli are solid, not fenestrated.


1. _Caminosphæra furcata_, n. sp.

Shell spherical or subspherical, with a variable number (four to eight) of
short cylindrical tubes, irregularly scattered, about as long as the radius
of the shell. Every tube forked, with two cylindrical branches of the same
size as the simple basal part of the tube. Mouth of the branches truncated,
not dilated. Pores of the shell between the tubes very small, all of the
same size, half as broad as their bars.  Fifteen to twenty pores in the
half meridian of the shell.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.001 to
0.002; length of the tubules 0.05 to 0.06, breadth of them 0.012 to 0.015.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.


2. _Caminosphæra elongata_, n. sp.

Shell spherical, with a large number (twelve to twenty) of long cylindrical
tubes, irregularly formed and scattered, somewhat longer than the diameter
of the shell. Every tube forked at {112}the distal end, with two or three
short irregular branches of unequal size and form; branches much shorter
than the undivided basal part of the tube. Mouth of the branches narrowed,
truncated. Pores of the shell between the tubes about half as broad,
irregularly roundish or polygonal, two to three times as broad as their
bars. Ten to twelve pores in the half meridian of the shell.

_Dimensions._--Diameter of the shell 0.05 to 0.07, of the pores 0.006 to
0.009; length of the tubules 0.06 to 0.09, breadth of them 0.015 to 0.02.

_Habitat._--Tropical Central Pacific, Station 271, depth 2425 fathoms.


3. _Caminosphæra dichotoma_, n. sp. (Pl. 7, fig. 2).

Shell spherical, with a variable number (ten to fifteen) of cylindrical
tubes, irregularly scattered, about as long as the radius of the shell.
Every tube furcated, with two cylindrical branches of the same size as the
simple basal part of the tube. Mouth of the branches dilated, funnel-like,
twice as broad as the tube; the edges irregularly dentated or lacerated.
Pores between the tubes small, one-third to one-sixth as broad as these,
half as broad as their bars. Ten to twelve pores in the half meridian of
the shell.

_Dimensions._--Diameter of the shell 0.12 to 0.14, of the pores 0.003 to
0.005; length of the tubules 0.06 to 0.08, breadth of them 0.02 to 0.03.

_Habitat._--Southern Pacific, Station 295, depth 1500 fathoms.


4. _Caminosphæra dendrophora_, n. sp. (Pl. 7, fig. 1).

Shell spherical, with a variable number (eight to twelve) of long
cylindrical tubes, irregularly branched and scattered, nearly as long as
the diameter of the shell. Every tube with two to six (commonly three to
four) branches of different sizes. Mouth of the branches dilated,
funnel-like; the edges irregularly dentated or lacerated. Pores between the
tubes half as broad as these, irregularly roundish, twice as broad as their
bars. Ten to twelve pores in the half meridian of the shell.

_Dimensions._--Diameter of the shell 0.12 to 0.15, of the pores 0.006 to
0.01; length of the tubules 0.1 to 0.13, breadth of them 0.02 to 0.025.

_Habitat._--Central Pacific, Station 266, depth 2750 fathoms.



Genus 40. _Solenosphæra_,[62] n. gen.

_Definition._--#Collosphærida# with simple shells, the pores of which are
prolonged into external simple radial tubuli with fenestrated wall; outer
mouth of the tubuli truncated, smooth.

The genus _Solenosphæra_ differs from _Siphonosphæra_ in the fenestration
of the external radial tubes. A large number of shells, appertaining to
this genus, were already described by Ehrenberg, and disposed in five
different genera corresponding to the {113}different numbers of the
tubuli:--_Disolenia_ with two tubes, _Trisolenia_ with three tubes,
_Tetrasolenia_ with four tubes, _Pentasolenia_ with five tubes,
_Polysolenia_ with six or more tubes. All these five genera are without
value, as those different numbers of tubes occur frequently intermingled in
the individual cells of one and the same colony, wherever the form and
structure of the tubes is inherited with sufficient constancy to determine
the species.



Subgenus 1. _Solenosphactra_, Haeckel.

_Definition._--Tubuli of the shell cylindrical or nearly cylindrical, the
outer and inner apertures nearly of the same size.


1. _Solenosphæra variabilis_, Haeckel.

  _Tetrasolenia quadrata_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
  Berlin, Taf. x. fig. 20.

Shell quite irregular roundish or polyhedral, with roundish pores of
different size. Ten to fifteen pores in the half meridian of the shell, two
to three times as broad as the bars. Porous tubuli of the shell in variable
number (in one and the same colony), three to nine, mostly four to six;
cylindrical or subcylindrical or somewhat conical, two to three times as
broad as long, not longer than the half radius of the shell. Inner aperture
of the tubuli commonly as broad as the half radius of the shell (or
somewhat smaller), about as large as the truncated outer aperture. This
species is closely related to _Collosphæra polyedra_ (p. 97), and may be
derived from it by a short tube-like prolongation of the larger apertures.

_Dimensions._--Diameter of the shell 0.1 to 0.16, of the pores 0.005 to
0.015; length of the tubules 0.02 to 0.03, breadth of them 0.04 to 0.06.

_Habitat._--Central area of the Tropical Pacific, Stations 270, 271, 272,
depths 2425 to 2925 fathoms.


2. _Solenosphæra pandora_, n. sp. (Pl. 7, figs. 10, 11).

Shell irregular roundish or subglobular, with roundish pores of different
sizes, mostly somewhat broader than the bars. About twelve to sixteen pores
on the half meridian of the shell. Porous tubuli of the shell of variable
number (in one and the same colony), one to six, mostly three to four;
cylindrical or nearly cylindrical, somewhat longer than broad, not longer
than the radius of the shell. Inner aperture of the tubuli commonly as
broad as the half radius of the shell, and a little smaller than the
truncated outer aperture.

_Dimensions._--Diameter of the shell 0.07 to 0.1, of the pores 0.003 to
0.006; length of the tubuli 0.03 to 0.05, breadth of them 0.02 to 0.03.

_Habitat._--Central area of the Tropical Pacific, Stations 266 to 274,
depths 2350 to 2925 fathoms.


{114}3. _Solenosphæra megalactis_, Haeckel.

  _Trisolenia megalactis_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 301, Taf. viii. fig. 19.

Shell irregularly polyhedrical, with very small roundish pores, scarcely
half as broad as the bars. Only eight to ten pores on the half meridian of
the shell. Porous tubuli of the shell of variable number (in one and the
same colony), two to five, mostly three or four; cylindrical, about as long
as the radius of the shell. Inner aperture of the tubuli commonly as broad
as the half radius of the shell, and quite as broad as the truncated outer
aperture.

_Dimensions._--Diameter of the shell 0.07 to 0.09, of the pores 0.002 to
0.004, of the bars 0.005 to 0.009; length of the tubuli 0.03 to 0.04,
breadth of them 0.02.

_Habitat._--Pacific; California, Philippine Sea, Ehrenberg; Stations 256 to
285, depths 310 to 3000 fathoms.


4. _Solenosphæra serpentina_, n. sp. (Pl. 7, fig. 7).

Shell nearly spherical, with very small circular pores, scarcely one-third
or one-fourth as broad as the bars. Only five to seven pores in the half
meridian of the shell. Porous tubuli of the shell of variable number (in
one and the same colony), two to nine, mostly seven or eight; cylindrical,
somewhat curved or contorted, once and a half or twice as long as the
diameter of the shell, with few very small and widely scattered pores.
Inner and outer aperture of the tubuli have the same diameter, about
one-fifth or one-fourth that of the shell. (This species is closely allied
to _Siphonosphæra serpula_, but is distinguished from it by the long
tortuous tubuli and the small scarce pores.)

_Dimensions._--Diameter of the shell 0.08 to 0.1, of the pores 0.001 to
0.002, of the bars 0.004 to 0.008; length of the tubuli 0.12 to 0.18,
breadth of them 0.02 to 0.025.

_Habitat._--North-eastern Pacific, between Sandwich Islands and California,
Haltermann, surface.



Subgenus 2. _Solenosphenia_, Haeckel.

_Definition._--Tubuli of the shell more or less conical, the inner aperture
much larger than the outer aperture.


5. _Solenosphæra venosa_, Haeckel.

  _Tetrasolenia venosa_, Ehrenberg, 1872, Abhandl. d. k. Akad. d. Wiss.
  Berlin, p. 301, Taf. vii. fig. 22.

Shell irregular polyhedral or roundish, with a delicate network of large
irregular polyhedral meshes, five to ten times as broad as the thin bars.
Eight to twelve meshes on the half meridian of the shell. Fenestrated
tubuli of the shell of variable number (in one and the same colony), one to
five, commonly three or four, shaped like a short truncated cone, about
half as long as broad on its base, shorter than the radius of the shell.
Inner aperture of the cone nearly as broad as the half radius of the shell,
about twice as broad as the truncated outer aperture.

