Title: A Mechanico-Physiological Theory of Organic Evolution
Author: Nägeli, Carl Von, 1817-1891
Language: English
As this book started as an ASCII text book there are no pictures available.


*** Start of this LibraryBlog Digital Book "A Mechanico-Physiological Theory of Organic Evolution" ***


produced from images generously made available by The
Internet Archive)



                                   A
                        MECHANICO-PHYSIOLOGICAL
                               THEORY OF

                                  BY
                            CARL VON NÄGELI


                            SECOND EDITION


                                CHICAGO
                     THE OPEN COURT PUBLISHING CO.
                                 1914



                            COPYRIGHT, 1898
                   BY THE OPEN COURT PUBLISHING CO.
                                CHICAGO



                            PREFATORY NOTE.


Mr. V. A. Clark, as a student in horticulture in the University
of Vermont, first undertook a critical examination of Nägeli's
_Mechanico-Physiological Theory of Evolution_ as a part of his regular
junior work. After a half year's study and the preparation of a short
thesis, Mr. Clark had become so far intimate with Nägeli's work as to
make it seem best for him to continue the study through his senior year.
This study involved extended translations from the text, including
Nägeli's _Summary_, which, considering its difficult accessibility
to American students, has been chosen for publication. The work has
been done chiefly by Mr. Clark, but has all been under my immediate
supervision, and I have given the whole matter a final restudy and
revision. Those who have had any experience with similar work will know
how impossible it is that all mistakes should have been avoided, and it
would be a kindness to the translators if readers would point out any
defects, in order that they may be corrected.

                                                        F. A. WAUGH.

University of Vermont,
    July 1, 1898.



                       A MECHANICO-PHYSIOLOGICAL
                           THEORY OF ORGANIC
                              EVOLUTION.



                               SUMMARY.


In this summary I shall in general pursue a course the reverse of that
which my main work follows.[A] I shall proceed from the primitive,
unorganized condition of matter and endeavor to show how organized
micellar substance has arisen in it, and how, from this micellar
substance, organisms with their manifold properties have arisen.
Since such a synthesis of organisms out of known forms of matter and
force is still far removed from a conclusion strictly in accord with
physical law, the process becomes comprehensible and obvious only by
exact knowledge of the discussion that has preceded. Although the
synthetic method reveals more clearly the weaknesses of the theory
than do analytic investigations, yet I considered it helpful to
make this presentation in order to give a clearer idea of the
mechanico-physiological theory, and at the same time to test its
worth.

    [A] See Appendix, Translators' Notes.


1. FORMATION OF UNORGANIZED BODIES (CRYSTALS).

When separated and promiscuously moving molecules of any substance in
solution or in a melted condition pass into the solid form by reason of
removal of the causes of separation and motion (warmth or solvent), they
arrange themselves into solid masses impermeable to liquids. These
minute bodies grow by accretion, and when molecular forces are permitted
to act undisturbed, assume the regular outer form and inner structure of
crystals. The number of crystals, their size, changes of form and
growth, all depend on external conditions.


2. FORMATION OF LIVING ORGANIZED (MICELLAR) BODIES.

Certain organic compounds, among them albumen, are neither soluble,
despite their great affinity for water, nor are they fusible, and hence
are produced in the micellar form. These compounds are formed in water,
where the molecules that arise immediately adjoining each other arrange
themselves into incipient crystals, or micellæ. Only such of the
molecules as are formed subsequently and come in contact with a micella
contribute to its increase in size, while the others, on account of
their insolubility, produce new micellæ. For this reason the micellæ
remain so small that they are invisible, even with the microscope.

On account of their great affinity for water the micellæ surround
themselves with a thick film of it. The attraction of these micellæ for
matter of their own kind is felt outside this film. Hence the micellæ
with their films unite themselves into solid masses permeated with
water, unless other forces overcome attraction and re-establish a
micellar solution (as in albumen, glue, gum), where the slightly moving
micellæ show a tendency to cling together in chain-like and other
aggregations. Very often there are found, especially in albumen, half
liquid modifications intermediate in fluidity between the solid masses
and the micellar solution.

The internal and external constitution of micellar bodies depends
essentially on the size, form and dynamic nature of their micellæ, since
these efficients condition the original arrangement of the micellæ and
the insertion in proper order of those formed later. External conditions
have slight influence on structure, and affect outer form chiefly in so
far as they can mechanically hinder free development.

The micellæ of albumen or plasma are susceptible of the greatest
diversity of form, size and chemical composition, since they originate
from unlike mixtures of various albumen compounds, and besides are mixed
with various organic and inorganic substances. For this reason the
plasma behaves, both chemically and physically, in many unlike ways, and
in consequence of the variable relation of the micellæ to water, the
plasma shows all degrees of micellar solution up to quite solid masses.


3. SPONTANEOUS GENERATION. LIFE. GROWTH.

If molecular forces are so combined in an inorganic substratum that
spontaneous formation of albumen takes place, then by the combination of
the micellæ the primordial plasma masses of spontaneous generation are
given. Within these plasma masses the production of albumen goes on more
easily under the influence of their molecular forces than in the liquid
without. Hence the compounds present in the organic substratum and
capable of forming albumen enter preferably into the masses of plasma,
and by intussusception of micellæ of albumen, cause growth. Here life
exists in its simplest form. (See page 47.)

Spontaneous generation presupposes the origin of plasma-micellæ from
molecules, and hence cannot be brought about by solutions of albumens or
peptones, since these are micellar solutions. Life presupposes the
intussusception of plasma-micellæ; hence it ceases as soon as the
arrangement of micellæ is so far disordered by injurious influences that
that process of growth becomes impossible.

The resulting organism must be perfectly simple, a mass of plasma with
micellæ as yet unarranged, because any organization without a preceding
organizing activity is inconceivable. For this reason known organisms
cannot have orginated spontaneously; a kingdom of simpler beings must
have preceded them (_Probien_--the sub-organic kingdom).

The growth of the masses of plasma continues as long as the conditions
of nutrition are favorable. If these become unfavorable, a resting
period (latent life) or partial or total death occurs, according to
circumstances (as lack of nutritive material, lowering of temperature,
comparative exsiccation). The growth of plants and animals is nothing
else than the continuation of the growth begun in the primordial plasma.
This growth still continues wherever the primordial plasma exists.


4. PARTIAL DEATH OF THE INDIVIDUAL: REPRODUCTION.

Since the primordial masses of plasma continue to attract nutritive
materials indefinitely and apply them to growth, the nutritive materials
are used up in one place and another and the substance which is no
longer nourished is in great measure disintegrated. A general condition
of equilibrium now sets in, in which the viable plasma masses continue
to gain just as much in growth as there is dead plasma broken down and
changed back into the original nutritive materials.

In the primordial condition this balancing process is irregular and
accidental and remains so even later in many of the lowest organisms.
Little by little it becomes phylogenetically more regular by individuals
attaining to a more definite size and term of life, while only the germs
detached from them remain viable. This phenomenon known as reproduction
has a double origin.

_A._ The portions of primordial plasma that grow to a more considerable
size as soft, half-liquid masses break up by the mechanical action of
external circumstances into smaller portions of indefinite number and
size. This typifies irregular and accidental reproduction of the lowest
order.

In the offspring of the primordial plasma division becomes gradually
more and more regular as a result of the increasing organization of the
substance, and especially as a result of the formation of an envelope
about it, till finally in the microscopically small masses, which are
now called cells, division into two parts always appears, after these
masses have grown to perhaps double their original size. After division
the two halves separate from each other and represent independent
individuals.

In the further course of phylogeny the division of the cells into two
parts takes place regularly. But the cells remain united to each other
and form multicellular individuals, which increase by cell division and
which at times in the lowest stages are divided at regular intervals
into smaller individuals, perhaps even at last into single cells, but
from which there are periodically given off cells that develop as germ
cells into new multicellular individuals.

_B._ Another phenomenon which appears in the primordial plasma or its
immediate offspring is the death of the greater part of the plasma under
certain unfavorable conditions of nutrition, while the smaller part
continues to be nourished at its expense and in that case remains viable
during the dormant period.

In the offspring this phenomenon gradually becomes free cell formation,
which takes place before the resting stage or before the death of many
unicellular and multicellular organisms, and which forms germ cells from
a part of the contents of the parent cells.

The formation of germ cells by cell division (_A_), or by free cell
formation (_B_) is reproduction of the organism. The germ cells are the
elements in which the life and growth of the parental individual are
continued.


5. MORPHOLOGY OF THE IDIOPLASM IN GENERAL.

The larger part of the unarranged, soft and homogenous primordial
plasma, which grows by intussusception, becomes watery soma-plasm, with
unarranged and easily movable micellæ. The smaller part is converted in
the course of phylogeny into idioplasm, in which at certain favorable
points the micellæ that are being stored up under the influence of
molecular forces arrange themselves into groups by similar orientations,
and hence form bodies of less water content and greater solidity. Each
body of idioplasm consists originally of only one group of micellæ,
which, however, necessarily breaks up with increasing additions into
several groups. On account of the dynamic influence of the groups of
micellæ upon their own growth, they become in part more distinct and
more definitely separated, in part again differentiated by new irregular
intussusception. This phylogenetic process is continued indefinitely,
by which the combination of forces produces a new configuration, and
conversely, by which a new configuration produces a new combination of
forces, so that the body of idioplasm merely takes on a continually
increasing complexity of configuration by the action of the internal
forces--that is, by the molecular forces of the micellæ of the albumen
under the influence of which growth proceeds. This constitutes the
_automatic perfecting process_ or progression of the idioplasm, and
entropy of organic matter. (See p. 47.)

