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Title: Evolution in Modern Thought
Author: Weismann, August, Haeckel, Ernst Heinrich Philipp August, 1834-1919, Thomson, J. Arthur
Language: English
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Copyright Status: Not copyrighted in the United States. If you live elsewhere check the laws of your country before downloading this ebook. See comments about copyright issues at end of book.

*** Start of this Doctrine Publishing Corporation Digital Book "Evolution in Modern Thought" ***

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                         EVOLUTION IN MODERN


                    BY HAECKEL, THOMSON, WEISMANN

                              AND OTHERS

                          THE MODERN LIBRARY

                      PUBLISHERS :: :: NEW YORK

       *       *       *       *       *



     J. Arthur Thomson, Professor of Natural History in the University of

II   _The Selection Theory_

     August Weismann, Professor of Zoology in the University of
       Freiburg (Baden)


     W. Bateson, Professor of Biology in the University of Cambridge


     G. Schwalbe, Professor of Anatomy in the University of Strassburg


     Ernst Haeckel, Professor of Zoology in the University of Jena


     C. Lloyd Morgan, Professor of Psychology at University College,


       H. Höffding, Professor of Philosophy in the University of Copenhagen


     Rev. P. H. Waggett


     J. B. Bury, Regious Professor of Modern History in the University
       of Cambridge


     C. Bouglé, Professor of Social Philosophy in the University of
       Toulouse, and Deputy-Professor at the Sorbonne, Paris

       *       *       *       *       *





_Professor of Natural History in the University of Aberdeen_

In seeking to discover Darwin's relation to his predecessors it is
useful to distinguish the various services which he rendered to the
theory of organic evolution.

(I) As everyone knows, the general idea of the Doctrine of Descent is
that the plants and animals of the present day are the lineal
descendants of ancestors on the whole somewhat simpler, that these
again are descended from yet simpler forms, and so on backwards
towards the literal "Protozoa" and "Protophyta" about which we
unfortunately know nothing. Now no one supposes that Darwin originated
this idea, which in rudiment at least is as old as Aristotle. What
Darwin did was to make it current intellectual coin. He gave it a form
that commended itself to the scientific and public intelligence of the
day, and he won widespread conviction by showing with consummate skill
that it was an effective formula to work with, a key which no lock
refused. In a scholarly, critical, and pre-eminently fair-minded way,
admitting difficulties and removing them, foreseeing objections and
forestalling them, he showed that the doctrine of descent supplied a
modal interpretation of how our present-day fauna and flora have come
to be.

(II) In the second place, Darwin applied the evolution-idea to
particular problems, such as the descent of man, and showed what a
powerful organon it is, introducing order into masses of uncorrelated
facts, interpreting enigmas both of structure and function, both
bodily and mental, and, best of all, stimulating and guiding further
investigation. But here again it cannot be claimed that Darwin was
original. The problem of the descent or ascent of man, and other
particular cases of evolution, had attracted not a few naturalists
before Darwin's day, though no one [except Herbert Spencer in the
psychological domain (1855)] had come near him in precision and
thoroughness of inquiry.

(III) In the third place, Darwin contributed largely to a knowledge of
the factors in the evolution-process, especially by his analysis of
what occurs in the case of domestic animals and cultivated plants, and
by his elaboration of the theory of Natural Selection which Alfred
Russel Wallace independently stated at the same time, and of which
there had been a few previous suggestions of a more or less vague
description. It was here that Darwin's originality was greatest, for
he revealed to naturalists the many different forms--often very
subtle--which natural selection takes, and with the insight of a
disciplined scientific imagination he realised what a mighty engine of
progress it has been and is.

(IV) As an epoch-marking contribution, not only to Ætiology but to
Natural History in the widest sense, we rank the picture which Darwin
gave to the world of the web of life, that is to say, of the
inter-relations and linkages in Nature. For the Biology of the
individual--if that be not a contradiction in terms--no idea is more
fundamental than that of the correlation of organs, but Darwin's most
characteristic contribution was not less fundamental,--it was the idea
of the correlation of organisms. This, again, was not novel; we find
it in the works of naturalists like Christian Conrad Sprengel,
Gilbert White, and Alexander von Humboldt, but the realisation of its
full import was distinctly Darwinian.

_As Regards the General Idea of Organic Evolution_

While it is true, as Prof. H. F. Osborn puts it, that "'Before and
after Darwin' will always be the _ante et post urbem conditam_ of
biological history," it is also true that the general idea of organic
evolution is very ancient. In his admirable sketch _From the Greeks to
Darwin_,[1] Prof. Osborn has shown that several of the ancient
philosophers looked upon Nature as a gradual development and as still
in process of change. In the suggestions of Empedocles, to take the
best instance, there were "four sparks of truth,--first, that the
development of life was a gradual process; second, that plants were
evolved before animals; third, that imperfect forms were gradually
replaced (not succeeded) by perfect forms; fourth, that the natural
cause of the production of perfect forms was the extinction of the
imperfect."[2] But the fundamental idea of one stage giving origin to
another was absent. As the blue Ægean teemed with treasures of beauty
and threw many upon its shores, so did Nature produce like a fertile
artist what had to be rejected as well as what was able to survive,
but the idea of one species emerging out of another was not yet

Aristotle's views of Nature[3] seem to have been more definitely
evolutionist than those of his predecessors, in this sense, at least,
that he recognised not only an ascending scale, but a genetic series
from polyp to man and an age-long movement towards perfection. "It is
due to the resistance of matter to form that Nature can only rise by
degrees from lower to higher types." "Nature produces those things
which, being continually moved by a certain principle contained in
themselves, arrive at a certain end."

To discern the outcrop of evolution-doctrine in the long interval
between Aristotle and Bacon seems to be very difficult, and some of
the instances that have been cited strike one as forced. Epicurus and
Lucretius, often called poets of evolution, both pictured animals as
arising directly out of the earth, very much as Milton's lion long
afterwards pawed its way out. Even when we come to Bruno who wrote
that "to the sound of the harp of the Universal Apollo (the World
Spirit), the lower organisms are called by stages to higher, and the
lower stages are connected by intermediate forms with the higher,"
there is great room, as Prof. Osborn points out,[4] for difference of
opinion as to how far he was an evolutionist in our sense of the term.

The awakening of natural science in the sixteenth century brought the
possibility of a concrete evolution theory nearer, and in the early
seventeenth century we find evidences of a new spirit--in the
embryology of Harvey and the classifications of Ray. Besides sober
naturalists there were speculative dreamers in the sixteenth and
seventeenth centuries who had at least got beyond static formulae,
but, as Professor Osborn points out,[5] "it is a very striking fact,
that the basis of our modern methods of studying the Evolution problem
was established not by the early naturalists nor by the speculative
writers, but by the Philosophers." He refers to Bacon, Descartes,
Leibnitz, Hume, Kant, Lessing, Herder, and Schelling. "They alone were
upon the main track of modern thought. It is evident that they were
groping in the dark for a working theory of the Evolution of life, and
it is remarkable that they clearly perceived from the outset that the
point to which observation should be directed was not the past but the
present mutability of species, and further, that this mutability was
simply the variation of individuals on an extended scale."

Bacon seems to have been one of the first to think definitely about
the mutability of species, and he was far ahead of his age in his
suggestion of what we now call a Station of Experimental Evolution.
Leibnitz discusses in so many words how the species of animals may be
changed and how intermediate species may once have linked those that
now seem discontinuous. "All natural orders of beings present but a
single chain".... "All advances by degrees in Nature, and nothing by
leaps." Similar evolutionist statements are to be found in the works
of the other "philosophers," to whom Prof. Osborn refers, who were,
indeed, more scientific than the naturalists of their day. It must be
borne in mind that the general idea of organic evolution--that the
present is the child of the past--is in great part just the idea of
human history projected upon the natural world, differentiated by the
qualification that the continuous "Becoming" has been wrought out by
forces inherent in the organisms themselves and in their environment.

A reference to Kant[6] should come in historical order after Buffon,
with whose writings he was acquainted, but he seems, along with Herder
and Schelling, to be best regarded as the culmination of the
evolutionist philosophers--of those at least who interested themselves
in scientific problems. In a famous passage he speaks of "the
agreement of so many kinds of animals in a certain common plan of
structure" ... an "analogy of forms" which "strengthens the
supposition that they have an actual blood-relationship, due to
derivation from a common parent." He speaks of "the great Family of
creatures, for as a Family we must conceive it, if the above-mentioned
continuous and connected relationship has a real foundation." Prof.
Osborn alludes to the scientific caution which led Kant, biology being
what it was, to refuse to entertain the hope "that a Newton may one
day arise even to make the production of a blade of grass
comprehensible, according to natural laws ordained by no intention."
As Prof. Haeckel finely observes, Darwin rose up as Kant's Newton.[7]

The scientific renaissance brought a wealth of fresh impressions and
some freedom from the tyranny of tradition, and the twofold stimulus
stirred the speculative activity of a great variety of men from old
Claude Duret of Moulins, of whose weird transformism (1609) Dr. Henry
de Varigny[8] gives us a glimpse, to Lorenz Oken (1779-1851) whose
writings are such mixtures of sense and nonsense that some regard him
as a far-seeing prophet and others as a fatuous follower of
intellectual will-o'-the-wisps. Similarly, for De Maillet, Maupertuis,
Diderot, Bonnet, and others, we must agree with Professor Osborn that
they were not actually in the main Evolution movement. Some have been
included in the roll of honour on very slender evidence, Robinet for
instance, whose evolutionism seems to us extremely dubious.[9]

The first naturalist to give a broad and concrete expression to the
evolutionist doctrine of descent was Buffon (1707-1788), but it is
interesting to recall the fact that his contemporary Linnæus
(1707-1778), protagonist of the counter-doctrine of the fixity of
species,[10] went the length of admitting (in 1762) that new species
might arise by inter-crossing. Buffon's position among the pioneers of
the evolution-doctrine is weakened by his habit of vacillating between
his own conclusions and the orthodoxy of the Sorbonne, but there is no
doubt that he had firm grasp of the general idea of "l'enchaînment des

Erasmus Darwin (1731-1802), probably influenced by Buffon, was another
firm evolutionist, and the outline of his argument in the
_Zoonomia_[11] might serve in part at least to-day. "When we revolve
in our minds the metamorphoses of animals, as from the tadpole to the
frog; secondly, the changes produced by artificial cultivation, as in
the breeds of horses, dogs, and sheep; thirdly, the changes produced
by conditions of climate and of season, as in the sheep of warm
climates being covered with hair instead of wool, and the hares and
partridges of northern climates becoming white in winter: when,
further, we observe the changes of structure produced by habit, as
seen especially in men of different occupations; or the changes
produced by artificial mutilation and prenatal influences, as in the
crossing of species and production of monsters; fourth, when we
observe the essential unity of plan in all warm-blooded animals,--we
are led to conclude that they have been alike produced from a similar
living filament".... "From thus meditating upon the minute portion of
time in which many of the above changes have been produced, would it
be too bold to imagine, in the great length of time since the earth
began to exist, perhaps millions of years before the commencement of
the history of mankind, that all warm-blooded animals have arisen from
one living filament?"... "This idea of the gradual generation of all
things seems to have been as familiar to the ancient philosophers as
to the modern ones, and to have given rise to the beautiful
hieroglyphic figure of the πρω̃τον ὠὁν, or first great egg,
produced by night, that is, whose origin is involved in obscurity, and
animated by Ἔρωσ, that is, by Divine Love; from whence
proceeded all things which exist."

Lamarck (1744-1829) seems to have become an evolutionist
independently of Erasmus Darwin's influence, though the parallelism
between them is striking. He probably owed something to Buffon, but he
developed his theory along a different line. Whatever view be held in
regard to that theory there is no doubt that Lamarck was a
thorough-going evolutionist. Professor Haeckel speaks of the
_Philosophie Zoologique_ as "the first connected and thoroughly
logical exposition of the theory of descent."[12]

Besides the three old masters, as we may call them, Buffon, Erasmus
Darwin, and Lamarck, there were other quite convinced pre-Darwinian
evolutionists. The historian of the theory of descent must take
account of Treviranus whose _Biology or Philosophy of Animate Nature_
is full of evolutionary suggestions; of Etienne Geoffroy St. Hilaire,
who in 1830, before the French Academy of Sciences, fought with
Cuvier, the fellow-worker of his youth, an intellectual duel on the
question of descent; of Goethe, one of the founders of morphology and
the greatest poet of Evolution--who, in his eighty-first year, heard
the tidings of Geoffrey St. Hilaire's defeat with an interest which
transcended the political anxieties of the time; and of many others
who had gained with more or less confidence and clearness a new
outlook on Nature. It will be remembered that Darwin refers to
thirty-four more or less evolutionist authors in his Historical
Sketch, and the list might be added to. Especially when we come near
to 1858 do the numbers increase, and one of the most remarkable, as
also most independent champions of the evolution-idea before that date
was Herbert Spencer, who not only marshalled the arguments in a very
forcible way in 1852, but applied the formula in detail in his
_Principles of Psychology_ in 1855.[13]

It is right and proper that we should shake ourselves free from all
creationist appreciations of Darwin, and that we should recognise the
services of pre-Darwinian evolutionists who helped to make the time
ripe, yet one cannot help feeling that the citation of them is apt to
suggest two fallacies. It may suggest that Darwin simply entered into
the labours of his predecessors, whereas, as a matter of fact, he knew
very little about them till after he had been for years at work. To
write, as Samuel Butler did, "Buffon planted, Erasmus Darwin and
Lamarck watered, but it was Mr. Darwin who said 'That fruit is ripe,'
and shook it into his lap" ... seems to us a quite misleading version
of the facts of the case. The second fallacy which the historical
citation is a little apt to suggest is that the filiation of ideas is
a simple problem. On the contrary, the history of an idea, like the
pedigree of an organism, is often very intricate, and the evolution of
the evolution-idea is bound up with the whole progress of the world.
Thus in order to interpret Darwin's clear formulation of the idea of
organic evolution and his convincing presentation of it, we have to do
more than go back to his immediate predecessors, such as Buffon,
Erasmus Darwin, and Lamarck; we have to inquire into the acceptance of
evolutionary conceptions in regard to other orders of facts, such as
the earth and the solar system;[14] we have to realise how the growing
success of scientific interpretation along other lines gave confidence
to those who refused to admit that there was any domain from which
science could be excluded as a trespasser; we have to take account of
the development of philosophical thought, and even of theological and
religious movements; we should also, if we are wise enough, consider
social changes. In short, we must abandon the idea that we can
understand the history of any science as such, without reference to
contemporary evolution in other departments of activity.

While there were many evolutionists before Darwin, few of them were
expert naturalists and few were known outside a small circle; what was
of much more importance was that the genetic view of Nature was
insinuating itself in regard to other than biological orders of facts,
here a little and there a little, and that the scientific spirit had
ripened since the days when Cuvier laughed Lamarck out of court. How
was it that Darwin succeeded where others had failed? Because, in the
first place, he had clear visions--"pensées de la jeunesse, executées
par l'âge mûr"--which a University curriculum had not made impossible,
which the _Beagle voyage_ made vivid, which an unrivalled British
doggedness made real--visions of the web of life, of the fountain of
change within the organism, of the struggle for existence and its
winnowing, and of the spreading genealogical tree. Because, in the
second place, he put so much grit into the verification of his
visions, putting them to the proof in an argument which is of its
kind--direct demonstration being out of the question--quite
unequalled. Because, in the third place, he broke down the opposition
which the most scientific had felt to the seductive modal formula of
evolution by bringing forward a more plausible theory of the process
than had been previously suggested. Nor can one forget, since
questions of this magnitude are human and not merely academic, that he
wrote so that all men could understand.

_As Regards the Factors of Evolution_

It is admitted by all who are acquainted with the history of biology
that the general idea of organic evolution as expressed in the
Doctrine of Descent was quite familiar to Darwin's grandfather and to
others before and after him, as we have briefly indicated. It must
also be admitted that some of these pioneers of evolutionism did more
than apply the evolution-idea as a modal formula of becoming, they
began to inquire into the factors in the process. Thus there were
pre-Darwinian theories of evolution, and to these we must now briefly

In all biological thinking we have to work with the categories
Organism--Function--Environment, and theories of evolution may be
classified in relation to these. To some it has always seemed that the
fundamental fact is the living organism,--a creative agent, a striving
will, a changeful Proteus, selecting its environment, adjusting itself
to it, self-differentiating and self-adaptive. The necessity of
recognising the importance of the organism is admitted by all
Darwinians who start with inborn variations, but it is open to
question whether the whole truth of what we might call the Goethian
position is exhausted in the postulate of inherent variability.

To others it has always seemed that the emphasis should be laid on
Function,--on use and disuse, on doing and not doing. Practice makes
perfect; _c'est à force de forger qu'on devient forgeron_. This is one
of the fundamental ideas of Lamarckism; to some extent it met with
Darwin's approval; and it finds many supporters to-day. One of the
ablest of these--Mr. Francis Darwin--has recently given strong reasons
for combining a modernised Lamarckism with what we usually regard as
sound Darwinism.[16]

To others it has always seemed that the emphasis should be laid on the
Environment, which wakes the organism to action, prompts it to change,
makes dints upon it, moulds it, prunes it, and finally, perhaps, kills it.
It is again impossible to doubt that there is truth in this view, for even
if environmentally induced "modifications" be not transmissible,
environmentally induced "variations" are; and even if the direct influence
of the environment be less important than many enthusiastic supporters of
this view--may we call them Buffonians--think, there remains the indirect
influence which Darwinians in part rely on,--the eliminative process. Even
if the extreme view be held that the only form of discriminate elimination
that counts is inter-organismal competition, this might be included under
the rubric of the animate environment.

In many passages Buffon[17] definitely suggested that environmental
influences--especially of climate and food--were directly productive
of changes in organisms, but he did not discuss the question of the
transmissibility of the modifications so induced, and it is difficult
to gather from his inconsistent writings what extent of transformation
he really believed in. Prof. Osborn says of Buffon: "The struggle for
existence, the elimination of the least-perfected species, the contest
between the fecundity of certain species and their constant
destruction, are all clearly expressed in various passages." He quotes
two of these:[18]

"Le cours ordinaire de la nature vivante, est en général toujours
constant, toujours le même; son mouvement, toujours régulier, roule
sur deux points inébranlables: l'un, la fécondité sans bornes donnée à
toutes les espèces; l'autre, les obstacles sans nombre qui réduisent
cette fécondité à une mesure déterminée et ne laissent en tout temps
qu'à peu près la même quantité d'individus de chaque espèce" ... "Les
espèces les moins parfaites, les plus délicates, les plus pesantes,
les moins agissantes, les moins armées, etc., ont déjà disparu ou

Erasmus Darwin[19] had a firm grip of the "idea of the gradual
formation and improvement of the Animal world," and he had his theory
of the process. No sentence is more characteristic than this: "All
animals undergo transformations which are in part produced by their
own exertions, in response to pleasures and pains, and many of these
acquired forms or propensities are transmitted to their posterity."
This is Lamarckism before Lamarck, as his grandson pointed out. His
central idea is that wants stimulate efforts and that these result in
improvements which subsequent generations make better still. He
realised something of the struggle for existence and even pointed out
that this advantageously checks the rapid multiplication. "As Dr.
Krause points out, Darwin just misses the connection between this
struggle and the Survival of the Fittest."[20]

Lamarck[21] (1744-1829) seems to have thought out his theory of
evolution without any knowledge of Erasmus Darwin's which it closely
resembled. The central idea of his theory was the cumulative
inheritance of functional modifications. "Changes in environment bring
about changes in the habits of animals. Changes in their wants
necessarily bring about parallel changes in their habits. If new wants
become constant or very lasting, they form new habits, the new habits
involve the use of new parts, or a different use of old parts, which
results finally in the production of new organs and the modification
of old ones." He differed from Buffon in not attaching importance, as
far as animals are concerned, to the direct influence of the
environment, "for environment can effect no direct change whatever
upon the organisation of animals," but in regard to plants he agreed
with Buffon that external conditions directly moulded them.

Treviranus[22] (1776-1837), whom Huxley ranked beside Lamarck, was on
the whole Buffonian, attaching chief importance to the influence of a
changeful environment both in modifying and in eliminating, but he was
also Goethian, for instance in his idea that species like individuals
pass through periods of growth, full bloom, and decline. "Thus, it is
not only the great catastrophes of Nature which have caused
extinction, but the completion of cycles of existence, out of which
new cycles have begun." A characteristic sentence is quoted by Prof.
Osborn: "In every living being there exists a capability of an endless
variety of form-assumption; each possesses the power to adapt its
organisation to the changes of the outer world, and it is this power,
put into action by the change of the universe, that has raised the
simple zoophytes of the primitive world to continually higher stages
of organisation, and has introduced a countless variety of species
into animate Nature."

Goethe[23] (1749-1832), who knew Buffon's work but not Lamarck's, is
peculiarly interesting as one of the first to use the evolution-idea
as a guiding hypothesis, e.g. in the interpretation of vestigial
structures in man, and to realise that organisms express an attempt to
make a compromise between specific inertia and individual change. He
gave the finest expression that science has yet known--if it has known
it--of the kernel-idea of what is called "bathmism," the idea of an
"inherent growth-force"--and at the same time he held that "the way of
life powerfully reacts upon all form" and that the orderly growth of
form "yields to change from externally acting causes."

Besides Buffon, Erasmus Darwin, Lamarck, Treviranus, and Goethe,
there were other "pioneers of evolution," whose views have been often
discussed and appraised. Étienne Geoffroy Saint-Hilaire (1772-1884),
whose work Goethe so much admired, was on the whole Buffonian,
emphasising the direct action of the changeful _milieu_. "Species vary
with their environment, and existing species have descended by
modification from earlier and somewhat simpler species." He had a
glimpse of the selection idea, and believed in mutations or sudden
leaps--induced in the embryonic condition by external influences. The
complete history of evolution-theories will include many instances of
guesses at truth which were afterwards substantiated, thus the
geographer von Buch (1773-1853) detected the importance of the
Isolation factor on which Wagner, Romanes, Gulick and others have laid
great stress, but we must content ourselves with recalling one other
pioneer, the author of the _Vestiges of Creation_ (1844), a work which
passed through ten editions in nine years and certainly helped to
harrow the soil for Darwin's sowing. As Darwin said, "it did excellent
service in this country in calling attention to the subject, in
removing prejudice, and in thus preparing the ground for the reception
of analogous views."[24] Its author, Robert Chambers (1802-1871) was
in part a Buffonian--maintaining that environment moulded organisms
adaptively, and in part a Goethian--believing in an inherent
progressive impulse which lifted organisms from one grade of
organisation to another.

_As Regards Natural Selection_

The only thinker to whom Darwin was directly indebted, so far as the
theory of Natural Selection is concerned, was Malthus, and we may once
more quote the well-known passage in the Autobiography: "In October,
1838, that is, fifteen months after I had begun my systematic enquiry,
I happened to read for amusement 'Malthus on Population,' and being
well prepared to appreciate the struggle for existence which
everywhere goes on from long-continued observation of the habits of
animals and plants, it at once struck me that under these
circumstances favourable variations would tend to be preserved, and
unfavourable ones to be destroyed. The result of this would be the
formation of new species."[25]

Although Malthus gives no adumbration of the idea of Natural Selection
in his exposition of the eliminative processes which go on in mankind,
the suggestive value of his essay is undeniable, as is strikingly
borne out by the fact that it gave to Alfred Russel Wallace also "the
long-sought clue to the effective agent in the evolution of organic
species."[26] One day in Ternate when he was resting between fits of
fever, something brought to his recollection the work of Malthus which
he had read twelve years before. "I thought of his clear exposition of
'the positive checks to increase'--disease, accidents, war, and
famine--which keep down the population of savage races to so much
lower an average than that of more civilized peoples. It then occurred
to me that these causes or their equivalents are continually acting in
the case of animals also; and as animals usually breed much more
rapidly than does mankind, the destruction every year from these
causes must be enormous in order to keep down the numbers of each
species, since they evidently do not increase regularly from year to
year, as otherwise the world would long ago have been densely crowded
with those that breed most quickly. Vaguely thinking over the enormous
and constant destruction which this implied, it occurred to me to ask
the question, Why do some die and some live? And the answer was
clearly, that on the whole the best fitted live. From the effects of
disease the most healthy escaped; from enemies the strongest, the
swiftest, or the most cunning; from famine the best hunters or those
with the best digestion; and so on. Then it suddenly flashed upon me
that this self-acting process would necessarily _improve the race_,
because in every generation the inferior would inevitably be killed
off and the superior would remain--that is, _the fittest would
survive_."[27] We need not apologise for this long quotation, it is a
tribute to Darwin's magnanimous colleague, the Nestor of the
evolutionist camp,--and it probably indicates the line of thought
which Darwin himself followed. It is interesting also to recall the
fact that in 1852, when Herbert Spencer wrote his famous _Leader_
article on "The Development Hypothesis" in which he argued powerfully
for the thesis that the whole animate world is the result of an
age-long process of natural transformation, he wrote for _The
Westminster Review_ another important essay, "A Theory of Population
deduced from the General Law of Animal Fertility," towards the close
of which he came within an ace of recognising that the struggle for
existence was a factor in organic evolution. At a time when pressure
of population was practically interesting men's minds, Darwin,
Wallace, and Spencer were being independently led from a social
problem to a biological theory. There could be no better illustration,
as Prof. Patrick Geddes has pointed out, of the Comtian thesis that
science is a "social phenomenon."

Therefore, as far more important than any further ferreting out of
vague hints of Natural Selection in books which Darwin never read, we
would indicate by a quotation the view that the central idea in
Darwinism is correlated with contemporary social evolution. "The
substitution of Darwin for Paley as the chief interpreter of the order
of nature is currently regarded as the displacement of an
anthropomorphic view by a purely scientific one: a little reflection,
however, will show that what has actually happened has been merely the
replacement of the anthropomorphism of the eighteenth century by that
of the nineteenth. For the place vacated by Paley's theological and
metaphysical explanation has simply been occupied by that suggested to
Darwin and Wallace by Malthus in terms of the prevalent severity of
industrial competition, and those phenomena of the struggle for
existence which the light of contemporary economic theory has enabled
us to discern, have thus come to be temporarily exalted into a
complete explanation of organic progress."[28] It goes without saying
that the idea suggested by Malthus was developed by Darwin into a
biological theory which was then painstakingly verified by being used
as an interpretative formula, and that the validity of a theory so
established is not affected by what suggested it, but the practical
question which this line of thought raises in the mind is this: if
Biology did thus borrow with such splendid results from social theory,
why should we not more deliberately repeat the experiment?

Darwin was characteristically frank and generous in admitting that the
principle of Natural Selection had been independently recognised by
Dr. W. C. Wells in 1813 and by Mr. Patrick Matthew in 1831, but he had
no knowledge of these anticipations when he published the first
edition of _The Origin of Species_. Wells, whose "Essay on Dew" is
still remembered, read in 1813 before the Royal Society a short paper
entitled "An Account of a White Female, part of whose skin resembles
that of a Negro" (published in 1818). In this communication, as Darwin
said, "he observes, firstly, that all animals tend to vary in some
degree, and, secondly, that agriculturists improve their domesticated
animals by selection; and then, he adds, but what is done in this
latter case 'by art, seems to be done with equal efficacy, though more
slowly, by nature, in the formation of varieties of mankind, fitted
for the country which they inhabit.'"[29] Thus Wells had the clear
idea of survival dependent upon a favourable variation, but he makes
no more use of the idea and applies it only to man. There is not in
the paper the least hint that the author ever thought of generalising
the remarkable sentence quoted above.

Of Mr. Patrick Matthew, who buried his treasure in an appendix to a
work on _Naval Timber and Arboriculture_, Darwin said that "he clearly
saw the full force of the principle of natural selection." In 1860
Darwin wrote--very characteristically--about this to Lyell: "Mr.
Patrick Matthew publishes a long extract from his work on _Naval
Timber and Arboriculture_, published in 1831, in which he briefly but
completely anticipates the theory of Natural Selection. I have ordered
the book, as some passages are rather obscure, but it is certainly, I
think, a complete but not developed anticipation. Erasmus always said
that surely this would be shown to be the case some day. Anyhow, one
may be excused in not having discovered the fact in a work on Naval

De Quatrefages and De Varigny have maintained that the botanist Naudin
stated the theory of evolution by natural selection in 1852. He
explains very clearly the process of artificial selection, and says
that in the garden we are following Nature's method. "We do not think
that Nature has made her species in a different fashion from that in
which we proceed ourselves in order to make our variations." But, as
Darwin said, "he does not show how selection acts under nature."
Similarly it must be noted in regard to several pre-Darwinian pictures
of the struggle for existence (such as Herder's, who wrote in 1790
"All is in struggle ... each one for himself" and so on), that a
recognition of this is only the first step in Darwinism.

Profs. E. Perrier and H. F. Osborn have called attention to a
remarkable anticipation of the selection-idea which is to be found in
the speculations of Étienne Geoffroy Saint-Hilaire (1825-1828) on the
evolution of modern Crocodilians from the ancient Teleosaurs. Changing
environment induced changes in the respiratory system and far-reaching
consequences followed. The atmosphere, acting upon the pulmonary
cells, brings about "modifications which are favourable or destructive
('funestes'); these are inherited, and they influence all the rest of
the organisation of the animal because if these modifications lead to
injurious effects the animals which exhibit them perish and are
replaced by others of a somewhat different form, a form changed so as
to be adapted to (à la convenance) the new environment."

Prof. E. B. Poulton[31] has shown that the anthropologist James Cowles
Prichard (1786-1848) must be included even in spite of himself among
the precursors of Darwin. In some passages of the second edition of
his _Researches into the Physical History of Mankind_ (1826), he
certainly talks evolution and anticipates Prof. Weismann in denying
the transmission of acquired characters. He is, however, sadly
self-contradictory and his evolutionism weakens in subsequent
editions--the only ones that Darwin saw. Prof. Poulton finds in
Prichard's work a recognition of the operation of Natural Selection.
"After inquiring how it is that 'these varieties are developed and
preserved in connexion with particular climates and differences of
local situation,' he gives the following very significant answer: 'One
cause which tends to maintain this relation is obvious. Individuals
and families, and even whole colonies perish and disappear in climates
for which they are, by peculiarity of constitution, not adapted. Of
this fact proofs have been already mentioned.'" Mr. Francis Darwin and
Prof. A. C. Seward discuss Prichard's "anticipations" in _More Letters
of Charles Darwin_, Vol. _I._ p. 43, and come to the conclusion that
the evolutionary passages are entirely neutralised by others of an
opposite trend. There is the same difficulty with Buffon.

Hints of the idea of Natural Selection have been detected elsewhere.
James Watt,[32] for instance, has been reported as one of the
anticipators (1851). But we need not prolong the inquiry further,
since Darwin did not know of any anticipations until after he had
published the immortal work of 1859, and since none of those who got
hold of the idea made any use of it. What Darwin did was to follow the
clue which Malthus gave him, to realise, first by genius and
afterwards by patience, how the complex and subtle struggle for
existence works out a natural selection of those organisms which vary
in the direction of fitter adaptation to the conditions of their life.
So much success attended his application of the Selection-formula that
for a time he regarded Natural Selection as almost the sole factor in
evolution, variations being pre-supposed; gradually, however, he came
to recognise that there was some validity in the factors which had
been emphasised by Lamarck and by Buffon, and in his well known
summing up in the sixth edition of the _Origin_ he says of the
transformation of species: "This has been effected chiefly through the
natural selection of numerous successive, slight, favourable
variations; aided in an important manner by the inherited effects of
the use and disuse of parts; and in an unimportant manner, that is, in
relation to adaptive structures, whether past or present, by the
direct action of external conditions, and by variations which seem to
us in our ignorance to arise spontaneously."

To sum up: the idea of organic evolution, older than Aristotle, slowly
developed from the stage of suggestion to the stage of verification,
and the first convincing verification was Darwin's; from being an _a
priori_ anticipation it has become an interpretation of nature, and
Darwin is still the chief interpreter; from being a modal
interpretation it has advanced to the rank of a causal theory, the
most convincing part of which men will never cease to call Darwinism.


[Footnote 1: _Columbia University Biological Series_, Vol. I. New York
and London, 1894. We must acknowledge our great indebtedness to this
fine piece of work.]

[Footnote 2: _op. cit._ p. 41.]

[Footnote 3: See G. J. Romanes, "Aristotle as a Naturalist,"
_Contemporary Review_, Vol. lix. p. 275, 1891; G. Pouchet, _La
Biologie Aristotélique_, Paris, 1885; E. Zeller, _A History of Greek
Philosophy_, London, 1881, and "Ueber die griechischen Vorgänger
Darwin's," _Abhandl. Berlin Akad._ 1878, pp. 111-124.]

[Footnote 4: _op. cit._ p. 81.]

[Footnote 5: _op. cit._ p. 87.]

[Footnote 6: See Brock, "Die Stellung Kant's zur Deszendenztheorie,"
_Biol. Centralbl._ viii. 1889, pp. 641-648. Fritz Schultze, _Kant und
Darwin_, Jena, 1875.]

[Footnote 7: Mr. Alfred Russel Wallace writes: "We claim for Darwin
that he is the Newton of natural history, and that, just so surely as
that the discovery and demonstration by Newton of the law of
gravitation established order in place of chaos and laid a sure
foundation for all future study of the starry heavens, so surely has
Darwin, by his discovery of the law of natural selection and his
demonstration of the great principle of the preservation of useful
variations in the struggle for life, not only thrown a flood of light
on the process of development of the whole organic world, but also
established a firm foundation for all future study of nature"
(_Darwinism_, London, 1889, p. 9). See also Prof. Karl Pearson's
_Grammar of Science_ (2nd edit.), London, 1900, p. 32. See Osborn,
_op. cit._ p. 100.]

[Footnote 8: _Experimental Evolution_. London, 1892. Chap. I. p. 14.]

[Footnote 9: See J. Arthur Thomson, _The Science of Life_. London,
1899, Chap. XVI. "Evolution of Evolution Theory."]

[Footnote 10: See Carus Sterne (Ernst Krause), _Die allgemeine
Weltanschauung in ihrer historischen Entwickelung_. Stuttgart, 1889.
Chapter entitled "Beständigkeit oder Veränderlichkeit der

[Footnote 11: _Zoonomia, or the Laws of Organic Life_, 2 vols. London,
1794; Osborn, _op. cit._ p. 145.]

[Footnote 12: See Alpheus S. Packard, _Lamarck, the Founder of
Evolution, His Life and Work, with Translations of his writings on
Organic Evolution_. London, 1901.]

[Footnote 13: See Edward Clodd, _Pioneers of Evolution_, London, p.
161, 1897.]

[Footnote 14: See Chapter ix. "The Genetic View of Nature" in J. T.
Merz's _History of European Thought in the Nineteenth Century_, Vol.
2, Edinburgh and London, 1903.]

[Footnote 15: See Prof. W. A. Locy's _Biology and its Makers_. New
York, 1908. Part II. "The Doctrine of Organic Evolution."]

[Footnote 16: Presidential Address to the British Association meeting
at Dublin in 1908.]

[Footnote 17: See in particular Samuel Butler, _Evolution Old and
New_, London, 1879; J. L. de Lanessan, "Buffon et Darwin," _Revue
Scientifique_, XLIII. pp. 385-391, 425-432, 1889.]

[Footnote 18: _op. cit._ p. 136.]

[Footnote 19: See Ernest Krause and Charles Darwin, _Erasmus Darwin_,
London, 1879.]

[Footnote 20: Osborn, _op. cit._ p. 142.]

[Footnote 21: See E. Perrier, _La Philosophie Zoologique avant
Darwin_, Paris, 1884; A. de Quatrefages, _Darwin et ses Précurseurs
Français_, Paris, 1870; Packard, _op. cit._; also Claus, _Lamarck als
Begründer der Descendenzlehre_, Wien, 1888; Haeckel, _Natural History
of Creation_, Eng. transl. London, 1879; Lang, _Zur Charakteristik der
Forschungswege von Lamarck und Darwin_, Jena, 1889.]

[Footnote 22: See Huxley's article "Evolution in Biology,"
_Encyclopaedia Britannica_ (9th edit.), 1879, pp. 744-751, and Sully's
article, "Evolution in Philosophy," _ibid._ pp. 751-772.]

[Footnote 23: See Haeckel, _Die Naturanschauung von Darwin, Goethe und
Lamarck_, Jena, 1882.]

[Footnote 24: _Origin of Species_ (6th edit.), p. xvii.]

[Footnote 25: _The Life and Letters of Charles Darwin_, Vol. 1. p. 83.
London, 1887.]

[Footnote 26: A. R. Wallace, _My Life, a Record of Events and
Opinions_, London, 1905, Vol. 1, p. 232.]

[Footnote 27: _My Life_, Vol. 1. p. 361.]

[Footnote 28: P. Geddes. article "Biology." _Chambers's

[Footnote 29: _Origin of Species_ (6th edit.), p. xv.]

[Footnote 30: _Life and Letters_, II, p. 301.]

[Footnote 31: _Science Progress_, New Series, Vol. 1. 1897. "A
Remarkable Anticipation of Modern Views on Evolution." See also Chap.
VI. in _Essays on Evolution_, Oxford, 1908.]

[Footnote 32: See Prof. Patrick Geddes's article "Variation and
Selection," _Encyclopaedia Britannica_ (9th edit.) 1888.]




_Professor of Zoology in the University of Freiburg_ (_Baden_)


Many and diverse were the discoveries made by Charles Darwin in the
course of a long and strenuous life, but none of them has had so
far-reaching an influence on the science and thought of his time as
the theory of selection. I do not believe that the theory of evolution
would have made its way so easily and so quickly after Darwin took up
the cudgels in favour of it if he had not been able to support it by a
principle which was capable of solving, in a simple manner, the
greatest riddle that living nature presents to us,--I mean the
purposiveness of every living form relative to the conditions of its
life and its marvellously exact adaptation to these.

Everyone knows that Darwin was not alone in discovering the principle
of selection, and that the same idea occurred simultaneously and
independently to Alfred Russel Wallace. At the memorable meeting of
the Linnean Society on 1st July, 1858, two papers were read
(communicated by Lyell and Hooker) both setting forth the same idea of
selection. One was written by Charles Darwin in Kent, the other by
Alfred Wallace in Ternate, in the Malay Archipelago. It was a splendid
proof of the magnanimity of these two investigators, that they thus in
all friendliness and without envy, united in laying their ideas
before a scientific tribunal: their names will always shine side by
side as two of the brightest stars in the scientific sky.

The idea of selection set forth by the two naturalists was at the time
absolutely new, but it was also so simple that Huxley could say of it
later, "How extremely stupid not to have thought of that." As Darwin
was led to the general doctrine of descent, not through the labours of
his predecessors in the early years of the century, but by his own
observations, so it was in regard to the principle of selection. He
was struck by the innumerable cases of adaptation, as, for instance,
that of the woodpeckers and tree-frogs to climbing, or the hooks and
feather-like appendages of seeds, which aid in the distribution of
plants, and he said to himself that an explanation of adaptations was
the first thing to be sought for in attempting to formulate a theory
of evolution.

But since adaptations point to _changes_ which have been undergone by
the ancestral forms of existing species, it is necessary, first of
all, to inquire how far species in general are _variable_. Thus
Darwin's attention was directed in the first place to the phenomenon
of variability, and the use man has made of this, from very early
times, in the breeding of his domesticated animals and cultivated
plants. He inquired carefully how breeders set to work, when they
wished to modify the structure and appearance of a species to their
own ends, and it was soon clear to him that _selection for breeding
purposes_ played the chief part.

But how was it possible that such processes should occur in free
nature? Who is here the breeder, making the selection, choosing out
one individual to bring forth offspring and rejecting others? That was
the problem that for a long time remained a riddle to him.

Darwin himself relates how illumination suddenly came to him. He had
been reading, for his own pleasure, Malthus' book on Population, and,
as he had long known from numerous observations, that every species
gives rise to many more descendants than ever attain to maturity, and
that, therefore, the greater number of the descendants of a species
perish without reproducing, the idea came to him that the decision as
to which member of a species was to perish and which was to attain to
maturity and reproduction might not be a matter of chance, but might
be determined by the constitution of the individuals themselves,
according as they were more or less fitted for survival. With this
idea the foundation of the theory of selection was laid.

In _artificial selection_ the breeder chooses out for pairing only
such individuals as possess the character desired by him in a somewhat
higher degree than the rest of the race. Some of the descendants
inherit this character, often in a still higher degree, and if this
method be pursued throughout several generations, the race is
transformed in respect of that particular character.

_Natural selection_ depends on the same three factors as _artificial
selection_: on _variability_, _inheritance_, and _selection for
breeding_, but this last is here carried out not by a breeder but by
what Darwin called the "struggle for existence." This last factor is
one of the special features of the Darwinian conception of nature.
That there are carnivorous animals which take heavy toll in every
generation of the progeny of the animals on which they prey, and that
there are herbivores which decimate the plants in every generation had
long been known, but it is only since Darwin's time that sufficient
attention has been paid to the facts that, in addition to this regular
destruction, there exists between the members of a species a keen
competition for space and food, which limits multiplication, and that
numerous individuals of each species perish because of unfavourable
climatic conditions. The "struggle for existence," which Darwin
regarded as taking the place of the human breeder in free nature, is
not a direct struggle between carnivores and their prey, but is the
assumed competition for survival between individuals _of the same_
species, of which, on an average, only those survive to reproduce
which have the greatest power of resistance, while the others, less
favourably constituted, perish early. This struggle is so keen, that,
within a limited area, where the conditions of life have long remained
unchanged, of every species, whatever be the degree of fertility, only
two, _on an average_, of the descendants of each pair survive; the
others succumb either to enemies, or to disadvantages of climate, or
to accident. A high degree of fertility is thus not an indication of
the special success of a species, but of the numerous dangers that
have attended its evolution. Of the six young brought forth by a pair
of elephants in the course of their lives only two survive in a given
area; similarly, of the millions of eggs which two thread-worms leave
behind them only two survive. It is thus possible to estimate the
dangers which threaten a species by its ratio of elimination, or,
since this cannot be done directly, by its fertility.

Although a great number of the descendants of each generation fall
victims to accident, among those that remain it is still the greater
or less fitness of the organism that determines the "selection for
breeding purposes," and it would be incomprehensible if, in this
competition, it were not ultimately, that is, on an average, the best
equipped which survive, in the sense of living long enough to

Thus the principle of natural selection is _the selection of the best
for reproduction_, whether the "best" refers to the whole
constitution, to one or more parts of the organism, or to one or more
stages of development. Every organ, every part, every character of an
animal, fertility and intelligence included, must be improved in this
manner, and be gradually brought up in the course of generations to
its highest attainable state of perfection. And not only may
improvement of parts be brought about in this way, but new parts and
organs may arise, since, through the slow and minute steps of
individual or "fluctuating" variations, a part may be added here or
dropped out there, and thus something new is produced.

The principle of selection solved the riddle as to how what was
purposive could conceivably be brought about without the intervention
of a directing power, the riddle which animate nature presents to our
intelligence at every turn, and in face of which the mind of a Kant
could find no way out, for he regarded a solution of it as not to be
hoped for. For, even if we were to assume an evolutionary force that
is continually transforming the most primitive and the simplest forms
of life into ever higher forms, and the homogeneity of primitive times
into the infinite variety of the present, we should still be unable to
infer from this alone how each of the numberless forms adapted to
particular conditions of life should have appeared _precisely at the
right moment in the history of the earth_ to which their adaptations
were appropriate, and precisely at the proper place in which all the
conditions of life to which they were adapted occurred: the
humming-birds at the same time as the flowers; the trichina at the
same time as the pig; the bark-coloured moth at the same time as the
oak, and the wasp-like moth at the same time as the wasp which
protects it. Without processes of selection we should be obliged to
assume a "pre-established harmony" after the famous Leibnitzian model,
by means of which the clock of the evolution of organisms is so
regulated as to strike in exact synchronism with that of the history
of the earth! All forms of life are strictly adapted to the conditions
of their life, and can persist under these conditions alone.

There must therefore be an intrinsic connection between the conditions
and the structural adaptations of the organism, and, _since the
conditions of life cannot be determined by the animal itself, the
adaptations must be called forth by the conditions_.

The selection theory teaches us how this is conceivable, since it
enables us to understand that there is a continual production of what
is non-purposive as well as of what is purposive, but the purposive
alone survives, while the non-purposive perishes in the very act of
arising. This is the old wisdom taught long ago by Empedocles.


Lamarck, as is well known, formulated a definite theory of evolution
at the beginning of the nineteenth century, exactly fifty years before
the Darwin-Wallace principle of selection was given to the world. This
brilliant investigator also endeavoured to support his theory by
demonstrating forces which might have brought about the
transformations of the organic world in the course of the ages. In
addition to other factors, he laid special emphasis on the increased
or diminished use of the parts of the body, assuming that the
strengthening or weakening which takes place from this cause during
the individual life, could be handed on to the offspring, and thus
intensified and raised to the rank of a specific character. Darwin
also regarded this _Lamarckian principle_, as it is now generally
called, as a factor in evolution, but he was not fully convinced of
the transmissibility of acquired characters.