{115}_Dimensions._--Diameter of the shell 0.07 to 0.12, of the pores 0.008
to 0.016, of the bars 0.001; length of the tubuli 0.02 to 0.03, inner
aperture 0.03 to 0.04, outer aperture 0.02 to 0.03.

_Habitat._--Indian Ocean, Sunda Strait, Rabbe.


6. _Solenosphæra ascensionis_, n. sp. (Pl. 7, fig. 9).

Shell somewhat irregular, subspherical, with polygonal pores of different
size. Twelve to fifteen pores in the half meridian of the shell, two to
eight times as broad as their bars. Porous tubuli of the shell of variable
number (in one and the same colony), three to nine, mostly five to seven;
conical or nearly cylindrical, irregular, about as long as broad at their
base. Inner aperture of the tubuli two to four times as broad as the
broadest pores, and double as broad as the truncated circular outer
aperture.

_Dimensions._--Diameter of the shell 0.1 to 0.12, of the pores 0.004 to
0.018, of the bars 0.002, length of the tubuli 0.04, inner aperture 0.04,
outer 0.02.

_Habitat._--South Atlantic, near Ascension Island, Station 343, surface.



Subgenus 3. _Solenosphyra_, Haeckel.

_Definition._--Tubuli of the shell funnel-like, the outer aperture much
larger than the inner.


7. _Solenosphæra cornucopia_, n. sp. (Pl. 7, fig. 8).

Shell spherical or subspherical, with roundish pores of different size. Ten
to twelve pores in the half meridian of the shell, two to three times as
broad as the bars. Porous tubuli of the shell of variable number (in one
and the same colony), four to eight, mostly five to seven, funnel-like,
about as long as the diameter of the shell. Inner aperture of the tubuli
commonly two-thirds or three-fourths as broad as the radius of the shell
(or somewhat smaller), only one-half or two-thirds as broad as the dilated
and truncated outer aperture.

_Dimensions._--Diameter of the shell 0.07 to 0.09, of the pores 0.006 to
0.018; length of the tubuli 0.06 to 0.08, diameter of the inner aperture
0.04 to 0.05, of the outer 0.06 to 0.08.

_Habitat._--Central Pacific, Station 271, depth 2425 fathoms.


8. _Solenosphæra amalthea_, n. sp.

Shell irregular roundish or spherical, with small circular pores of
different size. Fifteen to twenty pores in the half meridian of the shell,
but still not as broad as the bars. Porous tubuli of the shell of variable
number (in one and the same colony), three to six, commonly four or five,
funnel-like, about as long as the radius of the shell. Inner aperture of
the tubuli about half as broad as the radius of the shell, only one-half or
one-third as broad as the truncated outer aperture. (This species is
intermediate between the preceding and _Siphonosphæra chonophora_, Pl. 6,
fig. 5.)

{116}_Dimensions._--Diameter of the shell 0.09 to 0.11, of the pores 0.002
to 0.004, of the bars 0.003 to 0.006; length of the tubuli 0.05 to 0.06;
diameter of the inner aperture 0.02 to 0.03, of the outer aperture 0.05 to
0.07.

_Habitat._--Western part of the South Atlantic, Station 325, surface.



Genus 41. _Otosphæra_,[63] n. gen.

_Definition._--#Collosphærida# with simple shells, the pores of which are
prolonged into external simple radial tubuli with fenestrated walls; outer
mouth of the tubuli armed with a single tooth.

The genus _Otosphæra_ differs from _Solenosphæra_ by the single tooth on
the external mouth of the tubuli, from _Mazosphæra_ by the fenestration of
the walls of the tubuli.


1. _Otosphæra polymorpha_, n. sp. (Pl. 7, fig. 6).

Shell quite irregular, polyhedral or roundish, very variable in size and
form, with numerous very small pores, much smaller than the bars. Twenty to
thirty pores in the half meridian of the shell. Porous tubuli of the shell
commonly in variable number (one to four), but sometimes constant in number
(one, two, three, or four) in the one and same colony. Tubuli irregular
conical, commonly about as long as the radius of the shell; their outer
aperture obliquely truncated, on one side prolonged into one large,
prominent, bill-like, curved, acute tooth.

_Dimensions._--Diameter of the shell 0.12 to 0.15, of the pores 0.001 to
0.002; length of the tubuli 0.06 to 0.08, inner aperture 0.03, outer
aperture 0.02.

_Habitat._--Indian Ocean, Madagascar, Rabbe, surface.


2. _Otosphæra auriculata_, n. sp. (Pl. 7, fig. 5).

Shell quite irregular, of extremely variable form, now inclining to
roundish, now to polyhedral, with very numerous small pores, irregularly
formed and distributed. Twelve to twenty-four pores in the half meridian of
the shell, of very different size, for the most part larger than the bars.
Porous tubuli of the shell of variable number (in one and the same colony),
one to five, mostly three or four, of conical form, irregularly formed and
scattered, commonly about half as long as the radius of the shell. Outer
aperture of the tubuli obliquely truncated, with one large prominent, often
curved, acute tooth.

_Dimensions._--Diameter of the shell 0.1 to 0.2, of the pores 0.003 to
0.005; length of the tubuli 0.01 to 0.05, inner aperture 0.04, outer
aperture 0.03.

_Habitat._--Central Tropical Pacific, Stations 268 to 272, depths 2425 to
2925 fathoms.



{117}Genus 42. _Coronosphæra_,[64] n. gen.

_Definition._--#Collosphærida# with simple shells, the pores of which are
prolonged into external simple radial tubuli with fenestrated walls; outer
mouth of the tubuli armed with a coronal of spines.

The genus _Coronosphæra_ differs from _Solenosphæra_ by the coronated mouth
of the tubuli, from _Trypanosphæra_ by the fenestration of the walls of the
tubuli.


1. _Coronosphæra diadema_, n. sp. (Pl. 7, fig. 3).

Shell spherical or subspherical, with a variable number (fifteen to twenty)
of short, coronal-like tubules, irregularly scattered, about half as long
as the radius of the shell. Outer aperture of the tubuli irregularly
dentated, a little dilated, and not much broader than the inner aperture,
one-half or one-third as broad as the shell radius. Pores of the shell and
of the tubuli circular or roundish, very irregularly scattered, mostly
one-half or one-third as broad as the bars.

_Dimensions._--Diameter of the shell 0.11 to 14, of the pores 0.002 to
0.004, of the bars 0.006 to 0.012; length of the tubuli 0.03, inner
aperture 0.02 to 0.03, outer aperture 0.03 to 0.04.

_Habitat._--Central Pacific, Stations 268 to 270, depths 2550 to 2925
fathoms.


2. _Coronosphæra calycina_, n. sp. (Pl. 7, fig. 4).

Shell spherical or subspherical, with a variable number (eight to twelve)
of large, funnel-like tubules, irregularly scattered, about as long as the
radius of the shell. Outer aperture of the tubuli irregularly dentated,
much dilated, somewhat broader than the shell radius, three to four times
as broad as the inner circular aperture. Pores of the shell and of the
tubuli circular or roundish, of very different size, one to three times as
broad as the bars.

_Dimensions._--Diameter of the shell 0.1 to 0.3, of the pores 0.003 to
0.01, of the bars 0.002 to 0.004; length of the tubuli 0.1, inner aperture
0.02 to 0.03, outer aperture 0.06 to 0.18.

_Habitat._--Central Pacific, Stations 271, 272, depths 2425 and 2600
fathoms respectively.


3. _Coronosphæra convolvulus_, n. sp.

Shell irregular roundish, with a variable number (five to ten) of long,
curved tubules, about as long as the shell diameter. The inner half of the
tubuli is narrow, cylindrical; the outer half funnel-like dilated, similar
to the flower of _Convolvulus_. The outer aperture is elegantly dentated,
five to six times as broad as the inner aperture. Pores of the shell and of
the tubuli very irregular roundish, about as broad as the bars.

_Dimensions._--Diameter of the shell 0.08 to 0.09, of the pores and bars
0.004 to 0.008; length of the tubuli 0.07 to 0.1, inner aperture 0.01,
outer aperture 0.05.

_Habitat._--Tropical Atlantic, Station 347, surface.



{118}Subfamily CLATHROSPHÆRIDA, Haeckel, 1881, Prodromus, p. 472.

_Definition._--#Collosphærida# with a double lattice-shell around every
central capsule of the coenobium; both concentric shells connected by
irregular or subradial beams, commonly solid or lamellar staffs, rarely
hollow tubes.