The above described phylogenetic perfecting process of the idoplasm,
which operates through internal causes, is scarcely affected by
differences of nutrition and by climatic conditions influencing
nutrition. On the other hand all those external forces which act as
stimuli during a long period of time in an unvarying manner have a very
noticeable influence on the intussusception of micellæ in the idioplasm
and on the molecular processes going on among the micellæ. The action of
stimuli determines the particular structure of the groups of micellæ
added under the direction of the perfecting process. Thus the
configuration of the idioplasm becomes continually more and more complex
and at the same time assumes a local adaptation corresponding to
external conditions. This constitutes adaptation of the idioplasm.


6. FUNCTION OF THE IDIOPLASM IN GENERAL.

The unarranged micellæ of the albumen of the spontaneously generated
plasma are as yet in no way superior to the unorganized condition from
which they have arisen, except in this that under the influence of their
molecular forces the formation of similar new albumen micellæ follows
more easily. But as by the further action of molecular forces
idioplasmic bodies are formed with groups of smilarly oriented micellæ,
the molecular forces of these micellæ amount by summation to molar
forces and thereby new chemical processes are introduced; plastic
products are formed from plasmic and non-plasmic materials, and molar
movements are introduced. And since idioplasmic bodies are formed under
the influence of external stimuli, their plastic products always appear
with a definite character of adaptation to environment.

Then, as the idioplasmic body becomes continually more complex in the
further course of phylogeny, and consists of a greater number of groups
of micellæ differing from each other, the organisms become more complex
and differentiate into a greater number of parts, because each group of
micellæ of the idioplasm produces its specific effect with regard to
inner structure, outer form, and function.


7. DETERMINANTS: THEIR ORIGIN AND DISAPPEARANCE.

Since a particular cluster or group of micellæ of the idioplasm produces
a particular phenomenon in the organism, the former is designated as the
determinant (_Anlage_, see p. 49) of the latter. Thus the organism must
contain at least as many determinants in its idioplasm as there are
different phenomena in its inheritable ontogeny; and if new phenomena
appear in it, new clusters of micellæ must previously have been
introduced into the idioplasm, or the orientation and arrangement of
clusters already present must have been changed. The formation of such a
determinant, whether it concerns the perfecting of the organism or its
adaptation to environment, always proceeds very slowly, and as a rule
has no effect before its completion. Hence along with perfected
determinants the idioplasm always contains growing and incomplete
determinants.

If a phylogenetic line comes under the influence of other external
conditions and other external stimuli than those which have hitherto
acted upon it, a new and corresponding arrangement of the micellæ
appears phylogenetically in the idioplasm. At the same time the other
adaptation determinants remain either undisturbed, or the new
determinant is formed at the expense of related determinants which are
already present and which may at last entirely vanish. Hence along with
growing and complete determinants the idioplasm always contains likewise
weakened and vanishing determinants. From the fact that a phylogenetic
race is thrown repeatedly among different external conditions, it may at
last unite in its idioplasm a large number of developing, mature, and
vanishing adaptation determinants. This number is noticeably increased
if in consequence of interbreeding a fusion of related idioplasms take
place.


8. DEFINITE NOTIONS WITH REGARD TO THE MORPHOLOGY OF THE IDIOPLASM.

Since in the phylogenetic development of the plasma the thicker
idioplasm is differentiated from the more fluid soma-plasm (§ 5), the
former has the tendency by nature to assume a reticular arrangement. The
strands of this network consist, in conformity with their origin, of
parallel rows of micellæ extending lengthwise. These rows of micellæ
are combined into more or less complex arrangements, so that the cross
section of the strand represents the configuration of the idioplasm.[B]

    [B] Nägeli makes his idioplasm ramify throughout the organism in
    unbroken continuity, much like a system of nerves in the higher
    animals. This idea with Nägeli was purely speculative. It was
    known that the protoplasm is in connection throughout the
    organism, but it has been proved more recently that only the
    somatic protoplasm is thus connected. The part in which the
    essential nature of the organism is contained is localized
    in the nucleus and hence might properly be designated as
    nucleoplasm, as Weismann suggests. If the idioplasm is
    localized in the nucleus, it cannot be continuous throughout
    the system, as Nägeli assumes. But this objection applies only
    to a detail of the theory and does not affect the fundamental
    conception,--that of a portion of the protoplasm which is
    differentiated from the rest and represents a definite molecular
    structure which determines the specific nature of the
    organism.--_Trans._

Each ontogeny (individual) begins in a minute germ cell, in which a
small quantity of idioplasm is contained. In the cell divisions, by
which the organism grows, the idioplasm divides into as many parts as
there are single cells, while it continually increases in quantity in a
corresponding degree. The ontogenetic increase of the idioplasm takes
place by length growth of the strands--that is, by intercalation of
micellæ in each row of cells of the strands, which thereby grow in
length without changing the configuration of the cross section.[C]
Accordingly, each strand of idioplasm contains all the determinants that
the particular individual has inherited in the germ cell, and each cell
of the organism is idioplasmatically qualified to become the germ cell
of a new individual. Whether this qualification may be realized depends
upon the nature of the soma-plasm. In the lower plants this power
belongs to each individual cell; in the higher plants many cells have
lost it; in the animal kingdom it is possessed in general only by cells
normally set apart as asexual or sexual reproductive cells.

    [C] Hence, according to Nägeli, every cell of the organism has
    idioplasm of identical structure. This at once suggests the
    objection, how can the idioplasm, for instance, of a pollen
    grain be the same as that of a leaf? Identical idioplasms should
    always produce identical structures. Nägeli attempts to explain
    this difficulty by attributing the different results to
    different "conditions of tension and movement," i.e., a
    dynamical difference between the idioplasms of the different
    parts of the organism. (_Abstammungslehre_, p. 53.)

    This idea of differences of structure being due to dynamic
    rather than to material causes plays a considerable part in
    Nägeli's theory, but is the point on which he speaks with least
    certainty--in fact with a noticeable hesitation. He does not
    clearly explain the phrase "conditions of tension and movement,"
    nor does he give a convincing explanation of the known phenomena
    as results of the action of dynamic influence.

    Nägeli is not the only one who posits dynamic rather than
    material differences as to the basis of diversities of
    structure. More recently, Cope has built up a system of
    evolution founded largely on this idea.--_Trans._

The continued phylogenetic formation of the threads of idioplasm takes
place by growth in the cross section, which contains the sum of all the
determinants and changes in general only when new rows of micellæ are
intercalated. But the rows of micellæ of the idioplasm join closely to
each other, according to their thickness, so that only rarely new rows
can enter, and then only at those definite places where the cohesion is
less strong and hence is overcome. The cohesion varies irregularly
because the configuration of the cross section, conformably to its
origin, is never regular; the disruptive tensions are brought about by
the unequal growth in length of the individual rows of micellæ. Dynamic
influences have a decisive effect upon cohesion and disruptive tensions.
The groups of micellæ of the configuration already obtained exercise
these dynamic influences upon each other; and these dynamic influences
can be modified by stimuli from without.

The idioplasm continually alters its configuration with its growth in
successive ontogenies, but comparatively very slowly, so that it makes a
minute advance from the germ of one generation to the germ of the next.
The summation of these increments of advance through a whole line of
evolution represents the race history of an organism, since the latter
is connected only by its idioplasm in unbroken continuity with the
micellar beginning of its race.


9. DEFINITE NOTIONS REGARDING THE FUNCTION OF THE IDIOPLASM.

A plasmic substance causes definite chemical and physical changes only
when it is present in a certain condition of motion. The peculiar agency
which the idioplasm has in each ontogenetic stage of development and in
each part of the organism depends on the activity of a definite group of
micellæ in the cross section of the strand or of a complex of such
groups, while this local stimulus controls the chemical and physical
processes by dynamic influence and by transmission of a specific mode of
motion, even to a microscopically small distance.

The effective stimulus in a plasmic substance is dependent on its own
nature and the influence which it receives from without. Which group of
micellæ in the idioplasm receives the stimulus depends on the
configuration, on the preceding stimuli and on the position in the
individual organism in which the idioplasm is found. The determinants
have arisen one after another during the whole period of evolution from
the primordial cell. The configuration of the idioplasm is a character
of phylogeny and the determinants in it have by nature the tendency to
develop in the order in which they were formed. Further, since the
ontogeny begins as a unicellular organism with the formation of a germ
cell, that determinant of the idioplasm comes first to development,
which has developed in the unicellular ancestor. Just so the succeeding
stages of ontogeny depend for the time being on the development of the
determinants having their origin in the corresponding stage of
phylogeny. Both causes acting together--the phylogenetic configuration
of the idioplasm and the successive morphological stages of development
of the individual conditioned on it--necessarily result in the ontogeny
being the repetition of the phylogeny.