As I have here to deal only with the theory of selection, I need not
discuss the Lamarckian hypothesis, but I must express my opinion that
there is room for much doubt as to the coöperation of this principle
in evolution. Not only is it difficult to imagine how the transmission
of functional modifications could take place, but, up to the present
time, notwithstanding the endeavours of many excellent investigators,
not a single actual proof of such inheritance has been brought
forward. Semon's experiments on plants are, according to the botanist
Pfeffer, not to be relied on, and even the recent, beautiful
experiments made by Dr. Kammerer on salamanders, cannot, as I hope to
show elsewhere, be regarded as proof, if only because they do not deal
at all with functional modifications, that is, with modifications
brought about by use, and it is to these _alone_ that the Lamarckian
principle refers.


(_a_) _Saltatory evolution_

The Darwinian doctrine of evolution depends essentially on _the
cumulative augmentation_ of minute variations in the direction of
utility. But can such minute variations, which are undoubtedly
continually appearing among the individuals of the same species,
possess any selection-value; can they determine which individuals are
to survive, and which are to succumb; can they be increased by natural
selection till they attain to the highest development of a purposive

To many this seems so improbable that they have urged a theory of
evolution by leaps from species to species. Kölliker, in 1872,
compared the evolution of species with the processes which we can
observe in the individual life in cases of alternation of generations.
But a polyp only gives rise to a medusa because it has itself arisen
from one, and there can be no question of a medusa ever having arisen
suddenly and _de novo_ from a polyp-bud, if only because both forms
are adapted in their structure as a whole, and in every detail to the
conditions of their life. A sudden origin, in a natural way, of
numerous adaptations is inconceivable. Even the degeneration of a
medusoid from a free-swimming animal to a mere brood-sac (gonophore)
is not sudden and saltatory, but occurs by imperceptible modifications
throughout hundreds of years, as we can learn from the numerous stages
of the process of degeneration persisting at the same time in
different species.

If, then, the degeneration to a simple brood-sac takes place only by
very slow transitions, each stage of which may last for centuries, how
could the much more complex _ascending_ evolution possibly have taken
place by sudden leaps? I regard this argument as capable of further
extension, for wherever in nature we come upon degeneration, it is
taking place by minute steps and with a slowness that makes it not
directly perceptible, and I believe that this in itself justifies us
in concluding that _the same must be true of ascending_ evolution. But
in the latter case the goal can seldom be distinctly recognised while
in cases of degeneration the starting-point of the process can often
be inferred, because several nearly related species may represent
different stages.

In recent years Bateson in particular has championed the idea of
saltatory, or so-called discontinuous evolution, and has collected a
number of cases in which more or less marked variations have suddenly
appeared. These are taken for the most part from among domesticated
animals which have been bred and crossed for a long time, and it is
hardly to be wondered at that their much mixed and much influenced
germ-plasm should, under certain conditions, give rise to remarkable
phenomena, often indeed producing forms which are strongly suggestive
of monstrosities, and which would undoubtedly not survive in free
nature, unprotected by man. I should regard such cases as due to an
intensified germinal selection--though this is to anticipate a
little--and from this point of view it cannot be denied that they have
a special interest. But they seem to me to have no significance as far
as the transformation of species is concerned, if only because of the
extreme rarity of their occurrence.

There are, however, many variations which have appeared in a sudden
and saltatory manner, and some of these Darwin pointed out and
discussed in detail: the copper beech, the weeping trees, the oak with
"fern-like leaves," certain garden-flowers, etc. But none of them have
persisted in free nature, or evolved into permanent types.

On the other hand, wherever enduring types have arisen, we find traces
of a gradual origin by successive stages, even if, at first sight,
their origin may appear to have been sudden. This is the case with
_seasonal Dimorphism_, the first known cases of which exhibited marked
differences between the two generations, the winter and the summer
brood. Take for instance the much discussed and studied form
_Vanessa_ (_Araschnia_) _levana-prorsa_. Here the differences between
the two forms are so great and so apparently disconnected, that one
might almost believe it to be a sudden mutation, were it not that old
transition-stages can be called forth by particular temperatures, and
we know other butterflies, as for instance our Garden Whites, in which
the differences between the two generations are not nearly so marked;
indeed, they are so little apparent that they are scarcely likely to
be noticed except by experts. Thus here again there are small initial
steps, some of which, indeed, must be regarded as adaptations, such as
the green-sprinkled or lightly tinted under-surface which gives them a
deceptive resemblance to parsley or to Cardamine leaves.

Even if saltatory variations do occur, we cannot assume that these
_have ever led to forms which are capable of survival under the
conditions of wild life_. Experience has shown that in plants which
have suddenly varied the power of persistence is diminished.
Korschinsky attributes to them weaknesses of organisation in general;
"they bloom late, ripen few of their seeds, and show great
sensitiveness to cold." These are not the characters which make for
success in the struggle for existence.

We must briefly refer here to the views--much discussed in the last
decade--of H. de Vries, who believes that the roots of transformation
must be sought for in _saltatory variations arising from internal
causes_, and distinguishes such _mutations_, as he has called them,
from ordinary individual variations, in that they breed true, that is,
with strict in-breeding they are handed on pure to the next
generation. I have elsewhere endeavoured to point out the weaknesses
of this theory,[33] and I am the less inclined to return to it here
that it now appears[34] that the far-reaching conclusions drawn by de
Vries from his observations on the Evening Primrose, _Oenothera
lamarckiana_, rest upon a very insecure foundation. The plant from
which de Vries saw numerous "species"--his "mutations"--arise was not,
as he assumed, a _wild species_ that had been introduced to Europe
from America, but was probably a hybrid form which was first
discovered in the Jardin des Plantes in Paris, and which does not
appear to exist anywhere in America as a wild species.

This gives a severe shock to the "Mutation theory," for the other
_actually wild_ species with which de Vries experimented showed no
"mutations" but yielded only negative results.

Thus we come to the conclusion that Darwin[35] was right in regarding
transformations as taking place by minute steps, which, if useful, are
augmented in the course of innumerable generations, because their
possessors more frequently survive in the struggle for existence.

(_b_) _Selection-value of the initial steps_

Is it possible that the insignificant deviations which we know as
"individual variations" can form the beginning of a process of
selection? Can they decide which is to perish and which to survive? To
use a phrase of Romanes, can they have _selection-value_?

Darwin himself answered this question, and brought together many
excellent examples to show that differences, apparently insignificant
because very small, might be of decisive importance for the life of
the possessor. But it is by no means enough to bring forward cases of
this kind, for the question is not merely whether finished adaptations
have selection-value, but whether the first beginnings of these, and
whether the small, I might almost say minimal increments, which have
led up from these beginnings to the perfect adaptation, have also had
selection-value. To this question even one who, like myself, has been
for many years a convinced adherent of the theory of selection, can
only reply: _We must assume so, but we cannot prove it in any case_.
It is not upon demonstrative evidence that we rely when we champion
the doctrine of selection as a scientific truth; we base our argument
on quite other grounds. Undoubtedly there are many apparently
insignificant features, which can nevertheless be shown to be
adaptations--for instance, the thickness of the basin-shaped shell of
the limpets that live among the breakers on the shore. There can be no
doubt that the thickness of these shells, combined with their flat
forms, protects the animals from the force of the waves breaking upon
them,--but how have they become so thick? What proportion of thickness
was sufficient to decide that of two variants of a limpet one should
survive, the other be eliminated? We can say nothing more than that we
infer from the present state of the shell, that it must have varied in
regard to differences in shell-thickness, and that these differences
must have had selection-value,--no proof therefore, but an assumption
which we must show to be convincing.

For a long time the marvellously complex _radiate_ and _lattice-work_
skeletons of Radiolarians were regarded as a mere outflow of "Nature's
infinite wealth of form," as an instance of a purely morphological
character with no biological significance. But recent investigations
have shown that these, too, have an adaptive significance (Häcker).
The same thing has been shown by Schütt in regard to the lowly
unicellular plants, the Peridineae, which abound alike on the surface
of the ocean and in its depths. It has been shown that the long
skeletal processes which grow out from these organisms have
significance not merely as a supporting skeleton, but also as an
extension of the superficial area, which increases the contact with
the water-particles, and prevents the floating organisms from sinking.
It has been established that the processes are considerably shorter in
the colder layers of the ocean, and that they may be twelve times as
long[36] in the warmer layers, thus corresponding to the greater or
smaller amount of friction which takes place in the denser and less
dense layers of the water.

The Peridineae of the warmer ocean layers have thus become long-rayed,
those of the colder layers short-rayed, not through the direct effect
of friction on the protoplasm, but through processes of selection,
which favoured the longer rays in warm water, since they kept the
organism afloat, while those with short rays sank and were eliminated.
If we put the question as to selection-value in this case, and ask how
great the variations in the length of processes must be in order to
possess selection-value; what can we answer except that these
variations must have been minimal, and yet sufficient to prevent too
rapid sinking and consequent elimination? Yet this very case would
give the ideal opportunity for a mathematical calculation of the
minimal selection-value, although of course it is not feasible from
lack of data to carry out the actual calculation.

But even in organisms of more than microscopic size there must
frequently be minute, even microscopic differences which set going the
process of selection, and regulate its progress to the highest
possible perfection.

Many tropical trees possess thick, leathery leaves, as a protection
against the force of the tropical raindrops. The _direct_ influence of
the rain cannot be the cause of this power of resistance, for the
leaves, while they were still thin, would simply have been torn to
pieces. Their toughness must therefore be referred to selection, which
would favour the trees with slightly thicker leaves, though we cannot
calculate with any exactness how great the first stages of increase in
thickness must have been. Our hypothesis receives further support from
the fact that, in many such trees, the leaves are drawn out into a
beak-like prolongation (Stahl and Haberlandt) which facilitates the
rapid falling off of the rain water, and also from the fact that the
leaves, while they are still young, hang limply down in bunches which
offer the least possible resistance to the rain. Thus there are here
three adaptations which can only be interpreted as due to selection.
The initial stages of these adaptations must undoubtedly have had

But even in regard to this case we are reasoning in a circle, not
giving "proofs," and no one who does not wish to believe in the
selection-value of the initial stages can be forced to do so. Among
the many pieces of presumptive evidence a particularly weighty one
seems to me to be _the smallness of the steps of progress_ which we
can observe in certain cases, as for instance in leaf-imitation among
butterflies, and in mimicry generally. The resemblance to a leaf, for
instance of a particular Kallima, seems to us so close as to be
deceptive, and yet we find in another individual, or it may be in many
others, a spot added which increases the resemblance, and which could
not have become fixed unless the increased deceptiveness so produced
had frequently led to the overlooking of its much persecuted
possessor. But if we take the selection-value of the initial stages
for granted, we are confronted with the further question which I
myself formulated many years ago: How does it happen _that the
necessary beginnings of a useful variation are always present_? How
could insects which live upon or among green leaves become all green,
while those that live on bark become brown? How have the desert
animals become yellow and the Arctic animals white? Why were the
necessary variations always present? How could the green locust lay
brown eggs, or the privet caterpillar develop white and lilac-coloured
lines on its green skin?

It is of no use answering to this that the question is wrongly
formulated[37] and that it is the converse that is true; that the
process of selection takes place in accordance with the variations
that present themselves. This proposition is undeniably true, but so
also is another, which apparently negatives it: the variation required
has in the majority of cases actually presented itself. Selection
cannot solve this contradiction; it does not call forth the useful
variation, but simply works upon it. The ultimate reason why one and
the same insect should occur in green and in brown, as often happens
in caterpillars and locusts, lies in the fact that variations towards
brown presented themselves, and so also did variations towards green:
_the kernel of the riddle lies in the varying_, and for the present we
can only say, that small variations in different directions present
themselves in every species. Otherwise so many different kinds of
variations could not have arisen. I have endeavoured to explain this
remarkable fact by means of the intimate processes that must take
place within the germ-plasm, and I shall return to the problem when
dealing with "germinal selection."

We have, however, to make still greater demands on variation, for it
is not enough that the necessary variation should occur in isolated
individuals, because in that case there would be small prospect of its
being preserved, notwithstanding its utility. Darwin at first
believed, that even single variations might lead to transformation of
the species, but later he became convinced that this was impossible,
at least without the coöperation of other factors, such as isolation
and sexual selection.

In the case of the _green caterpillars with bright longitudinal
stripes_, numerous individuals exhibiting this useful variation must
have been produced to start with. In all higher, that is,
multicellular organisms, the germ-substance is the source of all
transmissible variations, and this germ-plasm is not a simple
substance but is made up of many primary constituents. The question
can therefore be more precisely stated thus: How does it come about
that in so many cases the useful variations present themselves in
numbers just where they are required, the white oblique lines in the
leaf-caterpillar on the under surface of the body, the accompanying
coloured stripes just above them? And, further, how has it come about
that in grass caterpillars, not oblique but longitudinal stripes,
which are more effective for concealment among grass and plants, have
been evolved? And finally, how is it that the same Hawk-moth
caterpillars, which to-day show oblique stripes, possessed
longitudinal stripes in Tertiary times? We can read this fact from the
history of their development, and I have before attempted to show the
biological significance of this change of colour.[38]

For the present I need only draw the conclusion that one and the same
caterpillar may exhibit the initial stages of both, and that it
depends on the manner in which these marking elements are
_intensified_ and _combined_ by natural selection whether whitish
longitudinal or oblique stripes should result. In this case then the
"useful variations" were actually "always there," and we see that in
the same group of Lepidoptera, e.g. species of Sphingidae, evolution
has occurred in both directions according to whether the form lived
among grass or on broad leaves with oblique lateral veins, and we can
observe even now that the species with oblique stripes have
longitudinal stripes when young, that is to say, while the stripes
have no biological significance. The white places in the skin which
gave rise, probably first as small spots, to this protective marking
could be combined in one way or another according to the requirements
of the species. They must therefore either have possessed
selection-value from the first, or, if this was not the case at their
earliest occurrence, there must have been _some other factors_ which
raised them to the point of selection-value. I shall return to this in
discussing germinal selection. But the case may be followed still
farther, and leads us to the same alternative on a still more secure

Many years ago I observed in caterpillars of _Smerinthus populi_ (the
poplar hawk-moth), which also possess white oblique stripes, that
certain individuals showed _red spots_ above these stripes; these
spots occurred only on certain segments, and never flowed together to
form continuous stripes. In another species (_Smerinthus tiliae_)
similar blood-red spots unite to form a line-like coloured seam in the
last stage of larval life, while in _S. ocellata_ rust-red spots
appear in individual caterpillars, but more rarely than in _S.
populi_, and they show no tendency to flow together.

Thus we have here the origin of a new character, arising from small
beginnings, at least in _S. tiliae_, in which species the coloured
stripes are a normal specific character. In the other species, _S.
populi_ and _S. ocellata_, we find the beginnings of the same
variation, in one more rarely than in the other, and we can imagine
that, in the course of time, in these two species, coloured lines over
the oblique stripes will arise. In any case these spots are the
elements of variation, out of which coloured lines _may_ be evolved,
if they are combined in this direction through the agency of natural
selection. In _S. populi_ the spots are often small, but sometimes it
seems as though several had united to form large spots. Whether a
process of selection in this direction will arise in _S. populi_ and
_S. ocellata_, or whether it is now going on cannot be determined,
since we cannot tell in advance what biological value the marking
might have for these two species. It is conceivable that the spots may
have no selection-value as far as these species are concerned, and may
therefore disappear again in the course of phylogeny, or, on the other
hand, that they may be changed in another direction, for instance
towards imitation of the rust-red fungoid patches on poplar and willow
leaves. In any case we may regard the smallest spots as the initial
stages of variation, the larger as a cumulative summation of these.
Therefore either these initial stages must already possess
selection-value, or, as I said before: _There must be some other
reason for their cumulative summation_. I should like to give one more
example, in which we can infer, though we cannot directly observe, the
initial stages.

All the Holothurians or sea-cucumbers have in the skin calcereous
bodies of different forms, usually thick and irregular, which make the
skin tough and resistant. In a small group of them--the species of
Synapta--the calcareous bodies occur in the form of delicate anchors
of microscopic size. Up till 1897 these anchors, like many other
delicate microscopic structures, were regarded as curiosities, as
natural marvels. But a Swedish observer, Oestergren, has recently
shown that they have a biological significance: they serve the
footless Synapta as auxiliary organs of locomotion, since, when the
body swells up in the act of creeping, they press firmly with their
tips, which are embedded in the skin, against the substratum on which
the animal creeps, and thus prevent slipping backwards. In other
Holothurians this slipping is made impossible by the fixing of the
tube-feet. The anchors act automatically, sinking their tips towards
the ground when the corresponding part of the body thickens, and
returning to the original position at an angle of 45 degrees to the
upper surface when the part becomes thin again. The arms of the anchor
do not lie in the same plane as the shaft, and thus the curve of the
arms forms the outermost part of the anchor, and offers no further
resistance to the gliding of the animal. Every detail of the anchor,
the curved portion, the little teeth at the head, the arms, etc., can
be interpreted in the most beautiful way, above all the form of the
anchor itself, for the two arms prevent it from swaying round to the
side. The position of the anchors, too, is definite and significant;
they lie obliquely to the longitudinal axis of the animal, and
therefore they act alike whether the animal is creeping backwards or
forwards. Moreover, the tips would pierce through the skin if the
anchors lay in the longitudinal direction. Synapta burrows in the
sand; it first pushes in the thin anterior end, and thickens this
again, thus enlarging the hole, then the anterior tentacles displace
more sand, the body is worked in a little farther, and the process
begins anew. In the first act the anchors are passive, but they begin
to take an active share in the forward movement when the body is
contracted again. Frequently the animal retains only the posterior end
buried in the sand, and then the anchors keep it in position, and make
rapid withdrawal possible.

Thus we have in these apparently random forms of the calcereous
bodies, complex adaptations in which every little detail as to
direction, curve, and pointing is exactly determined. That they have
selection-value in their present perfected form is beyond all doubt,
since the animals are enabled by means of them to bore rapidly into
the ground and so to escape from enemies. We do not know what the
initial stages were, but we cannot doubt that the little improvements,
which occurred as variations of the originally simple slimy bodies of
the Holothurians, were preserved because they already possessed
selection-value for the Synaptidae. For such minute microscopic
structures whose form is so delicately adapted to the rôle they have
to play in the life of the animal, cannot have arisen suddenly and as
a whole, and every new variation of the anchor, that is, in the
direction of the development of the two arms, and every curving of the
shaft which prevented the tips from projecting at the wrong time, in
short, every little adaptation in the modelling of the anchor must
have possessed selection-value. And that such minute changes of form
fall within the sphere of fluctuating variations, that is to say,
_that they occur_ is beyond all doubt.

In many of the Synaptidae the anchors are replaced by calcareous rods
bent in the form of an S, which are said to act in the same way.
Others, such as those of the genus Ankyroderma, have anchors which
project considerably beyond the skin, and, according to Oestergren,
serve "to catch plant-particles and other substances" and so mask the
animal. Thus we see that in the Synaptidae the thick and irregular
calcareous bodies of the Holothurians have been modified and
transformed in various ways in adaptation to the footlessness of these
animals, and to the peculiar conditions of their life, and we must
conclude that the earlier stages of these changes presented themselves
to the processes of selection in the form of microscopic variations.
For it is as impossible to think of any origin other than through
selection in this case as in the case of the toughness, and the
"drip-tips" of tropical leaves. And as these last could not have been
produced directly by the beating of the heavy raindrops upon them, so
the calcareous anchors of Synapta cannot have been produced directly
by the friction of the sand and mud at the bottom of the sea, and,
since they are parts whose function is _passive_ the Lamarckian factor
of use and disuse does not come into question. The conclusion is
unavoidable, that the microscopically small variations of the
calcareous bodies in the ancestral forms have been intensified and
accumulated in a particular direction, till they have led to the
formation of the anchor. Whether this has taken place by the action of
natural selection alone, or whether the laws of variation and the
intimate processes within the germ-plasm have coöperated will become
clear in the discussion of germinal selection. This whole process of
adaptation has obviously taken place within the time that has elapsed
since this group of sea-cucumbers lost their tube-feet, those
characteristic organs of locomotion which occur in no group except the
Echinoderms, and yet have totally disappeared in the Synaptidae. And
after all what would animals that live in sand and mud do with

(_c_) _Coadaptation_

Darwin pointed out that one of the essential differences between
artificial and natural selection lies in the fact that the former can
modify only a few characters, usually only one at a time, while Nature
preserves in the struggle for existence all the variations of a
species, at the same time and in a purely mechanical way, if they
possess selection-value.

Herbert Spencer, though himself an adherent of the theory of selection,
declared in the beginning of the nineties that in his opinion the range of
this principle was greatly over-estimated, if the great changes which have
taken place in so many organisms in the course of ages are to be
interpreted as due to this process of selection alone, since no
transformation of any importance can be evolved by itself; it is always
accompanied by a host of secondary changes. He gives the familiar example
of the Giant Stag of the Irish peat, the enormous antlers of which required
not only a much stronger skull cap, but also greater strength of the
sinews, muscles, nerves and bones of the whole anterior half of the animal,
if their mass was not to weigh down the animal altogether. It is
inconceivable, he says, that so many processes of selection should take
place _simultaneously_, and we are therefore forced to fall back on the
Lamarckian factor of the use and disuse of functional parts. And how, he
asks, could natural selection follow two opposite directions of evolution
in different parts of the body at the same time, as for instance in the
case of the kangaroo, in which the forelegs must have become shorter, while
the hind legs and the tail were becoming longer and stronger?

Spencer's main object was to substantiate the validity of the
Lamarckian principle, the coöperation of which with selection had been
doubted by many. And it does seem as though this principle, if it
operates in nature at all, offers a ready and simple explanation of
all such secondary variations. Not only muscles, but nerves, bones,
sinews, in short all tissues which function actively, increase in
strength in proportion as they are used, and conversely they decrease
when the claims on them diminish. All the parts, therefore, which
depend on the part that varied first, as for instance the enlarged
antlers of the Irish Elk, must have been increased or decreased in
strength, in exact proportion to the claims made upon them,--just as
is actually the case.

But beautiful as this explanation would be, I regard it as untenable,
because it assumes the _transmissibility of functional modifications_
(so-called "acquired" characters), and this is not only
undemonstrable, but is scarcely theoretically conceivable, for the
secondary variations which accompany or follow the first as
correlative variations, occur also in cases in which the animals
concerned are sterile and _therefore cannot transmit anything to their
descendants_. This is true of _worker bees_, and particularly of
_ants_, and I shall here give a brief survey of the present state of
the problem as it appears to me.

Much has been written on both sides of this question since the
published controversy on the subject in the nineties between Herbert
Spencer and myself. I should like to return to the matter in detail,
if the space at my disposal permitted, because it seems to me that the
arguments I advanced at that time are equally cogent to-day,
notwithstanding all the objections that have since been urged against
them. Moreover, the matter is by no means one of subordinate interest;
it is the very kernel of the whole question of the reality and value
of the principle of selection. For if selection alone does not suffice
to explain "_harmonious adaptation_" as I have called Spencer's
_Coadaptation_, and if we require to call in the aid of the Lamarckian
factor it would be questionable whether selection would explain any
adaptations whatever. In this particular case--of worker bees--the
Lamarckian factor may be excluded altogether, for it can be
demonstrated that here at any rate the effects of use and disuse
cannot be transmitted.

But if it be asked why we are unwilling to admit the coöperation of
the Darwinian factor of selection and the Lamarckian factor, since
this would afford us an easy and satisfactory explanation of the
phenomena, I answer: _Because the Lamarckian principle is fallacious,
and because by accepting it we close the way towards deeper insight_.
It is not a spirit of combativeness or a desire for self-vindication
that induces me to take the field once more against the Lamarckian
principle, it is the conviction that the progress of our knowledge is
being obstructed by the acceptance of this fallacious principle, since
the facile explanation it apparently affords prevents our seeking
after a truer explanation and a deeper analysis.

The workers in the various species of ants are sterile, that is to
say, they take no regular part in the reproduction of the species,
although individuals among them may occasionally lay eggs. In addition
to this they have lost the wings, and the _receptaculum seminis_, and
their compound eyes have degenerated to a few facets. How could this
last change have come about through disuse, since the eyes of workers
are exposed to light in the same way as are those of the sexual
insects and thus in this particular case are not liable to "disuse" at
all? The same is true of the _receptaculum seminis_, which can only
have been disused as far as its glandular portion and its stalk are
concerned, and also of the wings, the nerves tracheae and epidermal
cells of which could not cease to function until the whole wing had
degenerated, for the chitinous skeleton of the wing does not function
at all in the active sense.

But, on the other hand, the workers in all species have undergone
modifications in a positive direction, as, for instance, the greater
development of brain. In many species large workers have evolved,--the
so-called _soldiers_, with enormous jaws and teeth, which defend the
colony,--and in others there are _small_ workers which have taken over
other special functions, such as the rearing of the young Aphides.
This kind of division of the workers into two castes occurs among
several tropical species of ants, but it is also present in the
Italian species, _Colobopsis truncata_. Beautifully as the size of the
jaws could be explained as due to the increased use made of them by
the "soldiers," or the enlarged brain as due to the mental activities
of the workers, the fact of the infertility of these forms is an
insurmountable obstacle to accepting such an explanation. Neither jaws
nor brain can have been evolved on the Lamarckian principle.

The problem of coadaptation is no easier in the case of the ant than
in the case of the Giant Stag. Darwin himself gave a pretty
illustration to show how imposing the difference between the two kinds
of workers in one species would seem if we translated it into human
terms. In regard to the Driver ants (Anomma) we must picture to
ourselves a piece of work, "for instance the building of a house,
being carried on by two kinds of workers, of which one group was five
feet four inches high, the other sixteen feet high."[39]

Although the ant is a small animal as compared with man or with the
Irish Elk, the "soldier" with its relatively enormous jaws is hardly
less heavily burdened than the Elk with its antlers, and in the ant's
case, too, a strengthening of the skeleton, of the muscles, the nerves
of the head, and of the legs must have taken place parallel with the
enlargement of the jaws. _Harmonious adaptation_ (coadaptation) has
here been active in a high degree, and yet these "soldiers" are
sterile! There thus remains nothing for it but to refer all their
adaptations, positive and negative alike, to processes of selection
which have taken place in the rudiments of the workers within the egg
and sperm-cells of their parents. There is no way out of the
difficulty except the one Darwin pointed out. He himself did not find
the solution of the riddle at once. At first he believed that the case
of the workers among social insects presented "the most serious
special difficulty" in the way of his theory of natural selection; and
it was only after it had become clear to him that it was not the
sterile insects themselves but their parents that were selected,
according as they produced more or less well adapted workers, that he
was able to refer to this very case of the conditions among ants "_in
order to show the power of natural selection_."[40] He explains his
view by a simple but interesting illustration. Gardeners have
produced, by means of long continued artificial selection, a variety
of Stock, which bears entirely double, and therefore infertile
flowers.[41] Nevertheless the variety continues to be reproduced from
seed, because, in addition to the double and infertile flowers, the
seeds always produce a certain number of single, fertile blossoms, and
these are used to reproduce the double variety. These single and
fertile plants correspond "to the males and females of an ant-colony,
the infertile plants, which are regularly produced in large numbers,
to the neuter workers of the colony."

This illustration is entirely apt, the only difference between the
two cases consisting in the fact that the variation in the flower is
not a useful, but a disadvantageous one, which can only be preserved
by artificial selection on the part of the gardener, while the
transformations that have taken place parallel with the sterility of
the ants are useful, since they procure for the colony an advantage in
the struggle for existence, and they are therefore preserved by
natural selection. Even the sterility itself in this case is not
disadvantageous, since the fertility of the true females has at the
same time considerably increased. We may therefore regard the sterile
forms of ants, which have gradually been adapted in several directions
to varying functions, _as a certain proof_ that selection really takes
place in the germ-cells of the fathers and mothers of the workers, and
that _special complexes of primordia_ (_ids_) are present in the
workers and in the males and females, and these complexes contain the
primordia of the individual parts (_determinants_). But since all
living entities vary, the determinants must also vary, now in a
favourable, now in an unfavourable direction. If a female produces
eggs, which contain favourably varying determinants in the worker-ids,
then these eggs will give rise to workers modified in the favourable
direction, and if this happens with many females, the colony concerned
will contain a better kind of worker than other colonies.

I digress here in order to give an account of the intimate processes,
which, according to my view, take place within the germ-plasm, and
which I have called "_germinal selection_." These processes are of
importance since they form the roots of variation, which in its turn
is the root of natural selection. I cannot here do more than give a
brief outline of the theory in order to show how the Darwin-Wallace
theory of selection has gained support from it.

With others, I regard the minimal amount of substance which is
contained within the nucleus of the germ-cells, in the form of rods,
bands, or granules, as the _germ-substance_ or _germ-plasm_, and I
call the individual granules _ids_. There is always a multiplicity of
such ids present in the nucleus, either occurring individually, or
united in the form of rods or bands (chromosomes). Each id contains
the primary constituents of a _whole_ individual, so that several ids
are concerned in the development of a new individual.

In every being of complex structure thousands of primary constituents
must go to make up a single id; these I call _determinants_, and I
mean by this name very small individual particles, far below the
limits of microscopic visibility, vital units which feed, grow, and
multiply by division. These determinants control the parts of the
developing embryo,--in what manner need not here concern us. The
determinants differ among themselves, those of a muscle are
differently constituted from those of a nerve-cell or a glandular
cell, etc., and every determinant is in its turn made up of minute
vital units, which I call _biophores_, or the bearers of life.
According to my view, these determinants not only assimilate, like
every other living unit, but they _vary_ in the course of their
growth, as every living unit does; they may vary qualitatively if the
elements of which they are composed vary, they may grow and divide
more or less rapidly, and their variations give rise to
_corresponding_ variations of the organ, cell, or cell-group which
they determine. That they are undergoing ceaseless fluctuations in
regard to size and quality seems to me the inevitable consequence of
their unequal nutrition; for although the germ-cell as a whole usually
receives sufficient nutriment, minute fluctuations in the amount
carried to different parts within the germ-plasm cannot fail to occur.

Now, if a determinant, for instance of a sensory cell, receives for a
considerable time more abundant nutriment than before, it will grow
more rapidly--become bigger, and divide more quickly, and, later, when
the id concerned develops into an embryo, this sensory cell will
become stronger than in the parents, possibly even twice as strong.
This is an instance of a _hereditary individual variation_, arising
from the germ.

The nutritive stream which, according to our hypothesis, favours the
determinant _N_ by chance, that is, for reasons unknown to us, may
remain strong for a considerable time, or may decrease again; but even
in the latter case it is conceivable that the ascending movement of
the determinant may continue, because the strengthened determinant now
_actively_ nourishes itself more abundantly,--that is to say, it
attracts the nutriment to itself, and to a certain extent withdraws it
from its fellow-determinants. In this way, it may--as it seems to
me--get into _permanent upward movement, and attain a degree of
strength from which there is no falling back_. Then positive or
negative selection sets in, favouring the variations which are
advantageous, setting aside those which are disadvantageous.

In a similar manner a _downward_ variation of the determinants may
take place, if its progress be started by a diminished flow of
nutriment. The determinants which are weakened by this diminished flow
will have less affinity for attracting nutriment because of their
diminished strength, and they will assimilate more feebly and grow
more slowly, unless chance streams of nutriment help them to recover
themselves. But, as will presently be shown, a change of direction
cannot take place at _every_ stage of the degenerative process. If a
certain critical stage of downward progress be passed, even favourable
conditions of food-supply will no longer suffice permanently to change
the direction of the variation. Only two cases are conceivable; if the
determinant corresponds to a _useful_ organ, only its removal can
bring back the germ-plasm to its former level; therefore personal
selection removes the id in question, with its determinants, from the
germ-plasm, by causing the elimination of the individual in the
struggle for existence. But there is another conceivable case; the
determinants concerned may be those of an organ which has become
_useless_, and they will then continue unobstructed, but with
exceeding slowness, along the downward path, until the organ becomes
vestigial, and finally disappears altogether.

The fluctuations of the determinants hither and thither may thus be
transformed into a lasting ascending or descending movement; and _this
is the crucial point of these germinal processes_.

This is not a fantastic assumption; we can read it in the fact of the
degeneration of disused parts. _Useless organs are the only ones which
are not helped to ascend again by personal selection, and therefore in
their case alone can we form any idea of how the primary constituents
behave, when they are subject solely to intra-germinal forces_.

The whole determinant system of an id, as I conceive it, is in a state
of continual fluctuation upwards and downwards. In most cases the
fluctuations will counteract one another, because the passive streams
of nutriment soon change, but in many cases the limit from which a
return is possible will be passed, and then the determinants concerned
will continue to vary in the same direction, till they attain positive
or negative selection-value. At this stage personal selection
intervenes and sets aside the variation if it is disadvantageous, or
favours--that is to say, preserves--it if it is advantageous. Only
_the determinant of a useless organ is uninfluenced by personal
selection_, and, as experience shows, it sinks downwards; that is, the
organ that corresponds to it degenerates very slowly but
uninterruptedly till, after what must obviously be an immense stretch
of time, it disappears from the germ-plasm altogether.

Thus we find in the fact of the degeneration of disused parts the
proof that not all the fluctuations of a determinant return to
equilibrium again, but that, when the movement has attained to a
certain strength, it continues _in the same direction_. We have entire
certainty in regard to this as far as the downward progress is
concerned, and we must assume it also in regard to ascending
variations, as the phenomena of artificial selection certainly justify
us in doing. If the Japanese breeders were able to lengthen the
tail-feathers of the cock to six feet, it can only have been because
the determinants of the tail-feathers in the germ-plasm had already
struck out a path of ascending variation, and this movement was taken
advantage of by the breeder, who continually selected for reproduction
the individuals in which the ascending variation was most marked. For
all breeding depends upon the unconscious selection of germinal

Of course these germinal processes cannot be proved mathematically,
since we cannot actually see the play of forces of the passive
fluctuations and their causes. We cannot say how great these
fluctuations are, and how quickly or slowly, how regularly or
irregularly they change. Nor do we know how far a determinant must be
strengthened by the passive flow of the nutritive stream if it is to
be beyond the danger of unfavourable variations, or how far it must be
weakened passively before it loses the power of recovering itself by
its own strength. It is no more possible to bring forward actual
proofs in this case than it was in regard to the selection-value of
the initial stages of an adaptation. But if we consider that all
heritable variations must have their roots in the germ-plasm, and
further, that when personal selection does not intervene, that is to
say, in the case of parts which have become useless, a degeneration of
the part, and therefore also of its determinant must inevitably take
place; then we must conclude that processes such as I have assumed are
running their course within the germ-plasm, and we can do this with as
much certainty as we were able to infer, from the phenomena of
adaptation, the selection-value of their initial stages. The fact of
the degeneration of disused parts seems to me to afford irrefutable
proof that the fluctuations within the germ-plasm _are the real root
of all hereditary variation_, and the preliminary condition for the
occurrence of the Darwin-Wallace factor of selection. Germinal
selection supplies the stones out of which personal selection builds
her temples and palaces: _adaptations_. The importance for the theory
of the process of degeneration of disused parts cannot be
over-estimated, especially when it occurs in sterile animal forms,
where we are free from the doubt as to the alleged _Lamarckian factor_
which is apt to confuse our ideas in regard to other cases.

If we regard the variation of the many determinants concerned in the
transformation of the female into the sterile worker as having come
about through the gradual transformation of the ids into worker-ids,
we shall see that the germ-plasm of the sexual ants must contain three
kinds of ids, male, female, and worker ids, or if the workers have
diverged into soldiers and nest-builders, then four kinds. We
understand that the worker-ids arose because their determinants struck
out a useful path of variation, whether upward or downward, and that
they continued in this path until the highest attainable degree of
utility of the parts determined was reached. But in addition to the
organs of positive or negative selection-value, there were some which
were indifferent as far as the success and especially the functional
capacity of the workers was concerned: wings, ovarian tubes,
_receptaculum seminis_, a number of the facets of the eye, perhaps
even the whole eye. As to the ovarian tubes it is is possible that
their degeneration was an advantage for the workers, in saving energy,
and if so selection would favour the degeneration; but how could the
presence of eyes diminish the usefulness of the workers to the colony?
or the minute _receptaculum seminis_, or even the wings? These parts
have therefore degenerated _because they were of no further value to
the insect_. But if selection did not influence the setting aside of
these parts because they were neither of advantage nor of disadvantage
to the species, then the Darwinian factor of selection is here
confronted with a puzzle which it cannot solve alone, but which at
once becomes clear when germinal selection is added. For the
determinants of organs that have no further value for the organism,
must, as we have already explained, embark on a gradual course of
retrograde development.

In ants the degeneration has gone so far that there are no
wing-rudiments present in _any_ species, as is the case with so many
butterflies, flies, and locusts, but in the larvae the imaginable
discs of the wings are still laid down. With regard to the ovaries,
degeneration has reached different levels in different species of
ants, as has been shown by the researches of my former pupil,
Elizabeth Bickford. In many species there are twelve ovarian tubes,
and they decrease from that number to one; indeed, in one species no
ovarian tube at all is present. So much at least is certain from what
has been said, that in this case _everything_ depends on the
fluctuations of the elements of the germ-plasm. Germinal selection,
here as elsewhere, presents the variations of the determinants, and
personal selection favours or rejects these, or,--if it be a question
of organs which have become useless,--it does not come into play at
all, and allows the descending variation free course.

It is obvious that even the problem of _coadaptation in sterile
animals_ can thus be satisfactorily explained. If the determinants are
oscillating upwards and downwards in continual fluctuation, and
varying more pronouncedly now in one direction now in the other,
useful variations of every determinant will continually present
themselves anew, and may, in the course of generations, be combined
with one another in various ways. But there is one character of the
determinants that greatly facilitates this complex process of
selection, that, after a certain limit has been reached, they go on
varying in the same direction. From this it follows that development
along a path once struck out may proceed without the continual
intervention of personal selection. This factor only operates, so to
speak, at the beginning, when it selects the determinants which are
varying in the right direction, and again at the end, when it is
necessary to put a check upon further variation. In addition to this,
enormously long periods have been available for all these adaptations,
as the very gradual transition stages between females and workers in
many species plainly show, and thus this process of transformation
loses the marvellous and mysterious character that seemed at the first
glance to invest it, and takes rank, without any straining, among the
other processes of selection. It seems to me that, from the facts that
sterile animal forms can adapt themselves to new vital functions,
their superfluous parts degenerate, and the parts more used adapt
themselves in an ascending direction, those less used in a descending
direction, we must draw the conclusion that harmonious adaptation here
comes about _without the coöperation of the Lamarckian principle_.
This conclusion once established, however, we have no reason to refer
the thousands of cases of harmonious adaptation, which occur in
exactly the same way among other animals or plants, to a principle,
the _active intervention of which in the transformation of species is
nowhere proved. We do not require it to explain the facts, and
therefore we must not assume it._

The fact of coadaptation, which was supposed to furnish the strongest
argument against the principle of selection, in reality yields the
clearest evidence in favour of it. We _must_ assume it, _because no
other possibility of explanation is open to us, and because these
adaptations actually exist, that is to say, have really taken place_.
With this conviction I attempted, as far back as 1894, when the idea
of germinal selection had not yet occurred to me, to make "harmonious
adaptation" (coadaptation) more easily intelligible in some way or
other, and so I was led to the idea, which was subsequently expounded
in detail by Baldwin, and Lloyd Morgan, and also by Osborn, and Gulick
as _Organic Selection_. It seemed to me that it was not necessary that
all the germinal variations required for secondary variations should
have occurred _simultaneously_, since, for instance, in the case of
the stag, the bones, muscles, sinews, and nerves would be incited by
the increasing heaviness of the antlers to greater activity in _the
individual life_, and so would be strengthened. The antlers can only
have increased in size by very slow degrees, so that the muscles and
bones may have been able to keep pace with their growth in the
individual life, until the requisite germinal variations presented
themselves. In this way a disharmony between the increasing weight of
the antlers and the parts which support and move them would be
avoided, since time would be given for the appropriate germinal
variations to occur, and so to set agoing the _hereditary_ variation
of the muscles, sinews and bones.[42]

I still regard this idea as correct, but I attribute less importance
to "organic selection" than I did at that time, in so far that I do
not believe that it _alone_ could effect complex harmonious
adaptations. Germinal selection now seems to me to play the chief part
in bringing about such adaptations. Something the same is true of the
principle I have called _Panmixia_. As I became more and more
convinced, in the course of years, that the _Lamarckian principle_
ought not to be called in to explain the dwindling of disused parts, I
believed that this process might be simply explained as due to the
cessation of the conservative effect of natural selection. I said to
myself that, from the moment in which a part ceases to be of use,
natural selection withdraws its hand from it, and then it must
inevitably fall from the height of its adaptiveness, because inferior
variants would have as good a chance of persisting as better ones,
since all grades of fitness of the part in question would be mingled
with one another indiscriminately. This is undoubtedly true, as
Romanes pointed out ten years before I did, and this mingling of the
bad with the good probably does bring about a deterioration of the
part concerned. But it cannot account for the steady diminution, which
always occurs when a part is in process of becoming rudimentary, and
which goes on until it ultimately disappears altogether. The process
of dwindling cannot therefore be explained as due to panmixia alone:
we can only find a sufficient explanation in germinal selection.


The impetus in all directions given by Darwin through his theory of
selection has been an immeasurable one, and its influence is still
felt. It falls within the province of the historian of science to
enumerate all the ideas which, in the last quarter of the nineteenth
century, grew out of Darwin's theories, in the endeavour to penetrate
more deeply into the problem of the evolution of the organic world.
Within the narrow limits to which this paper is restricted, I cannot
attempt to discuss any of these.


(_a_) _Sexual Selection_

Sexual selection goes hand in hand with natural selection. From the
very first I have regarded sexual selection as affording an extremely
important and interesting corroboration of natural selection, but,
singularly enough, it is precisely against this theory that an adverse
judgment has been pronounced in so many quarters, and it is only quite
recently, and probably in proportion as the wealth of facts in proof
of it penetrates into a wider circle, that we seem to be approaching a
more general recognition of this side of the problem of adaptations.
Thus Darwin's words in his preface to the second edition (1874) of his
book, _The Descent of Man and Sexual Selection_, are being justified:
"My conviction as to the operation of natural selection remains
unshaken," and further, "If naturalists were to become more familiar
with the idea of sexual selection, it would, I think, be accepted to a
much greater extent, and already it is fully and favourably accepted
by many competent judges." Darwin was able to speak thus because he
was already acquainted with an immense mass of facts, which, taken
together, yield overwhelming evidence of the validity of the principle
of sexual selection.

_Natural selection_ chooses out for reproduction the individuals that
are best equipped for the struggle for existence, and it does so at
every stage of development; it thus improves the species in all its
stages and forms. _Sexual selection_ operates only on individuals
that are already capable of reproduction, and does so only in relation
to the attainment of reproduction. It arises from the rivalry of one
sex, usually the male, for the possession of the other, usually the
female. Its influence can therefore only _directly_ affect one sex, in
that it equips it better for attaining possession of the other. But
the effect may extend indirectly to the female sex, and thus the whole
species may be modified, without, however, becoming any more capable
of resistance in the struggle for existence, for sexual selection only
gives rise to adaptations which are likely to give their possessor the
victory over rivals in the struggle for possession of the female, and
which are therefore peculiar to the wooing sex: the manifold
"secondary sexual characters." The diversity of these characters is so
great that I cannot here attempt to give anything approaching a
complete treatment of them, but I should like to give a sufficient
number of examples to make the principle itself, in its various modes
of expression, quite clear.

One of the chief preliminary postulates of sexual selection is the
unequal number of individuals in the two sexes, for if every male
immediately finds his mate there can be no competition for the
possession of the female. Darwin has shown that, for the most part,
the inequality between the sexes is due simply to the fact that there
are more males than females, and therefore the males must take some
pains to secure a mate. But the inequality does not always depend on
the numerical preponderance of the males, it is often due to polygamy;
for, if one male claims several females, the number of females in
proportion to the rest of the males will be reduced. Since it is
almost always the males that are the wooers, we must expect to find
the occurrence of secondary sexual characters chiefly among them, and
to find it especially frequent in polygamous species. And this is
actually the case.

If we were to try to guess--without knowing the facts--what means the
male animals make use of to overcome their rivals in the struggle for
the possession of the female, we might name many kinds of means, but
it would be difficult to suggest any which is not actually employed in
some animal group of other. I begin with the mere difference in
strength, through which the male of many animals is so sharply
distinguished from the female, as, for instance, the lion, walrus,
"sea-elephant," and others. Among these the males fight violently for
the possession of the female, who falls to the victor in the combat.
In this simple case no one can doubt the operation of selection, and
there is just as little room for doubt as to the selection-value of
the initial stages of the variation. Differences in bodily strength
are apparent even among human beings, although in their case the
struggle for the possession of the female is no longer decided by
bodily strength alone.