Genus 43. _Clathrosphæra_,[65] Haeckel, 1881, Prodromus, p. 472.

_Definition._--#Collosphærida# with a double lattice-shell around every
central capsule of the coenobium; surface of the outer shell smooth.

The genus _Clathrosphæra_ (with smooth surface) and the following
_Xanthiosphæra_ (with spiny surface) form together the small subfamily,
Clathrosphærida, different from the other Collosphærida by the double
lattice-shell. From the surface of the inner primary shell arise either
solid spines or hollow tubes, which unite by the anastomosis of irregular
branches and so form the outer secondary shell, often very incomplete and
irregular. All Clathrosphærida seem to inhabit great depths.



Subgenus 1. _Clathrosphærula_, Haeckel.

_Definition._--The connecting staffs between both shells are hollow tubes
(derived from _Siphonosphæra_).


1. _Clathrosphæra circumtexta_, n. sp. (Pl. 8, fig. 6).

Inner shell spherical, with irregular roundish large meshes, now broader
now smaller than their bars. Eight to ten meshes in the half meridian of
the shell. All these meshes are prolonged into short cylindrical hollow
tubes, about as long as broad, somewhat constricted in the middle. From the
margins of the outer openings of these tubes proceed very numerous and
delicate siliceous filaments, which all lie on the same spherical face,
branch, anastomose, and twine over the openings and the intervals between
them, forming a very thin, arachnoid spherical outer shell. The meshes of
this are quite irregular polygonal, of very different size and form. The
radius of the inner shell bears to that of the outer a ratio = 5 : 6.

_Dimensions._--Diameter of the inner shell 0.11 to 0.13, of the outer 0.13
to 0.16; meshes of the inner shell 0.005 to 0.02, of the outer 0.005 to
0.04.

_Habitat._--North Pacific, Stations 238 to 253, depths 2050 to 3950
fathoms.



Subgenus 2. _Clathrosphærium_, Haeckel.

_Definition._--The connecting staffs between the two shells are solid rods
or lamellar spines (derived from _Acrosphæra_).


{119}2. _Clathrosphæra arachnoides_, n. sp. (Pl. 8, fig. 7).

Inner shell spherical, with irregular roundish meshes, two or three times
as broad as the bars. Ten to twelve meshes in the half meridian of the
shell. From its surface arise numerous conical radial spines (with base
often fenestrated), which at equal distances from the surface send out
lateral branches. All these branches lie on a spherical face, and form by
communications the irregular, very delicate, arachnoid network of the outer
shell, quite unlike that of the inner, with large polygonal meshes of very
different size. Eight to sixteen meshes in the half meridian of the shell.
Surface of the outer shell nearly spherical, somewhat uneven, like a
spider's web. The radius of the inner shell bears to that of the outer a
ratio = 3 : 4.

_Dimensions._--Diameter of the inner shell 0.12 to 0.14, of the outer 0.15
to 0.18; pores of the inner shell 0.003 to 0.02, of the outer 0.01 to 0.04.

_Habitat._--Central area of the Tropical Pacific, Station 268, depth 2900
fathoms.


3. _Clathrosphæra lamellosa_, n. sp. (Pl. 8, fig. 8).

Inner shell spherical or subspherical, with irregular roundish meshes,
about half as broad as the bars. Twelve to sixteen meshes in the half
meridian of the shell. From its surface arise numerous oblique irregular
staffs or broad and thin lamellæ, which branch quite irregularly, and by
communications of the branches form the thin outer shell. This is quite
irregular roundish or subspherical, very unlike the inner, with large
polygonal meshes of different size, six to twelve in the half meridian of
the shell. Bridges between the meshes very variable, now very thin
filamentous, now very broad lamellar. Outer surface very uneven or
tuberculated, but not spinous. The radius of the inner shell bears to that
of the outer a ratio = 5 : 6.

_Dimensions._--Diameter of the inner shell 0.1 to 0.13, of the outer 0.12
to 0.18; pores of the inner shell 0.003 to 0.009, of the outer 0.01 to
0.04.

_Habitat._--Central area of the Tropical Pacific, Stations 270 to 274,
depths 2350 to 2925 fathoms.



Genus 44. _Xanthiosphæra_,[66] Haeckel, 1881, Prodromus, p. 472.

_Definition._--#Collosphærida# with a double lattice-shell around every
central capsule of the coenobium; surface of the outer shell thorny or
spiny.

The genus _Xanthiosphæra_ differs from the foregoing _Clathrosphæra_ by
spines or thorns arising from the surface of the outer shell, commonly very
irregular.


1. _Xanthiosphæra capillacea_, n. sp.

Inner shell spherical, with irregular polygonal meshes, three to five times
as broad as their narrow bars. Six to eight meshes in the half meridian of
the shell. From its surface arise at the nodes of the network numerous thin
radial spines, which, at equal distances from the surface, {120}send out
lateral branches. All these branches lie on a spherical face, and form by
communications the irregular delicate network of the outer shell, very like
that of the inner, with large polygonal meshes, six to eight meshes in the
half meridian of the shell. Surface of the outer shell covered with
numerous straight spines, prolongations of the inner spines, but only half
as long as these. The radius of the inner shell bears to that of the outer
a ratio = 3 : 5.

_Dimensions._--Diameter of the inner shell 0.1 to 0.12, of the outer 0.15
to 0.19; pores of the inner shell 0.02 to 0.04 to 0.06, of the outer 0.04
to 0.06 to 0.08; length of the outer spines 0.01 to 0.02.

_Habitat._--Central area of the Tropical Pacific, Station 263, depth 2650
fathoms.


2. _Xanthiosphæra erinacea_, n. sp. (Pl. 8, fig. 9).

Inner shell spherical, with irregular roundish meshes, one-half to two
times as broad as the bars. Fifteen to twenty meshes in the half meridian
of the shell. From its surface arise numerous thin radial spines, which at
equal distances from the surface send out lateral branches. All these
branches lie on the face of a sphere, and form by communications the
irregular delicate network of the outer shell, very unlike that of the
inner, with large polygonal meshes, twelve to twenty-four in the half
meridian of the shell. Surface of the outer shell covered with numerous
straight spines, prolongations of the inner spines, and of the same length.
The radius of the inner shell bears to that of the outer a ratio = 3 : 4.

_Dimensions._--Diameter of the inner shell 0.1 to 0.12, of the outer 0.13
to 0.16; pores of the inner shell 0.002 to 0.008, of the outer 0.01 to
0.03; length of the outer spines 0.02 to 0.03.

_Habitat._--Central area of the Tropical Pacific, Stations 270, 272, depth
2925 and 2600 fathoms respectively.


3. _Xanthiosphæra lappacea_, n. sp. (Pl. 8, figs. 10, 11).

Inner shell spherical or subspherical, with very small roundish pores,
quite irregularly scattered, one-fourth to three-fourth as broad as their
bars. Ten to twenty pores in the half meridian of the shell. From its
surface arise in an extremely irregular and variable manner numerous
oblique spines, often curved, often lamellar, and perforated by pores,
sometimes hollow, fenestrated cones. At different distances from the
surface these spines send out lateral curved branches, which by
communications form the delicate and very irregular network of the outer
shell. This network is often incomplete and very unlike that of the inner
shell, with large polygonal meshes, six to eighteen in the half meridian of
the shell. Surface of the outer shell covered with numerous small, curved,
and oblique spines, prolongations of the inner spines, but scarcely
one-third to one-half as long as these. The radius of the inner shell bears
to that of the outer a ratio = 3 : 4.

_Dimensions._--Diameter of the inner shell 0.08 to 0.12, of the outer 0.11
to 0.15; pores of the inner shell 0.001 to 0.009, of the outer 0.01 to
0.04; length of the outer spines 0.005 to 0.009.

_Habitat._--Central area of the Tropical Pacific, Stations 263 to 274,
depths 2350 to 3000 fathoms.



{121}Family VII. #STYLOSPHÆRIDA#, Haeckel (Pls. 13-17).

_Stylosphærida_, Haeckel, 1881, Prodromus, p. 449.

_Definition._--#Sphæroidea# with two radial spines on the surface of the
spherical shell, opposite in one axis; living solitary (not associated in
colonies).

The family #Stylosphærida# comprises a large number of very common
#Sphæroidea#, and is distinguished from all others by the possession of two
radial spines which are placed in one axis of the spherical shell.[67] By
the expression of this "main axis" as a solid rod they form the transition
to the #Prunoidea#, in which the whole shell is more or less transformed
according to this "monaxial growth." But in these latter the shell, as well
as the central capsule, becomes ellipsoidal, prolonged in one axis, whilst
in the former they remain spherical. However, the distinction of both
nearly allied groups is sometimes difficult.