If the whole remaining line of idioplasmic determinants in an ontogeny
has reached development, the development of the germ-forming
determinants finally follows as well from the configuration of the
idioplasm as from the nature of the organism. The individual is capable
of reproduction and the new ontogenies begin in the reproductive cells.


10. TRANSMISSION OF IDIOPLASMIC DETERMINANTS IN LOCAL VARIATION AND IN
FECUNDATION.

The automatic progressive or perfecting transformation of the idioplasm
is probably active in all stages of development, and proceeds regularly
in all parts of the organism, because the idioplasm preserves its
configuration at all times and places during the ontogeny. External
stimuli impign upon the organism usually at a definite point, but they
not only effect a local transformation of the idioplasm but also
reproduce themselves in a dynamic manner in the entire idioplasm, which
is in unbroken connection throughout the whole individual. The idioplasm
is thus changed everywhere in the same manner, so that the germ cells
that are given off at any point feel and inherit the effects of those
local stimuli.

In the formation of the germ cells in sexual reproduction, the
idioplasms of both parents must come into contact with each other,
whereupon there results either a material union and formation of a mixed
idioplasm or perhaps rather a dynamic action; and through these agencies
there is produced a remodeled form which is, however, exactly equivalent
to the combined idioplasms entering into it. Fertilization by diosmose
of the spermatic substance is impossible.[D]

    [D] This assertion is a direct corollary from the structure of
    the determinants and the idioplasm. If the idioplasm of the
    fertilizing cell were to pass through the membrane about the
    ovum by osmosis, its organized structure would be
    lost.--_Trans._

In the idioplasm of a germ cell arising from the crossing of unlike
individuals the micellar rows of the individual determinants have
sometimes an intermediate constitution and produce characteristics in
the organism which are intermediate between the characteristics of the
parents. Sometimes the micellar rows derived from the father and mother
respectively lie side by side unchanged in the idioplasm of the
offspring in distinct groupings and may reproduce in the organism their
respective characteristics side by side, or only one of them may
develop, while the other remains latent.

On account of the union of both idioplasms as the result of fecundation,
two sexually mature organisms are the more able to form with each other
a viable germ cell, the nearer they are genetically related--that is,
the more nearly the male and female idioplasms correspond in their
configuration and chemical nature, because in this case the micellar
arrangements are best suited to each other, and the idioplasm of the new
fertile germ cell receives its most suitable nourishment from the
mother. If, however, self-fecundation or the closest in-and-in breeding
often yields products of less virility and is avoided by nature, this
is the result of injurious influences which make themselves felt later
on. This is because incompatibilities may be present in too closely
related idioplasms and these are sources of weakness in unrestricted
development. The more complicated is the idioplasm, the oftener this
occurs, whereas absolute lack of crossing is not detrimental to the
simplest (asexual) organisms.


11. ACTION OF EXTERNAL INFLUENCES.[E]

The environment provides the organism above all with force and matter
for its life processes. It causes no permanent variation and has only an
ontogenetic significance, if the limits of the idioplasmic elasticity
are not exceeded; it maintains the growth and metabolic assimilation of
the individual, and conditions individual (not hereditary) differences,
which constitute "nutrition varieties." (See page 30.) These appear as
the direct results of operating causes.

    [E] In order to explain adaptations Nägeli assumes that external
    influences, if acting at the same point in a given manner for a
    long time, may induce slight adaptive variations which are
    perpetuated and increased. On the important subject of
    adaptation in general Nägeli is almost diametrically opposed to
    Darwin and Weismann. Nägeli assigns to the principle of utility
    a very limited sphere; Weismann regards adaptation as
    all-powerful. According to Nägeli, the organic world would have
    become much what it is, if natural selection and adaptation had
    performed no part in the operations of nature. He aptly says,
    that natural selection prunes the phylogenetic tree, but does
    not cause new branches to grow. He allows that the principle of
    selection is well suited to explain the adaptation of organisms
    to their environment and the suitableness and physiological
    peculiarities of their structure, but he asserts that in the
    definiteness of variation of plants and in their progressive
    differentiation there is evidence of a higher and controlling
    perfecting principle.--_Trans._

When the stress of environment exceeds the limits of idioplasmic
elasticity, its influence brings about permanent variations, which are
imperceptibly small, it is true, in the single individual, but which,
when the stimulus is active for a long period of time in the same
manner, increase to perceptible magnitude. These variations are
inheritable in the phylogenetic sense and contribute to the formation of
varieties and species; they always appear as the results of more or less
secondary reactions which make their appearance with stimuli exerted by
external causes.

External stimuli exerted on the organism are reproduced in the
idioplasm. Since the stimulus is discontinued with each change of the
ontogeny and only the idioplasm persists, permanent variations are
produced only in the idioplasm by those conditions that produce visible
transformations in the mature organism.

The phylogenetic action of external stimuli gives the definite character
of adaptation to the idioplasm as it becomes more complex from inner
causes and probably these external stimuli have the power to alter this
impress only as new idioplasm is automatically formed.

If an external cause acts continuously upon a phylogenetic line, the
corresponding variation of the idioplasm reaches, after a time, a
maximum, and thus comes to an end, either because the nature of the
substance permits no new rearrangement or because the stimulus is no
longer active. The cessation of the stimulus results from a micellar
rearrangement which indicates the character of the adaptation. If the
action of the stimulus lasts for only a short time, the incipient
rearrangement of the idioplasm stops, or proceeds independently on
account of the impulse received, and the determinant becomes capable of
development, even after the impulse has long ceased to act.

Since various intervening transpositions follow upon a stimulus in the
organism, the final result which appears as a reaction may turn out
variously. The same external causes may, according to the nature of the
organism and other circumstances, have very unlike variations as a
result. But the internal rearrangement produces in a definite case very
definite variations.

On account of the various intermediate steps it is often difficult to
discover the external cause of a given adaptive variation. In many cases
we recognize it without difficulty in a definite mechanical process or
in warmth, light or evaporation. For the most part the stimulus awakens
in the organism merely a want, which the reaction of the organism
endeavors to supply. Hence it appears that want or lack alone is able to
bring about such reactions. Moreover, in the sphere of sex, electric(?)
attractions and repulsions co-operate between the idioplasmic
determinants to produce phylogenetic variations.

The adaptations of the fully developed organism, which are the results
of external influences, consist either only of a specific molecular
character (irritability), by virtue of which the individual is capable
of responding to those influences with temporary or permanent phenomena,
or they consist of finished arrangements. The latter have, in general, a
double function: either they protect the organism from external
influences whose results they are, or they place it in a condition to
apply such environmental influences to their advantage. The
preponderance of the one or the other led to the development of the
plant or the animal kingdom. In the one case the primordial plasma
formed in the cellulose cell wall a stimulus-proof covering. On account
of this cell membrane being insensible to stimuli, adaptations in the
plant kingdom were restricted essentially to the spheres of nutrition
and reproduction. In the other case the irritability and mobility of the
primordial plasma increased so that it was placed in a condition to
avoid the irritant or make it serviceable by accommodating itself to it.
The cells sensible to irritants led in the animal kingdom to the
formation of organs of sense and the nervous system.


12. CONDITIONS OF PHYLOGENETIC DEVELOPMENT OF THE DETERMINANTS. ATAVISM.

In the primordial condition, formation and development of the
determinants coincide, since the plasma constituting the organism
possesses the capability of growing by intussusception of new micellæ
and of changing this growth through the action of inner and outer
causes. But as the primordial plasma differentiates into idioplasm and
soma-plasm, the formation of determinants consists in the transformation
of the idioplasm, while the development of determinants consists in the
production of soma-plasm and of non-plasmic substances under the
influence of the idioplasm.

Only the mature determinant is able to develop, especially if, at the
same time, a related and heretofore active determinant must be forced
back into the latent condition. But the determinant of an absolutely new
form of adaptation, which does not take the place of a preceding one,
must develop enough before it can become outwardly manifest, for it to
be possessed of a sufficient amount of molecular energy to render its
activity possible. For this reason the characteristics of the developed
organism change abruptly, notwithstanding the fact that the
transformation of the idioplasm has proceeded very gradually.

The configuration of the idioplasm becomes continually more complex
through the automatic action of the perfecting process, and by this
means the organism ascends to higher stages of organization. Hence the
viable determinants of organization or perfection are always overtaken
after a certain time by that movement and forced into the latent
condition. They then become continually weaker, and are at last
completely destroyed. Only in the first period after their becoming
latent can such determinants pass again into a developmental condition
and thus allow the organism to revert to the next preceding stage of
organization.

Since the configuration of the idioplasm, which becomes more complex
from internal causes, always assumes a definite character of adaptation
in consequence of the action of external causes, the adaptation
determinants capable of development may become more and more weakened
and at last latent when other external causes produce other adaptation
determinants. But these determinants may be revived by the renewed
activity of the former causes, and thus rendered capable of development.
Hence the organism may show the most various reversions with respect to
its adaptations. But in such reversions the earlier forms never quite
return, because in the meanwhile the idioplasm has changed somewhat in
consequence of its automatic progress, and therefore lends to the
adaptations which assume the earlier character a somewhat different
expression.