Combats between male animals are often violent and obstinate, and the
employment of the natural weapons of the species in this way has led
to perfecting of these, e.g. the tusks of the boar, the antlers of the
stag, and the enormous, antler-like jaws of the stag-beetle. Here
again it is impossible to doubt that variations in these organs
presented themselves, and that these were considerable enough to be
decisive in combat, and so to lead to the improvement of the weapon.

Among many animals, however, the females at first withdraw from the
males; they are coy, and have to be sought out, and sometimes held by
force. This tracking and grasping of the females by the males has
given rise to many different characters in the latter, as, for
instance, the larger eyes of the male bee, and especially of the males
of the Ephemerids (May-flies), some species of which show, in addition
to the usual compound eyes, large, so-called turban-eyes, so that the
whole head is covered with seeing surfaces. In these species the
females are very greatly in the minority (1-100), and it is easy to
understand that a keen competition for them must take place, and that,
when the insects of both sexes are floating freely in the air, an
unusually wide range of vision will carry with it a decided
advantage. Here again the actual adaptations are in accordance with
the preliminary postulates of the theory. We do not know the stages
through which the eye has passed to its present perfected state, but,
since the number of simple eyes (facets) has become very much greater
in the male than in the female, we may assume that their increase is
due to a gradual duplication of the determinants of the ommatidium in
the germ-plasm, as I have already indicated in regard to sense-organs
in general. In this case, again, the selection-value of the initial
stages hardly admits of doubt; better vision _directly_ secures

In many cases _the organ of smell_ shows a similar improvement. Many
lower Crustaceans (Daphnidae) have better developed organs of smell in
the male sex. The difference is often slight and amounts only to one
or two olfactory filaments, but certain species show a difference of
nearly a hundred of these filaments (Leptodora). The same thing occurs
among insects.

We must briefly consider the clasping or grasping organs which have
developed in the males among many lower Crustaceans, but here natural
selection plays its part along with sexual selection, for the union of
the sexes is an indispensable condition for the maintenance of the
species, and as Darwin himself pointed out, in many cases the two
forms of selection merge into each other. This fact has always seemed
to me to be a proof of natural selection, for, in regard to sexual
selection, it is quite obvious that the victory of the best-equipped
could have brought about the improvement only of the organs concerned,
the factors in the struggle, such as the eye and the olfactory organ.

We come now to the _excitants_; that is, to the group of sexual
characters whose origin through processes of selection has been most
frequently called in question. We may cite the _love-calls_ produced
by many male insects, such as crickets and cicadas. These could only
have arisen in animal groups in which the female did not rapidly flee
from the male, but was inclined to accept his wooing from the first.
Thus, notes like the chirping of the male cricket serve to entice the
females. At first they were merely the signal which showed the
presence of a male in the neighbourhood, and the female was gradually
enticed nearer and nearer by the continued chirping. The male that
could make himself heard to the greatest distance would obtain the
largest following, and would transmit the beginnings, and, later, the
improvement of his voice to the greatest number of descendants. But
sexual excitement in the female became associated with the hearing of
the love-call, and then the sound-producing organ of the male began to
improve, until it attained to the emission of the long-drawn-out soft
notes of the mole-cricket or the maenad-like cry of the cicadas. I
cannot here follow the process of development in detail, but will call
attention to the fact that the original purpose of the voice, the
announcing of the male's presence, became subsidiary, and the exciting
of the female became the chief goal to be aimed at. The loudest
singers awakened the strongest excitement, and the improvement
resulted as a matter of course. I conceive of the origin of bird-song
in a somewhat similar manner, first as a means of enticing, then of
exciting the female.

One more kind of secondary sexual character must here be mentioned:
the odour which emanates from so many animals at the breeding season.
It is possible that this odour also served at first merely to give
notice of the presence of individuals of the other sex, but it soon
became an excitant, and as the individuals which caused the greatest
degree of excitement were preferred, it reached as high a pitch of
perfection as was possible to it. I shall confine myself here to the
comparatively recently discovered fragrance of butterflies. Since
Fritz Müller found out that certain Brazilian butterflies gave off
fragrance "like a flower," we have become acquainted with many such
cases, and we now know that in all lands, not only many diurnal
Lepidoptera but nocturnal ones also give off a delicate odour, which
is agreeable even to man. The ethereal oil to which this fragrance is
due is secreted by the skin-cells, usually of the wing, as I showed
soon after the discovery of the _scent-scales_. This is the case in
the males; the females have no _special_ scent-scales recognisable as
such by their form, but they must, nevertheless, give off an extremely
delicate fragrance, although our imperfect organ of smell cannot
perceive it, for the males become aware of the presence of a female,
even at night, from a long distance off, and gather round her. We may
therefore conclude, that both sexes have long given forth a very
delicate perfume, which announced their presence to others of the same
species, and that in many species (_not in all_) these small
beginnings become, in the males, particularly strong scent-scales of
characteristic form (lute, brush, or lyre-shaped). At first these
scales were scattered over the surface of the wing, but gradually they
concentrated themselves, and formed broad, velvety bands, or strong,
prominent brushes, and they attained their highest pitch of evolution
when they became enclosed within pits or folds of the skin, which
could be opened to let the delicious fragrance stream forth suddenly
towards the female. Thus in this case also we see that characters, the
original use of which was to bring the sexes together, and so to
maintain the species, have been evolved in the males into means for
exciting the female. And we can hardly doubt, that the females are
most readily enticed to yield to the butterfly that sends out the
strongest fragrance,--that is to say, that excites them to the highest
degree. It is a pity that our organs of smell are not fine enough to
examine the fragrance of male Lepidoptera in general, and to compare
it with other perfumes which attract these insects.[43] As far as we
can perceive them they resemble the fragrance of flowers, but there
are Lepidoptera whose scent suggests musk. A smell of musk is also
given off by several plants: it is a sexual excitant in the
musk-deer, the musk-sheep, and the crocodile.

As far as we know, then, it is perfumes similar to those of flowers
that the male Lepidoptera give off in order to entice their mates and
this is a further indication that animals, like plants, can to a large
extent meet the claims made upon them by life, and produce the
adaptations which are most purposive,--a further proof, too, of my
proposition that the useful variations, so to speak, are _always
there_. The flowers developed the perfumes which entice their
visitors, and the male Lepidoptera developed the perfumes which entice
and excite their mates.

There are many pretty little problems to be solved in this connection,
for there are insects, such as some flies, that are attracted by
smells which are unpleasant to us, like those from decaying flesh and
carrion. But there are also certain flowers, some orchids for
instance, which give forth no very agreeable odour, but one which is
to us repulsive and disgusting; and we should therefore expect that
the males of such insects would give off a smell unpleasant to us, but
there is no case known to me in which this has been demonstrated.

In cases such as we have discussed, it is obvious that there is no
possible explanation except through selection. This brings us to the
last kind of secondary sexual characters, and the one in regard to
which doubt has been most frequently expressed,--decorative colours
and decorative forms, the brilliant plumage of the male pheasant, the
humming-birds, and the bird of Paradise, as well as the bright colours
of many species of butterfly, from the beautiful blue of our little
Lycaenidae to the magnificent azure of the large Morphinae of Brazil.
In a great many cases, though not by any means in all, the male
butterflies are "more beautiful" than the females, and in the Tropics
in particular they shine and glow in the most superb colours. I really
see no reason why we should doubt the power of sexual selection, and I
myself stand wholly on Darwin's side. Even though we certainly cannot
assume that the females exercise a conscious choice of the
"handsomest" mate, and deliberate like the judges in a court of
justice over the perfections of their wooers, we have no reason to
doubt that distinctive forms (decorative feathers), and colours have a
particularly exciting effect upon the female, just as certain odours
have among animals of so many different groups, including the
butterflies. The doubts which existed for a considerable time, as a
result of fallacious experiments, as to whether the colours of flowers
really had any influence in attracting butterflies have now been set
at rest through a series of more careful investigations; we now know
that the colours of flowers are there on account of the butterflies,
as Sprengel first showed, and that the blossoms of Phanerogams are
selected in relation to them, as Darwin pointed out.

Certainly it is not possible to bring forward any convincing proof of
the origin of decorative colours through sexual selection, but there
are many weighty arguments in favour of it, and these form a body of
presumptive evidence so strong that it almost amounts to certainty.

In the first place, there is the analogy with other secondary sexual
characters. If the song of birds and the chirping of the cricket have
been evolved through sexual selection, if the penetrating odours of
male animals,--the crocodile, the musk-deer, the beaver, the
carnivores, and, finally, the flower-like fragrances of the
butterflies have been evolved to their present pitch in this way, why
should decorative colours have arisen in some other way? Why should
the eye be less sensitive to _specifically male_ colours and other
_visible_ signs _enticing to the female_, than the olfactory sense to
specifically male odours, or the sense of hearing to specifically male
sounds? Moreover, the decorative feathers of birds are almost always
spread out and displayed before the female during courtship. I have
elsewhere[44] pointed out that decorative colouring and
sweet-scentedness may replace one another in Lepidoptera as well as in
flowers, for just as some modestly coloured flowers (mignonette and
violet) have often a strong perfume, while strikingly coloured ones
are sometimes quite devoid of fragrance, so we find that the most
beautiful and gaily-coloured of our native Lepidoptera, the species of
Vanessa, have no scent-scales, while these are often markedly
developed in grey nocturnal Lepidoptera. Both attractions may,
however, be combined in butterflies, just as in flowers. Of course, we
cannot explain why both means of attraction should exist in one genus,
and only one of them in another, since we do not know the minutest
details of the conditions of life of the genera concerned. But from
the sporadic distribution of scent-scales in Lepidoptera, and from
their occurrence or absence in nearly related species, we may conclude
that fragrance is a relatively _modern_ acquirement, more recent than
brilliant colouring.

One thing in particular that stamps decorative colouring as a product
of selection is _its gradual intensification_ by the addition of new
spots, which we can quite well observe, because in many cases the
colours have been first acquired by the males, and later transmitted
to the females by inheritance. The scent-scales are never thus
transmitted, probably for the same reason that the decorative colours
of many birds are often not transmitted to the females: because with
these they would be exposed to too great elimination by enemies.
Wallace was the first to point out that in species with concealed
nests the beautiful feathers of the male occurred in the female also,
as in the parrots, for instance, but this is not the case in species
which brood on an exposed nest. In the parrots one can often observe
that the general brilliant colouring of the male is found in the
female, but that certain spots of colour are absent, and these have
probably been acquired comparatively recently by the male and have not
yet been transmitted to the female.

Isolation of the group of individuals which is in process of varying
is undoubtedly of great value in sexual selection, for even a solitary
conspicuous variation will become dominant much sooner in a small
isolated colony, than among a large number of members of a species.

Any one who agrees with me in deriving variations from germinal
selection will regard that process as an essential aid towards
explaining the selection of distinctive courtship-characters, such as
coloured spots, decorative feathers, horny outgrowths in birds and
reptiles, combs, feather-tufts, and the like, since the beginnings of
these would be presented with relative frequency in the struggle
between the determinants within the germ-plasm. The process of
transmission of decorative feathers to the female results, as Darwin
pointed out and illustrated by interesting examples, in the
_colour-transformation of a whole species_, and this process, as the
phyletically older colouring of young birds shows, must, in the course
of thousands of years, have repeated itself several times in a line of

If we survey the wealth of phenomena presented to us by secondary
sexual characters, we can hardly fail to be convinced of the truth of
the principle of sexual selection. And certainly no one who has
accepted natural selection should reject sexual selection, for, not
only do the two processes rest upon the same basis, but they merge
into one another, so that it is often impossible to say how much of a
particular character depends on one and how much on the other form of

(_b_) _Natural Selection_

An actual proof of the theory of sexual selection is out of the
question, if only because we cannot tell when a variation attains to
selection-value. It is certain that a delicate sense of smell is of
value to the male moth in his search for the female, but whether the
possession of one additional olfactory hair, or of ten, or of twenty
additional hairs leads to the success of its possessor we are unable
to tell. And we are groping even more in the dark when we discuss the
excitement caused in the female by agreeable perfumes, or by striking
and beautiful colours. That these do make an impression is beyond
doubt; but we can only assume that slight intensifications of them
give any advantage, and we _must_ assume this _since otherwise
secondary sexual characters remain inexplicable_.

The same thing is true in regard to natural selection. It is not
possible to bring forward any actual proof of the selection-value of
the initial stages, and the stages in the increase of variations, as
has been already shown. But the selection-value of a finished
adaptation can in many cases be statistically determined. Cesnola and
Poulton have made valuable experiments in this direction. The former
attached forty-five individuals of the green, and sixty-five of the
brown variety of the praying mantis (_Mantis religiosa_), by a silk
thread to plants, and watched them for seven days. The insects which
were on a surface of a colour Similar to their own remained uneaten,
while twenty-five green insects on brown parts of plants had all
disappeared in eleven days.

The experiments of Poulton and Sanders[45] were made with 600 pupae of
_Vanessa urticae_, the "tortoise-shell butterfly." The pupae were
artificially attached to nettles, tree-trunks, fences, walls, and to
the ground, some at Oxford, some at St. Helens in the Isle of Wight.
In the course of a month 93% of the pupae at Oxford were killed,
chiefly by small birds, while at St. Helens 68% perished. The
experiments showed very clearly that the colour and character of the
surface on which the pupa rests--and thus its own conspicuousness--are
of the greatest importance. At Oxford only the four pupae which were
fastened to nettles emerged; all the rest--on bark, stones and the
like--perished. At St. Helens the elimination was as follows: on
fences where the pupae were conspicuous, 92%; on bark, 66%; on walls,
54%; and among nettles, 57%. These interesting experiments confirm our
views as to protective coloration, and show further, _that the ratio
of elimination in the species is a very high one, and that therefore
selection must be very keen_.

We may say that the process of selection follows as a logical
necessity from the fulfilment of the three preliminary postulates of
the theory: variability, heredity, and the struggle for existence,
with its enormous ratio of elimination in all species. To this we must
add a fourth factor, the _intensification_ of variations which Darwin
established as a fact, and which we are now able to account for
theoretically on the basis of germinal selection. It may be objected
that there is considerable uncertainty about this _logical_ proof,
because of our inability to demonstrate the selection-value of the
initial stages and the individual stages of increase. We have
therefore to fall back on _presumptive evidence_. This is to be found
in _the interpretative value of the theory_. Let us consider this
point in greater detail.

In the first place it is necessary to emphasize what is often
overlooked, namely, that the theory not only explains the
_transformations_ of species, it also explains _their remaining the
same_; in addition to the principle of varying, it contains within
itself that of _persisting_. It is part of the essence of selection,
that it not only causes a part to _vary_ till it has reached its
highest pitch of adaptation, but that it _maintains it at this pitch.
This conserving influence of natural selection_ is of great
importance, and was early recognised by Darwin; it follows naturally
from the principle of the survival of the fittest.

We understand from this how it is that a species which has become
fully adapted to certain conditions of life ceases to vary, but
remains "constant," as long as the conditions of life _for_ it remain
unchanged, whether this be for thousands of years, or for whole
geological epochs. But the most convincing proof of the power of the
principle of selection lies in the innumerable multitude of phenomena
which cannot be explained in any other way. To this category belong
all structures which are only _passively_ of advantage to the
organism, because none of these can have arisen by the alleged
_Lamarckian principle_. These have been so often discussed that we
need do no more than indicate them here. Until quite recently the
sympathetic coloration of animals--for instance, the whiteness of
Arctic animals--was referred, at least in part, to the _direct_
influence of external factors, but the facts can best be explained by
referring them to the processes of selection, for then it is
unnecessary to make the gratuitous assumption that many species are
sensitive to the stimulus of cold and that others are not. The great
majority of Arctic land-animals, mammals and birds, are white, and
this proves that they were all able to present the variation which was
most useful for them. The sable is brown, but it lives in trees, where
the brown colouring protects and conceals it more effectively. The
musk-sheep (_Ovibos moschatus_) is also brown, and contrasts sharply
with the ice and snow, but it is protected from beasts of prey by its
gregarious habit, and therefore it is of advantage to be visible from
as great a distance as possible. That so many species have been able
to give rise to white varieties does not depend on a special
sensitiveness of the skin to the influence of cold, but to the fact
that Mammals and Birds have a general tendency to vary towards white.
Even with us, many birds--starlings, blackbirds, swallows,
etc.--occasionally produce white individuals, but the white variety
does not persist, because it readily falls a victim to the carnivores.
This is true of white fawns, foxes, deer, etc. The whiteness,
therefore, arises from internal causes, and only persists when it is
useful. A great many animals living in a _green environment_ have
become clothed in green, especially insects, caterpillars, and
Mantidae, both persecuted and persecutors.

That it is not the direct effect of the environment which calls forth
the green colour is shown by the many kinds of caterpillar which rest
on leaves and feed on them, but are nevertheless brown. These feed by
night and betake themselves through the day to the trunk of the tree,
and hide in the furrows of the bark. We cannot, however, conclude
from this that they were _unable_ to vary towards green, for there are
Arctic animals which are white only in winter and brown in summer
(Alpine hare, and the ptarmigan of the Alps), and there are also green
leaf-insects which remain green only while they are young and
difficult to see on the leaf, but which become brown again in the last
stage of larval life, when they have outgrown the leaf. They then
conceal themselves by day, sometimes only among withered leaves on the
ground, sometimes in the earth itself. It is interesting that in one
genus, Chaerocampa, one species is brown in the last stage of larval
life, another becomes brown earlier, and in many species the last
stage is not wholly brown, a part remaining green. Whether this is a
case of a double adaptation, or whether the green is being gradually
crowded out by the brown, the fact remains that the same species, even
the same individual, can exhibit both variations. The case is the same
with many of the leaf-like Orthoptera, as, for instance, the praying
mantis (_Mantis religiosa_) which we have already mentioned.

But the best proofs are furnished by those of ten-cited cases in which
the insect bears a deceptive resemblance to another object. We now
know many such cases, such as the numerous imitations of green or
withered leaves, which are brought about in the most diverse ways,
sometimes by mere variations in the form of the insect and in its
colour, sometimes by an elaborate marking, like that which occurs in
the Indian leaf-butterflies, _Kallima inachis_. In the single
butterfly-genus Anaea, in the woods of South America, there are about
a hundred species which are all gaily coloured on the upper surface,
and on the reverse side exhibit the most delicate imitation of the
colouring and pattern of a leaf, generally without any indication of
the leaf-ribs, but extremely deceptive nevertheless. Anyone who has
seen only one such butterfly may doubt whether many of the
insignificant details of the marking can really be of advantage to the
insect. Such details are for instance the apparent holes and splits
in the apparently dry or half-rotten leaf, which are usually due to
the fact that the scales are absent on a circular or oval patch so
that the colourless wing-membrane lies bare, and one can look through
the spot as through a window. Whether the bird which is seeking or
pursuing the butterflies takes these holes for dewdrops, or for the
work of a devouring insect, does not affect the question; the
mirror-like spot undoubtedly increases the general deceptiveness, for
the same thing occurs in many leaf-butterflies, though not in all, and
in some cases it is replaced in quite a peculiar manner. In one
species of Anaea (_A. divina_), the resting butterfly looks exactly
like a leaf out of the outer edge of which a large semi-circular piece
has been eaten, possibly by a caterpillar; but if we look more closely
it is obvious that there is no part of the wing absent, and that the
semi-circular piece is of a clear, pale yellow colour, while the rest
of the wing is of a strongly contrasted dark brown.

But the deceptive resemblance may be caused in quite a different
manner. I have often speculated as to what advantage the brilliant
white C could give to the otherwise dusky-coloured "Comma butterfly"
(_Grapta C. album_). Poulton's recent observations[46] have shown that
this represents the imitation of a crack such as is often seen in dry
leaves, and is very conspicuous because the light shines through it.

The utility obviously lies in presenting to the bird the very familiar
picture of a broken leaf with a clear shining slit, and we may
conclude, from the imitation of such small details, that the birds are
very sharp observers and that the smallest deviation from the usual
arrests their attention and incites them to closer investigation. It
is obvious that such detailed--we might almost say such
subtle--deceptive resemblances could only have come about in the
course of long ages through the acquirement from time to time of
something new which heightened the already existing resemblance.

In face of facts like these there can be no question of chance and no
one has succeeded so far in finding any other explanation to replace
that by selection. For the rest, the apparent leaves are by no means
perfect copies of a leaf; many of them only represent the torn or
broken piece, or the half or two-thirds of a leaf, but then the leaves
themselves frequently do not present themselves to the eye as a whole,
but partially concealed among other leaves. Even those butterflies
which, like the species of Kallima and Anaea, represent the whole of a
leaf with stalk, ribs, apex, and the whole breadth, are not actual
copies which would satisfy a botanist; there is often much wanting. In
Kallima the lateral ribs of the leaf are never all included in the
markings; there are only two or three on the left side and at more
four or five on the right, and in many individuals these are rather
obscure, while in others they are comparatively distinct. This
furnishes us with fresh evidence in favour of their origin through
processes of selection, for a botanically perfect picture could not
arise in this way; there could only be a fixing of such details as
heightened the deceptive resemblance.

Our postulate of origin through selection also enables us to
understand why the leaf-imitation is on the lower surface of the wing
in the diurnal Lepidoptera, and on the upper surface in the nocturnal
forms, corresponding to the attitude of the wings in the resting
position of the two groups.

The strongest of all proofs of the theory, however, is afforded by
cases of true "mimicry," those adaptations discovered by Bates in
1861, consisting in the imitation of one species by another, which
becomes more and more like its model. The model is always a species
that enjoys some special protection from enemies, whether because it
is unpleasant to taste, or because it is in some way dangerous.

It is chiefly among insects and especially among butterflies that we
find the greatest number of such cases. Several of these have been
minutely studied and every detail has been investigated so that it is
difficult to understand how there can still be disbelief in regard to
them. If the many and exact observations which have been carefully
collected and critically discussed for instance by Poulton[47] were
thoroughly studied the arguments which are still frequently urged
against mimicry would be found untenable; we can hardly hope to find
more convincing proof of the actuality of the processes of selection
than these cases put into our hands. The preliminary postulates of the
theory of mimicry have been disputed, for instance, that diurnal
butterflies are persecuted and eaten by birds, but observations
specially directed towards this point in India, Africa, America and
Europe have placed it beyond all doubt. If it were necessary I could
myself furnish an account of my own observations on this point.

In the same way it has been established by experiment and observation
in the field that in all the great regions of distribution there are
butterflies which are rejected by birds and lizards, their chief
enemies, on account of their unpleasant smell or taste. These
butterflies are usually gaily and conspicuously coloured and thus--as
Wallace first interpreted it--are furnished with an easily
recognisable sign: a sign of unpalatableness or _warning colours_. If
they were not thus recognisable easily and from a distance, they would
frequently be pecked at by birds, and then rejected because of their
unpleasant taste; but as it is, the insect-eaters recognise them at
once as unpalatable booty and ignore them. Such _immune_[48] species,
wherever they occur, are imitated by other palatable species, which
thus acquire a certain degree of protection.

It is true that this explanation of the bright, conspicuous colours
is only a hypothesis, but its foundations--unpalatableness, and the
liability of other butterflies to be eaten,--are certain, and its
consequences--the existence of mimetic palatable forms--conform it in
the most convincing manner. Of the many cases now known I select one,
which is especially remarkable, and which has been thoroughly
investigated, _Papilla dardanus_ (_merope_), a large, beautiful,
diurnal butterfly which ranges from Abyssinia throughout the whole of
Africa to the south coast of Cape Colony.

The males of this form are everywhere _almost_ the same in colour and
in form of wings, save for a few variations in the sparse black
markings on the pale yellow ground. But the females occur in several
quite different forms and colourings, and one of these only, the
Abyssinian form, is like the male, while the other three or four are
_mimetic_, that is to say, they copy a butterfly of quite a different
family the Danaids, which are among the _immune_ forms. In each region
the females have thus copied two or three different immune species.
There is much that is interesting to be said in regard to these
species, but it would be out of keeping with the general tenor of this
paper to give details of this very complicated case of polymorphism in
_P. Dardanus_. Anyone who is interested in the matter will find a full
and exact statement of the case in as far as we know it, in Poulton's
_Essays on Evolution_ (pp. 373-375[49]). I need only add that three
different mimetic female forms have been reared from the eggs of a
single female in South Africa. The resemblance of the forms to their
immune models goes so far that even the details of the _local_ forms
of the models are copied by the mimetic species.

It remains to be said that in Madagascar a butterfly,

_Papilio meriones_, occurs, of which both sexes are very similar in
form and markings to the non-mimetic male of _P. dardanus_, so that it
probably represents the ancestor of this latter species.

In face of such facts as these every attempt at another explanation
must fail. Similarly all the other details of the case fulfil the
preliminary postulates of selection, and leave no room for any other
interpretation. That the males do not take on the protective colouring
is easily explained, because they are in general more numerous, and
the females are more important for the preservation of the species,
and must also live longer in order to deposit their eggs. We find the
same state of things in many other species, and in one case (_Elymnias
undularis_) in which the male is also mimetically coloured, it copies
quite a differently coloured immune species from the model followed by
the female. This is quite intelligible when we consider that if there
were _too many_ false immune types, the birds would soon discover that
there were palatable individuals among those with unpalatable warning
colours. Hence the imitation of different immune species by _Papilio

I regret that lack of space prevents my bringing forward more examples
of mimicry and discussing them fully. But from the case of _Papilio
dardanus_ alone there is much to be learnt which is of the highest
importance for our understanding of transformations. It shows us
chiefly what I once called, somewhat strongly perhaps, _the
omnipotence of natural selection_ in answer to an opponent who had
spoken of its "inadequacy." We here see that one and the same species
is capable of producing four or five different patterns of colouring
and marking; thus the colouring and marking are not, as has often been
supposed, a necessary outcome of the specific nature of the species,
but a true adaptation, which cannot arise as a direct effect of
climatic conditions, but solely through what I may call the sorting
out of the variations produced by the species, according to their
utility. That caterpillars may be either green or brown is already
something more than could have been expected according to the old
conception of species, but that one and the same butterfly should be
now pale yellow, with black; now red with black and pure white; now
deep black with large, pure white spots; and again black with a large
ocheous-yellow spot, and many small white and yellow spots; that in
one sub-species it may be tailed like the ancestral form, and in
another tailless like its Danaid model,--all this shows a far-reaching
capacity for variation and adaptation that we could never have
expected if we did not see the facts before us. How it is possible
that the primary colour-variations should thus be intensified and
combined remains a puzzle even now; we are reminded of the modern
three-colour printing,--perhaps similar combinations of the primary
colours take place in this case; in any case the direction of these
primary variations is determined by the artist whom we know as natural
selection, for there is no other conceivable way in which the model
could affect the butterfly that is becoming more and more like it. The
same climate surrounds all four forms of female; they are subject to
the same conditions of nutrition. Moreover, _Papilio dardanus_ is by
no means the only species of butterfly which exhibits different kinds
of colour-pattern on its wings. Many species of the Asiatic genus
Elymnias have on the upper surface a very good imitation of an immune
Euploeine (Danainae), often with a steel-blue ground-colour, while the
under surface is well concealed when the butterfly is at rest,--thus
there are two kinds of protective coloration each with a different
meaning! The same thing may be observed in many non-mimetic
butterflies, for instance in all our species of Vanessa, in which the
under side shows a grey-brown or brownish-black protective coloration,
but we do not yet know with certainty what may be the biological
significance of the gaily coloured upper surface.

In general it may be said that mimetic butterflies are comparatively
rare species, but there are exceptions, for instance _Limenitis
archippus_ in North America, of which the immune model (_Danaida
plexippus_) also occurs in enormous numbers.

In another mimicry-category the imitators are often more numerous than
the models, namely in the case of the imitation of _dangerous insects_
by harmless species. Bees and wasps are dreaded for their sting, and
they are copied by harmless flies of the genera Eristalis and Syrphus,
and these mimics often occur in swarms about flowering plants without
damage to themselves or to their models; they are feared and are
therefore left unmolested.

In regard also to the _faithfulness of the copy_ the facts are quite
in harmony with the theory, according to which the resemblance must
have arisen and increased _by degrees_. We can recognise this in many
cases, for even now the mimetic species show very _varying degrees of
resemblance_ to their immune model. If we compare, for instance, the
many different imitators of _Danaida chrysippus_ we find that, with
their brownish-yellow ground-colour, and the position and size, and
more or less sharp limitation of their clear marginal spots, they have
reached very different degrees of nearness to their model. Or compare
the female of _Elymnias undularis_ with its model _Danaida genutia_;
there is a general resemblance, but the marking of the Danaida is very
roughly imitated in Elymnias.

Another fact that bears out the theory of mimicry is, that even when
the resemblance in colour-pattern is very great, the _wing-venation_,
which is so constant, and so important in determining the systematic
position of butterflies, is never affected by the variation. The
pursuers of the butterfly have no time to trouble about entomological

I must not pass over a discovery of Poulton's which is of great
theoretical importance--that mimetic butterflies may reach the same
effect by very different means.[50] Thus the glass-like transparency
of the wing of a certain Ithomiine (Methona) and its Pierine mimic
(_Dismorphia orise_) depends on a diminution in the size of the
scales; in the Danaine genus Itune it is due to the fewness of the
scales and in a third imitator, a moth (_Castnia linus var.
heliconoides_) the glass-like appearance of the wing is due neither to
diminution nor to absence of scales, but to their absolute
colourlessness and transparency, and to the fact that they stand
upright. In another moth mimic (Anthomyza) the arrangement of the
transparent scales is normal. Thus it is not some unknown external
influence that has brought about the transparency of the wing in these
five forms, as has sometimes been supposed. Nor is it a hypothetical
_internal_ evolutionary tendency, for all three vary in a different
manner. The cause of this agreement can only lie in selection, which
preserves and intensifies in each species the favourable variations
that present themselves. The great faithfulness of the copy is
astonishing in these cases, for it is not _the whole_ wing which is
transparent; certain markings are black in colour, and these contrast
sharply with the glass-like ground. It is obvious that the pursuers of
these butterflies must be very sharp-sighted, for otherwise the
agreement between the species could never have been pushed so far. The
less the enemies see and observe, the more defective must the
imitation be, and if they had been blind, no visible resemblance
between the species which required protection could ever have arisen.

A seemingly irreconcilable contradiction to the mimicry theory is
presented in the following cases, which were known to Bates, who,
however, never succeeded in bringing them into line with the principle
of mimicry.

In South America there are, as we have already said, many mimics of
the immune Ithomiinae (or as Bates called them Heliconidae). Among
these there occur not merely species which are edible, and thus
require the protection of a disguise, but others which are rejected on
account of their unpalatableness. How could the Ithomiine dress have
developed in their case, and of what use is it, since the species
would in any case be immune? In Eastern Brazil, for instance, there
are four butterflies, which bear a most confusing resemblance to one
another in colour, marking, and form of wing, and all four are
unpalatable to birds. They belong to four different genera and three
sub-families, and we have to inquire: Whence came this resemblance and
what end does it serve? For a long time no satisfactory answer could
be found, but Fritz Müller,[51] seventeen years after Bates, offered a
solution to the riddle, when he pointed out that young birds could not
have an instinctive knowledge of the unpalatableness of the
Ithomiines, but must learn by experience which species were edible and
which inedible. Thus each young bird must have tasted at least one
individual of each inedible species and discovered its unpalatability,
before it learnt to avoid, and thus to spare the species. But if the
four species resemble each other very closely the bird will regard
them all as of the same kind, and avoid them all. Thus there developed
a process of selection which resulted in the survival of the
Ithomiine-like individuals, and in so great an increase of resemblance
between the four species, that they are difficult to distinguish one
from another even in a collection. The advantage for the four species,
living side by side as they do e.g. in Bahia, lies in the fact that
only one individual from the _mimicry-ring_ ("inedible association")
need be tasted by a young bird, instead of at least four individuals,
as would otherwise be the case. As the number of young birds is great,
this makes a considerable difference in the ratio of elimination. The
four Brazilian species are _Lycorea halia_ (Danainae), _Heliconius
narcaea_ (_eucrate_) (Heliconinae), _Melinaea ethra_, and _Mechanitis
lysimnia_ (Ithomiinae).

These interesting mimicry-rings (trusts), which have much significance
for the theory, have been the subject of numerous and careful
investigations, and at least their essential features are now fully
established. Müller took for granted, without making any
investigations, that young birds only learn by experience to
distinguish between different kinds of victims. But Lloyd Morgan's[52]
experiments with young birds proved that this is really the case, and
at the same time furnished an additional argument against the
_Lamarckian principle_.

In addition to the mimicry-rings first observed in South America,
others have been described from Tropical India by Moore, and by
Poulton and Dixey from Africa, and we may expect to learn many more
interesting facts in this connection. Here again the preliminary
postulates of the theory are satisfied. And how much more that would
lead to the same conclusion might be added!

As in the case of mimicry many species have come to resemble one
another through processes of selection, so we know whole classes of
phenomena in which plants and animals have become adapted to one
another, and have thus been modified to a considerable degree. I refer
particularly to the relation between flowers and insects. Darwin has
shown that the originally inconspicuous blossoms of the phanerogams
were transformed into flowers through the visits of insects, and that,
conversely, several large orders of insects have been gradually
modified by their association with flowers, especially as regards the
parts of their body actively concerned. Bees and butterflies in
particular have become what they are through their relation to
flowers. In this case again all that is apparently contradictory to
the theory can, on closer investigation, be beautifully interpreted in
corroboration of it. Selection can give rise only to what is of use to
the organism actually concerned, never to what is of use to some other
organism, and we must therefore expect to find that in flowers only
characters of use to _themselves_ have arisen, never characters which
are of use to insects only, and conversely that in the insects
characters useful to them and not merely to the plants would have
originated. For a long time it seemed as if an exception to this rule
existed in the case of the fertilisation of the yucca blossoms by a
little moth, _Pronuba yuccasella_. This little moth has a
sickle-shaped appendage to its mouth-parts which occurs hi no other
Lepidopteron, and which is used for pushing the yellow pollen into the
opening of the pistil, thus fertilising the flower. Thus it appears as
if a new structure, which is useful only to the plant, has arisen in
the insect. But the difficulty is solved as soon as we learn that the
moth lays its eggs in the fruit-buds of the Yucca, and that the
larvae, when they emerge, feed on the developing seeds. In effecting
the fertilisation of the flower the moth is at the same time making
provision for its own offspring, since it is only after fertilisation
that the seeds begin to develop. There is thus nothing to prevent our
referring this structural adaptation in _Pronuba yuccasella_ to
processes of selection, which have gradually transformed the maxillary
palps of the female into the sickle-shaped instrument for collecting
the pollen, and which have at the same time developed in the insect
the instinct to press the pollen into the pistil.

In this domain, then, the theory of selection finds nothing but
corroboration, and it would be impossible to substitute for it any
other explanation, which now that the facts are so well known, could
be regarded as a serious rival to it. That selection is a factor, and
a very powerful factor in the evolution of organisms, can no longer be
doubted. Even although we cannot bring forward formal proofs of it _in
detail_, cannot calculate definitely the size of the variations which
present themselves, and their selection-value, cannot, in short,
reduce the whole process to a mathematical formula, yet we must assume
selection, because it is the only possible explanation applicable to
whole classes of phenomena, and because, on the other hand, it is made
up of factors which we know can be proved actually to exist, and
which, _if_ they exist, must of logical necessity coöperate in the
manner required by the theory. _We must accept it because the
phenomena of evolution and adaptation must have a natural basis, and
because it is the only possible explanation of them._[53]

Many people are willing to admit that selection explains adaptations,
but they maintain that only a part of the phenomena are thus
explained, because everything does not depend upon adaptation. They
regard adaptation as, so to speak, a special effort on the part of
Nature, which she keeps in readiness to meet particularly difficult
claims of the external world on organisms. But if we look at the
matter more carefully we shall find that adaptations are by no means
exceptional, but that they are present everywhere in such enormous
numbers, that it would be difficult in regard to any structure
whatever, to prove that adaptation had _not_ played a part in its

How often has the senseless objection been urged against selection
that it can create nothing, it can only reject. It is true that it
cannot create either the living substance or the variations of it;
both must be given. But in rejecting one thing it preserves another,
intensifies it, combines it, and in this way _creates_ what is new.
_Everything_ in organisms depends on adaptation; that is to say,
everything must be admitted through the narrow door of selection,
otherwise it can take no part in the building up of the whole. But, it
is asked, what of the direct effect of external conditions,
temperature, nutrition, climate and the like? Undoubtedly these can
give rise to variations, but they too must pass through the door of
selection, and if they cannot do this they are rejected, eliminated
from the constitution of the species.

It may, perhaps, be objected that such external influences are often
of a compelling power, and that every animal must submit to them, and
that thus selection has no choice and can neither select nor reject.
There may be such cases; let us assume for instance that the effect
of the cold of the Arctic regions was to make all the mammals become
black; the result would be that they would all be eliminated by
selection, and that no mammals would be able to live there at all. But
in most cases a certain percentage of animals resists these strong
influences, and thus selection secures a foothold on which to work,
eliminating the unfavourable variation, and establishing a useful
colouring, consistent with what is required for the maintenance of the

Everything depends upon adaptation! We have spoken much of adaptation
in colouring, in connection with the examples brought into prominence
by Darwin, because these are conspicuous, easily verified, and at the
same time convincing for the theory of selection. But is it only
desert and polar animals whose colouring is determined through
adaptation? Or the leaf-butterflies, and the mimetic species, or the
terrifying markings, and "warning-colours" and a thousand other kinds
of sympathetic colouring? It is, indeed, never the colouring alone
which makes up the adaptation; the structure of the animal plays a
part, often a very essential part, in the protective disguise, and
thus _many_ variations may cooperate towards _one_ common end. And it
is to be noted that it is by no means only external parts that are
changed; internal parts are _always_ modified at the same time--for
instance, the delicate elements of the nervous system on which depend
the _instinct_ of the insect to hold its wings, when at rest, in a
perfectly definite position, which, in the leaf-butterfly, has the
effect of bringing the two pieces on which the marking occurs on the
anterior and posterior wing into the same direction, and thus
displaying as a whole the fine curve of the midrib on the seeming
leaf. But the wing-holding instinct is not regulated in the same way
in all leaf-butterflies; even our indigenous species of Vanessa, with
their protective ground-colouring, have quite a distinctive way of
holding their wings so that the greater part of the anterior wing is
covered by the posterior when the butterfly is at rest. But the
protective colouring appears on the posterior wing and on the tip of
the anterior, _to precisely the distance to which it is left
uncovered_. This occurs, as Standfuss has shown, in different degrees
in our two most nearly allied species, the uncovered portion being
smaller in _V. urticae_ than in _V. polychloros_. In this case, as in
most leaf-butterflies, the holding of the wing was probably the
primary character; only after that was thoroughly established did the
protective marking develop. In any case, the instinctive manner of
holding the wings is associated with the protective colouring, and
must remain as it is if the latter is to be effective. How greatly
instincts may change, that is to say, may be adapted, is shown by the
case of the Noctuid "shark" moth, _Xylina vetusta_. This form bears a
most deceptive resemblance to a piece of rotten wood, and the
appearance is greatly increased by the modification of the innate
impulse to flight common to so many animals, which has here been
transformed into an almost contrary instinct. This moth does not fly
away from danger, but "feigns death," that is, it draws antennae, legs
and wings close to the body, and remains perfectly motionless. It may
be touched, picked up, and thrown down again, and still it does not
move. This remarkable instinct must surely have developed
simultaneously with the wood-colouring; at all events, both
coöperating variations are now present, and prove that both the
external and the most minute internal structure have undergone a
process of adaptation.

The case is the same with all structural variations of animal parts,
which are not absolutely insignificant. When the insects acquired
wings they must also have acquired the mechanism with which to move
them--the musculature, and the nervous apparatus necessary for its
automatic regulation. All instincts depend upon compound reflex
mechanisms and are just as indispensable as the parts they have to set
in motion, and all may have arisen through processes of selection if
the reasons which I have elsewhere given for this view are

Thus there is no lack of adaptations within the organism, and
particularly in its most important and complicated parts, so that we
may say that there is no actively functional organ that has not
undergone a process of adaptation relative to its function and the
requirements of the organism. Not only is every gland structurally
adapted, down to the very minutest histological details, to its
function, but the function is equally minutely adapted to the needs of
the body. Every cell in the mucous lining of the intestine is exactly
regulated in its relation to the different nutritive substances, and
behaves in quite a different way towards the fats, and towards
nitrogenous substances, or peptones.

I have elsewhere called attention to the many adaptations of the whale
to the surrounding medium, and have pointed out--what has long been
known, but is not universally admitted, even now--that in it a great
number of important organs have been transformed in adaptation to the
peculiar conditions of aquatic life, although the ancestors of the
whale must have lived, like other hair-covered mammals, on land. I
cited a number of these transformations--the fish-like form of the
body, the hairlessness of the skin, the transformation of the
fore-limbs to fins, the disappearance of the hind-limbs and the
development of a tail fin, the layer of blubber under the skin, which
affords the protection from cold necessary to a warm-blooded animal,
the disappearance of the ear-muscles and the auditory passages, the
displacement of the external nares to the forehead for the greater
security of the breathing-hole during the brief appearance at the
surface, and certain remarkable changes in the respiratory and
circulatory organs which enable the animal to remain for a long time
under water. I might have added many more, for the list of adaptations
in the whale to aquatic life is by no means exhausted; they are found
in the histological structure and in the minutest combinations in the
nervous system. For it is obvious that a tail-fin must be used in
quite a different way from a tail, which serves as a fly-brush in
hoofed animals, or as an aid to springing in the kangaroo or as a
climbing organ; it will require quite different reflex-mechanisms and
nerve combinations in the motor centres.

I used this example in order to show how unnecessary it is to assume a
special internal evolutionary power for the phylogenesis of species,
for this whole order of whales is, so to speak, _made up of
adaptations_; it deviates in many essential respects from the usual
mammalian type, and all the deviations are adaptations to aquatic
life. But if precisely the most essential features of the organisation
thus depend upon adaptation, what is left for a phyletic force to do,
since it is these essential features of the structure it would have to
determine? There are few people now who believe in a phyletic
evolutionary power, which is not made up of the forces known to
us--adaptation and heredity--but the conviction that _every_ part of
an organism depends upon adaptation has not yet gained a firm footing.
Nevertheless, I must continue to regard this conception as the correct
one, as I have long done.

I may be permitted one more example. The feather of a bird is a
marvellous structure, and no one will deny that as a whole it depends
upon adaptation. But what part of it _does not_ depend upon
adaptation? The hollow quill, the shaft with its hard, thin, light
cortex, and the spongy substance within it, its square section
compared with the round section of the quill, the flat barbs, their
short, hooked barbules which, in the flight-feathers, hook into one
another with just sufficient firmness to resist the pressure of the
air at each wing-beat, the lightness and firmness of the whole
apparatus, the elasticity of the vane, and so on. And yet all this
belongs to an organ which is only passively functional, and therefore
can have nothing to do with the _Lamarckian principle_. Nor can the
feather have arisen through some magical effect of temperature,
moisture, electricity, or specific nutrition, and thus selection is
again our only anchor of safety.

But--it will be objected--the substance of which the feather consists,
this peculiar kind of horny substance, did not first arise through
selection in the course of the evolution of the birds, for it formed
the covering of the scales of their reptilian ancestors. It is quite
true that a similar substance covered the scales of the Reptiles, but
why should it not have arisen among them through selection? Or in what
other way could it have arisen, since scales are also passively useful
parts? It is true that if we are only to call adaptation what has been
acquired by the species we happen to be considering, there would
remain a great deal that could not be referred to selection; but we
are postulating an evolution which has stretched back through aeons,
and in the course of which innumerable adaptations took place, which
had not merely ephemeral persistence in a genus, a family or a class,
but which was continued into whole Phyla of animals, with continual
fresh adaptations to the special conditions of each species, family,
or class, yet with persistence of the fundamental elements. Thus the
feather, once acquired, persisted in all birds, and the vertebral
column, once gained by adaptation in the lowest forms, has persisted
in all the Vertebrates from Amphioxus upwards, although with constant
readaptation to the conditions of each particular group. Thus
everything we can see in animals is adaptation, whether of to-day, or
of yesterday, or of ages long gone by; every kind of cell, whether
glandular, muscular, nervous, epidermic, or skeletal, is adapted to
absolutely definite and specific functions, and every organ which is
composed of these different kinds of cells contains them in the proper
proportions, and in the particular arrangement which best serves the
function of the organ; it is thus adapted to its function.

All parts of the organism are tuned to one another, that is, _they are
adapted to one another_, and in the same way _the organism as a whole
is adapted to the conditions of its life, and it is so at every stage
of its evolution._

But all adaptations _can_ be referred to selection; the only point
that remains doubtful is whether they all _must_ be referred to it.

However that may be, whether the _Lamarckian principle_ is a factor
that has coöperated with selection in evolution, or whether it is
altogether fallacious, the fact remains, that selection is the cause
of a great part of the phyletic evolution of organisms on our earth.
Those who agree with me in rejecting the _Lamarckian principle_ will
regard selection as the only _guiding_ factor in evolution, which
creates what is new out of the transmissible variations, by ordering
and arranging these, selecting them in relation to their number and
size, as the architect does his building-stones so that a particular
style must result.[55] But the building-stones themselves, the
variations, have their basis in the influences which cause variation
in those vital units which are handed on from one generation to
another, whether, taken together they form the _whole_ organism, as in
Bacteria and other low forms of life, or only a germ-substance, as in
unicellular and multicellular organisms.