The most simple Stylosphærida are the _Xiphostylida_, with one single
spherical lattice-shell. To this ancestral group all other subfamilies can
be opposed as "Stylosphærida concentrica," as their carapace is composed of
two or more concentric lattice-shells: two in the Sphærostylida, three in
the Amphistylida, four in the Cromyostylida, five or more in the
Caryostylida. In all these four subfamilies the concentric shells are
simple (not spongy) fenestrated spheres. In a sixth subfamily, in the
Spongostylida, the shell is wholly or partially composed of a spongy
irregular wicker-work, with or without a medullary shell in the centre.

Both the radial spines in all Stylosphærida are opposed normally in one
axis; but in many species besides the normal form occur individual
abnormalities, in which the two spines are not accurately opposed in this
main axis, but placed in two different axes, intersecting at a smaller or
larger angle. In the majority of the Stylosphærida both opposite spines
have the same size and form; but in some genera they are more or less
different, often in a very striking degree. The same differences occur in
the nearly allied groups of #Prunoidea#, in the Ellipsida and Druppulida.

The distal ends of both spines are commonly free; but in the small group of
Saturnalida (_Saturnalis_ with one single shell, _Saturnulus_ with two
concentric shells, _Saturninus_ with three concentric shells) the distal
ends of both spines are united, at equal distances from the centre, by a
circular or elliptical ring. This remarkable peculiarity occurs in no other
group of #Sphæroidea#, and consequently brings the Saturnalida into close
relation with the #Discoidea#.

{122}_Synopsis of the Genera of Stylosphærida._

                  {              {Both spines
                  {Polar spines  { equal,      45. _Xiphosphæra_.
                  { free, without{
  I. Subfamily    { connecting   {Spines
    Xiphostylida. { ring on the  { different
  (Spherical shell{ distal ends. { in size
    simple.)      {              { or form,    46. _Xiphostylus_.
                  {
                  {Both polar spines united by
                  { a circular or elliptical
                  { ring,                      47. _Saturnalis_.

                  {              {Both spines
                  {              { equal,      48. _Stylosphæra_.
                  {Polar spines  {
  II. Subfamily   { free.        {Spines
    Sphærostylida.{              { different in
  (Two concentric {              { size or
    spheres.)     {              { form,       49. _Sphærostylus_.
                  {
                  {Both polar spines united by
                  { a circular or elliptical
                  { ring,                      50. _Saturnulus_.

                  {              {Both spines
                  {              { equal,      51. _Amphisphæra_.
                  {Polar spines  {
  III. Subfamily  { free.        {Spines
    Amphistylida. {              { different in
  (Three          {              { size or
    concentric    {              { form,       52. _Amphistylus_.
    spheres.)     {
                  {Both polar spines united by
                  { a circular or elliptical
                  { ring,                      53. _Saturninus_.

  IV. Subfamily   }              {Both spines
    Cromyostylida.}Polar spines  { equal,      54. _Stylocromyum_.
  (Four concentric} free.        {
    spheres.)     }              {Spines
                  }              { different,  55. _Cromyostylus_.

  V. Subfamily    }
    Caryostylida. }Polar spines  {Both spines
  (Five or more   } free.        { equal,      56. _Caryostylus_.
    concentric    }
    spheres.)     }

                  {Shell a solid spongy sphere
                  { without central medullary
                  { shell,                     57. _Spongolonchis_.
  VI. Subfamily   {
    Spongostylida.{              {One central
  (Spherical shell{              { medullary
    partially or  {In the centre { shell,      58. _Spongostylus_.
    wholly of a   { of the spongy{
    spongy        { sphere one or{Two
    structure.)   { two medullary{ concentric
                  { shells.      { medullary
                  {              { shells,     59. _Spongostylidium_.



Subfamily XIPHOSTYLIDA, Haeckel, 1881, Prodromus, pp. 449, 450.

_Definition._--#Stylosphærida# with one simple spherical lattice-shell.



Genus 45. _Xiphosphæra_,[68] Haeckel, 1881, Prodromus, p. 450.

_Definition._--#Stylosphærida# with one single lattice-sphere and two free
spines of equal size and form.

The genus _Xiphosphæra_ is the most simple form of all Stylosphærida, and
may be regarded as the common ancestral form of this family. On the surface
of a simple {123}spherical lattice-shell, enclosing the central capsule,
arise two equal, free, radial spines, opposite to each other on the poles
of one axis.



Subgenus 1. _Xiphosphærantha_, Haeckel.

_Definition._--Pores of the spherical shell regular, of nearly equal size
and form; surface smooth or a little rough, without spines or thorns (other
than the two polar spines).


1. _Xiphosphæra planeta_, n. sp.

Pores regular, hexagonal, eight to nine times as broad as the thin bars.
Ten to twelve pores on the half equator. Shell very thin walled; surface
smooth. Polar spines three-sided pyramidal, about as long as the axis of
the sphere, as broad at the base as one pore.

_Dimensions._--Diameter of the sphere 0.12 to 0.13, pores 0.016 to 0.018,
bars 0.002; length of the polar spines 0.1 to 0.15, basal thickness 0.02.

_Habitat._--Pacific, central area, surface; Stations 271 to 274, depths
2425 to 2750 fathoms.


2. _Xiphosphæra gæa_, n. sp. (Pl. 14, fig. 5).

Pores regular, circular, with prominent hexagonal crests between them. On
the half equator ten to twelve pores, of the same breadth as the crested
bars. Shell thin walled; surface smooth. Polar spines three-sided
prismatic, about twice as long as the axis of the sphere, twice as broad at
the base as one pore.

_Dimensions._--Diameter of the sphere 0.07 to 0.09, pores and bars 0.005;
length of the polar spines 0.15 to 0.2, basal thickness 0.01.

_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms.


3. _Xiphosphæra venus_, n. sp. (Pl. 14, fig. 2).

Pores regular, circular, with prominent hexagonal frames. On the half
equator fifteen to eighteen pores, of the same breadth as the bars. Shell
very thick walled; surface smooth, honeycomb-like. Polar spines conical,
smooth, about as long as the axis of the shell, twice as broad at the base
as one pore.

_Dimensions._--Diameter of the sphere 0.12 to 0.13, pores and bars 0.005;
thickness of the shell wall 0.013; length of the polar spines 0.12 to 0.15,
basal breadth 0.01.

_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.


4. _Xiphosphæra luna_, n. sp.

Pores regular, circular, hexagonally lobed or rosette-shaped, three times
as broad as the bars. Ten to twelve pores on the half equator. Shell thick
walled; surface smooth. Polar spines three-sided pyramidal, one to two
times as long as the axis of the shell, as broad at the base as one pore
{124}(very similar to _Xiphostylus phasianus_, Pl. 13, fig. 9, but
different in the equal size and similar form of the two large polar
spines).

_Dimensions._--Diameter of the sphere 0.12, pores 0.015, bars 0.005; length
of the polar spines 0.1 to 0.2, basal breadth 0.02.

_Habitat._--Indian Ocean, Cocos Islands, surface, Rabbe.


5. _Xiphosphæra hebe_, n. sp.

Pores regular, circular, three times as broad as the bars. On the half
equator sixteen to twenty pores. Shell thick walled; surface smooth. Polar
spines conical or nearly cylindrical, about as long as the axis of the
sphere, as broad at the base as two pores.

_Dimensions._--Diameter of the sphere 0.1 to 0.13, pores 0.006, bars 0.002;
polar spines 0.1 to 0.15 long, 0.01 thick.

_Habitat._--Pacific, central area, Stations 265 to 268, depths 2700 to 2900
fathoms.


6. _Xiphosphæra maxima_, n. sp.

Pores regular, circular, twice as broad as the bars, funnel-shaped. Twenty
to thirty pores on the half equator. Shell very thick walled; surface
smooth. Polar spines three-sided pyramidal, about as long as the radius of
the sphere, as broad at the base as two pores.

_Dimensions._--Diameter of the sphere 0.22 to 0.35, pores 0.008 to 0.01,
bars 0.005; polar spines 0.1 to 0.15 long, 0.02 thick.

_Habitat._--Equatorial Atlantic, Station 347, depth 2250 fathoms.


7. _Xiphosphæra euphrosyne_, n. sp.

Pores regular, circular, about as broad as the bars, double contoured.
Eight to ten on the half equator. Shell thin walled; surface smooth. Polar
spines conical, about as long as the radius of the sphere, as broad at the
base as one pore.