13. ONTOGENETIC DEVELOPMENT OF THE DETERMINANTS.

Since the capability of the primordial plasma to grow is the original
and only vital quality (_Anlage_), the whole ontogeny in this first
stage consists in the growth of the detached parts to the adult size. In
the same way the development of the determinants in all the following
stages is nothing more than the growth of the substance detached as a
germ cell after the manner of the changes in the character of the
idioplasm in the course of phylogeny. In this manner all determinants
may in the lower stages of organization reach development, but in the
higher stages an increasing number of them must remain latent.

Among the viable determinants there are some that develop
unconditionally during each ontogenetic period; there are also
alternative determinants of which one or the other unconditionally
develops; lastly, there are some that develop only under favorable
circumstances. Which of two alternative determinants shall develop
depends sometimes on internal, sometimes on external causes, according
as the specific determinant has arisen phylogenetically through the
action of internal or external causes. Climatic and nutritive influences
especially affect the appearance of indefinitely developing
determinants. Just so, when a determinant may develop repeatedly (as is
so common in the plant kingdom) it depends especially on nutrition
whether the corresponding phenomenon is repeated at intervals of greater
or less length. A weakened determinant is sometimes temporarily
developed by the operation of a definite stimulus.

If the integrity of the organism sustains an injury in consequence of
abnormal interferences, determinants develop exceptionally at unusual
points. The process is induced by accumulation of nutritive matter and
by external stimuli under the force of necessity, to which the injured
organism is sensible.


14. ESSENTIAL NATURE OF THE ORGANISM.

The essential nature of a thing is the sum total of its causes and
effects. Organisms arise from a germ cell which consists of idioplasm
and in turn they produce like germ cells. Their nature depends also on
their idioplasm, _i.e._, on the sum total of their idioplasmic
determinants. Observation of organisms, even in their fullest life
history, gives us an imperfect and even false conception of their true
nature. This is because observation reveals only the outer gross
characters, and even these in a modification dependent upon accidental
effects of nutrition, and does not reveal the finer characters founded
in molecular physiology and morphology, and especially the characters
latent in the idioplasm.

For the examination of idioplasmic differences we are restricted to
visible characters. Hence a knowledge of the nature of an organism
presupposes a complete investigation of its characters in their
succession during the whole ontogeny. The results must, however, be
tested and completed by comparison with other organisms and by the most
comprehensive experimental procedure, possible, (as by culture under
various conditions, and crossing with nearer and more remote relatives).
The characteristics of nutrition varieties and accidental crosses must
be separated from specific characteristics by experimental procedure,
and latent determinants must be brought out by the same means.


15. REPRODUCTION, AND RELATION BETWEEN PARENTS AND OFFSPRING.

Reproduction is nothing more than a transition from one generation to
the next following, mediated by the idioplasm of the germ cell. In
asexual (monogenic) reproduction there is continuity of the same
idioplasm. Therefore the parent continues in the offspring its specific
life, as the stem continues its specific life in the branch. All the
peculiarities conditioned by the idioplasm remain unchanged in the
offspring. The latter, as the immediate continuation of the preceding
ontogeny, starts from the point at which the germ cell left it, so that
immediately after the germ cell is separated at the close of the
ontogeny or before, the offspring passes at one time rapidly through
the whole ontogeny, at another only the remainder or a part of it (the
latter in alternation of generations and in asexual propagation of
phanerogams).

In sexual (digenic) reproduction the formation of the germ cell is
brought about by the union in equal parts of both parental idioplasms.
The offspring is the organism resulting from the union of the force and
matter of the parents, and represents in its nature the united
continuation of their ontogenies. The characteristics of development of
the child depend however on the viability of the determinants of the
mingled idioplasms in which a new equilibrium has been formed. Hence if
the child bears more resemblance to the father or to the mother, it
follows that some of the inherited determinants develop while the others
remain latent. If the child has certain visible characteristics more
marked than either parent, it becomes possible only by the development
of determinants which had previously been latent. The fact that the
mother furnishes the germ cell with nutritive plasm and that she
nourishes it for a considerable time does not increase the number of
maternal determinants nor their capability of development.

If two corresponding characters, one derived from the father, the other
from the mother, come into conflict in sexual reproduction, the one or
the other, or even a third alternative characteristic, which heretofore
was present as a latent determinant, may develop in the child. But also
both parental characters may appear at once and in various combinations.
Whether the development follows in the one way or the other depends on
the strength of the individual determinants, on the kind of their
idioplasmic arrangement, and on their agreement with the nature of the
newly formed idioplasm.


16. HEREDITY AND VARIATION.

If heredity and variation are defined according to the true nature of
organisms, they are only apparent opposites. Since idioplasm alone is
transmitted from one ontogeny to the next following, the phylogenetic
development consists solely in the continual progress of the idioplasm
and the whole genealogical tree from the primordial drop of plasma up to
the organism of the present day (plant or animal) is, strictly speaking,
nothing else than an individual consisting of idioplasm, which at each
ontogeny forms a new individual body, corresponding to its advance.

In this idioplasmic individual the _automatic_ or _perfecting variation_
is always active, so that the idioplasm of a phylogenetic line always
grows by propagation of the determinants contained within it, as a tree
grows larger through its whole duration of life by branching. On the
other hand the _adaptation variation_ caused by external stimuli is
present only in those periods of the phylogenetic line in which the
idioplasm, and together with this the individual, do not possess the
obtainable maximum of adaptation to their environment for the time
being. Both of these variations of the idioplasm take place so slowly
that only after a long series of generations do the new determinants
become capable of developing and revealing themselves in the
transmutation of visible characters.

Aside from the phylogenetic variations already named, which take place
according to the measure of ontogenetic growth, the idioplasm undergoes,
as a result of crossing, as well as in changes of the ontogeny,
_gamogenic variations_ which may be designated as stationary, since in
the mingling of sexually different idioplasms there arise only new
arrangements of determinants already present, but no new formation of
determinants takes place. Hence in this way arise also new combinations
of developmental characteristics.

As a result of external injurious influences, abnormal variations, or
_pathological variations_, appear in the idioplasm. These consist of
disturbances of equilibrium, which take place also without new formation
of determinants. Thereby the determinants already present are caused to
develop in abnormal relations, and mostly in reversions.

Apart from the inheritable variations of the idioplasm just enumerated,
and the transformations of visible characters involved in it, the
soma-plasm and the non-plasmic substances experience, by the influence
of nutrition and climate, greater or less variations, which constitute
_nutrition varieties_, and since the idioplasm remains unaffected in
general, last only so long as the causes which called them forth.[F]

    [F] Nägeli, like Weismann, arrives at the conclusion that
    acquired characters are not inherited. He was not content,
    however, to rest the generalization upon purely speculative
    grounds, but undertook the experimental demonstration. After
    seventeen years of work by himself and son, especially upon
    several species of Hieracium, he satisfied himself that his
    theory was true to the facts. We all know now how far he fell
    short of settling the question.--_Trans._

If we have in mind the inner nature of the organism, there is, properly
speaking, no such specific phenomenon as heredity, since the
phylogenetic line is a continuous idioplasmic individual. In this sense
heredity is nothing more than the persistence of organized substance in
a movement in which variations are automatically induced, or the
necessary transition of one idioplasmic configuration into the next
following. It is present, not only among plant and animal individuals
which are ontogenetically separated, but also everywhere within these
individuals, where individual parts (cells, organs) follow each other in
time. Hereditary phenomena are those that necessarily pass over to
following generations, and in general those that are located in the
idioplasm, since non-idioplasmic substance can be hereditary only
through a limited number of cell generations.

Variations and heredity are generally estimated, not according to the
inner nature of the mature individuals, but according to their relation
in successive generations, since heredity is assumed when the
ontogenetic characters remain the same, and variation when previously
latent characters become visible. But these phenomena belong to another
department of science; they concern the possibility and reality of
development of the idioplasmic determinants.


17. VARIETY, RACE, MODIFICATION.

From the multifarious variations of organisms proceed various categories
of kinship. _Varieties_ arise by extremely slow changes in the idioplasm
due to the perfecting process and adaptation. Since these are
conditioned by the same causes, they follow in all individuals of the
same variety in uniform manner. Varieties are uniform, entirely constant
under the most various external conditions, in general cross only with
difficulty with related varieties, are not varied by accidental crosses,
and persist through geological periods. Varieties belong to feral nature
rather than to culture; they can assume all possible modifications
without injury to their specific characteristics, but can show no
distinctions of races, for all beginnings of race formation are
destroyed by free intercrossing. They differ from species only in that
they are to be designated as more closely related species, or species as
more remotely related varieties. Every other distinguishing
characteristic is wanting.