[Footnote 33: _Vorträge über Descendenztheorie_, Jena, 1904, II. 269.
Eng. Transl. London, 1904, II. p. 317.]

[Footnote 34: See Poulton, _Essays on Evolution_, Oxford, 1908. pp.

[Footnote 35: _Origin of Species_ (6th edit), pp. 176 _et seq._]

[Footnote 36: Chun, _Reise der Valdivia_, Leipzig, 1904.]

[Footnote 37: Plate, _Selektionsprinzip u. Probleme der Artbildung_
(3rd edit.), Leipzig, 1908.]

[Footnote 38: _Studien zur Descendenz-Theorie_ II., "Die Enstehung der
Zeichnung bei den Schmetterlings-raupen," Leipzig, 1876.]

[Footnote 39: _Origin of Species_ (6th edit.), p. 232.]

[Footnote 40: _Origin of Species_, p. 233; see also edit. 1, p. 242.]

[Footnote 41: _Ibid._ p. 230.]

[Footnote 42: _The Effect of External Influences upon Development_,
Romanes Lecture, Oxford, 1894.]

[Footnote 43: See Poulton, _Essays on Evolution_, 1908, pp. 316, 317.]

[Footnote 44: _The Evolution Theory_, London, 1904, I. p. 219.]

[Footnote 45: _Report of the British Association_ (Bristol, 1898),
London, 1899, pp. 906-909.]

[Footnote 46: _Proc. Ent. Soc._, London, May 6, 1903.]

[Footnote 47: _Essays on Evolution_, 1889-1907, Oxford, 1908,
_passim_, e.g. p. 269.]

[Footnote 48: The expression does not refer to all the enemies of this
butterfly; against ichneumon-flies, for instance, their unpleasant
smell usually gives no protection.]

[Footnote 49: Professor Poulton has corrected some wrong descriptions
which I had unfortunately overlooked in the Plates of my book
_Vorträge über Descendenztheorie_, and which refer to _Papilio
dardanus_ (_merope_). These mistakes are of no importance as far as an
understanding of the mimicry-theory is concerned, but I hope shortly
to be able to correct them in a later edition.]

[Footnote 50: _Journ. Linn. Soc. London_ (_Zool._), Vol. xxvi. 1898,
pp. 598-602.]

[Footnote 51: In _Kosmos_, 1879, p. 100.]

[Footnote 52: _Habit and Instinct_, London. 1896.]

[Footnote 53: This has been discussed in many of my earlier works. See
for instance _The All-Sufficiency of Natural Selection, a reply to
Herbert Spencer_, London, 1893.]

[Footnote 54: _The Evolution Theory_, London, 1904, p. 144.]

[Footnote 55: _Variation under Domestication_, 1875, II. pp. 426,




_Professor of Biology in the University of Cambridge_

Darwin's work has the property of greatness in that it may be admired
from more aspects than one. For some the perception of the principle
of Natural Selection stands out as his most wonderful achievement to
which all the rest is subordinate. Others, among whom I would range
myself, look up to him rather as the first who plainly distinguished,
collected, and comprehensively studied that new class of evidence from
which hereafter a true understanding of the process of Evolution may
be developed. We each prefer our own standpoint of admiration; but I
think that it will be in their wider aspect that his labours will most
command the veneration of posterity.

A treatise written to advance knowledge may be read in two moods. The
reader may keep his mind passive, willing merely to receive the
impress of the writer's thought; or he may read with his attention
strained and alert, asking at every instant how the new knowledge can
be used in a further advance, watching continually for fresh footholds
by which to climb higher still. Of Shelley it has been said that he
was a poet for poets: so Darwin was a naturalist for naturalists. It
is when his writings are used in the critical and more exacting spirit
with which we test the outfit for our own enterprise that we learn
their full value and strength. Whether we glance back and compare his
performance with the efforts of his predecessors, or look forward
along the course which modern research is disclosing, we shall honour
most in him not the rounded merit of finite accomplishment, but the
creative power by which he inaugurated a line of discovery endless in
variety and extension. Let us attempt thus to see his work in true
perspective between the past from which it grew, and the present which
is its consequence. Darwin attacked the problem of Evolution by
reference to facts of three classes: Variation; Heredity; Natural
Selection. His work was not as the laity suppose, a sudden and
unheralded revelation, but the first fruit of a long and hitherto
barren controversy. The occurrence of variation from type, and the
hereditary transmission of such variation had of course been long
familiar to practical men, and inferences as to the possible bearing
of those phenomena on the nature of specific difference had been from
time to time drawn by naturalists. Maupertuis, for example, wrote: "Ce
qui nous reste à examiner, c'est comment d'un seul individu, il a pu
naître tant d'espèces si différentes." And again: "La Nature contient
le fonds de toutes ces variétés: mais le hasard ou l'art les mettent
en œuvre. C'est ainsi que ceux dont l'industrie s'applique à
satisfaire le goût des curieux, sont, pour ainsi dire, créateurs
d'espèces nouvelles."[56]

Such passages, of which many (though few so emphatic) can be found in
eighteenth century writers, indicate a true perception of the mode of
Evolution. The speculations hinted at by Buffon,[57] developed by
Erasmus Darwin, and independently proclaimed above all by Lamarck,
gave to the doctrine of descent a wide renown. The uniformitarian
teaching which Lyell deduced from geological observation had gained
acceptance. The facts of geographical distribution[58] had been shown
to be obviously inconsistent with the Mosaic legend. Prichard, and
Lawrence, following the example of Blumenbach, had successfully
demonstrated that the races of Man could be regarded as different
forms of one species, contrary to the opinion up till then received.
These treatises all begin, it is true, with a profound obeisance to
the sons of Noah, but that performed, they continue on strictly modern
lines. The question of the mutability of species was thus prominently

Those who rate Lamarck no higher than did Huxley in his contemptuous
phrase "_buccinator tantum_," will scarcely deny that the sound of the
trumpet had carried far, or that its note was clear. If then there
were few who had already turned to evolution with positive conviction,
all scientific men must at least have known that such views had been
promulgated; and many must, as Huxley says, have taken up his own
position of "critical expectancy."[59]

Why, then, was it, that Darwin succeeded where the rest had failed?
The cause of that success was twofold. First, and obviously, in the
principle of Natural Selection he had a suggestion which would work.
It might not go the whole way, but it was true as far as it went.
Evolution could thus in great measure be fairly represented as a
consequence of demonstrable processes. Darwin seldom endangers the
mechanism he devised by putting on it strains much greater than it can
bear. He at least was under no illusion as to the omnipotence of
Selection; and he introduces none of the forced pleading which in
recent years has threatened to discredit that principle.

For example, in the latest text of the _Origin_[60] we find him

     "But as my conclusions have lately been much misrepresented,
     and it has been stated that I attribute the modification of
     species exclusively to natural selection, I may be permitted
     to remark that in the first edition of this work, and
     subsequently, I placed in a most conspicuous
     position--namely, at the close of the Introduction--the
     following words: 'I am convinced that natural selection has
     been the main but not the exclusive means of modification.'"

But apart from the invention of this reasonable hypothesis, which may
well, as Huxley estimated, "be the guide of biological and
psychological speculation for the next three or four generations,"
Darwin made a more significant and imperishable contribution. Not for
a few generations, but through all ages he should be remembered as the
first who showed clearly that the problems of Heredity and Variation
are soluble by observation, and laid down the course by which we must
proceed to their solution.[61] The moment of inspiration did not come
with the reading of Malthus, but with the opening of the "first
note-book on Transmutation of Species."[62] Evolution is a process of
Variation and Heredity. The older writers, though they had some vague
idea that it must be so, did not study Variation and Heredity. Darwin
did, and so begat not a theory, but a science.

The extent to which this is true, the scientific world is only
beginning to realise. So little was the fact appreciated in Darwin's
own time that the success of his writings was followed by an almost
total cessation of work in that special field. Of the causes which led
to these remarkable consequences I have spoken elsewhere. They
proceeded from circumstances peculiar to the time; but whatever the
causes there is no doubt that this statement of the result is
historically exact, and those who make it their business to collect
facts elucidating the physiology of Heredity and Variation are well
aware that they will find little to reward their quest in the leading
scientific Journals of the Darwinian epoch.

In those thirty years the original stock of evidence current and in
circulation even underwent a process of attrition. As in the story of
the Eastern sage who first wrote the collected learning of the
universe for his sons in a thousand volumes and by successive
compression and burning reduced them to one and from this by further
burning distilled the single ejaculation of the Faith "There is no god
but God and Mohammed is the Prophet of God," which was all his maturer
wisdom deemed essential:--so in the books of that period do we find
the _corpus_ of genetic knowledge dwindle to a few prerogative
instances and these at last to the brief formula of an unquestioned

And yet in all else that concerns biological science this period was,
in very truth, our Golden Age, when the natural history of the earth
was explored as never before; morphology and embryology were
exhaustively ransacked; the physiology of plants and animals began to
rival chemistry and physics in precision of method and in the rapidity
of its advances; and the foundations of pathology were laid.

In contrast with this immense activity elsewhere the neglect which
befel the special physiology of Descent, or Genetics as we now call
it, is astonishing. This may of course be interpreted as meaning that
the favoured studies seemed to promise a quicker return for effort,
but it would be more true to say that those who chose these other
pursuits did so without making any such comparison; for the idea that
the physiology of Heredity and Variation was a coherent science,
offering possibilities of extraordinary discovery, was not present to
their minds at all. In a word, the existence of such a science was
well nigh forgotten. It is true that in ancillary periodicals, as for
example those that treat of entomology or horticulture, or in the
writings of the already isolated systematists,[63] observations with
this special bearing were from time to time related, but the class of
fact on which Darwin built his conceptions of Heredity and Variation
was not seen in the highways of biology. It formed no part of the
official curriculum of biological students, and found no place among
the subjects which their teachers were investigating.

During this period nevertheless one distinct advance was made, that
with which Weismann's name is prominently connected. In Darwin's
genetic scheme the hereditary transmission of parental experience and
its consequences played a considerable role. Exactly how great that
role was supposed to be, he with his habitual caution refrained from
specifying, for the sufficient reason that he did not know.
Nevertheless much of the process of Evolution, especially that by
which organs have become degenerate and rudimentary, was certainly
attributed by Darwin to such inheritance, though since belief in the
inheritance of acquired characters fell into dispute, the fact has
been a good deal overlooked. The _Origin_ without "use and disuse"
would be a materially different book. A certain vacillation is
discernible in Darwin's utterances on this question, and the fact gave
to the astute Butler an opportunity for his most telling attack. The
discussion which best illustrates the genetic views of the period
arose in regard to the production of the rudimentary condition of the
wings of many beetles in the Madeira group of islands, and by
comparing passages from the _Origin_[64] Butler convicts Darwin of
saying first that this condition was in the main the result of
Selection, with disuse aiding, and in another place that the main
cause of degeneration was disuse, but that Selection had aided. To
Darwin however I think the point would have seemed one of dialetics
merely. To him the one paramount purpose was to show that somehow an
Evolution by means of Variation and Heredity might have brought about
the facts observed, and whether they had come to pass in the one way
or the other was a matter of subordinate concern.

To us moderns the question at issue has a diminished significance. For
over all such debates a change has been brought by Weismann's
challenge for evidence that use and disuse have any transmitted
effects at all. Hitherto the transmission of many acquired
characteristics had seemed to most naturalists so obvious as not to
call for demonstration.[65] Weismann's demand for facts in support of
the main proposition revealed at once that none having real cogency
could be produced. The time-honoured examples were easily shown to be
capable of different explanations. A few certainly remain which cannot
be so summarily dismissed, but--though it is manifestly impossible
here to do justice to such a subject--I think no one will dispute that
these residual and doubtful phenomena, whatever be their true nature,
are not of a kind to help us much in the interpretation of any of
those complex cases of adaptation which on the hypothesis of unguided
Natural Selection are especially difficult to understand. Use and
disuse were invoked expressly to help us over these hard places; but
whatever changes can be induced in offspring by direct treatment of
the parents, they are not of a kind to encourage hope of real
assistance from that quarter. It is not to be denied that through the
collapse of this second line of argument the Selection hypothesis has
had to take an increased and perilous burden. Various ways of meeting
the difficulty have been proposed, but these mostly resolve themselves
into improbable attempts to expand or magnify the powers of Natural

Weismann's interpellation, though negative in purpose, has had a
lasting and beneficial effect, for through his thorough demolition of
the old loose and distracting notions of inherited experience, the
ground has been cleared for the construction of a true knowledge of
heredity based on experimental fact.

In another way he made a contribution of a more positive character,
for his elaborate speculations as to the genetic meaning of
cytological appearances have led to a minute investigation of the
visible phenomena occurring in those cell-divisions by which
germ-cells arise. Though the particular views he advocated have very
largely proved incompatible with the observed facts of heredity, yet
we must acknowledge that it was chiefly through the stimulus of
Weismann's ideas that those advances in cytology were made; and though
the doctrine of the continuity of germ-plasm cannot be maintained in
the form originally propounded, it is in the main true and
illuminating.[66] Nevertheless in the present state of knowledge we
are still as a rule quite unable to connect cytological appearances
with any genetic consequences and save in one respect (obviously of
extreme importance--to be spoken of later) the two sets of phenomena
might, for all we can see, be entirely distinct.

I cannot avoid attaching importance to this want of connection between
the nuclear phenomena and the features of bodily organisation. All
attempts to investigate Heredity by cytological means lie under the
disadvantage that it is the nuclear changes which can alone be
effectively observed. Important as they must surely be, I have never
been persuaded that the rest of the cell counts for nothing. What we
know of the behaviour and variability of chromosomes seems in my
opinion quite incompatible with the belief that they alone govern
form, and are the sole agents responsible in heredity.[67]

If, then, progress was to be made in Genetics, work of a different
kind was required. To learn the laws of Heredity and Variation there
is no other way than that which Darwin himself followed, the direct
examination of the phenomena. A beginning could be made by collecting
fortuitous observations of this class, which have often thrown a
suggestive light, but such evidence can be at best but superficial and
some more penetrating instrument of research is required. This can
only be provided by actual experiments in breeding.

The truth of these general considerations was becoming gradually clear
to many of us when in 1900 Mendel's work was rediscovered.
Segregation, a phenomenon of the utmost novelty, was thus revealed.
From that moment not only in the problem of the origin of species, but
in all the great problems of biology a new era began. So unexpected
was the discovery that many naturalists were convinced it was untrue,
and at once proclaimed Mendel's conclusions as either altogether
mistaken, or if true, of very limited application. Many fantastic
notions about the workings of Heredity had been asserted as general
principles before: this was probably only another fancy of the same

Nevertheless those who had a preliminary acquaintance with the facts
of Variation were not wholly unprepared for some such revelation. The
essential deduction from the discovery of segregation was that the
characters of living things are dependent on the presence of definite
elements or factors, which are treated as units in the processes of
Heredity. These factors can thus be recombined in various ways. They
act sometimes separately, and sometimes they interact in conduction
with each other, producing their various effects. All this indicates a
definiteness and specific order in heredity, and therefore in
variation. This order cannot by the nature of the case be dependent on
Natural Selection for its existence, but must be a consequence of the
fundamental chemical and physical nature of living things. The study
of Variation had from the first shown that an orderliness of this kind
was present. The bodies and the properties of livings things are
cosmic, not chaotic. No matter how low in the scale we go, never do we
find the slightest hint of a diminution in that all-pervading
orderliness, nor can we conceive an organism existing for a moment in
any other state. Moreover not only does this order prevail in normal
forms, but again and again it is to be seen in newly-sprung varieties,
which by general consent cannot have been subjected to a prolonged
Selection. The discovery of Mendelian elements admirably coincided
with and at once gave a rationale of these facts. Genetic Variation is
then primarily the consequence of additions to, or omissions from, the
stock of elements which the species contains. The further
investigation of the species-problem must thus proceed by the
analytical method which breeding experiments provide.

In the nine years which have elapsed since Mendel's clue became
generally known, progress has been rapid. We now understand the
process by which a polymorphic race maintains its polymorphism. When a
family consists of dissimilar members, given the numerical proportions
in which these members are occurring, we can represent their
composition symbolically and state what types can be transmitted by
the various members. The difficulty of the "swamping effects of
inter-crossing" is practically at an end. Even the famous puzzle of
sex-limited inheritance is solved, at all events in its more regular
manifestations, and we know now how it is brought about that the
normal sisters of a colour-blind man can transmit the colour-blindness
while his normal brothers cannot transmit it.

We are still only on the fringe of the inquiry. It can be seen
extending and ramifying in many directions. To enumerate these here
would be impossible. A whole new range of possibilities is being
brought into view by study of the inter-relations between the simple
factors. By following up the evidence as to segregation, indications
have been obtained which can only be interpreted as meaning that when
many factors are being simultaneously redistributed among the
germ-cells, certain of them exert what must be described as a
repulsion upon other factors. We cannot surmise whither this discovery
may lead.

In the new light all the old problems wear a fresh aspect. Upon the
question of the nature of Sex, for example, the bearing of Mendelian
evidence is close. Elsewhere I have shown that from several sets of
parallel experiments the conclusion is almost forced upon us that, in
the types investigated, of the two sexes the female is to be regarded
as heterozygous in sex, containing one unpaired dominant element,
while the male is similarly homozygous in the absence of that
element.[68] It is not a little remarkable that on this point--which
is the only one where observations of the nuclear processes of
gameto-genesis have yet been brought into relation with the visible
characteristics of the organisms themselves--there should be
diametrical opposition between the results of breeding experiments and
those derived from cytology.

Those who have followed the researches of the American school will be
aware that, after it had been found in certain insects that the
spermatozoa were of two kinds according as they contained or did not
contain the accessory chromosome, E. B. Wilson succeeded in proving
that the sperms possessing this accessory body were destined to form
_females_ on fertilisation, while sperms without it form males, the
eggs being apparently indifferent. Perhaps the most striking of all
this series of observations is that lately made by T. H. Morgan,[69]
since confirmed by von Baehr, that in a Phylloxeran two kinds of
spermatids are formed, respectively with and without an accessory (in
this case, _double_) chromosome. Of these, only those possessing the
accessory body become functional spermatozoa, the others degenerating.
We have thus an elucidation of the puzzling fact that in these forms
fertilisation results in the formation of _females_ only. How the
males are formed--for of course males are eventually produced by the
parthenogenetic females--we do not know.

If the accessory body is really to be regarded as bearing the factor
for femaleness, then in Mendelian terms female is DD and male is DR.
The eggs are indifferent and the spermatozoa are each male, _or_
female. But according to the evidence derived from a study of the
sex-limited descent of certain features in other animals the
conclusion seems equally clear that in them female must be regarded as
DR and male as RR. The eggs are thus each either male or female and
the spermatozoa are indifferent. How this contradictory evidence is to
be reconciled we do not yet know. The breeding work concerns fowls,
canaries, and the Currant moth (_Abraxas grossulariata_). The
accessory chromosome has been now observed in most of the great
divisions of insects,[70] except, as it happens, Lepidoptera. At first
sight it seems difficult to suppose that a feature apparently so
fundamental as sex should be differently constituted in different
animals, but that seems at present the least improbable inference. I
mention these two groups of facts as illustrating the nature and
methods of modern genetic work. We must proceed by minute and specific
analytical investigation. Wherever we look we find traces of the
operation of precise and specific rules.

In the light of present knowledge it is evident that before we can
attack the Species-problem with any hope of success there are vast
arrears to be made up. He would be a bold man who would now assert
that there was no sense in which the term Species might not have a
strict and concrete meaning in contradistinction to the term Variety.
We have been taught to regard the difference between species and
variety as one of degree. I think it unlikely that this conclusion
will bear the test of further research. To Darwin the question, What
is a variation? presented no difficulties. Any difference between
parent and offspring was a variation. Now we have to be more precise.
First we must, as de Vries has shown, distinguish real, genetic,
variation from _fluctuational_ variations, due to environmental and
other accidents, which cannot be transmitted. Having excluded these
sources of error the variations observed must be expressed in terms of
the factors to which they are due before their significance can be
understood. For example, numbers of the variations seen under
domestication, and not a few witnessed in nature, are simply the
consequence of some ingredient being in an unknown way omitted from
the composition of the varying individual. The variation may on the
contrary be due to the addition of some new element, but to prove that
it is so is by no means an easy matter. Casual observation is useless,
for though these latter variations will always be dominants, yet many
dominant characteristics may arise from another cause, namely the
meeting of complementary factors, and special study of each case in
two generations at least is needed before these two phenomena can be

When such considerations are fully appreciated it will be realised
that medleys of most dissimilar occurrences are all confused together
under the term Variation. One of the first objects of genetic analysis
is to disentangle this mass of confusion.

To those who have made no study of heredity it sometimes appears that
the question of the effect of conditions in causing variation is one
which we should immediately investigate, but a little thought will
show that before any critical inquiry into such possibilities can be
attempted, a knowledge of the working of heredity under conditions as
far as possible uniform must be obtained. At the time when Darwin was
writing, if a plant brought into cultivation gave off an albino
variety, such an event was without hesitation ascribed to the change
of life. Now we see that albino _gametes_, germs, that is to say,
which are destitute of the pigment-forming factor, may have been
originally produced by individuals standing an indefinite number of
generations back in the ancestry of the actual albino, and it is
indeed almost certain that the variation to which the appearance of
the albino is due cannot have taken place in a generation later than
that of the grandparents. It is true that when a new _dominant_
appears we should feel greater confidence that we were witnessing the
original variation, but such events are of extreme rarity, and no such
case has come under the notice of an experimenter in modern times, as
far as I am aware. That they must have appeared is clear enough.
Nothing corresponding to the Brown-breasted Game fowl is known wild,
yet that colour is a most definite dominant, and at some moment since
_Gallus bankiva_ was domesticated, the element on which that special
colour depends must have at least once been formed in the germ-cell of
a fowl; but we need harder evidence than any which has yet been
produced before we can declare that this novelty came through
over-feeding, or change of climate, or any other disturbance
consequent on domestication. When we reflect on the intricacies of
genetic problems as we must now conceive them there come moments when
we feel almost thankful that the Mendelian principles were unknown to
Darwin. The time called for a bold pronouncement, and he made it, to
our lasting profit and delight. With fuller knowledge we pass once
more into a period of cautious expectation and reserve.

In every arduous enterprise it is pleasanter to look back at
difficulties overcome than forward to those which still seem
insurmountable, but in the next stage there is nothing to be stained
by disguising the fact that the attributes of living things are not
what we used to suppose. If they are more complex in the sense that
the properties they display are throughout so regular[71] that the
Selection of minute random variations is an unacceptable account of
the origin of their diversity, yet by virtue of that very regularity
the problem is limited in scope and thus simplified.

To begin with, we must relegate Selection to its proper place.
Selection permits the viable to continue and decides that the
non-viable shall perish; just as the temperature of our atmosphere
decides that no liquid carbon shall be found on the face of the earth:
but we do not suppose that the form of the diamond has been gradually
achieved by a process of Selection. So again, as the course of descent
branches in the successive generations, Selection determines along
which branch Evolution shall proceed, but it does not decide what
novelties that branch shall bring forth. "_La Nature contient le fonds
de toutes ces variétés, mais le hazard ou l'art les mettent en
œuvre_," as Maupertuis most truly said.

Not till knowledge of the genetic properties of organisms has attained
to far greater completeness can evolutionary speculations have more
than a suggestive value. By genetic experiment, cytology and
physiological chemistry aiding, we may hope to acquire such knowledge.
In 1872 Nathusius wrote:[72] "Das Gesetz der Vererbung ist noch nicht
erkannt; der Apfel ist noch nicht vom Baum der Erkenntniss gefallen,
welcher, der Sage nach, Newton auf den rechten Weg zur Ergründung der
Gravitationsgesetze führte." We cannot pretend that the words are not
still true, but in Mendelian analysis the seeds of that apple-tree at
last are sown.

If we were asked what discovery would do most to forward our inquiry,
what one bit of knowledge would more than any other illuminate the
problem, I think we may give the answer without hesitation. The
greatest advance that we can foresee will be made when it is found
possible to connect the geometrical phenomena of development with the
chemical. The geometrical symmetry of living things is the key to a
knowledge of their regularity, and the forces which cause it. In the
symmetry of the dividing cell the basis of that resemblance we call
Heredity is contained. To imitate the morphological phenomena of life
we have to devise a system which can divide. It must be able to
divide, and to segment as--grossly--a vibrating plate or rod does, or
as an icicle can do as it becomes ribbed in a continuous stream of
water; but with this distinction, that the distribution of chemical
differences and properties must simultaneously be decided and disposed
in orderly relation to the pattern of the segmentation. Even if a
model which would do this could be constructed it might prove to be a
useful beginning.

This may be looking too far ahead. If we had to choose some one piece
of more proximate knowledge which we would more especially like to
acquire, I suppose we should ask for the secret of interracial
sterility. Nothing has yet been discovered to remove the grave
difficulty, by which Huxley in particular was so much oppressed, that
among the many varieties produced under domestication--which we all
regard as analogous to the species seen in nature--no clear case of
interracial sterility has been demonstrated. The phenomenon is
probably the only one to which the domesticated products seem to
afford no parallel. No solution of the difficulty can be offered which
has positive value, but it is perhaps worth considering the facts in
the light of modern ideas. It should be observed that we are not
discussing incompatibility of two species to produce offspring (a
totally distinct phenomenon), but the sterility of the offspring which
many of them do produce.

When two species, both perfectly fertile severally, produce on crossing a
sterile progeny, there is a presumption that the sterility is due to the
development in the hybrid of some substance which can only be formed by the
meeting of two complementary factors. That some such account is correct in
essence may be inferred from the well-known observation that if the hybrid
is not totally sterile but only partially so, and thus is able to form some
good germ-cells which develop into new individuals, the sterility of these
daughter-individuals is sensibly reduced or may be entirely absent. The
fertility once re-established, the sterility does not return in the later
progeny, a fact strongly suggestive of segregation. Now if the sterility of
the cross-bred be really the consequence of the meeting of two
complementary factors, we see that the phenomenon could only be produced
among the divergent offspring of one species by the acquisition of at least
_two_ new factors; for if the acquisition of a single factor caused
sterility the line would then end. Moreover each factor must be separately
acquired by distinct individuals, for if both were present together, the
possessors would by hypothesis be sterile. And in order to imitate the case
of species each of these factors must be acquired by distinct breeds. The
factors need not, and probably would not, produce any other perceptible
effects; they might, like the colour-factors present in white flowers, make
no difference in the form or other characters. Not till the cross was
actually made between the two complementary individuals would either factor
come into play, and the effects even then might be unobserved until an
attempt was made to breed from the cross-bred.

Next, if the factors responsible for sterility were acquired, they
would in all probability be peculiar to certain individuals and would
not readily be distributed to the whole breed. Any member of the breed
also into which _both_ the factors were introduced would drop out of
the pedigree by virtue of its sterility. Hence the evidence that the
various domesticated breeds say of dogs or fowls can when mated
together produce fertile offspring, is beside the mark. The real
question is, Do they ever produce sterile offspring? I think the
evidence is clearly that sometimes they do, oftener perhaps than is
commonly supposed. These suggestions are quite amenable to
experimental tests. The most obvious way to begin is to get a pair of
parents which are known to have had any sterile offspring, and to find
the proportions in which these steriles were produced. If, as I
anticipate, these proportions are found to be definite, the rest is

In passing, certain other considerations may be referred to. First,
that there are observations favouring the view that the production of
totally sterile cross-breds is seldom a universal property of two
species, and that it may be a matter of individuals, which is just
what on the view here proposed would be expected. Moreover, as we all
know now, though incompatibility may be dependent to some extent on
the degree to which the species are dissimilar, no such principle can
be demonstrated to determine sterility or fertility in general. For
example, though all our Finches can breed together, the hybrids are
all sterile. Of Ducks some species can breed together without
producing the slightest sterility; others have totally sterile
offspring, and so on. The hybrids between several _genera_ of Orchids
are perfectly fertile on the female side, and some on the male side
also, but the hybrids produced between the Turnip (_Brassica napus_)
and the Swede (_Brassica campestris_), which, according to our
estimates of affinity, should be nearly allied forms, are totally
sterile.[73] Lastly, it may be recalled that in sterility we are
almost certainly considering a meristic phenomenon. _Failure to
divide_ is, we may feel fairly sure, the immediate "cause" of the
sterility. Now, though we know very little about the heredity of
meristic differences, all that we do know points to the conclusion
that the less-divided is dominant to the more-divided, and we are thus
justified in supposing that there are factors which can arrest or
prevent cell-division. My conjecture therefore is that in the case of
sterility of cross-breds we see the effect produced by a complementary
pair of such factors. This and many similar problems are now open to
our analysis.

The question is sometimes asked, Do the new lights on Variation and
Heredity make the process of Evolution easier to understand? On the
whole the answer may be given that they do. There is some appearance
of loss of simplicity, but the gain is real. As was said above, the
time is not ripe for the discussion of the origin of species. With
faith in Evolution unshaken--if indeed the word faith can be used in
application to that which is certain--we look on the manner and
causation of adapted differentiation as still wholly mysterious. As
Samuel Butler so truly said: "To me it seems that the 'Origin of
Variation,' whatever it is, is the only true 'Origin of Species,'"[74]
and of that Origin not one of us knows anything. But given
Variation--and it is given: assuming further that the variations are
not guided into paths of adaptation--and both to the Darwinian and to
the modern school this hypothesis appears to be sound if unproven--an
evolution of species proceeding by definite steps is more, rather than
less, easy to imagine than an evolution proceeding by the accumulation
of indefinite and insensible steps. Those who have lost themselves in
contemplating the miracles of Adaptation (whether real or spurious)
have not unnaturally fixed their hopes rather on the indefinite than
on the definite changes. The reasons are obvious. By suggesting that
the steps through which an adaptative mechanism arose were indefinite
and insensible, all further trouble is spared. While it could be said
that species arise by an insensible and imperceptible process of
variation, there was clearly no use in tiring ourselves by trying to
perceive that process. This labour-saving counsel found great favour.
All that had to be done to develop evolution-theory was to discover
the good in everything, a task which, in the complete absence of any
control or test whereby to check the truth of the discovery, is not
very onerous. The doctrine "_que tout est au mieux_" was therefore
preached with fresh vigour, and examples of that illuminating
principle were discovered with a facility that Pangloss himself might
have envied, till at last even the spectators wearied of such dazzling

But in all seriousness, why should indefinite and unlimited variation
have been regarded as a more probable account of the origin of
Adaptation? Only, I think, because the obstacle was shifted one plane
back, and so looked rather less prominent. The abundance of
Adaptation, we all grant, is an immense, almost an unsurpassable
difficulty in all non-Lamarckian views of Evolution; but if the steps
by which that adaptation arose were fortuitious, to imagine them
insensible is assuredly no help. In one most important respect indeed,
as has often been observed, it is a multiplication of troubles. For
the smaller the steps, the less could Natural Selection act upon them.
Definite variations--and of the occurrence of definite variations in
abundance we have now the most convincing proof--have at least the
obvious merit that they can make and often do make a real difference
in the chances of life.

There is another aspect of the Adaptation problem to which I can
allude very briefly. May not our present ideas of the universality and
precision of Adaptation be greatly exaggerated? The fit of organism to
its environment is not after all so very close--a proposition
unwelcome perhaps, but one which could be illustrated by very copious
evidence. Natural Selection is stern, but she has her tolerant moods.

We have now most certain and irrefragable proof that much definiteness
exists in living things apart from Selection, and also much that may
very well have been preserved and so in a sense constituted by
Selection. Here the matter is likely to rest. There is a passage in
the sixth edition of the _Origin_ which has I think been overlooked.
On page 70 Darwin says, "The tuft of hair on the breast of the wild
turkey-cock cannot be of any use, and it is doubtful whether it can be
ornamental in the eyes of the female bird." This tuft of hair is a
most definite and unusual structure, and I am afraid that the remark
that it "cannot be of any use" may have been made inadvertently; but
it may have been intended, for in the first edition the usual
qualification was given and must therefore have been deliberately
excised. Anyhow I should like to think that Darwin did throw over that
tuft of hair, and that he felt relief when he had done so. Whether
however we have his great authority for such a course or not, I feel
quite sure that we shall be rightly interpreting the facts of nature
if we cease to expect to find purposefulness wherever we meet with
definite structures or patterns. Such things are, as often as not, I
suspect rather of the nature of tool-marks, mere incidents of
manufacture, benefiting their possessor not more than the wire-marks
in a sheet of paper, or the ribbing on the bottom of an oriental plate
renders those objects more attractive in our eyes.

If Variation may be in any way definite, the question once more
arises, may it not be definite in direction? The belief that it is has
had many supporters, from Lamarck onwards, who held that it was guided
by need, and others who, like Nägeli, while laying no emphasis on
need, yet were convinced that there was guidance of some kind. The
latter view under the name of "Orthogenesis," devised I believe by
Eimer, at the present day commends itself to some naturalists. The
objection to such a suggestion is of course that no fragment of real
evidence can be produced in its support. On the other hand, with the
experimental proof that variation consists largely in the unpacking
and repacking of an original complexity, it is not so certain as we
might like to think that the order of these events is not

For instance the original "pack" may have been made in such a way that
at the _n_th division of the germ-cells of a Sweet Pea a colour-factor
might be dropped, and that at the _n_+_n_th division the hooded
variety be given off, and so on. I see no ground whatever for holding
such a view, but in fairness the possibility should not be forgotten,
and in the light of modern research it scarcely looks so absurdly
improbable as before.

No one can survey the work of recent years without perceiving that
evolutionary orthodoxy developed too fast, and that a great deal has
got to come down; but this satisfaction at least remains, that in the
experimental methods which Mendel inaugurated, we have means of
reaching certainty in regard to the physiology of Heredity and
Variation upon which a more lasting structure may be built.


[Footnote 56: _Vénus Physique, contenant deux Dissertations, l'une sur
l'origine des Hommes et des Animaux_; _Et l'autre sur l'origine des
Noirs_, La Haye, 1746, pp. 124 and 129. For an introduction to the
writings of Maupertuis I am indebted to an article by Professor
Lovejoy in _Popular Sci. Monthly_, 1902.]

[Footnote 57: For the fullest account of the views of these pioneers
of Evolution, see the works of Samuel Butler, especially _Evolution,
Old and New_ (2nd edit.) 1882. Butler's claims on behalf of Buffon
have met with some acceptance; but after reading what Butler has said,
and a considerable part of Buffon's own works, the word "hinted" seems
to me a sufficiently correct description of the part he played. It is
interesting to note that in the chapter on the Ass, which contains
some of his evolutionary passages, there is a reference to "_plusieurs
idées très-élevées sur la génération_" contained in the Letters of

[Footnote 58: See especially W. Lawrence, _Lectures on Physiology_,
London, 1823, pp. 213 f.]

[Footnote 59: See the chapter contributed to the _Life and Letters of
Charles Darwin_, II. p. 195. I do not clearly understand the sense in
which Darwin wrote (Autobiography, _ibid._ I. p. 87): "It has
sometimes been said that the success of the _Origin_ proved 'that the
subject was in the air,' or 'that men's minds were prepared for it.' I
do not think that this is strictly true, for I occasionally sounded
not a few naturalists, and never happened to come across a single one
who seemed to doubt about the permanence of species." This experience
may perhaps have been an accident due to Darwin's isolation. The
literature of the period abounds with indications of "critical
expectancy." A most interesting expression of that feeling is given in
the charming account of the "Early Days of Darwinism" by Alfred
Newton, _Macmillan's Magazine_, LVII. 1888, p. 241. He tells how in
1858 when spending a dreary summer in Iceland, he and his friend, the
ornithologist John Wolley, in default of active occupation, spent
their days in discussion. "Both of us taking a keen interest in
Natural History, it was but reasonable that a question, which in those
days was always coming up wherever two or more naturalists were
gathered together, should be continually recurring. That question was,
'What is a species?' and connected therewith was the other question,
'How did a species begin?'... Now we were of course fairly well
acquainted with what had been published on these subjects." He then
enumerates some of these publications, mentioning among others T.
Vernon Wollaston's _Variation of Species_--a work which has in my
opinion never been adequately appreciated. He proceeds: "Of course we
never arrived at anything like a solution of these problems, general
or special, but we felt very strongly that a solution ought to be
found, and that quickly, if the study of Botany and Zoology was to
make any great advance." He then describes how on his return home he
received the famous number of the _Linnean Journal_ on a certain
evening. "I sat up late that night to read it; and never shall I
forget the impression it made upon me. Herein was contained a
perfectly simple solution of all the difficulties which had been
troubling me for months past.... I went to bed satisfied that a
solution had been found."]

[Footnote 60: _Origin_, 6th edit. (1882), p. 421.]

[Footnote 61: Whatever be our estimate of the importance of Natural
Selection, in this we all agree. Samuel Butler, the most brilliant,
and by far the most interesting of Darwin's opponents--whose works are
at length emerging from oblivion--in his Preface (1882) to the 2nd
edition of _Evolution, Old and New_, repeats his earlier expression of
homage to one whom he had come to regard as an enemy: "To the end of
time, if the question be asked, 'Who taught people to believe in
Evolution?' the answer must be that it was Mr. Darwin. This is true,
and it is hard to see what palm of higher praise can be awarded to any

[Footnote 62: _Life and Letters_, I. pp. 276 and 83.]

[Footnote 63: This isolation of the systematists is the one most
melancholy sequela of Darwinism. It seems an irony that we should read
in the peroration to the _Origin_ that when the Darwinian view is
accepted "Systematists will be able to pursue their labours as at
present; but they will not be incessantly haunted by the shadowy doubt
whether this or that form be a true species. This, I feel sure, and I
speak after experience, will be no slight relief. The endless disputes
whether or not some fifty species of British brambles are good species
will cease." _Origin_, 6th edit. (1882), p. 425. True they have ceased
to attract the attention of those who lead opinion, but anyone who
will turn to the literature of systematics will find that they have
not ceased in any other sense. Should there not be something
disquieting in the fact that among the workers who come most into
contact with specific differences, are to be found the only men who
have failed to be persuaded of the unreality of those differences?]

[Footnote 64: 6th edit. pp. 109 and 401. See Butler, _Essays on Life,
Art, and Science_, p. 265, reprinted 1908, and _Evolution, Old and
New_, chap. XXII. (2nd edit.), 1882.]

[Footnote 65: W. Lawrence was one of the few who consistently
maintained the contrary opinion. Prichard, who previously had
expressed himself in the same sense, does not, I believe, repeat these
views in his later writings, and there are signs that he came to
believe in the transmission of acquired habits. See Lawrence, _Lect.
Physiol._ 1823, pp. 436-437, 447. Prichard, Edin. Inaug. Disp. 1808
[not seen by me], quoted _ibid._ and _Nat. Hist. Man_, 1843, pp. 34

[Footnote 66: It is interesting to see how nearly Butler was led by
natural penetration, and from absolutely opposite conclusions, back to
this underlying truth: "So that each ovum when impregnate should be
considered not as descended from its ancestors, but as being a
continuation of the personality of every ovum in the chain of its
ancestry, which every ovum _it actually is_ quite as truly as the
octogenarian _is_ the same identity with the ovum from which he has
been developed. This process cannot stop short of the primordial cell,
which again will probably turn out to be but a brief resting-place. We
therefore prove each one of us to _be actually_ the primordial cell
which never died nor dies, but has differentiated itself into the life
of the world, all living beings whatever, being one with it and
members one of another," _Life and Habit_, 1878, p. 86.]

[Footnote 67: This view is no doubt contrary to the received opinion.
I am however interested to see it lately maintained by Driesch
(_Science and Philosophy of the Organism_, London, 1907, p. 233), and
from the recent observations of Godlewski it has received distinct
experimental support.]

[Footnote 68: In other words, the ova are each _either_ female, _or
male_ (i.e. non-female), but the sperms are all non-female.]

[Footnote 69: Morgan, _Proc. Soc. Exp. Biol. Med._ V. 1908, and von
Baehr, _Zool. Anz._ XXXII. p. 507, 1908.]

[Footnote 70: As Wilson has proved, the unpaired body is not a
universal feature even in those orders in which it has been observed.
Nearly allied types may differ. In some it is altogether unpaired. In
others it is paired with a body of much smaller size, and by selection
of various types all gradations can be demonstrated ranging to the
condition in which the members of the pair are indistinguishable from
each other.]

[Footnote 71: I have in view, for example, the marvellous and specific
phenomena of regeneration, and those discovered by the students of
"_Entwicklungsmechanik_." The circumstances of its occurrence here
preclude any suggestion that this regularity has been brought about by
the workings of Selection. The attempts thus to represent the
phenomena have resulted in mere parodies of scientific reasoning.]

[Footnote 72: _Vorträge über Viehzucht und Rassenerkenntniss_, p. 120,
Berlin, 1872.]

[Footnote 73: See Sutton, A. W., _Journ. Linn. Soc._ XXXVIII. p. 341,

[Footnote 74: _Life and Habit_, London, p. 263, 1878]




_Professor of Anatomy in the University of Strassburg_

The problem of the origin of the human race, of the descent of man, is
ranked by Huxley in his epoch-making book _Man's Place in Nature_, as
the deepest with which biology has to concern itself, "the question of
questions,"--the problem which underlies all others. In the same
brilliant and lucid exposition, which appeared in 1863, soon after the
publication of Darwin's _Origin of Species_, Huxley stated his own
views in regard to this great problem. He tells us how the idea of a
natural descent of man gradually grew up in his mind. It was
especially the assertions of Owen in regard to the total difference
between the human and the simian brain that called forth strong
dissent from the great anatomist Huxley, and he easily succeeded in
showing that Owen's supposed differences had no real existence; he
even established, on the basis of his own anatomical investigations,
the proposition that the anatomical differences between the Marmoset
and the Chimpanzee are much greater than those between the Chimpanzee
and Man.

But why do we thus introduce the study of Darwin's _Descent of Man_,
which is to occupy us here, by insisting on the fact that Huxley had
taken the field in defence of the descent of man in 1863, while
Darwin's book on the subject did not appear till 1871? It is in order
that we may clearly understand how it happened that from this time
onwards Darwin and Huxley followed the same great aim in the most
intimate association.

Huxley and Darwin working at the same _Problema maximum_! Huxley
fiery, impetuous, eager for battle, contemptuous of the resistance of
a dull world, or energetically triumphing over it. Darwin calm,
weighing every problem slowly, letting it mature thoroughly,--not a
fighter, yet having the greater and more lasting influence by virtue
of his immense mass of critically sifted proofs. Darwin's friend,
Huxley, was the first to do him justice, to understand his nature, and
to find in it the reason why the detailed and carefully considered
book on the descent of man made its appearance so late. Huxley, always
generous, never thought of claiming priority for himself. In
enthusiastic language he tells how Darwin's immortal work, _The Origin
of Species_, first shed light for him on the problem of the descent of
man; the recognition of a _vera causa_ in the transformation of
species illuminated his thoughts as with a flash. He was now content
to leave what perplexed him, what he could not yet solve, as he says
himself, "in the mighty hands of Darwin." Happy in the bustle of
strife against old and deep-rooted prejudices, against intolerance and
superstition, he wielded his sharp weapons on Darwin's behalf; wearing
Darwin's armour he joyously overthrew adversary after adversary.
Darwin spoke of Huxley as his "general agent."[75] Huxley says of
himself "I am Darwin's bulldog."[76]

Thus Huxley openly acknowledged that it was Darwin's _Origin of
Species_ that first set the problem of the descent of man in its true
light, that made the question of the origin of the human race a
pressing one. That this was the logical consequence of his book Darwin
himself had long felt. He had been reproached with intentionally
shirking the application of his theory to Man. Let us hear what he
says on this point in his autobiography: "As soon as I had become, in
the year 1837 or 1838, convinced that species were mutable
productions, I could not avoid the belief that man must come under the
same law. Accordingly I collected notes on the subject for my own
satisfaction, and not for a long time with any intention of
publishing. Although in the 'Origin of Species' the derivation of any
particular species is never discussed, yet I thought it best, in order
_that no honourable man should accuse me of concealing my views_,[77]
to add that by the work 'light would be thrown on the origin of man
and his history.' It would have been useless and injurious to the
success of the book to have paraded, without giving any evidence, my
conviction with respect to his origin."[78]

In a letter written in January, 1860, to the Rev. L. Blomefield,
Darwin expresses himself in similar terms. "With respect to man, I am
very far from wishing to obtrude my belief; but I thought it dishonest
to quite conceal my opinion."[79]

The brief allusion in the _Origin of Species_ is so far from prominent
and so incidental that it was excusable to assume that Darwin had not
touched upon the descent of man in this work. It was solely the desire
to have his mass of evidence sufficiently complete, solely Darwin's
great characteristic of never publishing till he had carefully weighed
all aspects of his subject for years, solely, in short, his most
fastidious scientific conscience that restrained him from challenging
the world in 1859 with a book in which the theory of the descent of
man was fully set forth. Three years, frequently interrupted by
ill-health, were needed for the actual writing of the book:[80] the
first edition, which appeared in 1871, was followed in 1874 by a much
improved second edition, the preparation of which he very reluctantly

This, briefly, is the history of the work, which, with the _Origin of
Species_, marks an epoch in the history of biological sciences--the
work with which the cautious, peace-loving investigator ventured forth
from his contemplative life into the arena of strife and unrest, and
laid himself open to all the annoyances that deep-rooted belief and
prejudice, and the prevailing tendency of scientific thought at the
time could devise.