_Dimensions._--Diameter of the sphere 0.12 to 0.15, pores and bars 0.02;
polar spines 0.06 to 0.09 long, 0.02 thick.

_Habitat._--South Atlantic, Station 323, depth 1900 fathoms.



Subgenus 2. _Xiphosphærella_, Haeckel.

_Definition._--Pores of the spherical shell regular, of nearly equal size
and form; surface thorny or spiny, covered with regularly distributed
papillæ or thorns (in addition to the two large polar spines).


8. _Xiphosphæra pallas_, n. sp. (Pl. 14, fig. 4).

Pores regular, circular, separated by hexagonal elevated frames, the sharp
crest of which is elegantly denticulated; in each corner of the hexagons
(between three pores) is a short radial spine, {125}about as long as one
pore. On the half equator sixteen to twenty pores, of the same breadth as
the bars. Shell thick walled; whole surface spiny. Polar spines
cylindrical, at the apex conical, about as long as the axis of the sphere,
three to four times as broad as one pore.

_Dimensions._--Diameter of the sphere 0.1, pores and bars 0.005; length of
the polar spines 0.07 to 0.11, thickness 0.015 to 0.02.

_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.


9. _Xiphosphæra flora_, n. sp.

Pores regular, circular, with hexagonal frames, twice as broad as the bars.
Ten to twelve pores on the half equator. Shell thin walled, with spiny
surface; in each corner of the hexagons is one bristle-like radial spine
twice as long as one pore. Polar spines three-sided prismatic, at the apex
pyramidal, nearly twice as long as the axis of the sphere, as broad at the
base as two pores (similar to _Ellipsoxiphus palliatus_, Pl. 14, fig. 7).

_Dimensions._--Diameter of the sphere 0.15, pores 0.01, bars 0.005; length
of the polar spines 0.2 to 0.25, breadth 0.02.

_Habitat._--Tropical Atlantic, Station 342, depth 1445 fathoms.


10. _Xiphosphæra juno_, n. sp.

Pores regular, circular, as broad as the bars, funnel-shaped. Fifteen to
twenty pores on the half equator. Shell thick walled, covered with
bristle-like spines, about twice as long as one pore. Polar spines conical,
thick, about as long as the axis of the sphere, twice as broad at the base
as one pore.

_Dimensions._--Diameter of the sphere 0.12, pores and bars 0.01; length of
the polar spines 0.14, basal breadth 0.02.

_Habitat._--Fossil in the Barbados rocks; living in the greatest depth of
the Tropical Pacific, Station 225, depth 4475.


11. _Xiphosphæra gigantea_, n. sp.

Pores regular, circular, two to three times as broad as the bars;
twenty-eight to thirty-two on the half equator. Shell thick walled, covered
with short conical thorns. Polar spines three-sided pyramidal, about as
long as the radius of the sphere, as broad at the base as three pores.

_Dimensions._--Diameter of the sphere 0.25 to 0.3, pores 0.01, bars 0.004;
polar spines 0.1 to 0.15 long, 0.03 broad.

_Habitat._--Fossil in the Tertiary rocks of Barbados and Sicily
(Cattanisetta).



Subgenus 3. _Xiphosphærissa_, Haeckel.

_Definition._--Pores of the spherical shell irregular, of different size or
form; surface smooth or a little rough, without spines or thorns (other
than the polar spines).


{126}12. _Xiphosphæra ceres_, n. sp.

Pores irregular, roundish, of different sizes, two to four times as broad
as the bars. Sixteen to twenty pores on the half equator. Shell thin
walled, with smooth surface. Polar spines conical, about as long as the
axis of the sphere, very thick at the base.

_Dimensions._--Diameter of the sphere 0.15 to 0.2, pores 0.004 to 0.008,
bars 0.002; polar spines 0.18 to 0.24 long, at the base 0.02 thick.

_Habitat._--North Atlantic, Station 353, surface.


13. _Xiphosphæra clavigera_, n. sp.

Pores irregular, roundish, double contoured, of very unequal size, two to
seven times as broad as the bars; ten to twelve on the half equator. Shell
thick walled; surface a little rough. Polar spines club-shaped, with
prominent edges, about half as long as the axis of the sphere; thinner at
both ends than in the middle. (Differs from _Ellipsoxiphus claviger_, Pl.
14, fig. 3, in the spherical shell and shorter spines.)

_Dimensions._--Diameter of the sphere 0.2, pores 0.005 to 0.02, bars 0.003;
polar spines 0.06 long, 0.02 broad.

_Habitat._--Pacific, central area, Station 274, depth 2750 fathoms.



Subgenus 4. _Xiphosphæromma_, Haeckel.

_Definition._--Pores of the spherical shell irregular, of different size or
form; surface thorny or spiny (besides the two large polar spines).


14. _Xiphosphæra vesta_ n. sp. (Pl. 14, fig. 6).

Pores irregular, roundish, three to five times as broad as the bars;
fourteen to sixteen on the half equator. Scattered on the surface of the
thick-walled shell are from twenty to thirty strong three-sided pyramidal
spines of unequal size, the largest twice as long as the largest pores.
Polar spines very strong, nearly three-sided prismatic, with curved edges,
nearly as long as the axis of the sphere and twice as broad as the largest
pores.

_Dimensions._--Diameter of the sphere 0.17, pores 0.01 to 0.02, bars 0.004;
length of the polar spines 0.13, thickness 0.02 to 0.03.

_Habitat._--Pacific, central area. Station 266, depth 2750 fathoms,


15. _Xiphosphæra astræa_, n. sp.

Pores irregular, roundish, one to two times as broad as the bars; ten to
twelve on the half equator. Surface of the thick-walled shell covered with
numerous short conical thorns. Polar spines cylindro-conical, one and a
half to two times as long as the axis of the sphere.

{127}_Dimensions._--Diameter of the sphere 0.18, pores 0.01 to 0.015, bars
0.008; length of the polar spines 0.25 to 0.3, thickness 0.02.

_Habitat._--Indian Ocean, surface; Ceylon, Haeckel.



Genus 46. _Xiphostylus_,[69] Haeckel, 1881, Prodromus, p. 450.

_Definition._--#Stylosphærida# with one single lattice-sphere and two free
spines of different size or form.

The genus _Xiphostylus_ differs from the foregoing _Xiphosphæra_ in the
unequal size or form of both polar spines, which become more or less
differentiated.



Subgenus 1. _Xiphostylantha_, Haeckel.

_Definition._--Pores of the spherical shell regular, of nearly equal size
and form; surface smooth or a little rough, without spines or thorns.


1. _Xiphostylus alcedo_, n. sp. (Pl. 13, fig. 4).

Pores regular, circular, with elevated hexagonal frames, twice as broad as
the bars. Eight to ten pores on the half equator. Surface smooth. Polar
spines three-sided pyramidal, as broad at the base as one hexagon; the
major spine four to five times as long as the minor, which is about equal
to the radius of the sphere.

_Dimensions._--Diameter of the sphere 0.12, pores 0.012, bars 0.006; length
of the major polar spine 0.16 to 0.2, of the minor 0.04 to 0.06, basal
breadth 0.02.

_Habitat._--Western Tropical Pacific, Station 225, depth 4475.


2. _Xiphostylus phasianus_, n. sp. (Pl. 13, fig. 9).

Pores regular, circular, twice as broad as the bars. Eight to ten pores on
the half equator. Outer opening of each pore elegantly lobed, with eight
indentations. Surface a little rough. Polar spines very unequal; major
spine sword-like, sharply edged, about as long as the diameter of the
sphere; minor spine scarcely half so long, pommel-shaped, with nine (?)
wing-like edges.

_Dimensions._--Diameter of the sphere 0.13, inner circular opening of the
pores 0.01, outer eight-lobed opening 0.015, bars 0.005; length of the
major polar spine 0.14, of the minor 0.06, breadth 0.03.

_Habitat._--Australian Sea, Station 162, surface.


3. _Xiphostylus motacilla_, n. sp.

Pores regular, circular, three times as broad as the bars; sixteen to
twenty on the half equator. Surface smooth. Polar spines compressed,
two-edged, at the base three to four times as broad as {128}one pore; the
major spine somewhat longer than the diameter of the shell, the minor
scarcely one-third or one-half as long.

_Dimensions._--Diameter of the sphere 0.14, pores 0.006, bars 0.002; length
of the major spine 0.16 to 0.18, of the minor 0.05 to 0.07, basal breadth
0.02.

_Habitat._--Indian Ocean, Zanzibar, 2200 fathoms, Pullen.


4. _Xiphostylus gallus_, n. sp.

Pores regular, circular, five times as broad as the bars. Twelve to sixteen
pores on the half equator. Surface smooth. Polar spines very unequal; the
major conical spine one and a half to three times as long as the diameter
of the sphere; the minor pommel-shaped, scarcely one-third as long (length
of both spines very variable).