_Races_ arise from gamogenic or pathological variations of the
idioplasm. In the former case they presuppose crossing between related
varieties or species, in the latter case an increased sensibility and
weakening of the idioplasm. Very often both causes co-operate, since
crossing follows more easily when the idioplasm is weakened by hurtful
influences and since the irritability and weakening of the idioplasm
increases if crossing has preceded. Race formation begins in single
individuals. Among several individuals it begins in various directions
because the causes are different and hence may display a great
multiformity. Races are distinguished by more or less abnormal
characteristics; they arise quickly--often in a single generation--and
present various degrees of stability. This stability is insured to some
extent only by the strictest in-and-in breeding. All races disappear
through crossing, likewise many races that have arisen from pathological
variations disappear even in sexual reproduction (in self-fecundation).
Races belong exclusively to cultivation, where they can develop and
exist protected from free intercrossing.

While varieties and races arise by progressional or stationary variation
of the idioplasm, _modifications_ are produced by such influences of
nutrition and climate as act only on the soma-plasm and the non-plasmic
substances, and hence do not give rise to inheritable characters in the
organism. Modifications persist only so long as their causes, and under
other environments immediately pass over into the modifications
corresponding to them. The transition is completed in the lowest plants
during a limited number of cell generations; in an individual of the
higher plants on the same stem during the growth of a single year. Each
variety and each race appears clothed in a definite modification, and
can change it within a range peculiar to itself.[A]

    [G] The distinctions which Nägeli here erects are, of course,
    purely arbitrary, and his definitions are suitable for use only
    in his own thesis.--_Trans._


18. SOCIAL AND INDIVIDUAL ORIGIN OF SPECIES.

The species arises neither from the _nutrition variety_ nor from the
_race_; it is always a more advanced variety, and hence species
formation is identical with variety formation. Cause for variation and
consequently for variety formation is always shown, either when,
environment remaining the same, the automatic variation of the idioplasm
has advanced so far that the ontogeny is raised to a higher grade of
organization and division of labor, or when external stimuli act for a
sufficiently long time in a manner not in harmony with the previous
adaptation. Hence various varieties arise easily from a uniform kinship,
when these are thrown among unlike external influences by local
separation, because in the separated places on the one hand the
automatic evolution proceeds with unequal rapidity, and on the other
hand adaptation takes place unequally.

But in general different varieties arise socially from a uniform
kinship. This is because the related individuals living together are
unequally stimulated on account of the great inequality of external
influences which may exist at the smallest distances; and also because
with slight individual differences unlike reactions often follow upon
the same external influences. If identically similar individuals are
equally inclined to very different reactions toward the same stimulus,
sometimes the direction of the first variation decides the character of
the adaptation and therefore the nature of the variety, because the
variation, when once begun, progresses unswervingly even under somewhat
different circumstances.[H] Hence divergent variations are found growing
together in all places, which variations have begun at different though
neighboring points by transformation of the idioplasm and are soon
intermingled on account of the easy dissemination of seed.

    [H] It is interesting to compare this statement with Weismann's
    recent theory of Germinal Selection.--_Trans._

The social formation of varieties is not in general interrupted by
crossing, a process which governs only the formation of races. It is
confirmed according to experience by the universally recurring fact that
several beginnings of the most closely related varieties appear
together not only in the same region, but even at the same points, while
the geographical distribution of the more marked varieties and of
related species offers no conclusion as to their origin, but only as to
the last great migration of the plant world, because they arose before
this period, as indeed appears from their distribution.

Just as different varieties arise simultaneously from one kinship at the
same place, the same variety may arise in places far separated, when the
analogous external exciting causes occasion an identical transformation
in the idioplasm. The experimental proof lies in the fact that like
beginnings of varieties often appear at great distances from each other.

An apparent social origin of varieties is indicated, when, after having
come together in migration, they first develop the unlike determinants
which they have gained in various locations. An apparently individual
origin of the same or different varieties is indicated, when the
formation of the determinants take place at one and the same place, but
their development follows only after the kindred has been scattered by
migration.


19. GENERAL RELATION OF THE PHYLOGENETIC LINES IN THE ORGANIC KINGDOMS.

Since the nature of an organism is contained in the sum of its
idioplasmic determinants alone, the evolution of a phylogeny consists in
the evolution of the idioplasm. This is perceived from the succession
of the visible ontogenetic characteristics which in general run parallel
with it. The idioplasm varies in two ways: (1) by an _automatic
perfecting process_; (2) by _adaptation to environment_.

By virtue of the _automatic variation_ of the idioplasm the ontogenies
of a phylogenetic line attain to a continually more complex organization
and greater differentiation of function. In this differentiation,
however, only the qualitative differences are of importance;
quantitative and numerical gradations may be disregarded. The more
complex admits of more combinations than the simpler; hence if a
phylogeny reaches a higher stage by automatic evolution it may branch
into several lines, of which each appears as the continuation of the
parent stock.

Since _adaptive variations_ depend only on the transmutations of
environment, an organism may rise to a higher organization and division
of labor by continually adapting itself to the changed environment. But
the organism may also change its adaptation while it remains at the same
stage of organization. And since the adaptive variation is quickly
perfected as compared with automatic evolution, although extremely
slowly as compared with the duration of the ontogeny, an organization
may change its adaptation several times while it remains at the same
grade of organization and division of labor. Since there are also
numerous different kinds of adaptation, a phyletic line may divide at
each point into several adaptive forms, which appear in the taxonomic
system as species, genera, often even as whole families, while in other
cases various degrees of organization have appeared in one family.


20. LAWS OF EVOLUTION OF THE PLANT KINGDOM.

In the sub-organic kingdom, which precedes the plant and animal
kingdoms, (see page 5), there are gradually formed from the
spontaneously generated plasma independent cells with their
characteristic properties, _i.e._, growth by intussusception of micellæ,
formation of a plasmic cuticle, and a non-plasmic membrane about the
same, division of the cells, separation of the cells thus formed, and
free cell formation within the cell contents. These properties are
inherited from the sub-organic kingdom by the plants and animals which
follow in the next stage of phylogeny. The evolution of the plant
kingdom proceeds through the following regular processes, which continue
to operate through the entire phylogenetic series.

_Law of Phylogenetic Combination._--The simplest of all plants are cells
of round form, which grow and reproduce themselves by division, budding
or free cell formation. From the fact that the younger generation of
cells, instead of separating from each other and growing to independent
plant individuals, remain united with each other, multicellular plants
arise from unicellular. The same transformation of the reproductive
cells into non-separable tissue cells is repeated several times in
multicellular plants and serves to enlarge the individual. There is
manifested in this phylogenetic process the tendency of the plant to
combine in the higher stages into one complex whole those parts which in
the lower stages tend to be independent. A similar unifying tendency is
revealed also in those plant members which have arisen by
differentiation and represent a system only by their being connected at
certain points. These combine in the higher stages and form ultimately
continuous tissues.

_Law of Phylogenetic Complication or Ampliation, Differentiation and
Reduction._--The cells, and, in general, the parts of plants which lie
near each other in space or follow upon each other in time, are always
alike in the lower stages. By differentiation they become unlike, so
that the sum of the functions which at first fall to the lot of all
parts without distinction now is shared among the individual parts. By
this means each part can perform its own special function so much the
better. Differentiation is repeated in the course of the phylogeny,
since at first all parts of an ontogeny diverge into two or more parts,
then the parts of these parts divide again, etc. Along with this process
of division another process is always active, which, as it were,
prepares the way for the former, namely, ampliation, by virtue of which
the growth of the whole ontogeny or of single stages of it undergoes a
quantitative increase, so that an organ acquires a greater number of
cells, and an individual a greater number of organs. After this increase
in number of parts in a stage of ontogeny, differentiation follows as
far as the nature of the functions permits, by the parts most separated
passing into each other by intermediate gradations. By the further
phylogenetic process of reduction the intermediate forms are suppressed.
At last only the extreme products of differentiation lie near each other
in space or follow upon each other in time; and these products are as
limited in quantity and number as possible.

Along with the above named phylogenetic processes, which take place by
the automatic increase of the idioplasm, external influences are always
active. These lend to the organism at times a local stamp corresponding
to its environment, and follow the law of adaptation.


21. ALTERNATION OF GENERATIONS IN RELATION TO PHYLOGENY.

Since the simplest plants are cells and the more complex ones are formed
from cells, a whole phylogenetic line may be regarded as a series of
cell generations following one after another. In the lowest forms all
cell generations are like each other; in all others they show
differences which become continually greater and more numerous. Thus
alternation of generations in cells exists, because the successive
generations become more and more complicated at each succeeding period.
Among these periods the ontogenetic period or ontogeny embraces all
generations from one cell to the return of the exactly similar kind of
cell. In the lowest forms of cell differentiation the cells of
successive generations are all independent; the ontogenetic period
consists of a cycle of generations of unicellular plants. Later the cell
generations of an ontogeny are united by parts into plant individuals;
the ontogenetic period consists of a cycle of multicellular and
unicellular, or only of multicellular plant generations. If all the cell
generations of an ontogenetic period have been united into a single
individual, the successive plant generations are alike and alternation
of generations has ceased.