Darwin did not take this step lightly. Of great interest in this
connection is a letter written to Wallace on Dec. 22, 1857,[82] in
which he says, "You ask me whether I shall discuss 'man.' I think I
shall avoid the whole subject, as so surrounded with prejudices;
though I fully admit that it is the highest and most interesting
problem for the naturalist." But his conscientiousness compelled him
to state briefly his opinion on the subject in the _Origin of Species_
in 1859. Nevertheless he did not escape reproaches for having been so
reticent. This is unmistakably apparent from a letter to Fritz Müller
dated Feb. 22 [1869?], in which he says: "I am thinking of writing a
little essay on the Origin of Mankind, as I have been taunted with
concealing my opinions."[83]

It might be thought that Darwin behaved thus hesitatingly, and was so
slow in deciding on the full publication of his collected material in
regard to the descent of man, because he had religious difficulties to

But this was not the case, as we can see from his admirable confession
of faith, the publication of which we owe to his son Francis.[84]
Whoever wishes really to understand the lofty character of this great
man should read these immortal lines in which he unfolds to us in
simple and straightforward words the development of his conception of
the universe. He describes how, though he was still quite orthodox
during his voyage round the world on board the _Beagle_, he came
gradually to see, shortly afterwards (1836-1839) that the Old
Testament was no more to be trusted than the Sacred Books of the
Hindoos; the miracles by which Christianity is supported, the
discrepancies between the accounts in the different Gospels, gradually
led him to disbelieve in Christianity as a divine revelation. "Thus,"
he writes,[85] "disbelief crept over me at a very slow rate, but was
at last complete. The rate was so slow that I felt no distress." But
Darwin was too modest to presume to go beyond the limits laid down by
science. He wanted nothing more than to be able to go, freely and
unhampered by belief in authority or in the Bible, as far as human
knowledge could lead him. We learn this from the concluding words of
his chapter on religion "The mystery of the beginning of all things is
insoluble by us; and I for one must be content to remain an

Darwin was always very unwilling to give publicity to his views in
regard to religion. In a letter to Asa Gray on May 22, 1860,[87] he
declares that it is always painful to him to have to enter into
discussion of religious problems. He had, he said, no intention of
writing atheistically.

Finally, let us cite one characteristic sentence from a letter from
Darwin to C. Ridley[88] (Nov. 28, 1878). A clergyman, Dr. Pusey, had
asserted that Darwin had written the _Origin of Species_ with some
relation to theology. Darwin writes emphatically, "Many years ago when
I was collecting facts for the 'Origin,' my belief in what is called a
personal God was as firm as that of Dr. Pusey himself, and as to the
eternity of matter I never troubled myself about such insoluble
questions." The expression "many years ago" refers to the time of his
voyage round the world, as has already been pointed out. Darwin means
by this utterance that the views which had gradually developed in his
mind in regard to the origin of species were quite compatible with the
faith of the Church.

If we consider all these utterances of Darwin in regard to religion
and to his outlook on life (Weltanschauung), we shall see at least so
much, that religious reflection could in no way have influenced him in
regard to the writing and publishing of his book on _The Descent of
Man_. Darwin had early won for himself freedom of thought, and to this
freedom he remained true to the end of his life, uninfluenced by the
customs and opinions of the world around him.

Darwin was thus inwardly fortified and armed against the host of
calumnies, accusations, and attacks called forth by the publication of
the _Origin of Species_, and to an even greater extent by the
appearance of the _Descent of Man_. But in his defence he could rely
on the aid of a band of distinguished auxiliaries of the rarest
ability. His faithful confederate, Huxley, was joined by the botanist
Hooker, and, after longer resistance, by the famous geologist Lyell,
whose "conversion" afforded Darwin peculiar satisfaction. All three
took the field with enthusiasm in defence of the natural descent of
man. From Wallace, on the other hand, though he shared with him the
idea of natural selection, Darwin got no support in this matter.
Wallace expressed himself in a strange manner. He admitted everything
in regard to the morphological descent of man, but maintained, in a
mystic way, that something else, something of a spiritual nature must
have been added to what man inherited from his animal ancestors.
Darwin, whose esteem for Wallace was extraordinarily high, could not
understand how he could give utterance to such a mystical view in
regard to man; the idea seemed to him so "incredibly strange" that he
thought some one else must have added these sentences to Wallace's

Even now there are thinkers who, like Wallace, shrink from applying to
man the ultimate consequences of the theory of descent. The idea that
man is derived from ape-like forms is to them unpleasant and

So far I have been depicting the development of Darwin's work on the
descent of man. In what follows I shall endeavour to give a condensed
survey of the contents of the book.

It must at once be said that the contents of Darwin's work fall into
two parts, dealing with entirely different subjects. _The Descent of
Man_ includes a very detailed investigation in regard to secondary
sexual characters in the animal series, and on this investigation
Darwin founded a new theory, that of sexual selection. With
astonishing patience he gathered together an immense mass of material,
and showed, in regard to Arthropods and Vertebrates, the wide
distribution of secondary characters, which develop almost exclusively
in the male, and which enable him, on the one hand, to get the better
of his rivals in the struggle for the female by the greater perfection
of his weapons, and, on the other hand, to offer greater allurements
to the female through the higher development of decorative characters,
of song, or of scent-producing glands. The best equipped males will
thus crowd out the less well-equipped in the matter of reproduction,
and thus the relevant characters will be increased and perfected
through sexual selection. It is, of course, a necessary assumption
that these secondary sexual characters may be transmitted to the
female, although perhaps in rudimentary form.

As we have said, this story of sexual selection takes up a great deal
of space in Darwin's book, and it need only be considered here in so
far as Darwin applied it to the descent of man. To this latter problem
the whole of Part I is devoted, while Part III contains a discussion
of sexual selection in relation to man, and a general summary. Part
II treats of sexual selection in general, and may be disregarded in
our present study. Moreover, many interesting details must necessarily
be passed over in what follows, for want of space.

The first part of the _Descent of Man_ begins with an enumeration of
the proofs of the animal descent of man taken from the structure of
the human body. Darwin chiefly emphasises the fact that the human body
consists of the same organs and of the same tissues as those of the
other mammals; he shows also that man is subject to the same diseases
and tormented by the same parasites as the apes. He further dwells on
the general agreement exhibited by young embryonic forms, and he
illustrates this by two figures placed one above the other, one
representing a human embryo, after Ecker, the other a dog embryo,
after Bischoff.[89]

Darwin finds further proofs of the animal origin of man in the reduced
structures, in themselves extremely variable, which are either
absolutely useless to their possessors, or of so little use that they
could never have developed under existing conditions. Of such vestiges
he enumerates: the defective development of the _panniculus carnosus_
(muscle of the skin) so widely distributed among mammals, the
ear-muscles, the occasional persistence of the animal ear-point in
man, the rudimentary nictitating membrane (_plica semilunaris_) in the
human eye, the slight development of the organ of smell, the general
hairiness of the human body, the frequently defective development or
entire absence of the third molar (the wisdom tooth), the vermiform
appendix, the occasional reappearance of a bony canal (_foramen
supracondyloideum_) at the lower end of the humerus, the rudimentary
tail of man (the so-called taillessness), and so on. Of these
rudimentary structures the occasional occurrence of the animal
ear-point in man is most fully discussed. Darwin's attention was
called to this interesting structure by the sculptor Woolner. He
figures such a case observed in man, and also the head of an alleged
orang-foetus, the photograph of which he received from Nitsche.

Darwin's interpretation of Woolner's case as having arisen through a
folding over of the free edge of a pointed ear has been fully borne
out by my investigations on the external ear.[90] In particular, it
was established by these investigations that the human foetus, about
the middle of its embryonic life, possesses a pointed ear somewhat
similar to that of the monkey genus Macacus. One of Darwin's
statements in regard to the head of the orang-foetus must be
corrected. A _large_ ear with a point is shown in the photograph,[91]
but it can easily be demonstrated--and Deniker has already pointed
this out--that the figure is not that of an orang foetus at all, for
that form has much smaller ears with no point; nor can it be a
gibbon-foetus, as Deniker supposes, for the gibbon ear is also without
a point. I myself regard it as that of a Macacus-embryo. But this
mistake, which is due to Nitsche, in no way affects the fact
recognised by Darwin, that ear-forms showing the point characteristic
of the animal ear occur in man with extraordinary frequency.

Finally, there is a discussion of those rudimentary structures which
occur only in _one_ sex, such as the rudimentary mammary glands in the
male, the vesicula prostatica, which corresponds to the uterus of the
female, and others. All these facts tell in favour of the common
descent of man and all other vertebrates. The conclusion of this
section is characteristic: "_It is only our natural prejudice, and
that arrogance which made our forefathers declare that they were
descended from demi-gods, which leads us to demur to this conclusion.
But the time will before long come, when it will be thought wonderful
that naturalists, who were well acquainted with the comparative
structure and development of man, and other mammals, should have
believed that each was the work of a separate act of creation._"[92]

In the second chapter there is a more detailed discussion, again based
upon an extraordinary wealth of facts, of the problem as to the manner
in which, and the causes through which, man evolved from a lower form.
Precisely the same causes are here suggested for the origin of man, as
for the origin of species in general. Variability, which is a
necessary assumption in regard to all transformations, occurs in man
to a high degree. Moreover, the rapid multiplication of the human race
creates conditions which necessitate an energetic struggle for
existence, and thus afford scope for the intervention of natural
selection. Of the exercise of _artificial_ selection in the human
race, there is nothing to be said, unless we cite such cases as the
grenadiers of Frederick William I, or the population of ancient
Sparta. In the passages already referred to and in those which follow,
the transmission of acquired characters, upon which Darwin does not
dwell, is taken for granted. In man, direct effects of changed
conditions can be demonstrated (for instance in regard to bodily
size), and there are also proofs of the influence exerted on his
physical constitution by increased use or disuse. Reference is here
made to the fact, established by Forbes, that the Quechua Indians of
the high plateaus of Peru show a striking development of lungs and
thorax, as a result of living constantly at high altitudes.

Such special forms of variation as arrests of development
(microcephalism) and reversion to lower forms are next discussed.
Darwin himself felt[93] that these subjects are so nearly related to
the cases mentioned in the first chapter, that many of them might as
well have been dealt with there. It seems to me that it would have
been better so, for the citation of additional instances of reversion
at this place rather disturbs the logical sequence of his ideas as to
the conditions which have brought about the evolution of man from
lower forms. The instances of reversion here discussed are
microcephalism, which Darwin wrongly interpreted as atavistic,
supernumerary mammae, supernumerary digits, bicornuate uterus, the
development of abnormal muscles, and so on. Brief mention is also made
of correlative variations observed in man.

Darwin next discusses the question as to the manner in which man
attained to the erect position from the state of a climbing quadruped.
Here again he puts the influence of Natural Selection in the first
rank. The immediate progenitors of man had to maintain a struggle for
existence in which success was to the more intelligent, and to those
with social instincts. The hand of these climbing ancestors, which had
little skill and served mainly for locomotion, could only undergo
further development when some early member of the Primate series came
to live more on the ground and less among trees.

A bipedal existence thus became possible, and with it the liberation
of the hand from locomotion, and the one-sided development of the
human foot. The upright position brought about correlated variations
in the bodily structure; with the free use of the hand it became
possible to manufacture weapons and to use them; and this again
resulted in a degeneration of the powerful canine teeth and the jaws,
which were then no longer necessary for defence. Above all, however,
the intelligence immediately increased, and with it skull and brain.
The nakedness of man, and the absence of a tail (rudimentariness of
the tail vertebrae) are next discussed. Darwin is inclined to
attribute the nakedness of man, not to the action of natural selection
on ancestors who originally inhabited a tropical land, but to sexual
selection, which, for aesthetic reasons, brought about the loss of the
hairy covering in man, or primarily in woman. An interesting
discussion of the loss of the tail, which, however, man shares with
the anthropoid apes, some other monkeys and lemurs, forms the
conclusion of the almost superabundant material which Darwin worked
up in the second chapter. His object was to show that some of the most
distinctive human characters are in all probability directly or
indirectly due to natural selection. With characteristic modesty he
adds:[94] "Hence, if I have erred in giving to natural selection great
power, which I am very far from admitting, or in having exaggerated
its power, which is in itself probable, I have at least, as I hope,
done good service in aiding to overthrow the dogma of separate
creations." At the end of the chapter he touches upon the objection as
to man's helpless and defenceless condition. Against this he urges his
intelligence and social instincts.

The two following chapters contain a detailed discussion of the
objections drawn from the supposed great differences between the
mental powers of men and animals. Darwin at once admits that the
differences are enormous, but not that any fundamental difference
between the two can be found. Very characteristic of him is the
following passage: "In what manner the mental powers were first
developed in the lowest organisms, is as hopeless an enquiry as how
life itself first originated. These are problems for the distant
future, if they are ever to be solved by man."[95]

After some brief observations on instinct and intelligence, Darwin
brings forward evidence to show that the greater number of the
emotional states, such as pleasure and pain, happiness and misery,
love and hate are common to man and the higher animals. He goes on to
give various examples showing that wonder and curiosity, imitation,
attention, memory and imagination (dreams of animals), can also be
observed in the higher mammals, especially in apes. In regard even to
reason there are no sharply defined limits. A certain faculty of
deliberation is characteristic of some animals, and the more
thoroughly we know an animal the more intelligence we are inclined to
credit it with. Examples are brought forward of the intelligent and
deliberate actions of apes, dogs and elephants. But although no
sharply defined differences exist between man and animals, there is,
nevertheless, a series of other mental powers which are
characteristics usually regarded as absolutely peculiar to man. Some
of these characteristics are examined in detail, and it is shown that
the arguments drawn from them are not conclusive. Man alone is said to
be capable of progressive improvement; but against this must be placed
as something analogous in animals, the fact that they learn cunning
and caution through long continued persecution. Even the use of tools
is not in itself peculiar to man (monkeys use sticks, stones and
twigs), but man alone fashions and uses implements _designed for a
special purpose_. In this connection the remarks taken from Lubbock in
regard to the origin and gradual development of the earliest flint
implements will be read with interest; these are similar to the
observations on modern eoliths, and their bearing on the development
of the stone industry. It is interesting to learn from a letter to
Hooker,[96] that Darwin himself at first doubted whether the stone
implements discovered by Boucher de Perthes were really of the nature
of tools. With the relentless candour as to himself which
characterised him, he writes four years later in a letter to Lyell in
regard to this view of Boucher de Perthes' discoveries: "I know
something about his errors, and looked at his book many years ago, and
am ashamed to think that I concluded the whole was rubbish! Yet he has
done for man something like what Agassiz did for glaciers."[97]

To return to Darwin's further comparisons between the higher mental powers
of man and animals; He takes much of the force from the argument that man
alone is capable of abstraction and self-consciousness by his own
observations on dogs. One of the main differences between man and animals,
speech, receives detailed treatment. He points out that various animals
(birds, monkeys, dogs) have a large number of different sounds for
different emotions, that, further, man produces in common with animals a
whole series of inarticulate cries combined with gestures, and that dogs
learn to understand whole sentences of human speech. In regard to human
language, Darwin expresses a view contrary to that held by Max Müller:[98]
"I cannot doubt that language owes its origin to the imitation and
modification of various natural sounds, the voices of other animals, and
man's own instinctive cries, aided by signs and gestures." The development
of actual language presupposes a higher degree of intelligence than is
found in any kind of ape. Darwin remarks on this point:[99] "The fact of
the higher apes not using their vocal organs for speech no doubt depends on
their intelligence not having been sufficiently advanced."

The sense of beauty, too, has been alleged to be peculiar to man. In
refutation of this assertion Darwin points to the decorative colours
of birds, which are used for display. And to the last objection, that
man alone has religion, that he alone has a belief in God, it is
answered "that numerous races have existed, and still exist, who have
no idea of one or more gods, and who have no words in their languages
to express such an idea."[100]

The result of the investigations recorded in this chapter is to show
that, great as the difference in mental powers between man and the
higher animals may be, it is undoubtedly only a difference "of degree
and not of kind."[101]

In the fourth chapter Darwin deals with the _moral sense_ or
_conscience_, which is the most important of all differences between
man and animals. It is a result of social instincts, which lead to
sympathy for other members of the same society, to non-egoistic
actions for the good of others. Darwin shows that social tendencies
are found among many animals, and that among these love and
kin-sympathy exist, and he gives examples of animals (especially dogs)
which may exhibit characters that we should call moral in man (e.g.
disinterested self-sacrifice for the sake of others). The early
ape-like progenitors of the human race were undoubtedly social. With
the increase of intelligence the moral sense develops farther; with
the acquisition of speech public opinion arises, and finally, moral
sense becomes habit. The rest of Darwin's detailed discussions on
moral philosophy may be passed over.

The fifth chapter may be very briefly summarised. In it Darwin shows
that the intellectual and moral faculties are perfected through
natural selection. He inquires how it can come about that a tribe at a
low level of evolution attains to a higher, although the best and
bravest among them often pay for their fidelity and courage with their
lives without leaving any descendants. In this case it is the
sentiment of glory, praise and blame, the admiration of others, which
bring about the increase of the better members of the tribe. Property,
fixed dwellings, and the association of families into a community are
also indispensable requirements for civilisation. In the longer second
section of the fifth chapter Darwin acts mainly as recorder. On the
basis of numerous investigations, especially those of Greg, Wallace,
and Galton, he inquires how far the influence of natural selection can
be demonstrated in regard to civilised nations. In the final section,
which deals with the proofs that all civilised nations were once
barbarians, Darwin again uses the results gained by other
investigators, such as Lubbock and Tylor. There are two sets of facts
which prove the proposition in question. In the first place, we find
traces of a former lower state in the customs and beliefs of all
civilised nations, and in the second place, there are proofs to show
that savage races are independently able to raise themselves a few
steps in the scale of civilisation, and that they have thus raised

In the sixth chapter of the work, Morphology comes into the foreground
once more. Darwin first goes back, however, to the argument based on
the great difference between the mental powers of the highest animals
and those of man. That this is only quantitative, not qualitative, he
has already shown. Very instructive in this connection is the
reference to the enormous difference in mental powers in another
class. No one would draw from the fact that the cochineal insect
(Coccus) and the ant exhibit enormous differences in their mental
powers, the conclusion that the ant should therefore be regarded as
something quite distinct, and withdrawn from the class of insects

Darwin next attempts to establish the _specific_ genealogical tree of
man, and carefully weighs the differences and resemblances between the
different families of the Primates. The erect position of man is an
adaptive character, just as are the various characters referable to
aquatic life in the seals, which, notwithstanding these, are ranked as
a mere family of the carnivores. The following utterance is very
characteristic of Darwin:[102] "If man had not been his own
classifier, he would never have thought of founding a separate order
for his own reception." In numerous characters not mentioned in
systematic works, in the features of the face, in the form of the
nose, in the structure of the external ear, man resembles the apes.
The arrangement of the hair in man has also much in common with the
apes; as also the occurrence of hair on the forehead of the human
embryo, the beard, the convergence of the hair of the upper and under
arm towards the elbow, which occurs not only in the anthropoid apes,
but also in some American monkeys. Darwin here adopts Wallace's
explanation of the origin of the ascending direction of the hair in
the forearm of the orang,--that it has arisen through the habit of
holding the hands over the head in rain. But this explanation cannot
be maintained when we consider that this disposition of the hair is
widely distributed among the most different mammals, being found in
the dog, in the sloth, and in many of the lower monkeys.

After further careful analysis of the anatomical characters Darwin
reaches the conclusion that the New World monkeys (Platyrrhine) may be
excluded from the genealogical tree altogether, but that man is an
offshoot from the Old World monkeys (Catarrhine) whose progenitors
existed as far back as the Miocene period. Among these Old World
monkeys the forms to which man shows the greatest resemblance are the
anthropoid apes, which, like him, possess neither tail nor ischial
callosities. The platyrrhine and catarrhine monkeys have their
primitive ancestor among extinct forms of the Lemuridae. Darwin also
touches on the question of the original home of the human race and
supposes that it may have been in Africa, because it is there that
man's nearest relatives, the gorilla and the chimpanzee, are found.
But he regards speculation on this point as useless. It is remarkable
that, in this connection, Darwin regards the loss of the hair-covering
in man as having some relation to a warm climate, while elsewhere he
is inclined to make sexual selection responsible for it. Darwin
recognises the great gap between man and his nearest relatives, but
similar gaps exist at other parts of the mammalian genealogical tree:
the allied forms have become extinct. After the extermination of the
lower races of mankind, on the one hand, and of the anthropoid apes on
the other, which will undoubtedly take place, the gulf will be greater
than ever, since the baboons will then bound it on the one side, and
the white races on the other. Little weight need be attached to the
lack of fossil remains to fill up this gap, since the discovery of
these depends upon chance. The last part of the chapter is devoted to
a discussion of the earlier stages in the genealogy of man. Here
Darwin accepts in the main the genealogical tree, which had meantime
been published by Haeckel, who traces the pedigree back through
Monotrems, Reptiles, Amphibians, and Fishes, to Amphioxus.

Then follows an attempt to reconstruct, from the atavistic characters,
a picture of our primitive ancestor who was undoubtedly an arboreal
animal. The occurrence of rudiments of parts in one sex which only
come to full development in the other is next discussed. This state of
things Darwin regards as derived from an original hermaphroditism. In
regard to the mammary glands of the male he does not accept the theory
that they are vestigial, but considers them rather as not fully

The last chapter of Part I deals with the question whether the
different races of man are to be regarded as different species, or as
sub-species of a race of monophyletic origin. The striking differences
between the races are first emphasised, and the question of the
fertility or infertility of hybrids is discussed. That fertility is
the more usual is shown by the excessive fertility of the hybrid
population of Brazil. This, and the great variability of the
distinguishing characters of the different races, as well as the fact
that all grades of transition stages are found between these, while
considerable general agreement exists, tell in favour of the unity of
the races and lead to the conclusion that they all had a common
primitive ancestor.

Darwin therefore classifies all the different races as sub-species of
_one and the same species_. Then follows an interesting inquiry into
the reasons for the extinction of human races. He recognises as the
ultimate reason the injurious effects of a change of the conditions of
life, which may bring about an increase in infantile mortality, and a
diminished fertility. It is precisely the reproductive system, among
animals also, which is most susceptible to changes in the environment.

The final section of this chapter deals with the formation of the
races of mankind. Darwin discusses the question how far the direct
effect of different conditions of life, or the inherited effects of
increased use or disuse may have brought about the characteristic
differences between the different races. Even in regard to the origin
of the colour of the skin he rejects the transmitted effects of an
original difference of climate as an explanation. In so doing he is
following his tendency to exclude Lamarckian explanations as far as
possible. But here he makes gratuitous difficulties from which, since
natural selection fails, there is no escape except by bringing in the
principle of sexual selection, to which, he regarded it as possible,
skin-colouring, arrangement of hair, and form of features might be
traced. But with his characteristic conscientiousness he guards
himself thus: "I do not intend to assert that sexual selection will
account for all the differences between the races."[103]

I may be permitted a remark as to Darwin's attitude towards Lamarck.
While, at an earlier stage, when he was engaged in the preliminary
labours for his immortal work, _The Origin of Species_, Darwin
expresses himself very forcibly against the views of Lamarck, speaking
of Lamarckian "nonsense,"[104] and of Lamarck's "absurd, though clever
work"[105] and expressly declaring, "I attribute very little to the
direct action of climate, etc."[106] yet in later life he became more
and more convinced of the influence of external conditions. In 1876,
that is, two years after the appearance of the second edition of _The
Descent of Man_, he writes with his usual candid honesty: "In my
opinion the greatest error which I have committed, has been not
allowing sufficient weight to the direct action of the environment,
i.e. food, climate, etc. independently of a natural selection."[107]
It is certain from this change of opinion that, if he had been able to
make up his mind to issue a third edition of _The Descent of Man_, he
would have ascribed a much greater influence to the effect of
external conditions in explaining the different characters of the
races of man than he did in the second edition. He would also
undoubtedly have attributed less influence to sexual selection as a
factor in the origin of the different bodily characteristics, if
indeed he would not have excluded it altogether.

In Part III of the _Descent_ two additional chapters are devoted to
the discussion of sexual selection in relation to man. These may be
very briefly referred to. Darwin here seeks to show that sexual
selection has been operative on man and his primitive progenitor.
Space fails me to follow out his interesting arguments. I can only
mention that he is inclined to trace back hairlessness, the
development of the beard in man, and the characteristic colour of the
different human races to sexual selection. Since bareness of the skin
could be no advantage, but rather a disadvantage, this character
cannot have been brought about by natural selection. Darwin also
rejected a direct influence of climate as a cause of the origin of the
skin-colour. I have already expressed the opinion, based on the
development of his views as shown in his letters, that in a third
edition Darwin would probably have laid more stress on the influence
of external environment. He himself feels that there are gaps in his
proofs here, and says in self-criticism: "The views here advanced, on
the part which sexual selection has played in the history of man, want
scientific precision."[108] I need here only point out that it is
impossible to explain the graduated stages of skin-colour by sexual
selection, since it would have produced races sharply defined by their
colour and not united to other races by transition stages, and this,
it is well known, is not the case. Moreover, the fact established by
me,[109] that in all races the ventral side of the trunk is paler than
the dorsal side, and the inner surface of the extremities paler than
the outer side, cannot be explained by sexual selection in the
Darwinian sense.

With this I conclude my brief survey of the rich contents of Darwin's
book. I may be permitted to conclude by quoting the magnificent final
words of _The Descent of Man_: "We must, however, acknowledge, as it
seems to me, that man, with all his noble qualities, with sympathy
which feels for the most debased, with benevolence which extends not
only to other men but to the humblest living creature, with his
god-like intellect which has penetrated into the movements and
constitution of the solar system--with all these exalted powers--Man
still bears in his bodily frame the indelible stamp of his lowly

What has been the fate of Darwin's doctrines since his great
achievement? How have they been received and followed up by the
scientific and lay world? And what do the successors of the mighty
hero and genius think now in regard to the origin of the human race?

At the present time we are incomparably more favourably placed than
Darwin was for answering this question of all questions. We have at
our command an incomparably greater wealth of material than he had at
his disposal. And we are more fortunate than he in this respect, that
we now know transition-forms which help to fill up the gap, still
great, between the lowest human races and the highest apes. Let us
consider for a little the more essential additions to our knowledge
since the publication of _The Descent of Man_.

Since that time our knowledge of animal embryos has increased
enormously. While Darwin was obliged to content himself with comparing
a human embryo with that of a dog, there are now available the
youngest embryos of monkeys of all possible groups (Orang, Gibbon,
Semnopithecus, Macacus), thanks to Selenka's most successful tour in
the East Indies in search of such material. We can now compare
corresponding stages of the lower monkeys and of the Anthropoid apes
with human embryos, and convince ourselves of their great resemblance
to one another, thus strengthening enormously the armour prepared by
Darwin in defence of his view on man's nearest relatives. It may be
said that Selenka's material fills up the blanks in Darwin's array of
proofs in the most satisfactory manner.

The deepening of our knowledge of comparative anatomy also gives us much
surer foundations than those on which Darwin was obliged to build. Just of
late there have been many workers in the domain of the anatomy of apes and
lemurs, and their investigations extend to the most different organs. Our
knowledge of fossil apes and lemurs has also become much wider and more
exact since Darwin's time: the fossil lemurs have been especially worked up
by Cope, Forsyth Major, Ameghino, and others. Darwin knew very little about
fossil monkeys. He mentions two or three anthropoid apes as occurring in
the Miocene of Europe,[111] but only names _Dryopithecus_, the largest form
from the Miocene of France. It was erroneously supposed that this form was
related to _Hylobates_. We now know not only a form that actually stands
near to the gibbon (_Pliopithecus_), and remains of other anthropoids
(_Pliohylobates_ and the fossil chimpanzee, _Palaeopithecus_), but also
several lower catarrhine monkeys, of which _Mesopithecus_, a form nearly
related to the modern Sacred Monkeys (a species of _Semnopithecus_) and
found in strata of the Miocene period in Greece, is the most important.
Quite recently, too, Ameghino's investigations have made us acquainted with
fossil monkeys from South America (_Anthropops_, _Homunculus_), which,
according to their discoverer, are to be regarded as in the line of human

What Darwin missed most of all--intermediate forms between apes and
man--has been recently furnished. E. Dubois, as is well known,
discovered in 1893, near Trinil in Java, in the alluvial deposits of
the river Bengawan, an important form represented by a skull-cap, some
molars, and a femur. His opinion--much disputed as it has been--that
in this form, which he named _Pithecanthropus_, he has found a
long-desired transition-form is shared by the present writer. And
although the geological age of these fossils, which, according to
Dubois, belong to the uppermost Tertiary series, the Pliocene has
recently been fixed at a later date (the older Diluvium), the
_morphological value_ of these interesting remains, that is, the
intermediate position of _Pithecanthropus_, still holds good. Volz
says with justice,[112] that even if _Pithecanthropus_ is not _the_
missing link, it is undoubtedly _a_ missing link.

As on the one hand there has been found in _Pithecanthropus_ a form
which, though intermediate between apes and man, is nevertheless more
closely allied to the apes, so on the other hand, much progress has
been made since Darwin's day in the discovery and description of the
oldest human remains. Since the famous roof of a skull and the bones
of the extremities belonging to it were found in 1856 in the
Neandertal near Düsseldorf, the most varied judgments have been
expressed in regard to the significance of the remains and of the
skull in particular. In Darwin's _Descent of Man_ there is only a
passing allusion to them[113] in connection with the discussion of the
skull-capacity, although the investigations of Schaaffhausen, King,
and Huxley were then known. I believe I have shown, in a series of
papers, that the skull in question belongs to a form different from
any of the races of man now living, and, with King and Cope, I regard
it as at least a different species from living man, and have therefore
designated it _Homo primigenius_. The form unquestionably belongs to
the older Diluvium, and in the later Diluvium human forms already
appear, which agree in all essential points with existing human races.

As far back as 1886 the value of the Neandertal skull was greatly
enhanced by Fraipont's discovery of two skulls and skeletons from Spy
in Belgium. These are excellently described by their discoverer,[114]
and are regarded as belonging to the same group of forms as the
Neandertal remains. In 1899 and the following years came the discovery
by Gorjanovič-Kramberger of different skeletal parts of at least
ten individuals in a cave near Krapina in Croatia.[115] It is in
particular the form of the lower jaw which is different from that of
all recent races of man, and which clearly indicates the lowly
position of _Homo primigenius_, while, on the other hand, the
long-known skull from Gibraltar, which I[116] have referred to _Homo
primigenius_, and which has lately been examined in detail by
Sollas,[117] has made us acquainted with the surprising shape of the
eye-orbit, of the nose, and of the whole upper part of the face.
Isolated lower jaws found at La Naulette in Belgium, and at Malarnaud
in France, increase our material which is now as abundant as could be
desired. The most recent discovery of all is that of a skull dug up in
August of this year [1908] by Klaatsch and Hauser in the lower grotto
of the Le Moustier in Southern France, but this skull has not yet been
fully described. Thus _Homo primigenius_ must also be regarded as
occupying a position in the gap existing between the highest apes and
the lowest human races, _Pithecanthropus_, standing in the lower part
of it, and _Homo primigenius_ in the higher, near man. In order to
prevent misunderstanding, I should like here to emphasise that in
arranging this structural series--anthropoid apes, _Pithecanthropus_,
_Homo primigenius_, _Homo sapiens_--I have no intention of
establishing it as a direct genealogical series. I shall have
something to say in regard to the genetic relations of these forms,
one to another, when discussing the different theories of descent
current at the present day.[118]

In quite a different domain from that of morphological relationship,
namely in the physiological study of the blood, results have recently
been gained which are of the highest importance to the doctrine of
descent. Uhlenhuth, Nuttall, and others have established the fact that
the blood-serum of a rabbit which has previously had human blood
injected into it, forms a precipitate with human blood. This
biological reaction was tried with a great variety of mammalian
species, and it was found that those far removed from man gave no
precipitate under these conditions. But as in other cases among
mammals all nearly related forms yield an almost equally marked
precipitate, so the serum of a rabbit treated with human blood and
then added to the blood of an anthropoid ape gives _almost_ as marked
a precipitate as in human blood; the reaction to the blood of the
lower Eastern monkeys is weaker, that to the Western monkeys weaker
still; indeed in this last case there is only a slight clouding after
a considerable time and no actual precipitate. The blood of the
Lemuridae (Nuttall) gives no reaction or an extremely weak one, that
of the other mammals none whatever. We have in this not only a proof
of the literal blood relationship between man and apes, but the degree
of relationship with the different main groups of apes can be
determined beyond possibility of mistake.

Finally, it must be briefly mentioned that in regard to remains of
human handicraft also, the material at our disposal has greatly
increased of late years, that, as a result of this, the opinions of
archaeologists have undergone many changes, and that, in particular,
their views in regard to the age of the human race have been greatly
influenced. There is a tendency at the present time to refer the
origin of man back to Tertiary times. It is true that no remains of
Tertiary man have been found, but flints have been discovered which,
according to the opinion of most investigators, bear traces either of
use, or of very primitive workmanship. Since Rutot's time, following
Mortillet's example, investigators have called these "eoliths," and
they have been traced back by Verworn to the Miocene of the Auvergne,
and by Rutot even to the upper Oligocene. Although these eoliths are
even nowadays the subject of many different views, the preoccupation
with them has kept the problem of the age of the human race
continually before us.

Geology, too, has made great progress since the days of Darwin and
Lyell, and has endeavoured with satisfactory results to arrange the
human remains of the Diluvial period in chronological order (Penck). I
do not intend to enter upon the question of the primitive home of the
human race; since the space at my disposal will not allow of my
touching even very briefly upon all the departments of science which
are concerned in the problem of the descent of man. How Darwin would
have rejoiced over each of the discoveries here briefly outlined! What
use he would have made of the new and precious material, which would
have prevented the discouragement from which he suffered when
preparing the second edition of _The Descent of Man_! But it was not
granted to him to see this progress towards filling up the gaps in his
edifice of which he was so painfully conscious.

He did, however, have the satisfaction of seeing his ideas steadily
gaining ground, notwithstanding much hostility and deep-rooted
prejudice. Even in the years between the appearance of _The Origin of
Species_ and of the first edition of the _Descent_, the idea of a
natural descent of man, which was only briefly indicated in the work
of 1859, had been eagerly welcomed in some quarters. It has been
already pointed out how brilliantly Huxley contributed to the defence
and diffusion of Darwin's doctrines, and how in _Man's Place in
Nature_ he has given us a classic work as a foundation for the
doctrine of the descent of man. As Huxley was Darwin's champion in
England, so in Germany Carl Vogt, in particular, made himself master
of the Darwinian ideas. But above all it was Haeckel who, in energy,
eagerness for battle, and knowledge may be placed side by side with
Huxley, who took over the leadership in the controversy over the new
conception of the universe. As far back as 1866, in his _Generelle
Morphologie_, he had inquired minutely into the question of the
descent of man, and not content with urging merely the general theory
of descent from lower animal forms, he drew up for the first time
genealogical trees showing the close structural relationships of the
different animal groups; the last of these illustrated the
relationships of Mammals, and among them of all groups of the
Primates, including man. It was Haeckel's genealogical trees that
formed the basis of the special discussion of the relationships of
man, in the sixth chapter of Darwin's _Descent of Man_.

In the last section of this essay I shall return to Haeckel's
conception of the special descent of man, the main features of which
he still upholds, and rightly so. Haeckel has contributed more than
any one else to the spread of the Darwinian doctrine.

I can only allow myself a few words as to the spread of the theory of
the natural descent of man in other countries. The Parisian
anthropological school, founded and guided by the genius of Broca,
took up the idea of the descent of man, and made many notable
contributions to it (Broca, Manouvrier, Mahoudeau, Deniker and
others). In England itself Darwin's work did not die. Huxley took care
of that, for he, with his lofty and unprejudiced mind, dominated and
inspired English biology until his death on June 29, 1895. He had the
satisfaction shortly before his death of learning of Dubois'
discovery, which he illustrated by a humourous sketch.[119] But there
are still many followers in Darwin's footsteps in England. Keane has
worked at the special genealogical tree of the Primates; Keith has
inquired which of the anthropoid apes has the greatest number of
characters in common with man; Morris concerns himself with the
evolution of man in general, especially with his acquisition of the
erect position. The recent discoveries of _Pithecanthropus_ and _Homo
primigenius_ are being vigorously discussed; but the present writer is
not in a position to form an opinion of the extent to which the idea
of descent has penetrated throughout England generally.

In Italy independent work in the domain of the descent of man is being
produced, especially by Morselli; with him are associated, in the
investigation of related problems, Sergi and Giuffrida-Ruggeri. From
the ranks of American investigators we may single out in particular
the eminent geologist Cope, who championed with much decision the idea
of the specific difference of _Homo neandertalensis_ (_primigenius_)
and maintained a more direct descent of man from the fossil Lemuridae.
In South America too, in Argentina, new life is stirring in this
department of science. Ameghino in Buenos Ayres has awakened the
fossil primates of the Pampas formation to new life; he even believes
that in his _Tetraprothomo_, represented by a femur, he has discovered
a direct ancestor of man. Lehmann-Nitsche is working at the other side
of the gulf between apes and man, and he describes a remarkable first
cervical vertebra (atlas) from Monte Hermoso as belonging to a form
which may bear the same relation to _Homo sapiens_ in South America as
_Homo primigenius_ does in the Old World. After a minute investigation
he establishes a human species _Homo neogaeus_, while Ameghino
ascribes this atlas vertebra to his _Tetraprothomo_.

Thus throughout the whole scientific world there is arising a new
life, an eager endeavour to get nearer to Huxley's _problema maximum_,
to penetrate more deeply into the origin of the human race. There are
to-day very few experts in anatomy and zoology who deny the animal
descent of man in general. Religious considerations, old prejudices,
the reluctance to accept man, who so far surpasses mentally all other
creatures, as descended from "soulless" animals, prevent a few
investigators from giving full adherence to the doctrine. But there
are very few of these who still postulate a special act of creation
for man. Although the majority of experts in anatomy and zoology
accept unconditionally the descent of man from lower forms, there is
much diversity of opinion among them in regard to the special line of

In trying to establish any special hypothesis of descent, whether by
the graphic method of drawing up genealogical trees or otherwise, let
us always bear in mind Darwin's words[120] and use them as a critical
guiding line: "As we have no record of the lines of descent, the
pedigree can be discovered only by observing the degrees of
resemblance between the beings which are to be classed." Darwin
carries this further by stating "that resemblances in several
unimportant structures, in useless and rudimentary organs, or not now
functionally active, or in an embryological condition, are by far the
most serviceable for classification."[121] It has also to be
remembered that _numerous_ separate points of agreement are of much
greater importance than the amount of similarity or dissimilarity in a
few points.

The hypotheses as to descent current at the present day may be divided
into two main groups. The first group seeks for the roots of the human
race not among any of the families of the apes--the anatomically
nearest forms--nor among their very similar but less specialised
ancestral forms, the fossil representatives of which we can know only
in part, but, setting the monkeys on one side, it seeks for them lower
down among the fossil Eocene Pseudo-lemuridae or Lemuridae (Cope), or
even among the primitive pentadactylous Eocene forms, which may
either have led directly to the evolution of man (Adloff), or have
given rise to an ancestral form common to apes and men (Klaatsch,[122]
Giuffrida-Ruggeri). The common ancestral form, from which man and apes
are thus supposed to have arisen independently, may explain the
numerous resemblances which actually exist between them. That is to
say, all the characters upon which the great structural resemblance
between apes and man depends must have been present in their common
ancestor. Let us take an example of such a common character. The bony
external ear-passage is in general as highly developed in the lower
Eastern monkeys and the anthropoid apes as in man. This character
must, therefore, have already been present in the common primitive
form. In that case it is not easy to understand why the Western
monkeys have not also inherited the character, instead of possessing
only a tympanic ring. But it becomes more intelligible if we assume
that forms with a primitive tympanic ring were the original type, and
that from these were evolved, on the one hand, the existing New World
monkeys with persistent tympanic ring, and on the other an ancestral
form common to the lower Old World monkeys, the anthropoid apes and
man. For man shares with these the character in question, and it is
also one of the "unimportant" characters required by Darwin. Thus we
have two divergent lines arising from the ancestral form, the Western
monkeys (Platyrrhine) on the one hand, and an ancestral form common to
the lower Eastern monkeys, the anthropoid apes, and man, on the other.
But considerations similar to those which showed it to be impossible
that man should have developed from an ancestor common to him and the
monkeys, yet outside of and parallel with these, may be urged also
against the likelihood of a parallel evolution of the lower Eastern
monkeys, the anthropoid apes, and man. The anthropoid apes have in
common with man many characters which are not present in the lower
Old World monkeys. These characters must therefore have been present
in the ancestral form common to the three groups. But here, again, it
is difficult to understand why the lower Eastern monkeys should not
also have inherited these characters. As this is not the case, there
remains no alternative but to assume divergent evolution from an
indifferent form. The lower Eastern monkeys are carrying on the
evolution in one direction--I might almost say towards a blind
alley--while anthropoids and men have struck out a progressive path,
at first in common, which explains the many points of resemblance
between them, without regarding man as derived directly from the
anthropoids. Their many striking points of agreement indicate a common
descent, and cannot be explained as phenomena of convergence.

I believe I have shown in the above sketch that a theory which derives
man directly from lower forms without regarding apes as
transition-types leads _ad absurdum_. The close structural
relationship between man and monkeys can only be understood if both
are brought into the same line of evolution. To trace man's line of
descent directly back to the old Eocene mammals, alongside of, but
with no relation to these very similar forms, is to abandon the method
of exact comparison, which, as Darwin rightly recognised, alone
justifies us in drawing up genealogical trees on the basis of
resemblances and differences. The farther down we go the more does the
ground slip from beneath our feet. Even the Lemuridae show very
numerous divergent conditions, much more so the Eocene mammals
(Creodonta, Condylarthra), the chief resemblance of which to man
consists in the possession of pentadactylous hands and feet! Thus the
farther course of the line of descent disappears in the darkness of
the ancestry of the mammals. With just as much reason we might pass by
the Vertebrates altogether, and go back to the lower Invertebrates,
but in that case it would be much easier to say that man has arisen
independently, and has evolved, without relation to any animals, from
the lowest primitive form to his present isolated and dominant
position. But this would be to deny all value to classification, which
must after all be the ultimate basis of a genealogical tree. We can,
as Darwin rightly observed, only infer the line of descent from the
degree of resemblance between single forms. If we regard man as
directly derived from primitive forms very far back, we have no way of
explaining the many points of agreement between him and the monkeys in
general, and the anthropoid apes in particular. These must remain an
inexplicable marvel.

I have thus, I trust, shown that the first class of special theories
of descent, which assumes that man has developed, parallel with the
monkeys, but without relation to them, from very low primitive forms
cannot be upheld, because it fails to take into account the close
structural affinity of man and monkeys. I cannot but regard this
hypothesis as lamentably retrograde, for it makes impossible any
application of the facts that have been discovered in the course of
the anatomical and embryological study of man and monkeys, and indeed
prejudges investigations of that class as pointless. The whole method
is perverted; an unjustifiable theory of descent is first formulated
with the aid of the imagination, and then we are asked to declare that
all structural relations between man and monkeys, and between the
different groups of the latter, are valueless,--the fact being that
they are the only true basis on which a genealogical tree can be

So much for this most modern method of classification, which has
probably found adherents because it would deliver us from the
relationship to apes which many people so much dislike. In contrast to
it we have the second class of special hypotheses of descent, which
keeps strictly to the nearest structural relationship. This is the
only basis that justifies the drawing up of a special hypothesis of
descent. If this fundamental proposition be recognised, it will be
admitted that the doctrine of special descent upheld by Haeckel, and
set forth in Darwin's _Descent of Man_, is still valid to-day. In the
genealogical tree, man's place is quite close to the anthropoid apes;
these again have as their nearest relatives the lower Old World
monkeys, and their progenitors must be sought among the less
differentiated Platyrrhine monkeys, whose most important characters
have been handed on to the present day New World monkeys. How the
different genera are to be arranged within the general scheme
indicated depends in the main on the classificatory value attributed
to individual characters. This is particularly true in regard to
_Pithecanthropus_, which I consider as the root of a branch which has
sprung from the anthropoid ape root and has led up to man; the latter
I have designated the family of the Hominidae.