_Dimensions._--Diameter of the sphere 0.13, pores 0.01, bars 0.002; length
of the major spine 0.2 to 0.4, of the minor 0.05 to 0.08.

_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.


5. _Xiphostylus alauda_, n. sp. (Pl. 14, fig. 15).

  _Lithomespilus alauda_, Haeckel, 1881, Prodrom. et Atlas, _loc. cit._

Pores subregular, circular, three to four times as broad as the bars;
fifteen to eighteen on the half equator. Surface a little rough. Polar
spines irregularly conical or pyramidal, scarcely as long as the radius of
the sphere; one spine simple, the other composed of a bunch of four or five
spines united at the base.

_Dimensions._--Diameter of the sphere 0.11, pores 0.01, bars 0.003; length
of the polar spines 0.03 to 0.05, basal breadth 0.02.

_Habitat._--Pacific, central area, Station 272, depth 2600 fathoms.


6. _Xiphostylus anhinga_, Haeckel.

  _Rhabdolithis pipa_, Bury, 1862, Polycystins of Barbados, pl. iii. fig.
  4.

Pores subregular, circular, about the same breadth as the bars; eight to
ten on the half equator. Surface smooth or a little rough. Polar spines
cylindrical, very irregularly curved like S or contorted, the major three
to six times as long as the diameter of the sphere, the minor scarcely
one-fourth as long as the former, at the end truncated.

_Dimensions._--Diameter of the sphere 0.07, pores and bars 0.005; length of
the major polar spine 0.2 to 0.4, of the minor 0.06 to 0.09, basal breadth
0.01.

_Habitat._--Fossil in the Barbados rocks.



Subgenus 2. _Xiphostyletta_, Haeckel.

_Definition._--Pores of the spherical shell regular, of nearly equal size
and form; surface thorny or spiny (other than the two large polar spines).


{129}7. _Xiphostylus cuculus_, n. sp.

Pores regular, circular, hexagonally framed, three times as broad as the
bars; ten to twelve on the half equator. Surface thorny, between every
three pores a short conical thorn. Polar spines three-sided prismatic, the
major somewhat longer than the diameter of the sphere, the minor scarcely
one-third as long, pommel-shaped.

_Dimensions._--Diameter of the sphere 0.17, pores 0.012, bars 0.004; length
of the major polar spine 0.2, of the minor 0.05, basal breadth 0.015.

_Habitat._--South Atlantic, surface; Station 335, depth 1425 fathoms.


8. _Xiphostylus trochilus_, n. sp. (Pl. 13, fig. 10).

Pores regular, circular, four times as broad as the bars; eight to nine on
the half equator. Polar spines cylindrical, the major somewhat longer than
the axis of the sphere, the minor shorter, surrounded by a group of from
four to eight shorter conical spines. Surface of the opposite hemisphere
smooth, without by-spines.

_Dimensions._--Diameter of the sphere 0.07 to 0.08, pores 0.01, bars
0.0025.

_Habitat._--North Pacific, Station 244, depth 2900 fathoms.


9. _Xiphostylus picus_, n. sp. (Pl. 14, fig. 13).

  _Lithomespilus picus_, Haeckel, 1881, Prodrom. et Atlas.

Pores regular, circular, twice as broad as the bars; sixteen to eighteen on
the half equator. Polar spines cylindrical, conical at the apex, the major
once and a half to twice as long as the diameter of the shell, the minor
scarcely half so long; around the latter a group of twelve to twenty
shorter conical spines, irregularly scattered. Surface of the other
hemisphere smooth.

_Dimensions._--Diameter of the sphere 0.13, pores 0.006, bars 0.003; length
of the major polar spine 0.2 to 0.24, of the minor 0.08 to 0.09, basal
breadth 0.02.

_Habitat._--Central Pacific, Station 265, depth 2900 fathoms.



Subgenus 3. _Xiphostylissa_, Haeckel.

_Definition._--Pores of the spherical shell irregular, of unequal size or
form; surface smooth or a little rough, without thorns.


10. _Xiphostylus trogon_, n. sp. (Pl. 14, fig. 12).

  _Lithomespilus trogon_, Haeckel, 1881, Prodrom. et Atlas.

Pores irregular, roundish or subcircular, two to three times as broad as
the bars; ten to twelve on the half equator. Surface smooth. Major polar
spine three-sided prismatic, once and a half to twice as long as the axis
of the sphere; minor spine quite rudimentary, scarcely longer than broad,
but surrounded by a group of from three to six similar short spines.

{130}_Dimensions._--Diameter of the sphere 0.1, pores 0.005 to 0.015, bars
0.005 to 0.008; length of the major spine 0.15 to 0.18, of the minor 0.01
to 0.02, basal breadth 0.02.

_Habitat._--Western Tropical Pacific, Station 225, depth 4475 fathoms.


11. _Xiphostylus falco_, n. sp. (Pl. 13, fig. 14).

Pores irregular, roundish, two to five times as broad as the bars; sixteen
to eighteen on the half equator. Surface smooth. Polar spines cylindrical,
very stout, nearly half as thick as the radius of the shell; major spine
two to four times as long as the diameter of the shell; minor spine
obliquely inserted, scarcely longer than the diameter, divided at the end
into two short, hook-shaped, curved branches.

_Dimensions._--Diameter of the sphere 0.08, pores 0.002 to 0.005, bars
0.001; breadth of the spines 0.02, length of the major spine 0.15 to 0.2,
of the minor 0.09.

_Habitat._--South Pacific, Station 302, depth 1450 fathoms.


12. _Xiphostylus alca_, n. sp. (Pl. 13, fig. 13).

Pores irregular, roundish, two to six times as broad as the bars; six to
eight on the half equator. Each pore with three to six lobes, composed of
three to six confluent smaller pores. Surface smooth. Major spine conical,
curved, somewhat longer than the axis of the sphere; minor spine somewhat
shorter, pommel-like, edged.

_Dimensions._--Diameter of the sphere 0.07, pores 0.01 to 0.02, bars 0.003;
length of the major spine 0.08, of the minor 0.06, basal thickness 0.02.

_Habitat._--Indian Ocean, Sunda Strait, Rabbe, surface.


13. _Xiphostylus edolius_, n. sp. (Pl. 13, fig. 5).

Pores irregular, roundish, composed of two to six smaller confluent pores.
On the half equator six to eight large pores, and twenty to thirty small
pores; bars between the smaller very thin. Surface a little rough. Major
polar spine conical, S-shaped, about twice as long as the axis of the
shell; minor spine pommel-shaped, edged, scarcely as long as its radius.

_Dimensions._--Diameter of the sphere 0.12, large pores 0.01 to 0.03, small
pores 0.004 to 0.008, bars 0.001 to 0.004; length of the major spine 0.2,
of the minor 0.05, basal breadth 0.02.

_Habitat._--Central Pacific, Station 273, surface.



Subgenus 4. _Xiphostylomma_, Haeckel.

_Definition._--Pores of the spherical shell irregular, of different size or
form; surface thorny or spiny.


{131}14. _Xiphostylus emberiza_, n. sp. (Pl. 13, fig. 11).

Pores irregular, roundish, one to four times as broad as the bars; six to
eight on the half equator. Polar spines very unequal; major cylindrical,
twice as long as the axis of the sphere; minor scarcely half as long,
obliquely inserted, like a bird's head, surrounded by a group of ten to
twenty smaller conical spines. Opposite hemisphere smooth.

_Dimensions._--Diameter of the sphere 0.005, pores 0.002 to 0.008, bars
0.002; length of the major spine 0.09, of the minor 0.05, basal breadth
0.01.

_Habitat._--South Atlantic, Station 332, surface.


15. _Xiphostylus ardea_, n. sp.

Pores irregular, roundish, one to three times as broad as the bars; twelve
to sixteen on the half equator. Whole surface spiny. Major polar spine
three-sided pyramidal, somewhat longer than the diameter of the sphere;
minor scarcely so long as its half radius, pommel-like, edged.

_Dimensions._--Diameter of the sphere 0.12, pores 0.003 to 0.01, bars
0.003; length of the major polar spine 0.15, of the minor 0.03, basal
breadth 0.02.

_Habitat._--North Atlantic, Station 64, surface.



Genus 47. _Saturnalis_,[70] Haeckel, 1881, Prodromus, p. 450.

_Definition._--#Stylosphærida# with one single lattice-sphere and two equal
opposite spines, connected at the distal end by a circular or elliptical
ring.