The unlikeness of the generations arises either from inner causes of
temporary differentiation alone, or by temporary differentiation which
receives a definite imprint by the change of seasons. But in the latter
case the characteristic of adaptation is again lost in the course of the
phylogeny and alternation of generations follows then without regard to
the season. If the given adaptation is united in the lower plants with
alternation of generations during the ontogenetic periods, one of the
unlike plant generations is repeated an indefinite number of times
(repetitional generation), while the other unlike plant generation
appears only once and then at the beginning of the resting stage and
remains latent in the form of a resting spore till the beginning of the
next period of generation. With this peculiar transition generation,
which has arisen in the lower stages asexually, and in the following
higher stages by the union of a male and a female cell, and which hence
is hermaphrodite, there are generally associated later two other single
generations--_viz._, a generation preceding and one following the
hermaphrodite, the former as a sex-producing generation, the other as a
sex-produced generation.

The phylogenetic significance of the alternation of generations consists
in its representing a transition stage from the unicellular to the
simpler multicellular and from the latter to the more complex
multicellular plants. The plant generations of any phylogenetic stage
increase by ampliation, become unlike by differentiation in time
(alternation of generations), and unite in a plant individual, whose
unlike ontogenetic stages correspond to the unlike plant generations of
the earlier ancestral series.


22. MORPHOLOGY AS THE SCIENCE OF PHYLOGENY.

All organic phenomena belong, according to their causes, to two
different classes: (1) Those belonging to one group are the results of
external influences in each ontogeny and are not inherited; they
represent nutrition varieties, are experimentally demonstrable, and
constitute the subject matter of experimental physiology. (2) The others
are inherited and again transmitted; they belong to the physiology of
the idioplasm. This subject is mainly occupied with the origin of the
determinants, hence with the formation of varieties and species. It is
not the subject of experiment, and constitutes the phylogeny or the
physiology of the formation of determinants. A sub-division of this
subject is occupied with the development of the determinants already
present, hence with the formation of races. It is elucidated especially
by experiments in crossing and may be designated as the physiology of
the development of the determinants.

The morphological phenomena which find their application in taxonomy,
belong exclusively to phylogeny. Their ontogenetic history does not
explain their true significance; this can be known only in a
phylogenetic way by comparison of one phenomenon with those phenomena
from which it has arisen in the course of evolution.


23. PLANT CLASSIFICATION FROM THE STANDPOINT OF PHYLOGENY.

Spontaneous generation has taken place at all times and in all places,
in as far as the necessary conditions were concurrently present. (See
page 47). After spontaneous generation the automatic phylogenetic
evolution begins and advances constantly. Consequently the phylogenetic
line rises from time to time to higher stages of organization and
division of labor, but dies of old age if the automatic perfecting
process ceases. The phylogenetic lines of organisms now living have
therefore an unequal age; those of the most highly developed plants and
animals had their origin in the earliest periods of organic life, those
of the lowest organisms in the most recent periods. Hence no general
genetic relation exists among lines now living; only those that are
nearly related and have reached approximately equal stages of
organization may be regarded as branches of the same phylogenetic stock.
A phylogenetic plant system does not exist in fact, but only in figure.

If genetic relation between two races is assumed, either as a reality or
as a symbol, the degree of relationship is determined in a theoretically
exact manner by the number and length of the phylogenetic steps which
are found either between them both or between them and the common
starting point, according as races belong to the same or collateral
lines. The fact that two organisms belong to the same line of descent is
recognized from the ontogeny of the higher including the ontogeny of the
lower.

Since only a proportionately small number of known forms can appear as
types of the supposed stages of evolution, only a few phylogenetic
lines, and these only in a general way, may be established, on account
of the great incompleteness of the present plant world. Such a line
proceeds from the green filamentous algæ through the liverworts to the
vascular plants. Among the phanerogams, apparently so numerously
represented, only phylogenetic series of individual organs can be
ascertained, but no phylogenetic series of families. A phylogenetic
system of phanerogams is not to be hazarded in the roughest outline.
Even the relative rank of the two chief divisions of the angiosperms,
the monocotyledons and dicotyledons, is a matter of question, as also
which family in each of these divisions is to be considered the most
perfect.



APPENDIX.

TRANSLATORS' NOTES.


_The Mechanico-physiological Theory of Evolution_,
(_Mechanisch-Physiologische Theorie der Abstammungslehre_),
by Carl von Nägeli, was published in Munich and Leipsic in 1884 in a
large octavo volume of 822 pages, including two large appendices. The
_Abstammungslehre_ proper, including the summary, occupies 552 pages,
and constitutes, in its way, one of the most important contributions to
theoretical biology. It is difficult to understand how a work of so much
consequence should have received such comparatively small notice in this
country, especially as Nägeli's theories seemed calculated by nature to
appeal much more strongly to American students than do, for instance,
those of Weismann, who has been studied ten times as much as Nägeli.
This is doubtless due, in part, to the fact that we have had no English
translation of Nägeli's work, a circumstance much to be regretted.

The foregoing translation of the summary from _Abstammungslehre_
goes but a small way toward making Nägeli's theories accessible to
English-reading students, but it will, at least, be better than nothing.
The work covers a great range of subjects, all, however, having a
certain relationship to each other. In the main part of the book the
discussion is presented in the following order: (1) Idioplasm as bearer
of the inheritable determinants; (2) Spontaneous generation; (3) Causes
of variation; (4) Determinants and visible characters, in which the
origin and function of the determinants is presented; (5) Variety, race,
"nutrition variety," heredity and variation; (6) Criticism of the
Darwinian theory of natural selection, in which the author urges seven
objections to that theory; (7) Laws of evolution of the plant kingdom;
(8) Alternation of generations from the standpoint of phylogeny; (9)
Morphology and classification as phylogenetic sciences; (10) A
comprehensive summary of the whole work, a translation of which is
given in the foregoing pages.

In the first part of the work Nägeli sets forth his micellar theory of
the structure of organized bodies. This is one of his most important
contributions to science. Until recent years it has been the only theory
given in botanical text-books. At the present time its only competitor
is Strasburger's lamellar theory, and even this has not superseded
Nägeli's work to any great degree.

The reader who may not be familiar with the micellar theory will find
the general idea from the following brief sketch adapted from Vines's
_Plant Physiology_:

    "Nägeli's micellar theory was developed from his study of
    organized bodies, especially of cell walls and starch grains.
    From the behavior of organized substance toward water absorbed
    by it, he concluded that water does not penetrate into the
    micellæ, but only among them, thus merely separating them more
    from each other. He reasoned that if water should penetrate into
    the micella, its structure would be disintegrated. Hence he
    argued that organized bodies consist of solid micellæ, which,
    with their respective films of water, are held together by: (1)
    The attraction of the micellæ for each other, which varies
    inversely as the square of the distance. (2) The attraction of
    the micellæ for water, which varies inversely as some higher
    power of the distance. (3) The force which holds together the
    ultimate chemical molecules of which each micella consists.

    "Since the swelling up of organized bodies does not take place
    equally in all three dimensions of space, and on account of
    their double refraction, Nägeli inferred that in form the
    micellæ are crystals, probably parallelopipedal, with
    rectangular or rhomboidal bases."

The law that "bodies attract each other with a force which varies
inversely as the square of the distance," has been proven only in its
application to the heavenly bodies. Nägeli has applied this law to
molecules, unsupported, however, by any evidence other than that of
analogy. On the other hand, there is evidence that molecules do not
invariably act according to this law.

Spontaneous generation (p. 4) was an important item in Nägeli's
doctrine, and might almost be said to be fundamental to it, although it
is not really necessary to the internal perfecting principle, which may
be regarded as the chief feature of the Mechanico-Physiological Theory.
Up to 1865 Nägeli believed in the spontaneous origin of many fungi, and
thought that it could be demonstrated. He was obliged to abandon the
experimental evidence, but to the close of his life held the views of
abiogenesis presented in the accompanying translation.

The characteristic and most interesting feature of the
Mechanico-Physiological Theory is certainly Nägeli's conception of an
automatic perfecting principle (_Autonome Vervollkommnung_). This
conception may be briefly outlined as follows:

1. The essential part of the reproductive plasm, termed idioplasm, since
it divides and passes over from generation to generation, in higher as
well as in lower organisms, has a continuous or "immortal" existence.[I]

    [I] Nägeli's idioplasm corresponds in many respects, though by
    no means in all, to Weismann's germ-plasm. Weismann's idea of
    continuity or "immortality," which has been so widely noticed,
    is set forth with equal clearness, though with less emphasis, by
    Nägeli.

2. During this continuous life the idioplasm goes through a development
of its own, just as an individual organism goes through a certain cycle
of development during its individual life. This development consists in
a constantly increasing complexity of structure and differentiation of
function.

3. This development is automatic, resulting from internal forces or
movements, (_Vervollkommnungs-bewegungen_).

4. As a result of the increasing complexity of structure in the
idioplasm the entire organism, which in each generation rearises
therefrom, becomes, from generation to generation, more and more complex
with greater and greater differentiation of function. Thus the
progression of the idioplasm controls the phylogeny of the race. It
marks out the course of evolution.