For the rest, there are, as we have said, various possible ways of
constructing the narrower genealogy within the limits of this branch
including men and apes, and these methods will probably continue to
change with the accumulation of new facts. Haeckel himself has
modified his genealogical tree of the Primates in certain details
since the publication of his _Generelle Morphologie_ in 1866, but its
general basis remains the same.[123] All the special genealogical
trees drawn up on the lines laid down by Haeckel and Darwin--and that
of Dubois may be specially mentioned--are based, in general, on the
close relationship of monkeys and men, although they may vary in
detail. Various hypotheses have been formulated on these lines, with
special reference to the evolution of man. _Pithecanthropus_ is
regarded by some authorities as the direct ancestor of man, by others
as a side-track failure in the attempt at the evolution of man. The
problem of the monophyletic or polyphyletic origin of the human race
has also been much discussed. Sergi[124] inclines towards the
assumption of a polyphyletic origin of the three main races of man,
the African primitive form of which has given rise also to the
gorilla and chimpanzee, the Asiatic to the Orang, the Gibbon, and
_Pithecanthropus_. Kollmann regards existing human races as derived
from small primitive races (pigmies), and considers that _Homo
primigenius_ must have arisen in a secondary and degenerative manner.

But this is not the place, nor have I the space to criticise the
various special theories of descent. One, however, must receive
particular notice. According to Ameghino, the South American monkeys
(_Pitheculites_) from the oldest Tertiary of the Pampas are the forms
from which have arisen the existing American monkeys on the one hand,
and on the other, the extinct South American Homunculidae, which are
also small forms. From these last, anthropoid apes and man have, he
believes, been evolved. Among the progenitors of man, Ameghino reckons
the form discovered by him (_Tetraprothomo_), from which a South
American primitive man, _Homo pampaeus_, might be directly evolved,
while on the other hand all the lower Old World monkeys may have
arisen from older fossil South American forms (Clenialitidae), the
distribution of which may be explained by the bridge formerly existing
between South America and Africa, as may be the derivation of all
existing human races from _Homo pampaeus_.[125] The fossil forms
discovered by Ameghino deserve the most minute investigation, as does
also the fossil man from South America of which Lehmann-Nitsche[126]
has made a thorough study.

It is obvious that, notwithstanding the necessity for fitting man's
line of descent into the genealogical tree of the Primates, especially
the apes, opinions in regard to it differ greatly in detail. This
could not be otherwise, since the different Primate forms, especially
the fossile forms, are still far from being exhaustively known. But
one thing remains certain,--the idea of the close relationship between
man and monkeys set forth in Darwin's _Descent of Man_. Only those who
deny the many points of agreement, the sole basis of classification,
and thus of a natural genealogical tree, can look upon the position of
Darwin and Haeckel as antiquated, or as standing on an insufficient
foundation. For such a genealogical tree is nothing more than a
summarised representation of what is known in regard to the degree of
resemblance between the different forms.

Darwin's work in regard to the descent of man has not been surpassed;
the more we immerse ourselves in the study of the structural
relationships between apes and man, the more is our path illumined by
the clear light radiating from him, and through his calm and
deliberate investigation, based on a mass of material in the
accumulation of which he has never had an equal. Darwin's fame will be
bound up for all time with the unprejudiced investigation of the
question of all questions, the descent of the human race.


[Footnote 75: _Life and Letters of Thomas Henry Huxley_, Vol. I. p.
171, London, 1900.]

[Footnote 76: _Ibid._, p. 363.]

[Footnote 77: No italics in original.]

[Footnote 78: _Life and Letters of Charles Darwin_, Vol. I. p. 93.]

[Footnote 79: _Ibid._ Vol. II. p. 263.]

[Footnote 80: _Ibid._ Vol. I. p. 94.]

[Footnote 81: _Life and Letters_, Vol. III. p. 175.]

[Footnote 82: _Ibid._ Vol. II. p. 109.]

[Footnote 83: _Ibid._ Vol. III. p. 112.]

[Footnote 84: _Ibid._ Vol. I. pp. 304-317.]

[Footnote 85: _Life and Letters_, Vol. I. p. 309.]

[Footnote 86: _Loc. cit._ p. 313.]

[Footnote 87: _Ibid._ Vol. II. p. 310.]

[Footnote 88: _Ibid._ Vol. III. p. 236. ["C. Ridley," Mr. Francis
Darwin points out to me, should be H. N. Ridley. A.C.S.]]

[Footnote 89: _Descent of Man_ (Popular Edit., 1901), fig. 1, p. 14.]

[Footnote 90: G. Schwalbe, "Das Darwin'sche Spitzohr beim menschlichen
Embryo," _Anatom. Anzeiger_, 1889, pp. 176-189, and other papers.]

[Footnote 91: _Descent of Man_, fig. 3, p. 24.]

[Footnote 92: _Descent of man_, p. 6.]

[Footnote 93: _Ibid._ p. 54.]

[Footnote 94: _Descent of Man_, p. 92.]

[Footnote 95: _Ibid._ p. 100.]

[Footnote 96: _Life and letters_, Vol. II. p. 161, June 22, 1859.]

[Footnote 97: _Ibid._ Vol. III. p. 15, March 17, 1863.]

[Footnote 98: _Descent of Man_, p. 132.]

[Footnote 99: _Ibid._ pp. 136, 137.]

[Footnote 100: _Ibid._ p. 143.]

[Footnote 101: _Ibid._ p. 193.]

[Footnote 102: _Descent of Man_, p. 231.]

[Footnote 103: _Descent of Man_, p. 308.]

[Footnote 104: _Life and Letters_, Vol. II. p. 23.]

[Footnote 105: _Loc. cit._ p. 39.]

[Footnote 106: _Loc. cit._ (1856), p. 82.]

[Footnote 107: _Ibid._ Vol. III p. 159.]

[Footnote 108: _Descent of Man_, p. 924.]

[Footnote 109: "Die Hautfarbe des Menschen," _Mitteilungen der
Anthropologischen Gessellschaft in Wien_, Vol. XXXIV. pp. 331-352.]

[Footnote 110: _Ibid._ p. 947.]

[Footnote 111: _Descent of Man_, p. 240.]

[Footnote 112: "Das geologische Alter der Pithecanthropus-Schichten
bei Trinil, Ost-Java." _Neues Jahrb. f. Mineralogie_. Festband, 1907.]

[Footnote 113: _Descent of Man_, p. 82.]

[Footnote 114: "La race humaine de Néanderthal ou de Canstatt en
Belgique." _Arch. de Biologie_, VII. 1887.]

[Footnote 115: Gorjanovič-Kramberger. _Der diluviale Mensch van
Krapina in Kroatien_, 1906.]

[Footnote 116: _Studien zur Vorgeschichte des Menschen_, 1906, pp. 154

[Footnote 117: "On the cranial and facial characters of the Neandertal
Race." _Trans. R. Soc._ London, vol. 199, 1908, p. 281.]

[Footnote 118: Since this essay was written Schoetensack has
discovered near Heidelberg and briefly described an exceedingly
interesting lower jaw from rocks between the Pliocene and Diluvial
beds. This exhibits interesting differences from the forms of lower
jaw of _Homo primigenius_. (Schoetensack, _Der Unterkiefer des Homo
heidelbergensis_, Leipzig, 1908.) G. S.]

[Footnote 119: _Life and Letters of Thomas Henry Huxley_, Vol. II. p.

[Footnote 120: _Descent of Man_, p. 229.]

[Footnote 121: _Loc. cit._]

[Footnote 122: Klaatsch in his last publications speaks in the main
only of an ancestral form common to men and anthropoid apes.]

[Footnote 123: Haeckels latest genealogical tree is to be found in his
most recent work, _Unsere Ahnenreihe_. Jena, 1908.]

[Footnote 124: Sergi, G. _Europa_, 1908.]

[Footnote 125: _See_ Ameghino's latest paper, "_Notas preliminaries
sobre el Tetraprothomo argentinus_," etc. _Anales del Museo nacional
de Buenos Aires_, XVI. pp. 107-242, 1907.]

[Footnote 126: "Nouvelles recherches sur la formation pampéenne et
l'homme fossile de la République Argentine." _Rivista del Museo de la
Plata_, T. XIV. pp. 193-488.]




_Professor of Zoology in the University of Jena_

The great advance that anthropology has made in the second half of the
nineteenth century is due, in the first place, to Darwin's discovery
of the origin of man. No other problem in the whole field of research
is so momentous as that of "Man's place in nature," which was justly
described by Huxley (1863) as the most fundamental of all questions.
Yet the scientific solution of this problem was impossible until the
theory of descent had been established.

It is now a hundred years since the great French biologist Jean
Lamarck published his _Philosophie Zoologique_. By a remarkable
coincidence the year in which that work was issued, 1809, was the year
of the birth of his most distinguished successor, Charles Darwin.
Lamarck had already recognised that the descent of man from a series
of other Vertebrates--that is, from a series of Ape-like Primates--was
essentially involved in the general theory of transformation which he
had erected on a broad inductive basis; and he had sufficient
penetration to detect the agencies that had been at work in the
evolution of the erect bimanous man from the arboreal and quadrumanous
ape. He had, however, few empirical arguments to advance in support of
his hypothesis, and it could not be established until the further
development of the biological sciences--the founding of comparative
embryology by Baer (1828) and of the cell-theory by Schleiden and
Schwann (1838), the advance of physiology under Johannes Müller
(1833), and the enormous progress of palaeontology and comparative
anatomy between 1820 and 1860--provided this necessary foundation.
Darwin was the first to coordinate the ample results of these lines of
research. With no less comprehensiveness than discrimination he
consolidated them as a basis of a modified theory of descent, and
associated with them his own theory of natural selection, which we
take to be distinctive of "Darwinism" in the stricter sense. The
illuminating truth of these cumulative arguments was so great in every
branch of biology that, in spite of the most vehement opposition, the
battle was won within a single decade, and Darwin secured the general
admiration and recognition that had been denied to his forerunner,
Lamarck, up to the hour of his death (1829).

Before, however, we consider the momentous influence that Darwinism
has had in anthropology, we shall find it useful to glance at its
history in the course of the last half century, and notice the various
theories that have contributed to its advance. The first attempt to
give extensive expression to the reform of biology by Darwin's work
will be found in my _Generelle Morphologie_ (1866)[127] which was
followed by a more popular treatment of the subject in my _Natürliche
Schöpfungsgeschichte_ (1868),[128] a compilation from the earlier
work. In the first volume of the _Generelle Morphologie_ I endeavoured
to show the great importance of evolution in settling the fundamental
questions of biological philosophy, especially in regard to
comparative anatomy. In the second volume I dealt broadly with the
principle of evolution, distinguishing ontogeny and phylogeny as its
two coordinate main branches, and associating the two in the
Biogenetic Law. The Law may be formulated thus: "Ontogeny (embryology
or the development of the individual) is a concise and compressed
recapitulation of phylogeny (the palaeontological or genealogical
series) conditioned by laws of heredity and adaptation." The
"Systematic introduction to general evolution," with which the second
volume of the _Generelle Morphologie_ opens, was the first attempt to
draw up a natural system of organisms (in harmony with the principles
of Lamarck and Darwin) in the form of a hypothetical pedigree, and was
provisionally set forth in eight genealogical tables.

In the nineteenth chapter of the _Generelle Morphologie_--a part of
which has been republished, without any alteration, after a lapse of
forty years--I made a critical study of Lamarck's theory of descent
and of Darwin's theory of selection, and endeavoured to bring the
complex phenomena of heredity and adaptation under definite laws for
the first time. Heredity I divided into conservative and progressive:
adaptation into indirect (or potential) and direct (or actual). I then
found it possible to give some explanation of the correlation of the
two physiological functions in the struggle for life (selection), and
to indicate the important laws of divergence (or differentiation) and
complexity (or division of labor), which are the direct and inevitable
outcome of selection. Finally, I marked off dysteleology as the
science of the aimless (vestigial, abortive, atrophied, and useless)
organs and parts of the body. In all this I worked from a strictly
monistic standpoint, and sought to explain all biological phenomena on
the mechanical and naturalistic lines that had long been recognised in
the study of inorganic nature. Then (1866), as now, being convinced of
the unity of nature, the fundamental identity of the agencies at work
in the inorganic and the organic worlds, I discarded vitalism,
teleology, and all hypotheses of a mystic character.

It was clear from the first that it was essential, in the monistic
conception of evolution, to distinguish between the laws of
conservative and progressive heredity. Conservative heredity maintains
from generation to generation the enduring characters of the species.
Each organism transmits to its descendants a part of the morphological
and physiological qualities that it has received from its parents and
ancestors. On the other hand, progressive heredity brings new
characters to the species--characters that were not found in preceding
generations. Each organism may transmit to its offspring a part of the
morphological and physiological features that it has itself acquired,
by adaptation, in the course of its individual career, through the use
or disuse of particular organs, the influence of environment, climate,
nutrition, etc. At that time I gave the name of "progressive heredity"
to this inheritance of acquired characters, as a short and convenient
expression, but have since changed the term to "transformative
heredity" (as distinguished from conservative). This term is
preferable, as inherited regressive modifications (degeneration,
retrograde metamorphosis, etc.) come under the same head.

Transformative heredity--or the transmission of acquired
characters--is one of the most important principles in evolutionary
science. Unless we admit it most of the facts of comparative anatomy
and physiology are inexplicable. That was the conviction of Darwin no
less than of Lamarck, of Spencer as well as Virchow, of Huxley as well
as Gegenbaur, indeed of the great majority of speculative biologists.
This fundamental principle was for the first time called in question
and assailed in 1885 by August Weismann of Freiburg, the eminent
zoologist to whom the theory of evolution owes a great deal of
valuable support, and who has attained distinction by his extension of
the theory of selection. In explanation of the phenomena of heredity
he introduced a new theory, the "theory of the continuity of the
germ-plasm." According to him the living substance in all organisms
consists of two quite distinct kinds of plasm, somatic and germinal.
The permanent germ-plasm, or the active substance of the two
germ-cells (egg-cell and sperm-cell), passes unchanged through a
series of generations, and is not affected by environmental
influences. The environment modifies only the soma-plasm, the organs
and tissues of the body. The modifications that these parts undergo
through the influence of the environment or their own activity (use
and habit), do not affect the germ-plasm, and cannot therefore be

This theory of the continuity of the germ-plasm has been expounded by
Weismann during the last twenty-four years in a number of able
volumes, and is regarded by many biologists, such as Mr. Francis
Galton, Sir E. Ray Lankester, and Professor J. Arthur Thomson (who has
recently made a thorough-going defence of it in his important work
_Heredity_),[129] as the most striking advance in evolutionary
science. On the other hand, the theory has been rejected by Herbert
Spencer, Sir W. Turner, Gegenbaur, Kölliker, Hertwig, and many others.
For my part I have, with all respect for the distinguished Darwinian,
contested the theory from the first, because its whole foundation
seems to me erroneous, and its deductions do not seem to be in accord
with the main facts of comparative morphology and physiology.
Weismann's theory in its entirety is a finely conceived molecular
hypothesis, but it is devoid of empirical basis. The notion of the
absolute and permanent independence of the germ-plasm, as
distinguished from the soma-plasm, is purely speculative; as is also
the theory of germinal selection. The determinants, ids, and idants,
are purely hypothetical elements. The experiments that have been
devised to demonstrate their existence really prove nothing.

It seems to me quite improper to describe this hypothetical structure
as "Neodarwinism." Darwin was just as convinced as Lamarck of the
transmission of acquired characters and its great importance in the
scheme of evolution. I had the good fortune to visit Darwin at Down
three times and discuss with him the main principles of his system,
and on each occasion we were fully agreed as to the incalculable
importance of what I may call transformative inheritance. It is only
proper to point out that Weismann's theory of the germ-plasm is in
express contradiction to the fundamental principles of Darwin and
Lamarck. Nor is it more acceptable in what one may call its
"ultradarwinism"--the idea that the theory of selection explains
everything in the evolution of the organic world. This belief in the
"omnipotence of natural selection" was not shared by Darwin himself.
Assuredly, I regard it as of the utmost value, as the process of
natural selection through the struggle for life affords an explanation
of the mechanical origin of the adapted organisation. It solves the
great problem: how could the finely adapted structure of the animal or
plant body be formed unless it was built on a preconceived plan? It
thus enables us to dispense with the teleology of the metaphysician
and the dualist, and to set aside the old mythological and poetic
legends of creation. The idea had occurred in vague form to the great
Empedocles 2000 years before the time of Darwin, but it was reserved
for modern research to give it ample expression. Nevertheless, natural
selection does not of itself give the solution of all our evolutionary
problems. It has to be taken in conjunction with the transformism of
Lamarck, with which it is in complete harmony.

The monumental greatness of Charles Darwin, who surpasses every other
student of science in the nineteenth century by the loftiness of his
monistic conception of nature and the progressive influence of his
ideas, is perhaps best seen in the fact that not one of his many
successors has succeeded in modifying his theory of descent in any
essential point or in discovering an entirely new standpoint in the
interpretation of the organic world. Neither Nägeli nor Weismann,
neither De Vries nor Roux, has done this. Nägeli, in his
_Mechanisch-Physiologische Theorie der Abstammungslehre_[130] which is
to a great extent in agreement with Weismann, constructed a theory of
the idioplasm, that represents it (like the germ-plasm) as developing
continuously in a definite direction from internal causes. But his
internal "principle of progress" is at the bottom just as teleological
as the vital force of the Vitalists, and the micella structure of the
idioplasm is just as hypothetical as the "dominant" structure of the
germ-plasm. In 1889 Moritz Wagner sought to explain the origin of
species by migration and isolation, and on that basis constructed a
special "migration-theory." This, however, is not out of harmony with
the theory of selection. It merely elevates one single factor in the
theory to a predominant position. Isolation is only a special case of
selection, as I had pointed out in the fifteenth chapter of my
_Natural history of creation_. The "mutation-theory" of De Vries,[131]
that would explain the origin of species by sudden and saltatory
variations rather than by gradual modification, is regarded by many
botanists as a great step in advance, but it is generally rejected by
zoologists. It affords no explanation of the facts of adaptation, and
has no causal value.

Much more important than these theories is that of Wilhelm Roux[132]
of "the struggle of parts within the organism, a supplementation of
the theory of mechanical adaptation." He explains the functional
autoformation of the purposive structure by a combination of Darwin's
principle of selection with Lamarck's idea of transformative heredity,
and applies the two in conjunction to the facts of histology. He lays
stress on the significance of functional adaptation, which I had
described in 1866, under the head of cumulative adaptation, as the
most important factor in evolution. Pointing out its influence in the
cell-life of the tissues, he puts "cellular selection" above "personal
selection," and shows how the finest conceivable adaptations in the
structure of the tissue may be brought about quite mechanically,
without preconceived plan. This "mechanical teleology" is a valuable
extension of Darwin's monistic principle of selection to the whole
field of cellular physiology and histology, and is wholly destructive
of dualistic vitalism.

The most important advance that evolution has made since Darwin and
the most valuable amplification of his theory of selection is, in my
opinion, the work of Richard Semon: _Die Mneme als erhaltendes Prinzip
im Wechsel des organischen Geschehens_.[133] He offers a psychological
explanation of the facts of heredity by reducing them to a process of
(unconscious) memory. The physiologist Ewald Hering had shown in 1870
that memory must be regarded as a general function of organic matter,
and that we are quite unable to explain the chief vital phenomena,
especially those of reproduction and inheritance, unless we admit this
unconscious memory. In my essay _Die Perigenesis der Plastidule_[134]
I elaborated this far-reaching idea, and applied the physical
principle of transmitted motion to the plastidules, or active
molecules of plasm. I concluded that "heredity is the memory of the
plastidules, and variability their power of comprehension." This
"provisional attempt to give a mechanical explanation of the
elementary processes of evolution" I afterwards extended by showing
that sensitiveness is (as Carl Nägeli, Ernst Mach, and Albrecht Rau
express it) a general quality of matter. This form of panpsychism
finds its simplest expression in the "trinity of substance."

To the two fundamental attributes that Spinoza ascribed to
substance--Extension (matter as occupying space) and Cogitation
(energy, force)--we now add the third fundamental quality of Psychoma
(sensitiveness, soul). I further elaborated this trinitarian
conception of substance in the nineteenth chapter of my _Die
Lebenswunder_ (1904),[135] and it seems to me well calculated to
afford a monistic solution of many of the antitheses of philosophy.

This important Mneme-theory of Semon and the luminous physiological
experiments and observations associated with it not only throw
considerable light on transformative inheritance, but provide a sound
physiological foundation for the biogenetic law. I had endeavoured to
show in 1874, in the first chapter of my _Anthropogenie_,[136] that
this fundamental law of organic evolution holds good generally, and
that there is everywhere a direct causal connection between ontogeny
and phylogeny. "Phylogenesis is the mechanical cause of ontogenesis;"
in other words, "The evolution of the stem or race is--in accordance
with the laws of heredity and adaptation--the real cause of all the
changes that appear, in a condensed form, in the development of the
individual organism from the ovum, in either the embryo or the larva."

It is now fifty years since Charles Darwin pointed out, in the
thirteenth chapter of his epoch-making _Origin of Species_, the
fundamental importance of embryology in connection with his theory of

"The leading facts in embryology, which are second to none in
importance, are explained on the principle of variations in the many
descendants from some one ancient progenitor, having appeared at a not
very early period of life, and having been inherited at a
corresponding period."[137]

He then shows that the striking resemblance of the embryos and larvae
of closely related animals, which in the mature stage belong to widely
different species and genera, can only be explained by their descent
from a common progenitor. Fritz Müller made a closer study of these
important phenomena in the instructive instance of the Crustacean
larva, as given in his able work _Für Darwin_[138] (1864). I then, in
1872, extended the range so as to include all animals (with the
exception of the unicellular Protozoa) and showed, by means of the
theory of the Gastraea, that all multicellular, tissue-forming
animals--all the Metazoa--develop in essentially the same way from the
primary germ-layers.

I conceived the embryonic form, in which the whole structure consists of
only two layers of cells, and is known as the gastrula, to be the
ontogenetic recapitulation, maintained by tenacious heredity, of a
primitive common progenitor of all the Metazoa, the Gastraea. At a later
date (1895) Monticelli discovered that this conjectural ancestral form is
still preserved in certain primitive Coelenterata--Pemmatodiscus,
Kunstleria, and the nearly-related Orthonectida.

The general application of the biogenetic law to all classes of
animals and plants has been proved in my _Systematische
Phylogenie_.[139] It has, however, been frequently challenged, both by
botanists and zoologists, chiefly owing to the fact that many have
failed to distinguish its two essential elements, palingenesis and
cenogenesis. As early as 1874 I had emphasised, in the first chapter
of my _Evolution of Man_, the importance of discriminating carefully
between these two sets of phenomena:

"In the evolutionary appreciation of the facts of embryology we must
take particular care to distinguish sharply and clearly between the
primary, palingenetic evolutionary processes and the secondary,
cenogenetic processes. The palingenetic phenomena, or embryonic
_recapitulations_, are due to heredity, to the transmission of
characters from one generation to another. They enable us to draw
direct inferences in regard to corresponding structures in the
development of the species (e.g. the chorda or the branchial arches in
all vertebrate embryos). The cenogenetic phenomena, on the other hand,
or the embryonic _variations_, cannot be traced to inheritance from a
mature ancestor, but are due to the adaption of the embryo or the
larva to certain conditions of its individual development (e.g. the
amnion, the allantois, and the vitelline arteries in the embryos of
the higher vertebrates). These cenogenetic phenomena are later
additions; we must not infer from them that there were corresponding
processes in the ancestral history, and hence they are apt to

The fundamental importance of these facts of comparative anatomy,
atavism, and the rudimentary organs, was pointed out by Darwin in the
first part of his classic work, _The Descent of Man and Selection in
Relation to Sex_ (1871).[140] In the "General summary and conclusion"
(chap. xxi.) he was able to say, with perfect justice: "He who is not
content to look, like a savage, at the phenomena of nature as
disconnected, cannot any longer believe that man is the work of a
separate act of creation. He will be forced to admit that the close
resemblance of the embryo of man to that, for instance, of a dog--the
construction of his skull, limbs, and whole frame on the same plan
with that of other mammals, independently of the uses to which the
parts may be put--the occasional reappearance of various structures,
for instance of several muscles, which man does not normally possess,
but which are common to the Quadrumana--and a crowd of analogous
facts--all point in the plainest manner to the conclusion that man is
the co-descendant with other mammals of a common progenitor."

These few lines of Darwin's have a greater scientific value than
hundreds of those so-called "anthropological treatises," which give
detailed descriptions of single organs, or mathematical tables with
series of numbers and what are claimed to be "exact analyses," but are
devoid of synoptic conclusions and a philosophical spirit.

Charles Darwin is not generally recognised as a great anthropologist,
nor does the school of modern anthropologists regard him as a leading
authority. In Germany, especially, the great majority of the members
of the anthropological societies took up an attitude of hostility to
him from the very beginning of the controversy in 1860. _The Descent
of Man_ was not merely rejected, but even the discussion of it was
forbidden on the ground that it was "unscientific."

The centre of this inveterate hostility for thirty years--especially
after 1877--was Rudolph Virchow of Berlin, the leading investigator
in pathological anatomy, who did so much for the reform of medicine by
his establishment of cellular pathology in 1858. As a prominent
representative of "exact" or "descriptive" anthropology, and lacking a
broad equipment in comparative anatomy and ontogeny, he was unable to
accept the theory of descent. In earlier years, and especially during
his splendid period of activity at Würzburg (1848-1856), he had been a
consistent free-thinker, and had in a number of able articles
(collected in his _Gesammelte Abhandlungen_)[141] upheld the unity of
human nature, the inseparability of body and spirit. In later years at
Berlin, where he was more occupied with political work and sociology
(especially after 1866), he abandoned the positive monistic position
for one of agnosticism and scepticism, and made concessions to the
dualistic dogma of a spiritual world apart from the material frame.

In the course of a Scientific Congress at Munich in 1877 the conflict
of these antithetic views of nature came into sharp relief. At this
memorable Congress I had undertaken to deliver the first address
(September 18th) on the subject of "Modern evolution in relation to
the whole of science." I maintained that Darwin's theory not only
solved the great problem of the origin of species, but that its
implications, especially in regard to the nature of man, threw
considerable light on the whole of science, and on anthropology in
particular. The discovery of the real origin of man by evolution from
a long series of mammal ancestors threw light on his place in nature
in every respect, as Huxley had already shown in his excellent
lectures of 1863. Just as all the organs and tissues of the human body
had originated from those of the nearest related mammals, certain
ape-like forms, so we were bound to conclude that his mental qualities
also had been derived from those of his extinct primate ancestor.

This monistic view of the origin and nature of man, which is now admitted
by nearly all who have the requisite acquaintance with biology, and
approach the subject without prejudice, encountered a sharp opposition at
that time. The opposition found its strongest expression in an address that
Virchow delivered at Munich four days afterwards (September 22nd), on "The
freedom of science in the modern State." He spoke of the theory of
evolution as an unproved hypothesis, and declared that it ought not to be
taught in the schools, because it was dangerous to the State. "We must
not," he said, "teach that man has descended from the ape or any other
animal." When Darwin, usually so lenient in his judgment, read the English
translation of Virchow's speech, he expressed his disapproval in strong
terms. But the great authority that Virchow had--an authority well founded
in pathology and sociology--and his prestige as president of the German
Anthropological Society, had the effect of preventing any member of the
Society from raising serious opposition to him for thirty years. Numbers of
journals and treatises repeated his dogmatic statement: "It is quite
certain that man has descended neither from the ape nor from any other
animal." In this he persisted till his death in 1902. Since that time the
whole position of German anthropology has changed. The question is no
longer whether man was created by a distinct supernatural act or evolved
from other mammals, but to which line of the animal hierarchy we must look
for the actual series of ancestors. The interested reader will find an
account of this "battle of Munich" (1877) in my three Berlin lectures
(April, 1905), _Der Kampf um die Entwickelungs-Gedanken_.[142]

The main points in our genealogical tree were clearly recognised by
Darwin in the sixth chapter of the _Descent of Man_. Lowly organised
fishes, like the lancelot (Amphioxus), are descended from lower
invertebrates resembling the larvae of an existing Tunicate
(Appendicularia). From these primitive fishes were evolved higher
fishes of the ganoid type and others of the type of Lepidosiren
(Dipneusta). It is a very small step from these to the Amphibia:

"In the class of animals the steps are not difficult to conceive which
led from the ancient Monotremata to the ancient Marsupials; and from
these to the early progenitors of the placental mammals. We may thus
ascend to the Lemuridae; and the interval is not very wide from these
to the Simiadae. The Simiadae then branched off into two great stems,
the New World and Old World monkeys; and from the latter, at a remote
period, Man, the wonder and glory of the Universe, proceeded."[143]

In these few lines Darwin clearly indicated the way in which we were
to conceive our ancestral series within the vertebrates. It is fully
confirmed by all the arguments of comparative anatomy and embryology,
of palaeontology and physiology; and all the research of the
subsequent forty years have gone to establish it. The deep interest in
geology which Darwin maintained throughout his life and his complete
knowledge of palaeontology enabled him to grasp the fundamental
importance of the palaeontological record more clearly than
anthropologists and zoologists usually do.

There has been much debate in subsequent decades whether Darwin
himself maintained that man was descended from the ape, and many
writers have sought to deny it. But the lines I have quoted _verbatim_
from the conclusion of the sixth chapter of the _Descent of Man_
(1871) leave no doubt that he was as firmly convinced of it as was his
great precursor Jean Lamarck in 1809. Moreover, Darwin adds, with
particular explicitness, in the "general summary and conclusion"
(chap. xxi.) of that standard work:[144]

"By considering the embryological structure of man--the homologies
which he presents with the lower animals,--the rudiments which he
retains,--and the reversions to which he is liable, we can partly
recall in imagination the former condition of our early progenitors;
and can approximately place them in their proper place in the
zoological series. We thus learn that man is descended from a hairy,
tailed quadruped, probably arboreal in its habits, and an inhabitant
of the Old World. This creature, if its whole structure had been
examined by a naturalist, would have been classed amongst the
Quadrumana, as surely as the still more ancient progenitor of the Old
and New World monkeys."

These clear and definite lines leave no doubt that Darwin--so critical
and cautious in regard to important conclusions--was quite as firmly
convinced of the descent of man from the apes (the Catarrhinae, in
particular) as Lamarck was in 1809 and Huxley in 1863.

It is to be noted particularly that, in these and other observations
on the subject, Darwin decidedly assumes the monophyletic origin of
the mammals, including man. It is my own conviction that this is of
the greatest importance. A number of difficult questions in regard to
the development of man, in respect of anatomy, physiology, psychology,
and embryology, are easily settled if we do not merely extend our
_progonotaxis_ to our nearest relatives, the anthropoid apes and the
tailed monkeys from which these have descended, but go further back
and find an ancestor in the group of the Lemuridae, and still further
back to the Marsupials and Monotremata. The essential identity of all
the Mammals in point of anatomical structure and embryonic
development--in spite of their astonishing differences in external
appearance and habits of life--is so palpably significant that modern
zoologists are agreed in the hypothesis that they have all sprung from
a common root, and that this root may be sought in the earlier
Palaeozoic Amphibia.

The fundamental importance of this comparative morphology of the
Mammals, as a sound basis of scientific anthropology, was recognised
just before the beginning of the nineteenth century, when Lamarck
first emphasised (1794) the division of the animal kingdom into
Vertebrates and Invertebrates. Even thirteen years earlier (1781),
when Goethe made a close study of the mammal skeleton in the
Anatomical Institute at Jena, he was intensely interested to find that
the composition of the skull was the same in man as in the other
mammals. His discovery of the _os inter-maxillare_ in man (1784),
which was contradicted by most of the anatomists of the time, and his
ingenious "vertebral theory of the skull," were the splendid fruit of
his morphological studies. They remind us how Germany's greatest
philosopher and poet was for many years ardently absorbed in the
comparative anatomy of man and the mammals, and how he divined that
their wonderful identity in structure was no mere superficial
resemblance, but pointed to a deep internal connection. In my
_Generelle Morphologie_ (1866), in which I published the first
attempts to construct phylogenetic trees, I have given a number of
remarkable theses of Goethe, which may be called "phyletic
prophecies." They justify us in regarding him as a precursor of

In the ensuing forty years I have made many conscientious efforts to
penetrate further along that line of anthropological research that was
opened up by Goethe, Lamarck, and Darwin. I have brought together the many
valuable results that have constantly been reached in comparative anatomy,
physiology, ontogeny, and palaeontology, and maintained the effort to
reform the classification of animals and plants in an evolutionary sense.
The first rough drafts of pedigrees that were published in the _Generelle
Morphologie_ have been improved time after time in the ten editions of my
_Natürlich Schöpfungsgeschichte_ (1868-1902).[145] A sounded basis for my
phyletic hypotheses, derived from a discriminating combination of the three
great records--morphology, ontogeny, and palaeontology--was provided in the
three volumes of my _Systematische Phylogenie_[146] (1894 Protists and
Plants, 1895 Vertebrates, 1896 Invertebrates).

In my _Anthropogenie_[147] I endeavoured to employ all the known
facts of comparative ontogeny (embryology) for the purpose of
completing my scheme of human phylogeny (evolution). I attempted to
sketch the historical development of each organ of the body, beginning
with the most elementary structures in the germ-layers of the
Gastraea. At the same time I drew up a corrected statement of the most
important steps in the line of our ancestral series.

At the fourth International Congress of Zoology at Cambridge (August
26th, 1898) I delivered an address on "Our present knowledge of the
Descent of Man." It was translated into English, enriched with many
valuable notes and additions, by my friend and pupil in earlier days
Dr. Hans Gadow (Cambridge), and published under the title: _The Last
Link: our present knowledge of the Descent of Man_[148] The
determination of the chief animal forms that occur in the line of our
ancestry is there restricted to thirty types, and these are
distributed in six main groups.

The first half of this "Progonotaxis hominis," which has no support
from fossil evidence, comprises three groups: (i) Protista
(unicellular organisms, 1-5): (ii) Invertebrate Metazoa (Coelenteria
6-8, Vermalia 9-11): (iii) Monorrhine Vertebrates (Acrania 12-13,
Cyclostoma 14-15). The second half, which is based on fossil records,
also comprises three groups: (iv) Palaeozoic cold-blooded Craniota
(Fishes 16-18, Amphibia 19, Reptiles 20): (v) Mesozoic Mammals
(Monotrema 21, Marsupialia 22, Mallotheria 23): (vi) Cenozoic Primates
(Lemuridae 24-25, Tailed Apes 26-27, Anthropomorpha 28-30). An
improved and enlarged edition of this hypothetic "Progonotaxis
hominis" was published in 1908, in my essay _Unsere Ahnenreihe_.[149]

If I have succeeded in furthering, in some degree, by these
anthropological works, the solution of the great problem of Man's
place in nature, and particularly in helping to trace the definite
stages in our ancestral series, I owe the success, not merely to the
vast progress that biology has made in the last half century, but
largely to the luminous example of the great investigators who have
applied themselves to the problem, with so much assiduity and genius,
for a century and a quarter--I mean Goethe and Lamarck, Gegenbaur and
Huxley, but, above all, Charles Darwin. It was the great genius of
Darwin that first brought together that symmetrical temple of
scientific knowledge, the theory of descent. It was Darwin who put the
crown on the edifice by his theory of natural selection. Not until
this broad inductive law was firmly established was it possible to
vindicate the special conclusion, the descent of man from a series of
other Vertebrates. By his illuminating discovery Darwin did more for
anthropology than thousands of those writers, who are more
specifically titled anthropologists, have done by their technical
treatises. We may, indeed, say that it is not merely as an exact
observer and ingenious experimenter, but as a distinguished
anthropologist and far-seeing thinker, that Darwin takes his place
among the greatest men of science of the nineteenth century.

To appreciate fully the immortal merit of Darwin in connection with
anthropology, we must remember that not only did his chief work, _The
Origin of Species_, which opened up a new era in natural history in
1859, sustain the most virulent and widespread opposition for a
lengthy period, but even thirty years later, when its principles were
generally recognised and adopted, the application of them to man was
energetically contested by many high scientific authorities. Even
Alfred Russel Wallace, who discovered the principle of natural
selection independently in 1858, did not concede that it was
applicable to the higher mental and moral qualities of man. Dr.
Wallace still holds a spiritualist and dualist view of the nature of
man, contending that he is composed of a material frame (descended
from the apes) and an immortal immaterial soul (infused by a higher
power). This dual conception, moreover, is still predominant in the
wide circles of modern theology and metaphysics, and has the general
and influential adherence of the more conservative classes of society.

In strict contradiction to this mystical dualism, which is generally
connected with teleology and vitalism, Darwin always maintained the
complete unity of human nature, and showed convincingly that the
psychological side of man was developed, in the same way as the body,
from the less advanced soul of the anthropoid ape, and, at a still
more remote period, from the cerebral functions of the older
vertebrates. The eighth chapter of the _Origin of Species_, which is
devoted to instinct, contains weighty evidence that the instincts of
animals are subject, like all other vital processes, to the general
laws of historic development. The special instincts of particular
species were formed by adaptation, and the modifications thus acquired
were handed on to posterity by heredity; in their formation and
preservation natural selection plays the same part as in the
transformation of every other physiological function. The higher moral
qualities of civilised man have been derived from the lower mental
functions of the uncultivated barbarians and savages, and these in
turn from the social instincts of the mammals. This natural and
monistic psychology of Darwin's was afterwards more fully developed by
his friend George Romanes in his excellent works _Mental Evolution in
Animals_ and _Mental Evolution in Man_.[150]

Many valuable and most interesting contributions to this monistic
psychology of man were made by Darwin in his fine work on _The Descent
of Man and Selection in Relation to Sex_, and again in his
supplementary work, _The Expression of the Emotions in Man and
Animals_. To understand the historical development of Darwin's
anthropology one must read his life and the introduction to _The
Descent of Man_. From the moment that he was convinced of the truth
of the principle of descent--that is to say, from his thirtieth year,
in 1838--he recognised clearly that man could not be excluded from its
range. He recognised as a logical necessity the important conclusion
that "man is the co-descendant with other species of some ancient,
lower, and extinct form." For many years he gathered notes and
arguments in support of this thesis, and for the purpose of showing
the probable line of man's ancestry. But in the first edition of _The
Origin of Species_ (1859) he restricted himself to the single line,
that by this work "light would be thrown on the origin of man and his
history." In the fifty years that have elapsed since that time the
science of the origin and nature of man has made astonishing progress,
and we are now fairly agreed in a monistic conception of nature that
regards the whole universe, including man, as a wonderful unity,
governed by unalterable and eternal laws. In my philosophical book
_Die Welträtsel_ (1899)[151] and in the supplementary volume _Die
Lebenswunder_ (1904)[152] I have endeavoured to show that this pure
monism is securely established, and that the admission of the
all-powerful rule of the same principle of evolution throughout the
universe compels us to formulate a single supreme law--the
all-embracing "Law of Substance," or the united laws of the constancy
of matter and the conservation of energy. We should never have reached
this supreme general conception if Charles Darwin--a "monistic
philosopher" in the true sense of the word--had not prepared the way
by his theory of descent by natural selection, and crowned the great
work of his life by the association of this theory with a naturalistic


[Footnote 127: _Generelle Morphologie der Organismen_, 2 vols.,
Berlin, 1866.]

[Footnote 128: Eng. transl.; _The History of Creation_, London, 1876.]

[Footnote 129: London, 1908.]

[Footnote 130: Munich, 1884.]

[Footnote 131: _Die Mutationstheorie_, Leipzig, 1903.]

[Footnote 132: _Der Kampf der Theile im Organismus_, Leipzig, 1881.]

[Footnote 133: Leipzig, 1904.]

[Footnote 134: Berlin, 1876.]

[Footnote 135: _Wonders of Life_, London and New York, 1904.]

[Footnote 136: Eng. transl.; _The Evolution of Man_, 2 vols., London,
1879 and 1905.]

[Footnote 137: _Origin of Species_ (6th edit.), p. 396.]

[Footnote 138: Eng. transl.; _Facts and Arguments for Darwin_, London,

[Footnote 139: 3 vols., Berlin, 1894-96.]

[Footnote 140: _Descent of Man_ (Popular Edit.), p. 927.]

[Footnote 141: _Gesammelte Abhandlungen zur wissenschaftlichen
Medizin_, Berlin, 1856.]

[Footnote 142: Eng. transl.; _Last Words on Evolution_, London, 1906.]

[Footnote 143: _Descent of Man_, (Popular Edit.), p. 255.]

[Footnote 144: _Descent of Man_, p. 930.]

[Footnote 145: Eng. transl.; _The History of Creation_, London, 1876.]

[Footnote 146: Berlin, 1894-96.]

[Footnote 147: Leipzig, 1874, 5th edit. 1905. Eng. transl.; _The
Evolution of Man_, London, 1905.]

[Footnote 148: London, 1898.]

[Footnote 149: _Festschrift zur 350-jährigen Jubelfeier der Thüringer
Universität Jena_. Jena. 1908.]

[Footnote 150: London, 1885; 1888.]

[Footnote 151: _The Riddle of the Universe_, London and New York,

[Footnote 152: _The Wonders of Life_, London and New York, 1904.]




In developing his conception of organic evolution Charles Darwin was
of necessity brought into contact with some of the problems of mental
evolution. In _The Origin of Species_ he devoted a chapter to "the
diversities of instinct and of the other mental faculties in animals
of the same class."[153] When he passed to the detailed consideration
of _The Descent of Man_, it was part of his object to show "that there
is no fundamental difference between man and the higher mammals in
their mental faculties."[154] "If no organic being excepting man," he
said, "had possessed any mental power, or if his powers had been of a
wholly different nature, from those of the lower animals, then we
should never have been able to convince ourselves that our high
faculties had been gradually developed."[155] In his discussion of
_The Expression of the Emotions_ it was important for his purpose
"fully to recognise that actions readily become associated with other
actions and with various states of the mind."[156] His hypothesis of
sexual selection is largely dependent upon the exercise of choice on
the part of the female and her preference for "not only the more
attractive but at the same time the more vigourous and vicious
males."[157] Mental processes and physiological processes were for
Darwin closely correlated; and he accepted the conclusion "that the
nervous system not only regulates most of the existing functions of
the body, but has indirectly influenced the progressive development of
various bodily structures and of certain mental qualities."[158]

Throughout his treatment, mental evolution was for Darwin incidental
to and contributory to organic evolution. For specialised research in
comparative and genetic psychology, as an independent field of
investigation, he had neither the time nor the requisite training.
None the less his writings and the spirit of his work have exercised a
profound influence on this department of evolutionary thought. And,
for those who follow Darwin's lead, mental evolution is still in a
measure subservient to organic evolution. Mental processes are the
accompaniments or concomitants of the functional activity of specially
differentiated parts of the organism. They are in some way dependent
on physiological and physical conditions. But though they are not
physical in their nature, and though it is difficult or impossible to
conceive that they are physical in their origin, they are, for Darwin
and his followers, factors in the evolutionary process in its physical
or organic aspect. By the physiologist within his special and
well-defined universe of discourse they may be properly regarded as
epiphenomena; but by the naturalist in his more catholic survey of
nature they cannot be so regarded, and were not so regarded by Darwin.
Intelligence has contributed to evolution of which it is in a sense a

The facts of observation or of inference which Darwin accepted are
these: Conscious experience accompanies some of the modes of animal
behaviour; it is concomitant with certain physiological processes;
these processes are the outcome of development in the individual and
evolution in the race; the accompanying mental processes undergo a
like development. Into the subtle philosophical questions which arise
out of the naïve acceptance of such a creed it was not Darwin's
province to enter; "I have nothing to do," he said,[159] "with the
origin of the mental powers, any more than I have with that of life
itself." He dealt with the natural history of organisms, including not
only their structure but their modes of behaviour; with the natural
history of the states of consciousness which accompany some of their
actions; and with the relation of behaviour to experience. We will
endeavour to follow Darwin in his modesty and candour in making no
pretence to give ultimate explanations. But we must note one of the
implications of this self-denying ordinance of science. Development
and evolution imply continuity. For Darwin and his followers the
continuity is organic through physical heredity. Apart from
speculative hypothesis, legitimate enough in its proper place but here
out of court, we know nothing of continuity of mental evolution as
such: consciousness appears afresh in each succeeding generation.
Hence it is that for those who follow Darwin's lead, mental evolution
is and must ever be, within his universe of discourse, subservient to
organic evolution. Only in so far as conscious experience, or its
neural correlate, effects some changes in organic structure can it
influence the course of heredity; and conversely only in so far as
changes in organic structure are transmitted through heredity, is
mental evolution rendered possible. Such is the logical outcome of
Darwin's teaching.