The genus _Saturnalis_ (with simple lattice-sphere) and the two similar
genera _Saturnulus_ (with two concentric spheres) and _Saturninus_ (with
three spheres) form together the small peculiar group of Saturnalida,
distinguished by a remarkable circular or elliptical ring, connecting the
distal ends of the two equal opposite polar spines. This ring indicates a
certain equatorial plane, and therefore brings these #Sphæroidea# into
relation with the #Discoidea#.



Subgenus 1. _Saturnalina_, Haeckel.

_Definition._--Ring smooth, without spines or thorns.


1. _Saturnalis circularis_, n. sp.

Pores of the spherical shell regular, circular, hexagonally framed, twice
as broad as the bars. Ten to twelve pores on the half equator. Ring
circular, smooth, its diameter three times as great as that of the sphere.

{132}_Dimensions._--Diameter of the sphere 0.07, pores 0.005, bars 0.0025;
diameter of the circular ring 0.2, thickness of the axial beams and the
ring 0.01.

_Habitat._--South Atlantic, Station 332, depth 2200 fathoms.


2. _Saturnalis annularis_, n. sp. (Pl. 13, fig. 16).

Pores of the spherical shell regular, circular, with elevated hexagonal
frames, of the same breadth as the bars. Sixteen to twenty pores on the
half equator. Ring elliptical, smooth, somewhat constricted at the poles of
the axis, its diameter three times as great as that of the sphere.

_Dimensions._--Diameter of the sphere 0.09, pores and bars 0.005, major
axis of the elliptical ring 0.27 to 0.3, minor axis 0.19 to 0.2; thickness
of the ring and of the axial beams 0.01.

_Habitat._--Pacific, central area, Stations 270 to 274, surface.


3. _Saturnalis cyclus_, n. sp.

  _Lithocircus mesocena_, Bury, 1862, Polycystins of Barbados, pl. iii.
  fig. 1.

Pores of the spherical shell regular, circular, without hexagonal frames,
twice as broad as the bars. Eight to ten pores on the half equator. Ring
circular, smooth, its diameter four times as great as that of the sphere.

_Dimensions._--Diameter of the sphere 0.07, pores 0.006, bars 0.003;
diameter of the circular ring 0.28, thickness of the ring and both axial
beams 0.01.

_Habitat._--Fossil in the Barbados rocks.


4. _Saturnalis circoides_, n. sp. (Pl. 13, fig. 12).

Pores of the spherical shell irregular, roundish, often somewhat lobed, one
to three times as broad as the bars; fifteen to twenty on the half equator.
Ring circular, smooth, with four prominent edges, its diameter twice as
great as that of the sphere. (The figured specimen is a young or not fully
developed one; afterwards I found in the same locality other specimens with
quite perfect rings, similar to the edged ring of _Saturnulus annulus_, Pl.
16, fig. 17.)

_Dimensions._--Diameter of the sphere 0.09 to 0.1, pores 0.003 to 0.01,
bars 0.004; diameter of the circular ring 0.2 to 0.24, thickness of the
ring and the polar beams 0.01.

_Habitat._--Indian Ocean; fossil in the Nicobar rocks; living at great
depths near Zanzibar, 2200 fathoms, Pullen.



Subgenus 2. _Saturnalium_, Haeckel.

_Definition._--Ring armed on the periphery with numerous spines or thorns.


5. _Saturnalis trochoides_, n. sp.

  _Haliomma_ species, Bury, 1862, Polycystins of Barbados, pl. xx. fig. 2.

Pores of the spherical shell subregular, circular, twice as broad as the
bars. Twelve to sixteen pores on the half equator. Ring circular, armed
with ten to twelve strong conical, irregular spines, its diameter twice as
great as that of the sphere.

{133}_Dimensions._--Diameter of the sphere 0.08, pores 0.006, bars 0.003;
diameter of the circular ring 0.16; length of the radial spines 0.02 to
0.04; thickness of the ring and the axial beams 0.01.

_Habitat._--Fossil in the Barbados rocks.


6. _Saturnalis rotula_, n. sp. (Pl. 13, fig. 15).

Pores of the spherical shell regular, circular, twice as broad as the bars;
sixteen to twenty on the half equator. Ring circular, armed with fifteen to
twenty strong, conical, irregular spines, partly simple, partly divided
into two or three irregular branches; diameter of the ring two and a half
times as great as that of the sphere.

_Dimensions._--Diameter of the sphere 0.08, pores 0.004, bars 0.002;
diameter of the circular ring 0.2, length of its spines 0.02 to 0.03;
thickness of the ring and the radial beams 0.01.

_Habitat._--North Pacific, Station 244, surface.



Subfamily SPHÆROSTYLIDA, Haeckel, 1881, Prodromus, pp. 449, 451.

_Definition._--#Stylosphærida# with two concentric, spherical
lattice-shells.



Genus 48. _Stylosphæra_,[71] Ehrenberg, 1847, Monatsber. d. Berlin Akad.,
p. 54.

_Definition._--#Stylosphærida# with two concentric lattice-spheres and two
free spines of equal size and similar form.

The genus _Stylosphæra_, the most simple form of the Sphærostylida, can be
derived either from _Xiphosphæra_ by duplication of the spherical shell, or
from _Carposphæra_ by development of two opposite polar spines. The inner
or medullary shell is enclosed in the central capsule, whilst the outer or
cortical shell lies outside it; the two are connected by two or more radial
beams, piercing the wall of the capsule.



Subgenus 1. _Stylosphærantha_, Haeckel.

_Definition._--Pores of the cortical shell regular, of nearly equal size
and similar form; surface smooth or a little rough, without spines or
thorns.


1. _Stylosphæra musa_, n. sp.

Radial proportion of the two concentric spheres = 3 : 1. Cortical shell
thin walled, smooth, with regular, hexagonal pores, three times as broad as
the thin bars; twelve on the half equator. Polar spines three-sided
pyramidal, as long as the axis of the cortical shell, one-tenth as broad at
the base.

_Dimensions._--Diameter of the outer shell 0.2, pores 0.01, bars 0.003;
diameter of the inner shell 0.06; length of the polar spines 0.2, basal
breadth 0.02.

_Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms.


{134}2. _Stylosphæra urania_, n. sp.

Radial proportion of the two shells = 4 : 1. Cortical shell thin walled,
smooth; pores regular, circular, hexagonally framed, twice as broad as the
bars; ten on the half equator. Polar spines conical, as long as the radius
of the outer shell.

_Dimensions._--Diameter of the cortical shell 0.24, pores 0.012, bars
0.006; medullary shell 0.06; length of the polar spines 0.12, basal breadth
0.024.

_Habitat._--South Pacific, Station 285, depth 2375 fathoms.


3. _Stylosphæra calliope_, n. sp. (Pl. 16, fig. 6).

Radial proportion of the two shells = 3 : 1. Cortical shell thick walled,
smooth; pores regular, circular, three times as broad as the bars. Each
pore on its outer opening with eight regular lobules, flower-like. Nine to
ten pores on the half equator. Polar spines three-sided pyramidal, with
three strong prominent edges, about as long as the axis, as broad as one
pore. (Sometimes, as in the figured specimen, one spine is smaller than the
other; this variety, otherwise identical, may be called _Sphærostylus
calliope_.)

_Dimensions._--Diameter of the outer shell 0.12, pores 0.015, bars 0.005;
inner shell 0.04; length of the polar spine 0.08 to 0.12, breadth 0.02.

_Habitat._--Pacific, central area, Station 268, depth 2900 fathoms.


4. _Stylosphæra clio_, n. sp. (Pl. 16, fig. 7).

Radial proportion of the two shells = 2 : 1. Cortical shell thick walled,
smooth; pores regular, circular, three times as broad as the bars; fourteen
to sixteen on the half equator. Polar spines three-sided pyramidal, very
robust, with thick prismatic edges, about as long as the axis of the
cortical shell, one-third as broad at the base. (Sometimes, as in the
figured specimen, one spine is greater than the other; this form may be
called _Sphærostylus clio_.)

_Dimensions._--Diameter of the outer shell 0.12, pores 0.01, bars 0.003;
inner shell 0.06; length of the polar spines 0.08 to 0.12, basal breadth
0.03 to 0.04.

_Habitat._--Pacific, central area; Station 272, depth 2600 fathoms.


5. _Stylosphæra polyhymnia_, n. sp.

Radial proportion of the two spheres = 3 : 1. Cortical shell very thin
walled, smooth, with regular, circular pores, three times as broad as the
bars; sixteen to twenty on the half equator. Polar spines cylindrical,
pointed, once and a half to twice as long as the axis of the outer sphere,
scarcely broader than one pore. The two spheres are connected only by the
two opposite beams.