5. Since, according to Nägeli, new life with new idioplasms, may arise
wherever and whenever the necessary conditions combine, the present
organic world is not made up from branchings of a single original
idioplasm, but each race or group may have its own specific idioplasm;
and, since this has its own characteristic structure and its own
specific internal perfecting forces, it passes through its own peculiar
evolution, carrying with it its own depending race of organisms.

The fact that animals and plants at the present time show such various
degrees of organization is also accounted for on the last supposition,
for those of lowlier organization are merely of more recent origin and
have not progressed so far in idioplasmic development.

This automatic perfecting principle has been the mark of much criticism.
Some have confounded it with the mystical _nisus formativus_, or
formative principle of preceding theorists. But, as Weismann remarks,
Nägeli's phyletic force is conceived as a thoroughly scientific
mechanical principle. Nägeli has simply made application in the organic
world of the principle of entropy, as stated in the mechanical theory of
heat. Nägeli himself also compares his internal perfecting principle to
mechanical inertia. He says, "the force of evolution once started in a
given direction, tends to continue in the same direction. This
constitutes the law of inertia in the organic world."

       *       *       *       *       *

Two other matters remain to be noticed. The first of these is Nägeli's
use of the German word _Anlage_. We have been unable to give a perfectly
satisfactory translation of this word in its technical meaning. We have
received some comfort, though but little help, from the experience of
the translators of similar works. Selmar Schoenland, in translating from
Weismann, renders it variously as "germ," "germ of structure," "germ (of
Nägeli)," "germ of Nägeli," "Nägeli's preformed germ of structure,"
"preformed germs," "tendency." Another translator renders the word as
"constitutional element." The translation, "determinant," which we have
selected is an appropriation of an analogous but not absolutely
identical technical term from Weismann's _Germinal Selection_. The use
of the word in this connection is open to the objection that it has
previously been used technically for a somewhat different idea by
another author. M. C. Potter, in his translation of Warming's
_Systematic Botany_, following Dr. E. L. Mark, renders the word _Anlage_
as "fundament." Dr. H. C. Porter, in his translation of the _Bonn
Text-Book of Botany_, renders the same word as "rudiment."

In general the word Anlage means beginning, plan, disposition to
anything, and hence involves the ideas of origin, organization and
tendency. Sanders defines the word in one of its meanings as: "The act
of planning or beginning anything; the act of laying the foundation of
any work intended to be carried on toward completion, in order that from
the beginning made, a definite thing may be developed or may develop
itself"; (_i.e._, to determine, in the sense of limiting to a particular
purpose or direction, hence determinant). "Also, the thing begun or
planned, considered as the basis and germ of the further development of
that which has already originated."

In its restricted use as applied to organisms it would mean "germ," in
the sense of embryonic starting point. More specifically, it is a
portion of plastic, organized substance, functioning as an individual
and containing potentially an elemental organ plus a formative power. In
Nägeli's own words, "There exists an essential difference between the
substance of a mature organism which does not possess the capability of
further development, and the substance of an egg, which does possess
this capability. By virtue of this difference the egg-substance is
characterized as the _Anlage_, or germ of the mature organism. All
characteristics of the adult condition are potentially contained in the
ovum."

Nägeli was not the first to assume the existence of a unit of
organization intermediate between the molecule and the cell. E. B.
Wilson, in his _The Cell in Inheritance and Development_, states the
case as follows:

    "That the cell consists of more elementary units of
    organization, is indicated by _a priori_ evidence so cogent as
    to have driven many of the foremost leaders of biological
    thought into the belief that such units must exist, whether or
    not the microscope reveals them to view. The modern conception
    of ultra-cellular units, ranking between the molecule and the
    cell, was first definitely suggested by Brücke in 1861.

    "This idea of ultra-cellular units is common to most
    morphologists and physiologists. We are compelled by the most
    stringent evidence to admit that the ultimate basis of living
    matter is not a single chemical substance, but a mixture of many
    substances that are self-perpetuating without their loss of
    specific character."[J]

    [J] For a fuller discussion of the notion of these hypothetical
    units of organic existence, see Weismann's Germinal Selection,
    (Open Court Publishing Co., Chicago, 1896), especially the foot
    note, page 230.

Nägeli's _Laws of Evolution_ are also worth special notice. As stated in
the body of _Abstammungslehre_ they are as follows:

1. Asexual reproductive cells which arise by division, remain united and
become tissue cells.

2. Asexual reproductive cells which arise by budding, instead of
separating, become cell branches or branched cell threads.

3. Reproductive cells which arise by free cell formation become bodies
which form a part of the cell contents.

4. Parts of a plant which arise by differentiation lie side by side and
form a body of web-like or tissue-like structure.

5. A definite and previously limited growth continues, or a definite
formation of parts of an ontogeny which has previously been present but
once, is repeated. (Ampliation.)

6. The parts of an ontogeny become dissimilar, since the functions which
were previously united become differentiated and since new dissimilar
functions are produced in the various parts. This differentiation is
either one of space between the parts of the ontogeny that appear near
each other, or one of time between those that are derived from each
other.

7. Parts which have become dissimilar by differentiation undergo a
reduction, in which the intermediate forms are suppressed and at last
only the qualitatively dissimilar forms with qualitatively dissimilar
functions remain.

8. The environment in which plants live operates in different ways,
directly as a stimulus or indirectly as a felt necessity and by this
means lends to their forms and activities a definite expression of time
and place, and thus brings about different adaptations. These become
permanent through heredity, but are again gradually lost if other
adaptations supersede them.

Laws 1 to 4 may be expressed as one--the law of combination: Similar
parts that are wholly or partly separated have the tendency to unite
more and more completely and intimately into one continuous tissue.

The laws of ampliation (5), differentiation (6), and reduction (7), may
be summarized in one as follows: While increasing in size the similar
parts of an ontogeny become internally dissimilar and the dissimilarity
increases as the transition forms of the dissimilar parts vanish. Hence
only the extreme forms remain.

       *       *       *       *       *

It may also interest the reader to know that Nägeli was the first to
propose the general theory of cell formation as accepted at the present
day.



    BRIEF STATEMENT OF THE WORK OF THE OPEN COURT PUBLISHING COMPANY


If one asked for a brief description of the work of the Open Court
Company, one would probably get the answer that the Company publishes
books and articles on Science, Religion, and Philosophy. That is not
quite exact; for that describes the ideal to which the Open Court
Company is continually striving rather than the actual work it is doing.
The ideal is Religion on a firm basis of Science, a Science of
Philosophy, and a Philosophy of Science: the only path which can lead to
this great ideal synthesis is the detailed and careful study of
sciences, religions, and philosophies.

It was this ideal that prompted the late Mr. Edward Carl Hegeler of La
Salle, Illinois, in the United States of America, to found a Company to
publish books with the object of establishing ethics and religion upon a
scientific basis. Such ideals are as old as philosophy itself. Among
modern philosophies, that founded by Comte tried, probably in the most
explicit fashion of all, to found a religion on the basis of positive
science; and at one time it appeared likely to have a lasting success.
But it is now quite plain that no philosophy which hopes to be permanent
can neglect history or put itself into uncritical opposition to the
systems that have for centuries expressed some of the dearest and
highest aspirations of mankind. It is unprejudiced and fearless
historical and critical investigation--non-sectarian in the widest
sense--in both religion, science, and philosophy, that must go before
any satisfactory synthesis. This is a great part of the work of the Open
Court Company.

Let us consider what non-sectarianism means. We cannot, for example,
isolate a single domain of science in a particular country and at a
particular time--say, mechanics in England in the eighteenth
century--and hope to make of it a thoroughly complete object of study.
In natural science, for example, we make conventional divisions simply
with the object of saving labor when dealing with the huge mass of
material that experience offers. But the narrowest specialist knows that
all workers in science, religion, and philosophy seek the Truth; and
that the Truth is bounded neither by space nor by time nor by man-made
divisions. A man may rightly conclude that he stands little chance of
finding out very much of the Truth, and so he may voluntarily limit his
view to a certain roughly defined domain of facts and thoughts, and
become, for example, what is called a "biologist," a "physicist," a
"higher critic," or, if he thinks that he may discover rather more of
the Truth, a "philosopher."

And let us carry a clear understanding of a lofty aim into religion as
well. It is our duty, as rational beings, to be non-sectarian. It is not
a merit to allow ignorance to blind us to the glimpses of Truth that we
sometimes get from prophets, poets, and priests of other religions and
other philosophies than our own. If we think that there is more truth or
sacredness in our own, let us use every means to make this sacredness or
this truth appear evident to others. But, in justice, let us also
fearlessly discuss other religions and philosophies, and discover their
greater merits, if any, as compared with our own. If, after careful
investigation, we arrive at the belief in the truth or falsehood of
anything in these religions or philosophies, let us state our grounds
for believing so in the fullest possible way. Only by so doing can we
fulfil the duties of being true to ourselves and helpful to others.