Those who abide by the cardinal results of this teaching are bound to
regard all behaviour as the expression of the functional activities of
the living tissues of the organism, and all conscious experience as
correlated with such activities. For the purposes of scientific
treatment, mental processes are one mode of expression of the same
changes of which the physiological processes accompanying behaviour
are another mode of expression. This is simply accepted as a fact
which others may seek to explain. The behaviour itself is the adaptive
application of the energies of the organism; it is called forth by
some form of presentation or stimulation brought to bear on the
organism by the environment. This presentation is always an individual
or personal matter. But in order that the organism may be fitted to
respond to the presentation of the environment it must have undergone
in some way a suitable preparation. According to the theory of
evolution this preparation is primarily racial and is transmitted
through heredity. Darwin's main thesis was that the method of
preparation is predominantly by natural selection. Subordinate to
racial preparation, and always dependent thereon, is individual or
personal preparation through some kind of acquisition; of which the
guidance of behaviour through individually won experience is a typical
example. We here introduce the mental factor because the facts seem to
justify the inference. Thus there are some modes of behaviour which
are wholly and solely dependent upon inherited racial preparation;
there are other modes of behaviour which are also dependent, in part
at least, on individual preparation. In the former case the behaviour
is adaptive on the first occurrence of the appropriate presentation;
in the latter case accommodation to circumstances is only reached
after a greater or less amount of acquired organic modification of
structure, often accompanied (as we assume) in the higher animals by
acquired experience. Logically and biologically the two classes of
behaviour are clearly distinguishable: but the analysis of complex
cases of behaviour where the two factors coöperate, is difficult and
requires careful and critical study of life-history.

The foundations of the mental life are laid in the conscious
experience that accompanies those modes of behaviour, dependent
entirely on racial preparation, which may broadly be described as
instinctive. In the eighth chapter of _The Origin of Species_ Darwin
says,[160] "I will not attempt any definition of instinct.... Every
one understands what is meant, when it is said that instinct impels
the cuckoo to migrate and to lay her eggs in other birds' nests. An
action, which we ourselves require experience to enable us to perform,
when performed by an animal, more especially by a very young one,
without experience, and when performed by many individuals in the same
way, without their knowing for what purpose it is performed, is
usually said to be instinctive." And in the summary at the close of
the chapter he says,[161] "I have endeavoured briefly to show that the
mental qualities of our domestic animals vary, and that the variations
are inherited. Still more briefly I have attempted to show that
instincts vary slightly in a state of nature. No one will dispute that
instincts are of the highest importance to each animal. Therefore
there is no real difficulty, under changing conditions of life, in
natural selection accumulating to any extent slight modifications of
instinct which are in any way useful. In many cases habit or use and
disuse have probably come into play."

Into the details of Darwin's treatment there is neither space nor need
to enter. There are some ambiguous passages; but it may be said that
for him, as for his followers to-day, instinctive behaviour is wholly
the result of racial preparation transmitted through organic heredity.
For the performance of the instinctive act no individual preparation
under the guidance of personal experience is necessary. It is true
that Darwin quotes with approval Huber's saying that "a little dose of
judgment or reason often comes into play, even with animals low in the
scale of nature."[162] But we may fairly interpret his meaning to be
that in behaviour, which is commonly called instinctive, some element
of intelligent guidance is often combined. If this be conceded the
strictly instinctive performance (or part of the performance) is the
outcome of heredity and due to the direct transmission of parental or
ancestral aptitudes. Hence the instinctive response as such depends
entirely on how the nervous mechanism has been built up through
heredity; while intelligent behaviour, or the intelligent factor in
behaviour, depends also on how the nervous mechanism has been modified
and moulded by use during its development and concurrently with the
growth of individual experience in the customary situations of daily
life. Of course it is essential to the Darwinian thesis that what Sir
E. Ray Lankester has termed "educability," not less than instinct, is
hereditary. But it is also essential to the understanding of this
thesis that the differentiae of the hereditary factor should be
clearly grasped.

For Darwin there were two modes of racial preparation, (_1_) natural
selection, and (_2_) the establishment of individually acquired habit.
He showed that instincts are subject to hereditary variation; he saw
that instincts are also subject to modification through acquisition in
the course of individual life. He believed that not only the
variations but also, to some extent, the modifications are inherited.
He therefore held that some instincts (the greater number) are due to
natural selection but that others (less numerous) are due, or partly
due, to the inheritance of acquired habits. The latter involve
Lamarckian inheritance, which of late years has been the centre of so
much controversy. It is noteworthy however that Darwin laid especial
emphasis on the fact that many of the most typical and also the most
complex instincts--those of neuter insects--do not admit of such an
interpretation. "I am surprised," he says,[163] "that no one has
hitherto advanced this demonstrative case of neuter insects, against
the well-known doctrine of inherited habit, as advanced by Lamarck."
None the less Darwin admitted this doctrine as supplementary to that
which was more distinctively his own--for example in the case of the
instincts of domesticated animals. Still, even in such cases, "it may
be doubted," he says,[164] "whether any one would have thought of
training a dog to point, had not some one dog naturally shown a
tendency in this line ... so that habit and some degree of selection
have probably concurred in civilising by inheritance our dogs." But in
the interpretation of the instincts of domesticated animals, a more
recently suggested hypothesis, that of organic selection,[165] may be
helpful. According to this hypothesis any intelligent modification of
behaviour which is subject to selection is probably coincident in
direction with an inherited tendency to behave in this fashion. Hence
in such behaviour there are two factors: (1) an incipient variation in
the line of such behaviour, and (2) an acquired modification by which
the behaviour is carried further along the same line. Under natural
selection those organisms in which the two factors coöperate are
likely to survive. Under artificial selection they are deliberately
chosen out from among the rest.

Organic selection has been termed a compromise between the more
strictly Darwinian and the Lamarckian principles of interpretation.
But it is not in any sense a compromise. The principle of
interpretation of that which is instinctive and hereditary is wholly
Darwinian. It is true that some of the facts of observation relied
upon by Lamarckians are introduced. For Lamarckians however the
modifications which are admittedly factors in survival, are regarded
as the parents of inherited variations; for believers in organic
selection they are only the foster-parents or nurses. It is because
organic selection is the direct outcome of and a natural extension of
Darwin's cardinal thesis that some reference to it here is
justifiable. The matter may be put with the utmost brevity as follows:
(1) Variations (V) occur, some of which are in the direction of
increased adaptation (+), others in the direction of decreased
adaptation (-).

(2) Acquired modifications (M) also occur. Some of these are in the
direction of increased accommodation to circumstances (+), while
others are in the direction of diminished accommodation (-). Four
major combinations are

   (_b_) + V with - M,      (_c_) - V with + M,

   (_a_) + V with + M,      (_d_) - V with - M.

Of these (_d_) must inevitably be eliminated while (_a_) are selected.
The predominant survival of (_a_) entails the survival of the adaptive
variations which are inherited. The contributory acquisitions (+ M)
are not inherited; but there are none the less factors in determining
the survival of the coincident variations. It is surely abundantly
clear that this is Darwinism and has no tincture of Lamarck's
essential principle, the inheritance of acquired characters.

Whether Darwin himself would have accepted this interpretation of some
at least of the evidence put forward by Lamarckians is unfortunately a
matter of conjecture. The fact remains that in his interpretation of
instinct and in allied questions he accepted the inheritance of
individually acquired modifications of behaviour and structure.

Darwin was chiefly concerned with instinct from the biological rather
than from the psychological point of view. Indeed it must be confessed
that, from the latter standpoint, his conception of instinct as a
"mental faculty" which "impels" an animal to the performance of
certain actions, scarcely affords a satisfactory basis for genetic
treatment. To carry out the spirit of Darwin's teaching it is
necessary to link more closely biological and psychological evolution.
The first step towards this is to interpret the phenomena of
instinctive behaviour in terms of stimulation and response. It may be
well to take a particular case. Swimming on the part of a duckling is,
from the biological point of view, a typical example of instinctive
behaviour. Gently lower a recently hatched bird into water:
coordinated movements of the limbs follow in rhythmical sequence. The
behaviour is new to the individual though it is no doubt closely
related to that of walking, which is no less instinctive. There is a
group of stimuli afforded by the "presentation" which results from
partial immersion: upon this there follows as a complex response an
application of the functional activities in swimming; the sequence of
adaptive application on the appropriate presentation is determined by
racial preparation. We know, it is true, but little of the
physiological details of what takes place in the central nervous
system; but in broad outline the nature of the organic mechanism and
the manner of its functioning may at least be provisionally
conjectured in the present state of physiological knowledge. Similarly
in the case of the pecking of newly-hatched chicks; there is a visual
presentation, there is probably a coöperating group of stimuli from
the alimentary tract in need of food, there is an adaptive application
of the activities in a definite mode of behaviour. Like data are
afforded in a great number of cases of instinctive procedure,
sometimes occurring very early in life, not infrequently deferred
until the organism is more fully developed, but all of them dependent
upon racial preparation. No doubt there is some range of variation in
the behaviour, just such variation as the theory of natural selection
demands. But there can be no question that the higher animals inherit
a bodily organisation and a nervous system, the functional working of
which gives rise to those inherited modes of behaviour which are
termed instinctive.

It is to be noted that the term "instinctive" is here employed in the
adjectival form as a descriptive heading under which may be grouped
many and various modes of behaviour due to racial preparation. We
speak of these as inherited; but in strictness what is transmitted
through heredity is the complex of anatomical and physiological
conditions under which, in appropriate circumstances, the organism so
behaves. So far the term "instinctive" has a restricted biological
connotation in terms of behaviour. But the connecting link between
biological evolution and psychological evolution is to be sought,--as
Darwin fully realised,--in the phenomena of instinct, broadly
considered. The term "instinctive" has also a psychological
connotation. What is that connotation?

Let us take the case of the swimming duckling or the pecking chick,
and fix our attention on the first instinctive performance. Grant that
just as there is, strictly speaking, no inherited behaviour, but only
the conditions which render such behaviour under appropriate
circumstances possible; so too there is no inherited experience, but
only the conditions which render such experience possible; then the
cerebral conditions in both cases are the same. The biological
behaviour-complex, including the total stimulation and the total
response with the intervening or resultant processes in the sensorium,
is accompanied by an experience-complex including the initial
stimulation-consciousness and resulting response-consciousness. In the
experience-complex are comprised data which in psychological analysis
are grouped under the headings of cognition, affective tone and
conation. But the complex is probably experienced as an unanalysed
whole. If then we use the term "instinctive" so as to comprise all
congenital modes of behaviour which contribute to experience, we are
in a position to grasp the view that the net result in consciousness
constitutes what we may term the primary tissue of experience. To the
development of this experience each instinctive act contributes. The
nature and manner of organisation of this primary tissue of experience
are dependent on inherited biological aptitudes; but they are from the
outset onwards subject to secondary development dependent on acquired
aptitudes. Biological values are supplemented by psychological values
in terms of satisfaction or the reverse.

In our study of instinct we have to select some particular phase of
animal behaviour and isolate it so far as is possible from the life of
which it is a part. But the animal is a going concern, restlessly
active in many ways. Many instinctive performances, as Darwin pointed
out,[166] are serial in their nature. But the whole of active life is
a serial and coordinated business. The particular instinctive
performance is only an episode in a life-history, and every mode of
behaviour is more or less closely correlated with other modes. This
coordination of behaviour is accompanied by a correlation of the modes
of primary experience. We may classify the instinctive modes of
behaviour and their accompanying modes of instinctive experience under
as many heads as may be convenient for our purposes of interpretation,
and label them instincts of self-preservation, of pugnacity, of
acquisition, the reproductive instincts, the parental instincts, and
so forth. An instinct, in this sense of the term (for example the
parental instinct), may be described as a specialised part of the
primary tissue of experience differentiated in relation to some
definite biological end. Under such an instinct will fall a large
number of particular and often well-defined modes of behaviour, each
with its own peculiar mode of experience.

It is no doubt exceedingly difficult as a matter of observation and of
inference securely based thereon to distinguish what is primary from
what is in part due to secondary acquisition--a fact which Darwin
fully appreciated. Animals are educable in different degrees; but
where they are educable they begin to profit by experience from the
first. Only, therefore, on the occasion of the first instinctive act
of a given type can the experience gained be regarded as _wholly_
primary; all subsequent performance is liable to be in some degree,
sometimes more, sometimes less, modified by the acquired disposition
which the initial behaviour engenders. But the early stages of
acquisition are always along the lines predetermined by instinctive
differentiation. It is the task of comparative psychology to
distinguish the primary tissue of experience from its secondary and
acquired modifications. We cannot follow up the matter in further
detail. It must here suffice to suggest that this conception of
instinct as a primary form of experience lends itself better to
natural history treatment than Darwin's conception of an impelling
force, and that it is in line with the main trend of Darwin's thought.

In a characteristic work,--characteristic in wealth of detail, in
closeness and fidelity of observation, in breadth of outlook, in
candour and modesty,--Darwin dealt with _The Expression of the
Emotions in Man and Animals_. Sir Charles Bell in his _Anatomy of
Expression_ had contended that many of man's facial muscles had been
specially created for the sole purpose of being instrumental in the
expression of his emotions. Darwin claimed that a natural explanation,
consistent with the doctrine of evolution, could in many cases be
given and would in other cases be afforded by an extension of the
principles he advocated. "No doubt," he said,[167] "as long as man and
all other animals are viewed as independent creations, an effectual
stop is put to our natural desire to investigate as far as possible
the causes of Expression. By this doctrine, anything and everything
can be equally well explained.... With mankind, some expressions ...
can hardly be understood, except on the belief that man once existed
in a much lower and animal-like condition. The community of certain
expressions in distinct though allied species ... is rendered somewhat
more intelligible, if we believe in their descent from a common
progenitor. He who admits on general grounds that the structure and
habits of all animals have been gradually evolved, will look at the
whole subject of Expression in a new and interesting light."

Darwin relied on three principles of explanation. "The first of these
principles is, that movements which are serviceable in gratifying some
desire, or in relieving some sensation, if often repeated, become so
habitual that they are performed, whether or not of any service,
whenever the same desire or sensation is felt, even in a very weak
degree."[168] The modes of expression which fall under this head have
become instinctive through the hereditary transmission of acquired
habit. "As far as we can judge, only a few expressive movements are
learnt by each individual; that is, were consciously and voluntarily
performed during the early years of life for some definite object, or
in imitation of others, and then became habitual. The far greater
number of the movements of expression, and all the more important
ones, are innate or inherited; and such cannot be said to depend on
the will of the individual. Nevertheless, all those included under our
first principle were at first voluntarily performed for a definite
object,--namely, to escape some danger, to relieve some distress, or
to gratify some desire."[169]

"Our second principle is that of antithesis. The habit of voluntarily
performing opposite movements under opposite impulses has become
firmly established in us by the practice of our whole lives. Hence, if
certain actions have been regularly performed, in accordance with our
first principle, under a certain frame of mind, there will be a strong
and involuntary tendency to the performance of directly opposite
actions, whether or not these are of any use, under the excitement of
an opposite frame of mind."[170] This principle of antithesis has not
been widely accepted. Nor is Darwin's own position easy to grasp.

"Our third principle," he says,[171] "is the direct action of the
excited nervous system on the body, independently of the will, and
independently, in large part, of habit. Experience shows that
nerve-force is generated and set free whenever the cerebro-spinal
system is excited. The direction which this nerve-force follows is
necessarily determined by the lines of connection between the
nerve-cells, with each other and with various parts of the body."

Lack of space prevents our following up the details of Darwin's
treatment of expression. Whether we accept or do not accept his three
principles of explanation we must regard his work as a masterpiece of
descriptive analysis, packed full of observations possessing lasting
value. For a further development of the subject it is essential that
the instinctive factors in expression should be more fully
distinguished from those which are individually acquired--a difficult
task--and that the instinctive factors should be rediscussed in the
light of modern doctrines of heredity, with a view to determining
whether Lamarckian inheritance, on which Darwin so largely relied, is
necessary for an interpretation of the facts.

The whole subject as Darwin realised is very complex. Even the term
"expression" has a certain amount of ambiguity. When the emotion is in
full flood, the animal fights, flees, or faints. Is this full-tide
effect to be regarded as expression; or are we to restrict the term to
the premonitory or residual effects--the bared canine when the
fighting mood is being roused, the ruffled fur when reminiscent
representations of the object inducing anger cross the mind? Broadly
considered both should be included. The activity of premonitory
expression as a means of communication was recognised by Darwin; he
might, perhaps, have emphasised it more strongly in dealing with the
lower animals. Man so largely relies on a special means of
communication, that of language, that he sometimes fails to realise
that for animals with their keen powers of perception, and dependent
as they are on such means of communication, the more strictly
biological means of expression are full of subtle suggestiveness. Many
modes of expression, otherwise useless, are signs of behaviour that
may be anticipated,--signs which stimulate the appropriate attitude of
response. This would not, however, serve to account for the utility of
the organic accompaniments--heart-affection, respiratory changes,
vaso-motor effects and so forth, together with heightened muscular
tone,--on all of which Darwin lays stress[172] under his third
principle. The biological value of all this is, however, of great
importance, though Darwin was hardly in a position to take it fully
into account.

Having regard to the instinctive and hereditary factors of emotional
expression we may ask whether Darwin's third principle does not alone
suffice as an explanation. Whether we admit or reject Lamarckian
inheritance it would appear that all hereditary expression must be due
to pre-established connections within the central nervous system and
to a transmitted provision for coordinated response under the
appropriate stimulation. If this be so, Darwin's first and second
principles are subordinate and ancillary to the third, an expression,
so far as it is instinctive or heredity, being "the direct result of
the constitution of the nervous system."

Darwin accepted the emotions themselves as hereditary or acquired
states of mind and devoted his attention to their expression. But
these emotions themselves are genetic products and as such dependent
on organic conditions. It remained, therefore, for psychologists who
accepted evolution and sought to build on biological foundations to
trace the genesis of these modes of animal and human experience. The
subject has been independently developed by Professors Lange and
James;[173] and some modification of their view is regarded by many
evolutionists as affording the best explanation of the facts. We must
fix our attention on the lower emotions, such as anger or fear, and on
their first occurrence in the life of the individual organism. It is a
matter of observation that if a group of young birds which have been
hatched in an incubator are frightened by an appropriate presentation,
auditory or visual, they instinctively respond in special ways. If we
speak of this response as the expression, we find that there are many
factors. There are certain visible modes of behaviour, crouching at
once, scattering and then crouching, remaining motionless, the braced
muscles sustaining an attitude of arrest, and so forth, There are also
certain visceral or organic effects, such as affections of the heart
and respiration. These can be readily observed by taking the young
bird in the hand. Other effects cannot be readily observed; vaso-motor
changes, affections of the alimentary canal, the skin and so forth.
Now the essence of the James-Lange view, as applied to these
congenital effects, is that though we are justified in speaking of
them as effects of the stimulation, we are not justified, without
further evidence, in speaking of them as effects of the emotional
state. May it not rather be that the emotion as a primary mode of
experience is the concomitant of the net result of the organic
situation--the initial presentation, the instinctive mode of
behaviour, the visceral disturbances?

According to this interpretation the primary tissue of experience of
the emotional order, felt as an unanalysed complex, is generated by
the stimulation of the sensorium by afferent or incoming physiological
impulses from the special senses, from the organs concerned in the
responsive behaviour, from the viscere and vaso-motor system.

Some psychologists, however, contend that the emotional experience is
generated in the sensorium prior to, and not subsequent to, the
behaviour-response and the visceral disturbances. It is a direct and
not an indirect outcome of the presentation to the special senses. Be
this as it may, there is a growing tendency to bring into the closest
possible relation, or even to identify, instinct and emotion in their
primary genesis. The central core of all such interpretations is that
instinctive behaviour and experience, its emotional accompaniments,
and its expression, are but different aspects of the outcome of the
same organic occurrences. Such emotions are, therefore, only a
distinguishable aspect of the primary tissue of experience and exhibit
a like differentiation. Here again a biological foundation is laid for
a psychological doctrine of the mental development of the individual.

The intimate relation between emotion as a psychological mode of
experience and expression as a group of organic conditions has an
important bearing on biological interpretation. The emotion, as the
psychological accompaniment of orderly disturbances in the central
nervous system, profoundly influences behaviour and often renders it
more vigourous and more effective. The utility of the emotions in the
struggle for existence can, therefore, scarcely be over-estimated.
Just as keenness of perception has survival-value; just as it is
obviously subject to variation; just as it must be enhanced under
natural selection, whether individually acquired increments are
inherited or not; and just as its value lies not only in this or that
special perceptive act but in its importance for life as a whole; so
the vigourous effectiveness of activity has survival-value; it is
subject to variation; it must be enhanced under natural selection; and
its importance lies not only in particular modes of behaviour but in
its value for life as a whole. If emotion and its expression as a
congenital endowment are but different aspects of the same biological
occurrence; and if this is a powerful supplement to vigour
effectiveness and persistency of behaviour, it must on Darwin's
principles be subject to natural selection.

If we include under the expression of the emotions not only the
premonitory symptoms of the initial phases of the organic and mental
state, not only the signs or conditions of half-tide emotion, but the
full-tide manifestation of an emotion which dominates the situation,
we are naturally led on to the consideration of many of the phenomena
which are discussed under the head of sexual selection. The subject is
difficult and complex, and it was treated by Darwin with all the
strength he could summon to the task. It can only be dealt with here
from a special point of view--that which may serve to illustrate the
influence of certain mental factors on the course of evolution. From
this point of view too much stress can scarcely be laid on the
dominance of emotion during the period of courtship and pairing in the
more highly organised animals. It is a period of maximum vigour,
maximum activity, and, correlated with special modes of behaviour and
special organic and visceral accompaniments, a period also of maximum
emotional excitement. The combats of males, their dances and aerial
evolutions, their elaborate behaviour and display, or the flood of
song in birds, are emotional expressions which are at any rate
coincident in time with sexual periodicity. From the combat of the
males there follows on Darwin's principles the elimination of those
which are deficient in bodily vigour, deficient in special structures,
offensive or protective, which contribute to success, deficient in the
emotional supplement of which persistent and whole-hearted fighting is
the expression, and deficient in alertness and skill which are the
outcome of the psychological development of the powers of perception.
Few biologists question that we have here a mode of selection of much
importance, though its influence on psychological evolution often
fails to receive its due emphasis. Mr. Wallace[174] regards it as "a
form of natural selection"; "to it," he says, "we must impute the
development of the exceptional strength, size, and activity of the
male, together with the possession of special offensive and defensive
weapons, and of all other characters which arise from the development
of these or are correlated with them." So far there is little
disagreement among the followers of Darwin--for Mr. Wallace, with fine
magnanimity, has always preferred to be ranked as such,
notwithstanding his right, on which a smaller man would have
constantly insisted, to the claim of independent originator of the
doctrine of natural selection. So far with regard to sexual selection
Darwin and Mr. Wallace are agreed; so far and no farther. For Darwin,
says Mr. Wallace,[175] "has extended the principle into a totally
different field of action, which has none of that character of
constancy and of inevitable result that attaches to natural selection,
including male rivalry; for by far the larger portion of the
phenomena, which he endeavours to explain by the direct action of
sexual selection, can only be so explained on the hypothesis that the
immediate agency is female choice or preference. It is to this that he
imputes the origin of all secondary sexual characters other than
weapons of offence and defence.... In this extension of sexual
selection to include the action of female choice or preference, and in
the attempt to give to that choice such wide-reaching effects, I am
unable to follow him more than a very little way."

Into the details of Mr. Wallace's criticisms it is impossible to enter
here. We cannot discuss either the mode of origin of the variations in
structure which have rendered secondary sexual characters possible or
the modes of selection other than sexual which have rendered them,
within narrow limits, specifically constant. Mendelism and mutation
theories may have something to say on the subject when these theories
have been more fully correlated with the basal principles of
selection. It is noteworthy that Mr. Wallace says:[176] "Besides the
acquisition of weapons by the male for the purpose of fighting with
other males, there are some other sexual characters which may have
been produced by natural selection. Such are the various sounds and
odours which are peculiar to the male, and which serve as a call to
the female or as an indication of his presence. These are evidently a
valuable addition to the means of recognition of the two sexes, and
are a further indication, that the pairing season has arrived; and the
production, intensification, and differentiation of these sounds and
odours are clearly within the power of natural selection. The same
remark will apply to the peculiar calls of birds, and even to the
singing of the males." Why the same remark should not apply to their
colours and adornments is not obvious. What is obvious is that "means
of recognition" and "indication that the pairing season has arrived"
are dependent on the perceptive powers of the female who recognises
and for whom the indication has meaning. The hypothesis of female
preference, stripped of the aesthetic surplusage which is
psychologically both unnecessary and unproven, is really only
different in degree from that which Mr. Wallace admits in principle
when he says that it is probable that the female is pleased or excited
by the display.

Let us for our present purpose leave on one side and regard as _sub
judice_ the question whether the specific details of secondary sexual
characters are the outcome of female choice. For us the question is
whether certain psychological accompaniments of the pairing situation
have influenced the course of evolution and whether these
psychological accompaniments are themselves the outcome of evolution.
As a matter of observation, specially differentiated modes of
behaviour, often very elaborate, frequently requiring highly developed
skill, and apparently highly charged with emotional tone, are the
precursors of pairing. They are generally confined to the males, whose
fierce combats during the period of sexual activity are part of the
emotional manifestation. It is inconceivable that they have no
biological meaning; and it is difficult to conceive that they have any
other biological end than to evoke in the generally more passive
female the pairing impulse. They, are based on instinctive foundations
ingrained in the nervous constitution through natural (or may we not
say sexual?) selection in virtue of their profound utility. They are
called into play by a specialised presentation such as the sight or
the scent of the female at, or a little in advance of, a critical
period of the physiological rhythm. There is no necessity that the
male should have any knowledge of the end to which his strenuous
activity leads up. In presence of the female there is an elaborate
application of all the energies of behaviour, just because ages of
racial preparation have made him biologically and emotionally what he
is--a functionally sexual male that must dance or sing or go through
hereditary movements of display, when the appropriate stimulation
comes. Of course after the first successful courtship his future
behaviour will be in some degree modified by his previous experience.
No doubt during his first courtship he is gaining the primary data of
a peculiarly rich experience, instinctive and emotional. But the
biological foundations of the behaviour of courtship are laid in the
hereditary coordinations. It would seem that in some cases, not indeed
in all, perhaps especially in those cases in which secondary sexual
behaviour is most highly evolved,--correlative with the ardour of the
male is a certain amount of reluctance in the female. The pairing act
on her part only takes place after prolonged stimulation, for
affording which the behaviour of male courtship is the requisite
presentation. The most vigourous, defiant and mettlesome male is
preferred just because he alone affords a contributory stimulation
adequate to evoke the pairing impulse with its attendant emotional

It is true that this places female preference or choice on a much
lower psychological plane than Darwin in some passages seems to
contemplate where, for example, he says that the female appreciates
the display of the male and places to her credit a taste for the
beautiful. But Darwin himself distinctly states[177] that "it is not
probable that she consciously deliberates; but she is most excited or
attracted by the most beautiful, or melodious, or gallant males." The
view here put forward, which has been developed by Prof. Groos,[178]
therefore seems to have Darwin's own sanction. The phenomena are not
only biological; there are psychological elements as well. One can
hardly suppose that the female is unconscious of the male's presence;
the final yielding must surely be accompanied by heightened emotional
tone. Whether we call it choice or not is merely a matter of
definition of terms. The behaviour is in part determined by
supplementary psychological values. Prof. Groos regards the coyness of
females as "a most efficient means of preventing the too early and too
frequent yielding to the sexual impulse."[179] Be that as it may, it
is, in any case, if we grant the facts, a means through which male
sexual behaviour with all its biological and psychological
implications, is raised to a level otherwise perhaps unattainable by
natural means, while in the female it affords opportunities for the
development in the individual and evolution in the race of what we may
follow Darwin in calling appreciation, if we empty this word of the
aesthetic implications which have gathered round it in the mental life
of man.

Regarded from this standpoint of sexual selection, broadly considered,
has probably been of great importance. The psychological
accompaniments of the pairing situation have profoundly influenced the
course of biological evolution and are themselves the outcome of that

Darwin makes only passing reference to those modes of behaviour in
animals which go by the name of play. "Nothing," he says,[180] "is
more common than for animals to take pleasure in practising whatever
instinct they follow at other times for some real good." This is one
of the very numerous cases in which a hint of the master has served to
stimulate research in his disciples. It was left to Prof. Groos to
develop this subject on evolutionary lines and to elaborate in a
masterly manner Darwin's suggestion. "The utility of play," he
says,[181] "is incalculable. This utility consists in the practice and
exercise it affords for some of the more important duties of
life,"--that is to say, for the performance of activities which will
in adult life be essential to survival. He urges[182] that "the play
of young animals has its origin in the fact that certain very
important instincts appear at a time when the animal does not
seriously need them." It is, however, questionable whether any
instincts appear at a time when they are not needed. And it is
questionable whether the instinctive and emotional attitude of the
play-fight, to take one example, can be identified with those which
accompany fighting in earnest, though no doubt they are closely
related and have some common factors. It is probable that play, as
preparatory behaviour, differs in biological detail (as it almost
certainly does in emotional attributes) from the earnest of after-life
and that it has been evolved through differentiation and integration
of the primary tissue of experience, as a preparation through which
certain essential modes of skill may be acquired--those animals in
which the preparatory play-propensity was not inherited in due force
and requisite amount being subsequently eliminated in the struggle for
existence. In any case there is little question that Prof. Groos is
right in basing the play-propensity on instinctive foundations.[183]
None the less, as he contends, the essential biological value of play
is that it is a means of training the educable nerve-tissue, of
developing that part of the brain which is modified by experience and
which thus acquires new characters, of elaborating the secondary
tissue of experience on the predetermined lines of instinctive
differentiation and thus furthering the psychological activities which
are included under the comprehensive term "intelligent."

In _The Descent of Man_ Darwin dealt at some length with intelligence
and the higher mental faculties.[184] His object, he says, is to show
that there is no fundamental difference between man and the higher
mammals in their mental faculties; that these faculties are variable
and the variations tend to be inherited; and that under natural
selection beneficial variations of all kinds will have been preserved
and injurious ones eliminated.

Darwin was too good an observer and too honest a man to minimise the
"enormous difference" between the level of mental attainment of
civilised man and that reached by any animal. His contention was that
the difference, great as it is, is one of degree and not of kind. He
realised that, in the development of the mental faculties of man, new
factors in evolution have supervened--factors which play but a
subordinate and subsidiary part in animal intelligence.
Intercommunication by means of language, approbation and blame, and
all that arises out of reflective thought, are but foreshadowed in the
mental life of animals. Still he contends that these may be explained
on the doctrine of evolution. He urges[185] "that man is variable in
body and mind; and that the variations are induced, either directly or
indirectly, by the same general causes, and obey the same general
laws, as with the lower animals." He correlates mental development
with the evolution of the brain.[186] "As the various mental faculties
gradually developed themselves, the brain would almost certainly
become larger. No one, I presume, doubts that the large proportion
which the size of man's brain bears to his body, compared to the same
proportion in the gorilla or orang, is closely connected with his
higher mental powers." "With respect to the lower animals," he
says,[187] "M. E. Lartet,[188] by comparing the crania of tertiary and
recent mammals belonging to the same groups, has come to the
remarkable conclusion that the brain is generally larger and the
convolutions are more complex in the more recent form."

Sir E. Ray Lankester has sought to express in the simplest terms the
implications of the increase in size of the cerebrum. "In what," he
asks, "does the advantage of a larger cerebral mass consist?" "Man,"
he replies, "is born with fewer ready-made tricks of the
nerve-centres--these performances of an inherited nervous mechanism so
often called by the ill-defined term 'instincts'--than are the monkeys
or any other animal. Correlated with the absence of inherited
ready-made mechanism, man has a greater capacity of developing in the
course of his individual growth similar nervous mechanisms (similar
to but not identical with those of 'instinct') than any other
animal.... The power of being educated--'educability' as we may term
it--is what man possesses in excess as compared with the apes. I think
we are justified in forming the hypothesis that it is this
'educability' which is the correlative of the increased size of the
cerebrum." There has been natural selection of the more educable
animals, for "the character which we describe as 'educability' can be
transmitted, it is a congenital character. But the _results_ of
education can _not_ be transmitted. In each generation they have to be
acquired afresh, and with increased 'educability' they are more
readily acquired and a larger variety of them.... The fact is that
there is no community between the mechanisms of instinct and the
mechanisms of intelligence, and that the latter are later in the
history of the evolution of the brain than the former and can only
develop in proportion as the former become feeble and defective."[189]

In this statement we have a good example of the further development of
views which Darwin foreshadowed but did not thoroughly work out. It
states the biological case clearly and tersely. Plasticity of
behaviour in special accommodation to special circumstances is of
survival value; it depends upon acquired characters; it is correlated
with increase in size and complexity of the cerebrum; under natural
selection therefore the larger and more complex cerebrum as the organ
of plastic behaviour has been the outcome of natural selection. We
have thus the biological foundations for a further development of
genetic psychology.

There are diversities of opinion, as Darwin showed, with regard to the
range of instinct in man and the higher animals as contrasted with
lower types. Darwin himself said[190] that "Man, perhaps, has somewhat
fewer instincts than those possessed by the animals which come next to
him in the series." On the other hand, Prof. Wm. James says[191] that
man is probably the animal with most instincts. The true position is
that man and the higher animals have fewer complete and self-sufficing
instincts than those which stand lower in the scale of mental
evolution, but that they have an equally large or perhaps larger mass
of instinctive raw material which may furnish the stuff to be
elaborated by intelligent processes. There is, perhaps, a greater
abundance of the primary tissue of experience to be refashioned and
integrated by secondary modification; there is probably the same
differentiation in relation to the determining biological ends, but
there is at the outset less differentiation of the particular and
specific modes of behaviour. The specialised instinctive performances
and their concomitant experience-complexes are at the outset more
indefinite. Only through acquired connections, correlated with
experience, do they become definitely organised.

The full working-out of the delicate and subtle relationship of
instinct and educability--that is, of the hereditary and the acquired
factors in the mental life--is the task which lies before genetic and
comparative psychology. They interact throughout the whole of life,
and their interactions are very complex. No one can read the chapters
of _The Descent of Man_ which Darwin devotes to a consideration of the
mental characters of man and animals without noticing, on the one
hand, how sedulous he is in his search for hereditary foundations,
and, on the other hand, how fully he realises the importance of
acquired habits of mind. The fact that educability itself has innate
tendencies--is in fact a partially differentiated educability--renders
the unravelling of the factors of mental progress all the more

In his comparison of the mental powers of men and animals it was
essential that Darwin should lay stress on points of similarity rather
than on points of difference. Seeking to establish a doctrine of
evolution, with its basal concept of continuity of process and
community of character, he was bound to render clear and to emphasise
the contention that the difference in mind between man and the higher
animals, great as it is, is one of degree and not of kind. To this end
Darwin not only recorded a large number of valuable observations of
his own, and collected a considerable body of information from
reliable sources, he presented the whole subject in a new light and
showed that a natural history of mind might be written and that this
method of study offered a wide and rich field for investigation. Of
course those who regarded the study of mind only as a branch of
metaphysics smiled at the philosophical ineptitude of the mere man of
science. But the investigation, on natural history lines, has been
prosecuted with a large measure of success. Much indeed still remains
to be done; for special training is required, and the workers are
still few. Promise for the future is however afforded by the fact that
investigation is prosecuted on experimental lines and that something
like organised methods of research are taking form. There is now but
little reliance on casual observations recorded by those who have not
undergone the necessary discipline in these methods. There is also
some change of emphasis in formulating conclusions. Now that the
general evolutionary thesis is fully and freely accepted by those who
carry on such researches, more stress is laid on the differentiation
of the stages of evolutionary advance than on the fact of their
underlying community of nature. The conceptual intelligence which is
especially characteristic of the higher mental procedure of man is
more firmly distinguished from the perceptual intelligence which he
shares with the lower animals--distinguished now as a higher product
of evolution, no longer as differing in origin or different in kind.
Some progress has been made, on the one hand in rendering an account
of intelligent profiting by experience under the guidance of pleasure
and pain in the perceptual field, on lines predetermined by
instinctive differentiation for biological ends, and on the other hand
in elucidating the method of conceptual thought employed, for
example, by the investigator himself in interpreting the perceptual
experience of the lower animals.

Thus there is a growing tendency to realise more fully that there are
two orders of educability--first an educability of the perceptual
intelligence based on the biological foundation of instinct, and
secondly an educability of the conceptual intelligence which
refashions and rearranges the data afforded by previous inheritance
and acquisition. It is in relation to this second and higher order of
educability that the cerebrum of man shows so large an increase of
mass and a yet larger increase of effective surface through its rich
convolutions. It is through educability of this order that the human
child is brought intellectually and affectively into touch with the
ideal constructions by means of which man has endeavoured, with more
or less success, to reach an interpretation of nature, and to guide
the course of the further evolution of his race--ideal constructions
which form part of man's environment.

It formed no part of Darwin's purpose to consider, save in broad
outline, the methods, or to discuss in any fulness of detail the
results of the process by which a differentiation of the mental
faculties of man from those of the lower animals has been brought
about--a differentiation the existence of which he again and again
acknowledges. His purpose was rather to show that, notwithstanding
this differentiation, there is basal community in kind. This must be
remembered in considering his treatment of the biological foundations
on which man's systems of ethics are built. He definitely stated that
he approached the subject "exclusively from the side of natural
history."[192] His general conclusion is that the moral sense is
fundamentally identical with the social instincts, which have been
developed for the good of the community; and he suggests that the
concept which thus enables us to interpret the biological ground-plan
of morals also enables us to frame a rational ideal of the moral end.
"As the social instincts," he says,[193] "both of man and the lower
animals have no doubt been developed by nearly the same steps, it
would be advisable, if found practicable, to use the same definition
in both cases, and to take as the standard of morality, the general
good or welfare of the community, rather than the general happiness."
But the kind of community for the good of which the social instincts
of animals and primitive men were biologically developed may be
different from that which is the product of civilisation, as Darwin no
doubt realised. Darwin's contention was that conscience is a social
instinct and has been evolved because it is useful to the tribe in the
struggle for existence against other tribes. One the other hand J. S.
Mill urged that the moral feelings are not innate but acquired, and
Bain held the same view, believing that the moral sense is acquired by
each individual during his life-time. Darwin, who notes[194] their
opinion with his usual candour, adds that "on the general theory of
evolution this is at least extremely improbable." It is impossible to
enter into the question here: much turns on the exact connotation of
the terms "conscience" and "moral sense," and on the meaning we attach
to the statement that the moral sense is fundamentally identical with
the social instincts.

Presumably the majority of those who approach the subjects discussed
in the third, fourth, and fifth chapters of _The Descent of Man_ in
the full conviction that mental phenomena, not less than organic
phenomena, have a natural genesis, would, without hesitation, admit
that the intellectual and moral systems of civilised man are ideal
constructions, the products of conceptual thought, and that as such
they are, in their developed form, acquired. The moral sentiments are
the emotional analogues of highly developed concepts. This does not
however imply that they are outside the range of natural history
treatment. Even though it may be desirable to differentiate the moral
conduct of men from the social behaviour of animals (to which some
such term as "pre-moral" or "quasi-moral" may be applied), still the
fact remains that, as Darwin showed, there is abundant evidence of the
occurrence of such social behaviour--social behaviour which, even
granted that it is in large part intelligently acquired, and is itself
so far a product of educability, is of survival value. It makes for
that integration without which no social group could hold together and
escape elimination. Furthermore, even if we grant that such behaviour
is intelligently acquired, that is to say arises through the
modification of hereditary instincts and emotions, the fact remains
that only through these instinctive and emotional data is afforded the
primary tissue of the experience which is susceptible of such

Darwin sought to show, and succeeded in showing, that for the
intellectual and moral life there are instinctive foundations which a
biological treatment alone can disclose. It is true that he did not in
all cases analytically distinguish the foundations from the
superstructure. Even to-day we are scarcely in a position to do so
adequately. But his treatment was of great value in giving an impetus
to further research. This value indeed can scarcely be over-estimated.
And when the natural history of the mental operations shall have been
written, the cardinal fact will stand forth, that the instinctive and
emotional foundations are the outcome of biological evolution and have
been ingrained in the race through natural selection. We shall more
clearly realise that educability itself is a product of natural
selection, though the specific results acquired through cerebral
modifications are not transmitted through heredity. It will, perhaps,
also be realised that the instinctive foundations of social behaviour
are, for us, somewhat out of date and have undergone but little change
throughout the progress of civilisation, because natural selection has
long since ceased to be the dominant factor in human progress. The
history of human progress has been mainly the history of man's higher
educability, the products of which he has projected on to his
environment. This educability remains on the average what it was a
dozen generations ago; but the thought-woven tapestry of his
surroundings is refashioned and improved by each succeeding
generation. Few men have in greater measure enriched the
thought-environment with which it is the aim of education to bring
educable human beings into vital contact, than has Charles Darwin. His
special field of work was the wide province of biology; but he did
much to help us to realise that mental factors have contributed to
organic evolution and that in man, the highest product of Evolution,
they have reached a position of unquestioned supremacy.


[Footnote 153: _Origin of Species_ (6th edit.), p. 205.]

[Footnote 154: _Descent of man_ (2nd edit. 1888), Vol. I. p. 99;
Popular edit. p. 99.]

[Footnote 155: _Ibid._ p. 99.]

[Footnote 156: _The Expression of the Emotions_ (2nd edit.), p. 32.]

[Footnote 157: _Descent of Man_, Vol. II. p. 435.]

[Footnote 158: _Ibid._ 437, 438.]

[Footnote 159: _Origin of Species_ (6th edit.), p. 205.]

[Footnote 160: _Origin of Species_ (6th edit.), p. 205.]

[Footnote 161: _Ibid._ p. 233.]

[Footnote 162: _Ibid._ p. 205.]

[Footnote 163: _Origin of Species_ (6th edit.), p. 233.]

[Footnote 164: _Origin of Species_, pp. 210, 211.]

[Footnote 165: Independently suggested, on somewhat different lines,
by Profs. J. Mark Baldwin, Henry F. Osborn and the writer.]

[Footnote 166: _Origin of Species_ (6th edit.), p. 206.]

[Footnote 167: _Expression of the Emotions_, p. 13. The passage is
here somewhat condensed.]

[Footnote 168: _Ibid._ p. 368.]

[Footnote 169: _Expression of the Emotions_, pp. 373, 374.]

[Footnote 170: _Ibid._ p. 368.]

[Footnote 171: _Ibid._ p. 369.]

[Footnote 172: _Expression of the Emotions_, pp. 65 ff.]

[Footnote 173: Cf. William James, _Principles of Psychology_, Vol. II.
Chap. XXV, New York, 1890.]

[Footnote 174: _Darwinism_, pp. 282, 283, London, 1889.]

[Footnote 175: _Ibid._ p. 283.]

[Footnote 176: _Darwinism_, pp. 283, 284.]

[Footnote 177: _Descent of Man_ (2nd edit.), Vol. II. pp. 136, 137;
(Popular edit.), pp. 642, 643.]

[Footnote 178: _The Play of Animals_, p. 244, London, 1898.]

[Footnote 179: _Ibid._ p. 283.]

[Footnote 180: _Descent of Man_, Vol. II. p. 60; (Popular edit.), p.

[Footnote 181: _The Play of Animals_, p. 76.]

[Footnote 182: _Ibid._ p. 75.]

[Footnote 183: _The Play of Animals_ p. 24.]

[Footnote 184: _Descent of Man_ (1st edit.), Chaps. II, III, V; (2nd
edit.), Chaps. III, IV, V.]

[Footnote 185: _Descent of Man_, Vol. I. pp. 70, 71; (Popular edit.),
pp. 70, 71.]

[Footnote 186: _Ibid._ p. 81.]

[Footnote 187: _Ibid._ (Popular edit.), p. 82.]

[Footnote 188: _Comptes Rendus des Sciences_, June 1, 1868.]

[Footnote 189: _Nature_, Vol. LXI. pp. 624, 625 (1900).]

[Footnote 190: _Descent of Man_, Vol. I. p. 100.]

[Footnote 191: _Principles of Psychology_, Vol. II. p. 289.]

[Footnote 192: _Descent of Man_, Vol. I. p. 149.]

[Footnote 193: _Descent of Man_, p. 185.]

[Footnote 194: _Ibid._ p. 150 (footnote).]




_Professor of Philosophy in the University of Copenhagen_


It is difficult to draw a sharp line between philosophy and natural
science. The naturalist who introduces a new principle, or
demonstrates a fact which throws a new light on existence, not only
renders an important service to philosophy but is himself a
philosopher in the broader sense of the word. The aim of philosophy in
the stricter sense is to attain points of view from which the
fundamental phenomena and the principles of the special sciences can
be seen in their relative importance and connection. But philosophy in
this stricter sense has always been influenced by philosophy in the
broader sense. Greek philosophy came under the influence of logic and
mathematics, modern philosophy under the influence of natural science.
The name of Charles Darwin stands with those of Galileo, Newton, and
Robert Mayer--names which denote new problems and great alterations in
our conception of the universe.