_Dimensions._--Diameter of the outer shell 0.12 to 0.16, pores 0.006 to
0.009, bars 0.002 to 0.003; inner shell 0.04 to 0.05; length of the polar
spines 0.18 to 0.22, breadth 0.01.

_Habitat._--Cosmopolitan; Mediterranean, Atlantic, Indian, Pacific,
surface.


{135}6. _Stylosphæra dixyphos_, Haeckel.

  _Haliomma dixyphos_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, p. 83; Mikrogeol., Taf. xxii. fig. 31.

  _Haliomma dixyphos_, Haeckel, 1862, Monogr. d. Radiol.  p. 433.

Radial proportion of the two spheres = 2 : 1. Cortical shell thin walled,
smooth, with regular, circular pores, twice as broad as the bars; ten to
twelve on the half equator. Polar spines about as long as the axis of the
outer shell, three-sided pyramidal, at the base twice as broad as one pore.
(The two spheres connected by four beams, two opposite in the main axis,
two opposite in the equatorial axis.)

_Dimensions._--Diameter of the outer shell 0.1, pores 0.01, bars 0.05;
inner shell 0.05; length of the polar spines 0.08 to 0.1, basal breadth
0.02.

_Habitat._--South Atlantic, Station 332, surface; fossil in Tertiary rocks
of Sicily.



Subgenus 2. _Stylosphærella_, Haeckel.

_Definition._--Pores of the cortical shell regular, of nearly equal size
and similar form; surface thorny or spiny.


7. _Stylosphæra setosa_, Ehrenberg, 1872.

  _Stylosphæra setosa_, Ehrenberg, 1872, Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, p. 320; Abhandl. d. k. Akad. d. Wiss. Berlin, Taf. viii.
  fig. 15.

Radial proportion of the two shells = 2 : 1.  Cortical shell thin walled,
spiny; pores regular, hexagonal, four times as broad as the bars. Six to
eight pores on the half equator. Polar spines conical, thin, scarcely as
long as the radius of the cortical shell.

_Dimensions._--Diameter of the cortical shell 0.1, pores 0.002, bars 0.005;
medullary shell 0.05; length of the polar spines 0.04, basal breadth 0.01.

_Habitat._--Philippine Sea, depth 3300 fathoms, Ehrenberg; Station 206,
depth 2100 fathoms.


8. _Stylosphæra euterpe_, n. sp.

Radial proportion of the two shells = 3 : 1. Cortical shell thin walled,
spiny; pores regular, circular, with hexagonal frames, twice as broad as
the bars; eight to ten on the half equator. Polar spines conical, as thick
as one pore at the base, about as long as the axis of the cortical shell.

_Dimensions._--Diameter of the cortical shell 0.12, pores 0.012, bars
0.006; medullary shell 0.04; length of the polar spines 0.1, basal breadth
0.012.

_Habitat._--South Pacific, Station 302, depth 1450 fathoms.


9. _Stylosphæra melpomene_, n. sp. (Pl. 16, fig. 1).

Radial proportion of the two shells = 3 : 1. Cortical shell thin walled,
spiny, with regular, circular pores, four times as broad as the bars; eight
to ten on the half equator. Polar spines three-sided prismatic, pointed, as
broad as one pore, only one-third as long as the axis of the sphere (the
two shells connected by four thin beams, two opposite in the main axis, two
in the equatorial axis).

{136}_Dimensions._--Diameter of the outer shell 0.12, pores 0.012, bars
0.003; inner shell 0.04; length of the polar spines 0.04, thickness 0.013.

_Habitat._--Indian Ocean, Cocos Islands, Rabbe.


10. _Stylosphæra hispida_, Ehrenberg, 1854.

  _Stylosphæra hispida_, Ehrenberg, 1854, Monatsber. d. k. preuss. Akad. d.
  Wiss. Berlin, p. 246; Mikrogeol, Taf. xxxvi. fig. 26.

  _Haliomma hispidum_, Haeckel, 1862, Monogr. d. Radiol., p. 433.

Radial proportion of the two spheres = 3 : 1. Cortical shell thick walled,
spiny, with regular, circular pores of the same breadth as the bars; ten to
fifteen on the half equator. Polar spines three-sided prismatic, pointed,
about as long as the axis of the outer sphere, nearly as broad at the base
as the inner sphere. (Compare _Sphærostylus hispidus_; also Ehrenberg,
Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, 1874, p. 259.)

_Dimensions._--Diameter of the outer shell 0.1 to 0.12, pores and bars
0.004; inner shell 0.04; length of the polar spines 0.1 to 0.15, basal
breadth 0.03.

_Habitat._--Fossil in the Tertiary rocks of Sicily, Barbados, Nicobars, &c.


11. _Stylosphæra liostylus_, Ehrenberg, 1875.

  _Stylosphæra liostylus_, Ehrenberg, Abhandl. d. k. Akad. d. Wiss. Berlin,
  p. 84, Taf. xxv. fig. 3.

Radial proportion of the two spheres = 3 : 1. Cortical shell thick walled,
thorny, with regular, circular pores, three times as broad as the bars;
eight to ten on the half equator. Polar spines conical, once and a half to
twice as long as the axis of the outer sphere, half as broad at the base as
its radius. (This species, common in the Barbados rocks, is different from
_Sphærostylus liostylus_, _loc. cit._, fig. 2, which Ehrenberg believed
identical.)

_Dimensions._--Diameter of the outer shell 0.1, pores 0.01, bars 0.0035;
inner shell 0.03; length of the polar spines 0.14 to 0.18, basal breadth
0.02.

_Habitat._--Fossil in the Barbados rocks; living in the depths of the North
Atlantic, Gulf Stream, Florida.



Subgenus 3. _Stylosphærissa_, Haeckel.

_Definition._--Pores of the cortical shell irregular, of different size or
form; surface smooth or a little rough, without thorns or spines.


12. _Stylosphæra nana_, n. sp. (Pl. 16, figs. 12, 13).

Radial proportion of the two spheres = 2 : 1. Cortical shell thick walled,
somewhat irregular, smooth, with irregular, roundish pores, one to three
times as broad as the bars; eight to ten on the half equator. Polar spines
three-sided pyramidal, scarcely as long as the axis of the outer sphere,
and nearly as broad at the base as its radius.  (A very variable and
irregular form.)

_Dimensions._--Diameter of the outer shell 0.07 to 0.09, pores 0.003 to
0.009, bars 0.003; inner shell 0.03 to 0.04; length of the polar spines
0.04 to 0.07, basal breadth 0.03.

_Habitat._--North Pacific, Stations 241 to 253, surface.


{137}13. _Stylosphæra jugata_, n. sp.

Radial proportion of the two shells = 2 : 1. Cortical shell thick walled,
smooth, with irregular, roundish, double-contoured pores, confluent in
groups of two to six. On the half equator six to nine groups and fifteen to
twenty pores; bars between them of very variable breadth. Polar spines very
strong, three-sided pyramidal, twice as long as the axis of the outer
sphere, half as broad at the base as its radius. (Nearly allied to
_Lithatractus jugatus_, Pl. 16, fig. 2, but differs in the truly spherical
form of both shells and the double length of the polar spines.)

_Dimensions._--Diameter of the outer shell 0.15, pores 0.005 to 0.02; inner
shell 0.07; length of the polar spines 0.25 to 0.3, basal breadth 0.03.

_Habitat._--Western Tropical Pacific, Station 224, depth 1850 fathoms.


14. _Stylosphæra terpsichore_, n. sp.

Radial proportion of the two shells = 3 : 1 or 4 : 1. Cortical shell thick
walled, smooth, with irregular, roundish pores, one to three times as broad
as the bars; fifteen to twenty-five on the half equator. Polar spines
conical, about as long as the axis of the outer sphere, as broad at the
base as the inner shell.

_Dimensions._--Diameter of the outer shell 0.15 to 0.2, pores 0.005 to
0.02, bars 0.004 to 0.008; inner shell 0.05; length of the polar spines
0.15 to 0.25, basal breadth 0.05.

_Habitat._--Western Indian Ocean, Zanzibar, depth 2200 fathoms, Pullen.



Subgenus 4. _Stylosphæromma_, Haeckel.

_Definition._--Pores of the cortical shell irregular, of different size or
form; surface spiny or thorny.


15. _Stylosphæra thalia_, n. sp.

Radial proportion of the two shells = 2 : 1. Cortical shell thin walled,
thorny, with irregular, roundish pores, two to four times as broad as the
bars; eight to twelve on the half equator. Polar spines conical, one to one
and a half times as long as the axis of the outer sphere, one-fourth to
one-sixth as thick at the base. (Resembles _Sphærostylus ophi