Sometimes the work of a critic is said to be "merely destructive." This
idea rests on a most harmful misunderstanding. Criticism consists not
only in the pointing out of error, but in the pointing out of truth as
well. Error is simply a psychological condition of blindness to the
truth; and the discovery of errors committed by other people or
ourselves is not--as many superficial people like to say--the pulling
down of a structure already raised, unless an error can be called a
structure which is built out of the fictions of our imagination which
have no objective existence. Criticism often enables us to discover more
of the Truth, and nobody can do more than _discover_ Truth: nobody
_creates_ Truth, any more than Columbus created America.

Nowadays all intelligent men and women agree that all knowledge must be
subjected to criticism, and the best men and women act on these beliefs.
The books and magazines published by the Open Court Company are intended
to help these men and women.

We will dwell a little longer on the subject of religion, because it is
in religion that the majority of us have the one region of ideals above
our bodily needs. It is rare, though of course not unknown, that Science
or Philosophy satisfies the spiritual needs--the purest of human
cravings. Nowadays, most of us realize that an anti-scientific attitude
of religion is impossible. If there were an opposition between "science"
and "religion," there would be no question as to which side would be
victorious. More particularly during the last seventy years, "religion,"
conscious of the opposition which a rather crude doctrine which was
called "science" had towards it, has been gradually, and often somewhat
ludicrously, trying to bring itself more into conformity with that
"science." The result is painful to the student of human nature; though
it has its amusing sides, just as had the militant denial, on the part
of those who were "on the side of the angels" about fifty years ago, of
certain deductions from facts. What is called a "conflict between
religion and science" always has ended in a victory for "science" and an
agnosticism which ousted religion. And thus many see that it is
desirable that the matured results of science should enter into the
fabric of our religious convictions. For the realization of this
purpose, the Open Court Company publishes two periodicals, _The Monist_,
a quarterly magazine devoted to the philosophy of science, and _The Open
Court_, an illustrated monthly devoted to the science of religion and
the religion of science. In addition, the Open Court Company publishes
books that directly or indirectly advance its aim--books on Philosophy,
which, in contrast with the old metaphysicism, lay the foundations of a
philosophy of science; books on the history of philosophies; books on
mathematics and other lines of thought which are indispensable for a
rational and scientific conception of the world; books that have a
bearing on the doctrine of Evolution; books on the history of Religions,
especially on the development of Christianity and on Higher Criticism;
and books on Comparative Religion, on Psychology, on Education, and on
Ethics. Above all, in all the works careful, sympathetic, and scholarly
criticism is aimed at. Criticism is the joint result of love of Truth
and independence of thought; rightly understood, it is not only a
preliminary to a work of synthesis, but it is part of synthesis itself.
No synthesis, in fact, is more than a discovery of Truth: from past
history we know that syntheses have often blinded men to the Truth,
though that was naturally not their intention.

On the subject of independence of thought it may be proper shortly to
refer to the work of Dr. Paul Carus, who has been, since the end of
1887, closely associated with the Open Court Company and its
publications. Only two things need be said here. In the first place, it
was owing to the need he felt for keeping his independence of thought
that he resigned a post in Germany and came, first to England and then
to America. In the second place, his views, which are also, broadly
speaking, the views for which the Open Court Company works, may be
characterized both as monism and positivism, though his philosophy
differs considerably from Hæckel's monism, which is practically
materialism, and even more so from the French positivism of Comte and
from agnosticism, its English equivalent. In his philosophy, _form_
plays the most important part. Form is the significant feature of both
objective existence and subjective thought. Matter and energy only
denote reality, but form characterizes quality. Science traces form, and
the nature of all things, the human character included, is constituted
by form. In the formal sciences again, that which is the core of their
usefulness as general propositions is the character of _anyness_, the
use of which justifies the method of generalization. Here lies the root
of the kinship of Dr. Carus's philosophy with modern logic, and allows
him to reconstruct the old artistic and religious ideas upon a new and
modern ground. In this sense, he himself has characterized his
philosophy as a _philosophy of form_.



                    A Partial List of Books in the
                      OPEN COURT SCIENCE SERIES


                         PROBLEMS OF SCIENCE
                         BY FEDERIGO ENRIQUES

    Authorized translation by Katherine Royce, with an introduction
    by Josiah Royce. =Pp. 375. Price, $2.50.=

"The end for which we ought to strive today is a scientific education,
which shall enable the workers in any field whatsoever to understand
better how the object of their own research is subordinated to more
general problems."

The author is professor of projective geometry and geometric drawing in
the University of Bologna, and is one of the most conspicuous of
contemporary Italian scientists.


The Primary Factors of Organic Evolution                 By E. D. Cope

    =Illustrated. Cloth, $2.00 net=


The Soul of Man                                          By Paul Carus

    An investigation of the facts of physiological and experimental
    psychology. =Illustrated. Cloth, $1.50 net; paper, 85c.=


Plant Breeding                                        By Hugo De Vries

    Comments on the experiments of Nilsson and Burbank.
    =Illustrated. Cloth, gilt, $1.50 net=


The Rise of Man                                          By Paul Carus

    A sketch of the human race. =Illustrated. Boards, cloth back,
    75c net=


Species and Varieties, Their Origin and Mutation      By Hugo De Vries

    Edited by D. T. MacDougal. =Price, $5.00 net=


The Mutation Theory                                   By Hugo De Vries

    Experiments and observations on the origin of species in the
    vegetable kingdom. (2 vols.) Translated by Prof. A. B. Farmer
    and A. D. Darbishire. =Numerous illustrations, colored plates.
    Cloth, per volume $4.00 net.=


Intracellular Pangenesis                              By Hugo De Vries

    Including a paper on fertilization and hybridization. Translated
    from the German by C. Stuart Gager. =Cloth, $3.00 net.=


On Memory and the Specific Energies of the Nervous     By Ewald Hering
System

    New edition, including "The Theory of Nerve Activity."
    =Price, $1.00; paper, 30c.=


Psychology of the Nervous System                         By Paul Carus

    An extract from the author's larger work, "The Soul of Man."
    =Price, 30c.=


The Psychology of Reasoning                            By Alfred Binet

    Translated by Adam Gowan Whyte. =Cloth, 75c net=


Has the Psychological Laboratory Proved Helpful?       By L. M. Billia

    Translated from the French by Lydia G. Robinson. =Pp. 16. Paper,
    15c net.=


A Mechanico-Physiological Theory of
Organic Evolution                                   By Carl von Nageli

    Summary. =30c.=


Experiments on the Generation of Insects             By Francesco Redi

    Translated from the Italian edition of 1688 by Mab Bigelow.
    =Illustrated. Cloth, $2.00 net=


Science and Faith, or Man as an Animal, and Man
as a Member of Society, with a Discussion on
Animal Societies                                      By Paul Topinard

    Translated by T. J. McCormack. =Price, $1.50 net=


A First Book in Organic Evolution                  By D. Kerfoot Shute

    Written especially for the use of students. =Illustrated, seven
    colored plates, 2d ed. Cloth, $1.25; paper, 60c net=


On Germinal Selection as a Source of Definite
Variation                                           By August Weismann

    Translated by T. J. McCormack. =Paper, 30c=


Popular Scientific Lectures                              By Ernst Mach

    Translated by T. J. McCormack. =Illustrated. $1.50 net; paper,
    60c net=


Contributions to the Analysis of the Sensations          By Ernst Mach

    Translated by C. M. Williams. =Price, $1.25 net=


Space and Geometry in the Light of Physiological,
Psychological and Physical Inquiry                       By Ernst Mach

    Translated by T. J. McCormack. =Cloth, gilt top, $1.00 net=


The History and the Root of the Principle
of the Conservation of Energy                            By Ernst Mach

    Translated by Philip E. B. Jourdain. =Cloth, $1.25 net=


On the Inheritance of Acquired Characters           By Eugenio Rignano

    Translated by Basil C. H. Harvey. With an appendix "On the
    Mnemonic Origin and Nature of Affective Tendencies." =Cloth,
    $3.00 net=


Darwin and After Darwin                           By George J. Romanes

    An exposition of the Darwinian theory and a discussion of
    post-Darwinian Questions. =Three volumes, $4.00 net.=

    Part I. The Darwinian Theory. =Cloth, $2.00.=

    Part II. Post-Darwinian Questions: Heredity and Utility. =Cloth,
    $1.50.=

    Part III. Post-Darwinian Questions: Isolation and Physiological
    Selection. =Cloth, $1.00.=


An Examination of Weismannism                     By George J. Romanes

    =Cloth, $1.00 net; paper, 40c net.=


                        Send for complete list.

                       OPEN COURT PUBLISHING CO.
                   (Scientific and Educational Books)
                          122 S. Michigan Ave.
                                Chicago



                          TRANSCRIBER'S NOTES


1. Passages in italics are surrounded by _underscores_ and the ones in
bold are indicated by =bold=.

2. Footnotes have been moved from the middle of a paragraph to the end
of the paragraph referring to it.

3. Other than that, printer's inconsistencies in spelling, punctuation,
and ligature usage have been retained.





*** End of this LibraryBlog Digital Book "A Mechanico-Physiological Theory of Organic Evolution" ***

Copyright 2023 LibraryBlog. All rights reserved.