First of all we must lay stress on Darwin's own personality. His deep love
of truth, his indefatigable inquiry, his wide horizon, and his steady
self-criticism make him a scientific model, even if his results and
theories should eventually come to possess mainly an historical interest.
In the intellectual domain the primary object is to reach high summits
from which wide surveys are possible, to reach them toiling honestly
upwards by the way of experience, and then not to turn dizzy when a summit
is gained. Darwinians have sometimes turned dizzy, but Darwin never. He saw
from the first the great importance of his hypothesis, not only because of
its solution of the old problem as to the value of the concept of species,
not only because of the grand picture of natural evolution which it
unrolls, but also because of the life and inspiration its method would
impart to the study of comparative anatomy, of instinct and of heredity,
and finally because of the influence it would exert on the whole conception
of existence. He wrote in his note-book in the year 1837: "My theory would
give zest to recent and fossil comparative anatomy; it would lead to the
study of instinct, heredity, and mind-heredity, whole [of]

We can distinguish four main points in which Darwin's investigations
possess philosophical importance.

The evolution hypothesis is much older than Darwin; it is, indeed, one
of the oldest guessings of human thought. In the eighteenth century is
was put forward by Diderot and Lamettrie and suggested by Kant (1786).
As we shall see later, it was held also by several philosophers in the
first half of the nineteenth century. In his preface to _The Origin of
Species_, Darwin mentions the naturalists who were his forerunners.
But he has set forth the hypothesis of evolution in so energetic and
thorough a manner that it perforce attracts the attention of all
thoughtful men in a much higher degree than it did before the
publication of the _Origin_.

And further, the importance of his teaching rests on the fact that he,
much more than his predecessors, even than Lamarck, sought a
foundation for his hypothesis in definite facts. Modern science began
by demanding--with Kepler and Newton--evidence of _varae causae_; this
demand Darwin industriously set himself to satisfy--hence the wealth
of material which he collected by his observations and his
experiments. He not only revived an old hypothesis, but he saw the
necessity of verifying it by facts. Whether the special cause on which
he founded the explanation of the origin of species--Natural
Selection--is sufficient, is now a subject of discussion. He himself
had some doubt in regard to this question, and the criticisms which
are directed against his hypothesis hit Darwinism rather than Darwin.
In his indefatigable search for empirical evidence he is a model even
for his antagonists: he has compelled them to approach the problems of
life along other lines than those which were formerly followed.

Whether the special cause to which Darwin appealed is sufficient or not, at
least to it is probably due the greater part of the influence which he has
exerted on the general trend of thought. "Struggle for existence" and
"natural selection" are principles which have been applied, more or less,
in every department of thought. Recent research, it is true, has discovered
greater empirical discontinuity--leaps, "mutations"--whereas Darwin
believed in the importance of small variations slowly accumulated. It has
also been shown by the experimental method, which in recent biological work
has succeeded Darwin's more historical method, that types once constituted
possess great permanence, the fluctuations being restricted within clearly
defined boundaries. The problem has become more precise, both as to
variation and as to heredity. The inner conditions of life have in both
respects shown a greater independence than Darwin had supposed in his
theory, though he always admitted that the cause of variation was to him a
great enigma, "a most perplexing problem," and that the struggle for life
could only occur where variation existed. But, at any rate, it was of the
greatest importance that Darwin gave a living impression of the struggle
for life which is everywhere going on, and to which even the highest forms
of existence must be amenable. The philosophical importance of these ideas
does not stand or fall with the answer to the question, whether natural
selection is a sufficient explanation of the origin of species or not it
has an independent, positive value for everyone who will observe life and
reality with an unbiased mind.

In accentuating the struggle for life Darwin stands as a
characteristically English thinker: he continues a train of ideas
which Hobbes and Malthus had already begun. Moreover in his critical
views as to the conception of species he had English forerunners; in
the middle ages Occam and Duns Scotus, in the eighteenth century
Berkeley and Hume. In his moral philosophy, as we shall see later, he
is an adherent of the school which is represented by Hutcheson, Home
and Adam Smith. Because he is no philosopher in the stricter sense of
the term, it is of great interest to see that his attitude of mind is
that of the great thinkers of his nation.

In considering Darwin's influence on philosophy we will begin with an
examination of the attitude of philosophy to the conception of
evolution at the time when _The Origin of Species_ appeared. We will
then examine the effects which the theory of evolution, and especially
the idea of the struggle for life, has had, and naturally must have,
on the discussion of philosophical problems.


When _The Origin of Species_ appeared fifty years ago Romantic
speculation, Schelling's and Hegel's philosophy, still reigned on the
continent, while in England Positivism, the philosophy of Comte and
Stuart Mill, represented the most important trend of thought. German
speculation had much to say on evolution, it even pretended to be a
philosophy of evolution. But then the word "evolution" was to be taken
in an ideal, not in a real, sense. To speculative thought the forms
and types of nature formed a system of ideas, within which any form
could lead us by continuous transitions to any other. It was a
classificatory system which was regarded as a divine world of thought
or images, within which metamorphoses could go on--a condition
comparable with that in the mind of the poet when one image follows
another with imperceptible changes. Goethe's ideas of evolution, as
expressed in his _Metamorphosen der Pflanzen und der Thiere_, belong
to this category; it is, therefore, incorrect to call him a forerunner
of Darwin. Schelling and Hegel held the same idea; Hegel expressly
rejected the conception of a real evolution in time as coarse and
materialistic. "Nature," he says, "is to be considered as a _system of
stages_, the one necessarily arising from the other, and being the
nearest truth of that from which it proceeds; but not in such a way
that the one is _naturally_ generated by the other; on the contrary
[their connection lies] in the inner idea which is the ground of
nature. The _metamorphosis_ can be ascribed only to the notion as
such, because it alone is evolution.... It has been a clumsy idea in
the older as well as in the newer philosophy of nature, to regard the
transformation and the transition from one natural form and sphere to
a higher as an outward and actual production."[196]

The only one of the philosophers of Romanticism who believed in a
real, historical evolution, a real production of new species, was
Oken.[197] Danish philosophers, such as Treschow (1812) and Sibbern
(1846), have also broached the idea of an historical evolution of all
living beings from the lowest to the highest. Schopenhauer's
philosophy has a more realistic character than that of Schelling's and
Hegel's, his diametrical opposites, although he also belongs to the
romantic school of thought. His philosophical and psychological views
were greatly influenced by French naturalists and philosophers,
especially by Cabanis and Lamarck. He praises the "ever memorable
Lamarck," because he laid so much stress on the "will to live." But he
repudiates as a "wonderful error" the idea that the organs of animals
should have reached their present perfection through a development in
time, during the course of innumerable generations. It was, he said, a
consequence of the low standard of contemporary French philosophy,
that Lamarck came to the idea of the construction of living beings in
time through succession![198]

The positivistic stream of thought was not more in favour of a real
evolution than was the Romantic school. Its aim was to adhere to
positive facts: it looked with suspicion on far-reaching speculation.
Comte laid great stress on the discontinuity found between the
different kingdoms of nature, as well as within each single kingdom.
As he regarded as unscientific every attempt to reduce the number of
physical forces, so he rejected entirely the hypothesis of Lamarck
concerning the evolution of species; the idea of species would in his
eyes absolutely lose its importance if a transition from species to
species under the influence of conditions of life were admitted. His
disciples (Littré, Robin) continued to direct against Darwin the
polemics which their master had employed against Lamarck. Stuart Mill,
who, in the theory of knowledge, represented the empirical or
positivistic movement in philosophy--like his English forerunners from
Locke to Hume--founded his theory of knowledge and morals on the
experience of the single individual. He sympathised with the theory of
the original likeness of all individuals and derived their
differences, on which he practically and theoretically laid much
stress, from the influence both of experience and education, and,
generally, of physical and social causes. He admitted an individual
evolution, and, in the human species, an evolution based on social
progress; but no physiological evolution of species. He was afraid
that the hypothesis of heredity would carry us back to the old theory
of "innate" ideas.

Darwin was more empirical than Comte and Mill; experience disclosed to
him a deeper continuity than they could find; closer than before the
nature and fate of the single individual were shown to be interwoven
in the great web binding the life of the species with nature as a
whole. And the continuity which so many idealistic philosophers could
find only in the world of thought, he showed to be present in the
world of reality.


Darwin's energetic renewal of the old idea of evolution has its chief
importance in strengthening the conviction of this real continuity in
the world, of continuity in the series of form and events. It was a
great support for all those who were prepared to base their conception
of life on scientific grounds. Together with the recently discovered
law of the conservation of energy, it helped to produce the great
realistic movement which characterises the last third of the
nineteenth century. After the decline of the Romantic movement people
wished to have firmer ground under their feet and reality now asserted
itself in a more emphatic manner than in the period of Romanticism. It
was easy for Hegel to proclaim that "the real" was "the rational," and
that "the rational" was "the real": reality itself existed for him
only in the interpretation of ideal reason, and if there was anything
which could not be merged in the higher unity of thought, then it was
only an example of the "impotence of nature to hold to the idea." But
now concepts are to be founded on nature and not on any system of
categories too confidently deduced _à priori_. The new devotion to
nature had its recompense in itself, because the new points of view
made us see that nature could indeed "hold to ideas," though perhaps
not to those which we had cogitated beforehand.

A most important question for philosophers to answer was whether the
new views were compatible with an idealistic conception of life and
existence. Some proclaimed that we have now no need of any philosophy
beyond the principles of the conservation of matter and energy and the
principle of natural evolution: existence should and could be
definitely and completely explained by the laws of material nature.
But abler thinkers saw that the thing was not so simple. They were
prepared to give the new views their just place and to examine what
alterations the old views must undergo in order to be brought into
harmony with the new data.

The realistic character of Darwin's theory was shown not only in the
idea of natural continuity, but also, and not least, in the idea of
the cause whereby organic life advances step by step. This idea--the
idea of the struggle for life--implied that nothing could persist, if
it had no power to maintain itself under the given conditions. Inner
value alone does not decide. Idealism was here put to its hardest
trial. In continuous evolution it could perhaps still find an analogy
to the inner evolution of ideas in the mind; but in the demand for
power in order to struggle with outward conditions Realism seemed to
announce itself in its most brutal form. Every form of Idealism had to
ask itself seriously how it was going to "struggle for life" with this
new Realism.

We will now give a short account of the position which leading
thinkers in different countries have taken up in regard to this

I. Herbert Spencer was the philosopher whose mind was best prepared by his
own previous thinking to admit the theory of Darwin to a place in his
conception of the world. His criticism of the arguments which had been put
forward against the hypothesis of Lamarck, showed that Spencer, as a young
man, was an adherent to the evolution idea. In his _Social Statics_ (1850)
he applied this idea to human life and moral civilisation. In 1852 he wrote
an essay on _The Development Hypothesis_, in which he definitely stated his
belief that the differentiation of species, like the differentiation within
a single organism, was the result of development. In the first edition of
his _Psychology_ (1855) he took a step which put him in opposition to the
older English school (from Locke to Mill): he acknowledged "innate ideas"
so far as to admit the tendency of acquired habits to be inherited in the
course of generations, so that the nature and functions of the individual
are only to be understood through its connection with the life of the
species. In 1857, in his essay on _Progress_, he propounded the law of
differentiation as a general law of evolution, verified by examples from
all regions of experience, the evolution of species being only one of these
examples. On the effect which the appearance of _The Origin of Species_ had
on his mind he writes in his _Autobiography_: "Up to that time ... I held
that the sole cause of organic evolution is the inheritance of
functionally-produced modifications. The _Origin of Species_ made it clear
to me that I was wrong, and that the larger part of the facts cannot be due
to any such cause.... To have the theory of organic evolution justified was
of course to get further support for that theory of evolution at large with
which ... all my conceptions were bound up."[199] Instead of the
metaphorical expression "natural selection," Spencer introduced the term
"survival of the fittest," which found favour with Darwin as well as with

In working out his ideas of evolution, Spencer found that
differentiation was not the only form of evolution. In its simplest
form evolution is mainly a concentration, previously scattered
elements being integrated and losing independent movement.
Differentiation is only forthcoming when minor wholes arise within a
greater whole. And the highest form of evolution is reached when there
is a harmony between concentration and differentiation, a harmony
which Spencer calls equilibration and which he defines as a moving
equilibrium. At the same time this definition enables him to
illustrate the expression "survival of the fittest." "Every living
organism exhibits such a moving equilibrium--a balanced set of
functions constituting its life; and the overthrow of this balanced
set of functions or moving equilibrium is what we call death. Some
individuals in a species are so constituted that their moving
equilibria are less easily overthrown than those of other
individuals; and these are the fittest which survive, or, in Mr.
Darwin's language, they are the select which nature preserves."[200]
Not only in the domain of organic life, but in all domains, the summit
of evolution is, according to Spencer, characterised by such a
harmony--by a moving equilibrium.

Spencer's analysis of the concept of evolution, based on a great
variety of examples, has made this concept clearer and more definite
than before. It contains the three elements; integration,
differentiation and equilibration. It is true that a concept which is
to be valid for all domains of experience must have an abstract
character, and between the several domains there is, strictly
speaking, only a relation of analogy. So there is only analogy between
psychical and physical evolution. But this is no serious objection,
because general concepts do not express more than analogies between
the phenomena which they represent. Spencer takes his leading forms
from the material world in defining evolution (in the simplest form)
as integration of matter and dissipation of movement; but as he--not
always quite consistently[201]--assumed a correspondence of mind and
matter, he could very well give these terms an indirect importance for
psychical evolution. Spencer has always, in my opinion with full
right, repudiated the ascription of materialism. He is no more a
materialist than Spinoza. In his _Principles of Psychology_ (§ 63) he
expressed himself very clearly: "Though it seems easier to translate
so-called matter into so-called spirit, than to translate so-called
spirit into so-called matter--which latter is indeed wholly
impossible--yet no translation can carry us beyond our symbols." These
words lead us naturally to a group of thinkers whose starting-point
was psychical evolution. But we have still one aspect of Spencer's
philosophy to mention.

Spencer founded his "laws of evolution" on an inductive basis, but he
was convinced that they could be deduced from the law of the
conservation of energy. Such a deduction is, perhaps, possible for the
more elementary forms of evolution, integration and differentiation;
but it is not possible for the highest form, the equilibration, which
is a harmony of integration and differentiation. Spencer can no more
deduce the necessity for the eventual appearance of "moving
equilibria" of harmonious totalities than Hegel could guarantee the
"higher unities" in which all contradictions should be reconciled. In
Spencer's hands the theory of evolution acquired a more decidedly
optimistic character than in Darwin's; but I shall deal later with the
relation of Darwin's hypothesis to the opposition of optimism and

II. While the starting-point of Spencer was biological or
cosmological, psychical evolution being conceived as in analogy with
physical, a group of eminent thinkers--in Germany Wundt, in France
Fouillée, in Italy Ardigò--took, each in his own manner, their
starting-point in psychical evolution as an original fact and as a
type of all evolution, the hypothesis of Darwin coming in as a
corroboration and as a special example. They maintain the continuity
of evolution; they find this character most prominent in psychical
evolution, and this is for them a motive to demand a corresponding
continuity in the material, especially in the organic domain.

To Wundt and Fouillée the concept of will is prominent. They see the
type of all evolution in the transformation of the life of will from
blind impulse to conscious choice; the theories of Lamarck and Darwin
are used to support the view that there is in nature a tendency to
evolution in steady reciprocity with external conditions. The struggle
for life is here only a secondary fact. Its apparent prominence is
explained by the circumstance that the influence of external
conditions is easily made out, while inner conditions can be verified
only through their effects. For Ardigò the evolution of thought was
the starting-point and the type: in the evolution of a scientific
hypothesis we see a progress from the indefinite (_indistinto_) to the
definite (_distinto_), and this is a characteristic of all evolution,
as Ardigò has pointed out in a series of works. The opposition between
_indistinto_ and _distinto_ corresponds to Spencer's opposition
between homogeneity and heterogeneity. The hypothesis of the origin of
differences of species from more simple forms is a special example of
the general law of evolution.

In the views of Wundt and Fouillée we find the fundamental idea of
idealism psychical phenomena as expressions of the innermost nature of
existence. They differ from the older Idealism in the great stress
which they lay on evolution as a real, historical process which is
going on through steady conflict with external conditions. The
Romantic dread of reality is broken. It is beyond doubt that Darwin's
emphasis on the struggle for life as a necessary condition of
evolution has been a very important factor in carrying philosophy back
to reality from the heaven of pure ideas. The philosophy of Ardigò, on
the other side, appears more as a continuation and deepening of
positivism, though the Italian thinker arrived at his point of view
independently of French-English positivism. The idea of continuous
evolution is here maintained in opposition to Comte's and Mill's
philosophy of discontinuity. From Wundt and Fouillée Ardigò differs in
conceiving psychical evolution not as an immediate revelation of the
innermost nature of existence, but only as a single, though the most
accessible example, of evolution.

III. To the French philosophers Boutroux and Bergson, evolution proper
is continuous and qualitative, while outer experience and physical
science give us fragments only, sporadic processes and mechanical
combinations. To Bergson, in his recent work _L'Evolution Créatrice_,
evolution consists in an _élan de vie_ which to our fragmentary
observation and analytic reflexion appears as broken into a manifold
of elements and processes. The concept of matter in its scientific
form is the result of this breaking asunder, essential for all
scientific reflexion. In these conceptions the strongest opposition
between inner and outer conditions of evolution is expressed: in the
domain of internal conditions spontaneous development of qualitative
forms--in the domain of external conditions discontinuity and
mechanical combination.

We see, then, that the theory of evolution has influenced philosophy
in a variety of forms. It has made idealistic thinkers revise their
relation to the real world; it has led positivistic thinkers to find a
closer connection between the facts on which they based their views;
it has made us all open our eyes for new possibilities to arise
through the _prima facie_ inexplicable "spontaneous" variations which
are the condition of all evolution. This last point is one of peculiar
interest. Deeper than speculative philosophy and mechanical science
saw in the days of their triumph, we catch sight of new streams, whose
sources and laws we have still to discover. Most sharply does this
appear in the theory of mutation, which is only a stronger
accentuation of a main point in Darwinism. It is interesting to see
that an analogous problem comes into the foreground in physics through
the discovery of radioactive phenomena, and in psychology through the
assumption of psychical new formations (as held by Boutroux, William
James and Bergson). From this side, Darwin's ideas, as well as the
analogous ideas in other domains, incite us to renewed examination of
our first principles, their rationality and their value. On the other
hand, his theory of the struggle for existence challenges us to
examine the conditions and discuss the outlook as to the persistence
of human life and society and of the values that belong to them. It is
not enough to hope (or fear?) the rising of new forms; we have also to
investigate the possibility of upholding the forms and ideals which
have hitherto been the bases of human life. Darwin has here given his
age the most earnest and most impressive lesson. This side of Darwin's
theory is of peculiar interest to some special philosophical problems
to which I now pass.


Among philosophical problems the problem of knowledge has in the last
century occupied a foremost place. It is natural, then, to ask how
Darwin and the hypothesis whose most eminent representative he is,
stand to this problem.

Darwin started an hypothesis. But every hypothesis is won by inference
from certain presuppositions, and every inference is based on the
general principles of human thought. The evolution hypothesis
presupposes, then, human thought and its principles. And not only the
abstract logical principles are thus pre-supposed. The evolution
hypothesis purports to be not only a formal arrangement of phenomena,
but to express also the law of a real process. It supposes, then, that
the real data--all that in our knowledge which we do not produce
ourselves, but which we in the main simply receive--are subject to
laws which are at least analogous to the logical relations of our
thoughts; in other words, it assumes the validity of the principle of
causality. If organic species could arise without cause there would be
no use in framing hypotheses. Only if we assume the principle of
causality, is there a problem to solve.

Though Darwinism has had a great influence on philosophy considered as
a striving after a scientific view of the world, yet here is a point
of view--the epistemological--where philosophy is not only independent
but reaches beyond any result of natural science. Perhaps it will be
said: the powers and functions of organic beings only persist (perhaps
also only arise) when they correspond sufficiently to the conditions
under which the struggle of life is to go on. Human thought itself is,
then, a variation (or a mutation) which has been able to persist and
to survive. Is not, then, the problem of knowledge solved by the
evolution hypothesis? Spencer had given an affirmative answer to this
question before the appearance of _The Origin of Species_. For the
individual, he said, there is an _à priori_, original, basis (or
_Anlage_) for all mental life; but in the species all powers have
developed in reciprocity with extendal conditions. Knowledge is here
considered from the practical point of view, as a weapon in the
struggle for life, as an "organon" which has been continuously in use
for generations. In recent years the economic or pragmatic
epistemology, as developed by Avenarius and Mach in Germany, and by
James in America, points in the same direction. Science, it is said,
only maintains those principles and presuppositions which are
necessary to the simplest and clearest orientation be applied to
experience and to practical work, will successively be eliminated.

In these views a striking and important application is made of the
idea of struggle for life to the development of human thought. Thought
must, as all other things in the world, struggle for life. But this
whole consideration belongs to psychology, not to the theory of
knowledge (epistemology), which is concerned only with the validity of
knowledge, not with its historical origin. Every hypothesis to explain
the origin of knowledge must submit to cross-examination by the theory
of knowledge, because it works with the fundamental forms and
principles of human thought. We cannot go further back than these
forms and principles, which it is the aim of epistemology to ascertain
and for which no further reason can be given.[202]

But there is another side of the problem which is, perhaps, of more
importance and which epistemology generally overlooks. If new
variations can arise, not only in organic but perhaps also in
inorganic nature, new tasks are placed before the human mind. The
question is, then, if it has forms in which there is room for the new
matter? We are here touching a possibility which the great master of
epistemology did not bring to light. Kant supposed confidently that no
other matter of knowledge could stream forth from the dark source
which he called "the thing-in-itself," than such as could be
synthesised in our existing forms of knowledge. He mentions the
possibility of other forms than the human, and warns us against the
dogmatic assumption that the human conception of existence should be
absolutely adequate. But he seems to be quite sure that the
thing-in-itself works constantly, and consequently always gives us
only what our powers can master. This assumption was a consequence of
Kant's rationalistic tendency, but one for which no warrant can be
given. Evolutionism and systematism are opposing tendencies which can
never be absolutely harmonised one with the other. Evolution may at
any time break some form which the system-monger regards as finally
established. Darwin himself felt a great difference in looking at
variation as an evolutionist and as a systematist. When he was working
at his evolution theory, he was very glad to find variations; but they
were a hindrance to him when he worked as a systematist, in preparing
his work on Cirripedia. He says in a letter: "I had thought the same
parts of the same species more resemble (than they do anyhow in
Cirripedia) objects cast in the same mould. Systematic work would be
easy were it not for this confounded variation, which, however, is
pleasant to me as a speculatist, though odious to me as a
systematist."[203] He could indeed be angry with variations even as an
evolutionist; but then only because he could not explain them, not
because he could not classify them. "If, as I must think, external
conditions produce little _direct_ effect, what the devil determines
each particular variation?"[204] What Darwin experienced in this
particular domain holds good of all knowledge. All knowledge is
systematic, in so far as it strives to put phenomena in quite definite
relations, one to another. But the systematisation can never be
complete. And here Darwin has contributed much to widen the world, for
us. He has shown us forces and tendencies in nature which make
absolute systems impossible, at the same time that they give us new
objects and problems. There is still a place for what Lessing called
"the unceasing striving after truth," while "absolute truth" (in the
sense of a closed system) is unattainable so long as life and
experience are going on.

There is here a special remark to be made. As we have seen above,
recent research has shown that natural selection or struggle for life
is no explanation of variations. Hugo de Vries distinguishes between
partial and embryonal variations, or between variations and mutations,
only the last-named being heritable, and therefore of importance for
the origin of new species. But the existence of variations is not only
of interest for the problem of the origin of species; it has also a
more general interest. An individual does not lose its importance for
knowledge, because its qualities are not heritable. On the contrary,
in higher beings at least, individual peculiarities will become more
and more independent objects of interest. Knowledge takes account of
the biographies not only of species, but also of individuals: it seeks
to find the law of development of the single individual.[205] As
Leibnitz said long ago, individuality consists in the law of the
changes of a being: "La loi du changement fait l'individualité de
chaque substance." Here is a world which is almost new for science,
which till now has mainly occupied itself with general laws and forms.
But these are ultimately only means to understand the individual
phenomena, in whose nature and history a manifold of laws and forms
always coöperate. The importance of this remark will appear in the


To many people the Darwinian theory of natural selection or struggle
for existence seemed to change the whole conception of life, and
particularly all the conditions on which the validity of ethical ideas
depends. If only that has persistence which can be adapted to a given
condition, what will then be the fate of our ideals, of our standards
of good and evil? Blind force seems to reign, and the only thing that
counts seems to be the most heedless use of power. Darwinism, it was
said, has proclaimed brutality. No other difference seems permanent
save that between the sound, powerful and happy on the one side, the
sick, feeble and unhappy on the other; and every attempt to alleviate
this difference seems to lead to general enervation. Some of those who
interpreted Darwinism in this manner felt an aesthetic delight in
contemplating the heedlessness and energy of the great struggle for
existence and anticipated the realisation of a higher human type as
the outcome of it: so Nietzsche and his followers. Others recognising
the same consequences in Darwinism regarded these as one of the
strongest objections against it; so Dühring and Kropotkin (in his
earlier works).

This interpretation of Darwinism was frequent in the interval between
the two main works of Darwin--_The Origin of Species_ and _The Descent
of Man_. But even during this interval it was evident to an attentive
reader that Darwin himself did not found his standard of good and evil
on the features of the life of nature he had emphasised so strongly.
He did not justify the ways along which nature reached its ends; he
only pointed them out. The "real" was not to him, as to Hegel, one
with the "rational." Darwin has, indeed, by his whole conception of
nature, rendered a great service to ethics in making the difference
between the life of nature and the ethical life appear in so strong a
light. The ethical problem could now be stated in a sharper form than
before. But this was not the first time that the idea of the struggle
for life was put in relation to the ethical problem. In the
seventeenth century Thomas Hobbes gave the first impulse to the whole
modern discussion of ethical principles in his theory of _bellum
omnium contra omnes_. Men, he taught, are in the state of nature
enemies one of another, and they live either in fright or in the glory
of power. But it was not the opinion of Hobbes that this made ethics
impossible. On the contrary, he found a standard for virtue and vice
in the fact that some qualities and actions have a tendency to bring
us out of the state of war and to secure peace, while other qualities
have a contrary tendency. In the eighteenth century even Immanuel
Kant's ideal ethics had--so far as can be seen--a similar origin.
Shortly before the foundation of his definitive ethics, Kant wrote his
_Idee zu einer allgemeinen Weltgeschichte_ (1784), where--in a way
which reminds us of Hobbes, and is prophetic of Darwin--he describes
the forward-driving power of struggle in the human world. It is here
as with the struggle of the trees for light and air, through which
they compete with one another in height. Anxiety about war can only be
allayed by an ordinance which gives everyone his full liberty under
acknowledgment of the equal liberty of others. And such ordinance and
acknowledgment are also attributes of the content of the moral law, as
Kant proclaimed it in the year after the publication of his essay
(1785).[206] Kant really came to his ethics by the way of evolution,
though he afterwards disavowed it. Similarly the same line of thought
may be traced in Hegel though it has been disguised in the form of
speculative dialectics.[207] And in Schopenhauer's theory of the blind
will to live and its abrogation by the ethical feeling, which is
founded on universal sympathy, we have a more individualistic form of
the same idea.

It was, then, not entirely a foreign point of view which Darwin
introduced into ethical thought, even if we take no account of the
poetical character of the word "struggle" and of the more direct
adaptation, through the use and non-use of power, which Darwin also
emphasised. In _The Descent of Man_ he has devoted a special
chapter[208] to a discussion of the origin of the ethical
consciousness. The characteristic expression of this consciousness he
found, just as Kant did, in the idea of "ought"; it was the origin of
this new idea which should be explained. His hypothesis was that the
ethical "ought" has its origin in the social and parental instincts,
which, as well as other instincts (e.g. the instinct of
self-preservation), lie deeper than pleasure and pain. In many
species, not least in the human species, these instincts are fostered
by natural selection; and when the powers of memory and comparison are
developed, so that single acts can be valued according to the claims
of the deep social instinct, then consciousness of duty and remorse
are possible. Blind instinct has developed to conscious ethical will.

As already stated, Darwin, as a moral philosopher belongs to the
school that was founded by Shaftesbury, and was afterwards represented
by Hutcheson, Hume, Adam Smith, Comte and Spencer. His merit is,
first, that he has given this tendency of thought a biological
foundation, and that he has stamped on it a doughty character in
showing that ethical ideas and sentiments, rightly conceived, are
forces which are at work in the struggle for life.

There are still many questions to solve. Not only does the ethical
development within the human species contain features still
unexplained;[209] but we are confronted by the great problem whether
after all a genetic historical theory can be of decisive importance
here. To every consequent ethical consciousness there is a standard of
value, a primordial value which determines the single ethical
judgments as their last presupposition, and the "rightness" of this
basis, the "value" of this value can as little be discussed as the
"rationality" of our logical principles. There is here revealed a
possibility of ethical scepticism which evolutionistic ethics (as well
as intuitive or rationalistic ethics) has overlooked. No demonstration
can show that the results of the ethical development are definitive
and universal. We meet here again with the important opposition of
systematisation and evolution. There will, I think, always be an open
question here, though comparative ethics, of which we have so far only
the first attempts, can do much to throw light on it.

It would carry us too far to discuss all the philosophical works on
ethics, which have been influenced directly or indirectly by
evolutionism. I may, however, here refer to the book of C. M.
Williams, _A Review of the Systems of Ethics founded on the Theory of
Evolution_,[210] in which, besides Darwin, the following authors are
reviewed: Wallace, Haeckel, Spencer, Fiske, Rolph, Barratt, Stephen,
Carneri, Höffding, Gizycki, Alexander, Rée. As works which criticise
evolutionistic ethics from an intuitive point of view and in an
instructive way, may be cited: Guyau, _La morale anglaise
contemporaine_,[211] and Sorley, _Ethics of Naturalism_. I will only
mention some interesting contributions to ethical discussion which can
be found in Darwinism besides the idea of struggle for life.

The attention which Darwin has directed to variations has opened our
eyes to the differences in human nature as well as in nature
generally. There is here a fact of great importance for ethical
thought, no matter from what ultimate premiss it starts. Only from a
very abstract point of view can different individuals be treated in
the same manner. The most eminent ethical thinkers, men such as Jeremy
Bentham and Immanuel Kant, who discussed ethical questions from very
opposite standpoints, agreed in regarding all men as equal in respect
of ethical endowment. In regard to Bentham, Leslie Stephen remarks:
"He is determined to be thoroughly empirical, to take men as he found
them. But his utilitarianism supposed that men's views of happiness
and utility were uniform and clear, and that all that was wanted was
to show them the means by which their ends could be reached."[212] And
Kant supposed that every man would find the "categorical imperative"
in his consciousness, when he came to sober reflexion, and that all
would have the same qualifications to follow it. But if continual
variations, great or small, are going on in human nature, it is the
duty of ethics to make allowance for them, both in making claims, and
in valuing what is done. A new set of ethical problems have their
origin here.[213] It is an interesting fact that Stuart Mill's book
_On Liberty_ appeared in the same year as _The Origin of Species_.
Though Mill agreed with Bentham about the original equality of all
men's endowments, he regarded individual differences as a necessary
result of physical and social influences, and he claimed that free
play shall be allowed to differences of character so far as is
possible without injury to other men. It is a condition of individual
and social progress that a man's mode of action should be determined
by his own character and not by tradition and custom, nor by abstract
rules. This view was to be corroborated by the theory of Darwin.

But here we have reached a point of view from which the criticism,
which in recent years has often been directed against Darwin--that
small variations are of no importance in the struggle for life--is of
no weight. From an ethical standpoint, and particularly from the
ethical standpoint of Darwin himself, it is a duty to foster
individual differences that can be valuable, even though they can
neither be of service for physical preservation nor be physically
inherited. The distinction between variation and mutation is here
without importance. It is quite natural that biologists should be
particularly interested in such variations as can be inherited and
produce new species. But in the human world there is not only a
physical, but also a mental and social heredity. When an ideal human
character has taken form, then there is shaped a type, which through
imitation and influence can become an important factor in subsequent
development, even if it cannot form a species in the biological sense
of the word. Spiritually strong men often succumb in the physical
struggle for life; but they can nevertheless be victorious through the
typical influence they exert, perhaps on very distant generations, if
the remembrance of them is kept alive, be it in legendary or in
historical form. Their very failure can show that a type has taken
form which is maintained at all risks, a standard of life which is
adhered to in spite of the strongest opposition. The question "to be
or not to be" can be put from very different levels of being: it has
too often been considered a consequence of Darwinism that this
question is only to be put from the lowest level. When a stage is
reached, where ideal (ethical, intellectual, aesthetic) interests are
concerned, the struggle for life is a struggle for the preservation of
this stage. The giving up of a higher standard of life is a sort of
death; for there is not only a physical, there is also a spiritual,


The Socratic character of Darwin's mind appears in his wariness in
drawing the last consequences of his doctrine, in contrast both with
the audacious theories of so many of his followers and with the
consequences which his antagonists were busy in drawing. Though he, as
we have seen, saw from the beginning that his hypothesis would
occasion "a whole of metaphysics," he was himself very reserved as to
the ultimate questions, and his answers to such questions were
extorted from him.

As to the question of optimism and pessimism, Darwin held that though
pain and suffering were very often the ways by which animals were led
to pursue that course of action which is most beneficial to the
species, yet pleasurable feelings were the most habitual guides. "We
see this in the pleasure from exertion, even occasionally from great
exertion of the body or mind, in the pleasure of our daily meals, and
especially in the pleasure derived from sociability, and from loving
our families." But there was to him so much suffering in the world
that it was a strong argument against the existence of an intelligent
First Cause.[214]

It seems to me that Darwin was not so clear on another question, that
of the relation between improvement and adaptation. He wrote to Lyell:
"When you contrast natural selection and 'improvement,' you seem
always to overlook ... that every step in the natural selection of
each species implies improvement in that species _in relation to its
condition of life_.... Improvement implies, I suppose, _each form
obtaining many parts or organs_, all excellently adapted for their
functions." "All this," he adds, "seems to me quite compatible with
certain forms fitted for simple conditions, remaining unaltered, or
being, degraded."[215] But the great question is, if the conditions of
life will in the long run favour "improvement" in the sense of
differentiation (or harmony of differentiation and integration). Many
beings are best adapted to their conditions of life if they have few
organs and few necessities. Pessimism would not only be the
consequence, if suffering outweighed happiness, but also if the most
elementary forms of happiness were predominant, or if there were a
tendency to reduce the standard of life to the simplest possible, the
contentment of inertia or stable equilibrium. There are animals which
are very highly differentiated and active in their young state, but
later lose their complex organisation and concentrate themselves on
the one function of nutrition. In the human world analogies to this
sort of adaptation are not wanting. Young "idealists" very often end
as old "Philistines." Adaptation and progress are not the same.

Another question of great importance in respect to human evolution is,
whether there will be always a possibility for the existence of an
impulse to progress, an impulse to make great claims on life, to be
active and to alter the conditions of life instead of adapting to them
in a passive manner. Many people do not develop because they have too
few necessities, and because they have no power to imagine other
conditions of life than those under which they live. In his remarks on
"the pleasure from exertion" Darwin has a point of contact with the
practical idealism of former times--with the ideas of Lessing and
Goethe, of Condorcet and Fichte. The continual striving which was the
condition of salvation to Faust's soul, is also the condition of
salvation to mankind. There is a holy fire which we ought to keep
burning, if adaptation is really to be improvement. If, as I have
tried to show in my _Philosophy of Religion_, the innermost core of
all religion is faith in the persistence of value in the world, and if
the highest values express themselves in the cry "Excelsior!" then the
capital point is, that this cry should always be heard and followed.
We have here a corollary of the theory of evolution in its application
to human life.

Darwin declared himself an agnostic, not only because he could not
harmonise the large amount of suffering in the world with the idea of
a God as its first cause, but also because he "was aware that if we
admit a first cause, the mind still craves to know whence it came and
how it arose."[216] He saw, as Kant had seen before him and expressed
in his _Kritik der Urtheilskraft_, that we cannot accept either of the
only two possibilities which we are able to conceive: chance (or brute
force) and design. Neither mechanism nor teleology can give an
absolute answer to ultimate questions. The universe, and especially
the organic life in it, can neither be explained as a mere
combination of absolute elements nor as the effect of a constructing
thought. Darwin concluded, as Kant, and before him Spinoza, that the
oppositions and distinctions which our experience presents, cannot
safely be regarded as valid for existence in itself. And, with Kant
and Fichte, he found his stronghold in the conviction that man has
something to do, even if he cannot solve all enigmas. "The safest
conclusion seems to me that the whole subject is beyond the scope of
man's intellect; but man can do his duty."[217]

Is this the last word of human thought? Does not the possibility, that
man can do his duty, suppose that the conditions of life allow of
continuous ethical striving, so that there is a certain harmony
between cosmic order and human ideals? Darwin himself has shown how
the consciousness of duty can arise as a natural result of evolution.
Moreover there are lines of evolution which have their end in ethical
idealism, in a kingdom of values, which must struggle for life as all
things in the world must do, but a kingdom which has its firm
foundation in reality.


[Footnote 195: _Life and Letters of Charles Darwin_, Vol. I. p. 8.]

[Footnote 196: _Encyclopädie der philosophischen Wissenschaften_ (4th
edit.), Berlin, 1845, § 249.]

[Footnote 197: _Lehrbuch der Naturphilosophie_, Jena, 1809.]

[Footnote 198: _Ueber den Willen in der Natur_ (2nd edit.), Frankfurt
a. M., 1854, pp. 41-43.]

[Footnote 199: Spencer, _Autobiography_, Vol. II. p. 50, London and
New York, 1904.]

[Footnote 200: _Autobiography_, Vol. II. p. 100.]

[Footnote 201: Cf. my letter to him 1876, now printed in Duncan's
_Life and Letters of Herbert Spencer_, p. 178. London, 1908.]

[Footnote 202: The present writer, many years ago, in his _Psychology_
(Copenhagen, 1882; Eng. transl. London, 1891), criticised the
evolutionistic treatment of the problem of knowledge from the Kantian
point of view.]

[Footnote 203: _Life and Letters_, Vol. II. p. 37.]

[Footnote 204: _Ibid._ p. 232.]

[Footnote 205: The new science of Ecology occupies an intermediate
position between the biography of species and the biography of
individuals. Compare _Congress of Arts and Science_, St. Louis, Vol.
V. 1906 (The Reports of Drude and Robinson) and the work of my
colleague, E. Warming.]

[Footnote 206: Cf. my _History of Modern Philosophy_ (Eng. transl.
London, 1900), I. pp. 76-79.]

[Footnote 207: "Herrschaft und Knechtschaft," _Phönomenologie des
Geistes_, IV. A., Leiden, 1907.]

[Footnote 208: _The Descent of Man_, Vol. I. Ch. iii.]

[Footnote 209: The works of Westermarck and Hobhouse throw new light
on many of these features.]

[Footnote 210: New York and London, 1893.]

[Footnote 211: Paris, 1879.]

[Footnote 212: _English literature and society in the eighteenth
century_, London, 1904, p. 187.]

[Footnote 213: Cf. my paper, "The law of relativity in Ethics,"
_International Journal of Ethics_, Vol. I. 1891, pp. 37-62.]

[Footnote 214: _Life and Letters_, Vol. I. p. 310.]

[Footnote 215: _Ibid._ Vol. II. p. 177.]

[Footnote 216: _Life and Letters_, Vol. 1. p. 306.]

[Footnote 217: _Life and Letters_, p. 307.]





The object of this paper is first to point out certain elements of the
Darwinian influence upon Religious thought, and then to show reason
for the conclusion that it has been, from a Christian point of view,
satisfactory. I shall not proceed further to urge that the Christian
apologetic in relation to biology has been successful. A variety of
opinions may be held on this question, without disturbing the
conclusion that the movements of readjustment have been beneficial to
those who remain Christians, and this by making them more Christian
and not only more liberal. The theologians may sometimes have
retreated, but there has been an advance of theology. I know that this
account incurs the charge of optimism. It is not the worst that could
be made. The influence has been limited in personal range, unequal,
even divergent, in operation, and accompanied by the appearance of
waste and mischievous products. The estimate which follows requires
for due balance a full development of many qualifying considerations.
For this I lack space, but I must at least distinguish my view from
the popular one that our difficulties about religion and natural
science have come to an end.

Concerning the older questions about origins--the origin of the
world, of species, of man, of reason, conscience, religion--a large
measure of understanding has been reached by some thoughtful men. But
meanwhile new questions have arisen, questions about conduct,
regarding both the reality of morals and the rule of right action for
individuals and societies. And these problems, still far from
solution, may also be traced to the influence of Darwin. For they
arise from the renewed attention to heredity, brought about by the
search for the causes of variation, without which the study of the
selection of variations has no sufficient basis.

Even the existing understanding about origins is very far from
universal. On these points there were always thoughtful men who denied
the necessity of conflict, and there are still thoughtful men who deny
the possibility of a truce.

It must further be remembered that the earlier discussion now, as I
hope to show, producing favourable results, created also for a time
grave damage, not only in the disturbance of faith and the loss of
men--a loss not repaired by a change in the currents of debate--but in
what I believe to be a still more serious respect. I mean the
introduction of a habit of facile and untested hypothesis in religious
as in other departments of thought.

Darwin is not responsible for this, but he is in part the cause of it.
Great ideas are dangerous guests in narrow minds; and thus it has
happened that Darwin--the most patient of scientific workers, in whom
hypothesis waited upon research, or if it provisionally outstepped it
did so only with the most scrupulously careful acknowledgment--has led
smaller and less conscientious men in natural science, in history, and
in theology to an over-eager confidence in probable conjecture and a
loose grip upon the facts of experience. It is not too much to say
that in many quarters the age of materialism was the least
matter-of-fact age conceivable, and the age of science the age which
showed least of the patient temper of inquiry.

I have indicated, as shortly as I could, some losses and dangers
which in a balanced account of Darwin's influence would be discussed
at length.

One other loss must be mentioned. It is a defect in our thought which,
in some quarters, has by itself almost cancelled all the advantages
secured. I mean the exaggerated emphasis on uniformity or continuity;
the unwillingness to rest any part of faith or of our practical
expectation upon anything that from any point of view can be called
exceptional. The high degree of success reached by naturalists in
tracing, or reasonably conjecturing, the small beginnings of great
differences, has led the inconsiderate to believe that anything may in
time become anything else.

It is true that this exaggeration of the belief in uniformity has
produced in turn its own perilous reaction. From refusing to believe
whatever can be called exceptional, some have come to believe whatever
can be called wonderful.

But, on the whole, the discontinuous or highly various character of
experience received for many years too little deliberate attention.
The conception of uniformity which is a necessity of scientific
description has been taken for the substance of history. We have
accepted a postulate of scientific method as if it were a conclusion
of scientific demonstration. In the name of a generalisation which,
however just on the lines of a particular method, is the prize of a
difficult exploit of reflexion, we have discarded the direct
impressions of experience; or, perhaps it is more true to say, we have
used for the criticism of alleged experiences a doctrine of uniformity
which is only valid in the region of abstract science. For every
science depends for its advance upon limitation of attention, upon the
selection out of the whole content of consciousness of that part or
aspect which is measurable by the method of the science. Accordingly
there is a science of life which rightly displays the unity underlying
all its manifestations. But there is another view of life, equally
valid, and practically sometimes more important, which recognises the
immediate and lasting effect of crisis, difference, and revolution.
Our ardour for the demonstration of uniformity of process and of
minute continuous change needs to be balanced by a recognition of the
catastrophic element in experience, and also by a recognition of the
exceptional significance for us of events which may be perfectly
regular from an impersonal point of view.

An exorbitant jealousy of miracle, revelation, and ultimate moral
distinctions has been imported from evolutionary science into
religious thought. And it has been a damaging influence, because it
has taken men's attention from facts, and fixed them upon theories.


With this acknowledgment of important drawbacks, requiring many words
for their proper description, I proceed to indicate certain results of
Darwin's doctrine which I believe to be in the long run wholly
beneficial to Christian thought. These are:

The encouragement in theology of that evolutionary method of
observation and study, which has shaped all modern research:

The recoil of Christian apologetics towards the ground of religious
experience, a recoil produced by the pressure of scientific criticism
upon other supports of faith:

The restatement, or the recovery of ancient forms of statement, of the
doctrines of Creation and of divine Design in Nature, consequent upon
the discussion of evolution and of natural selection as its guiding

(1) The first of these is quite possibly the most important of all. It
was well defined in a notable paper read by Dr. Gore, now Bishop of
Birmingham, to the Church Congress at Shrewsbury in 1896. We have
learnt a new caution both in ascribing and in denying significance to
items of evidence, in utterance or in event. There has been, as in
art, a study of values, which secures perspective and solidity in our
representation of facts. On the one hand, a given utterance or event
cannot be drawn into evidence as if all items were of equal
consequence, like sovereigns in a bag. The question whence and whither
must be asked, and the particular thing measured as part of a series.
Thus measured it is not less truly important, but it may be important
in a lower degree. On the other hand, and for exactly the same reason,
nothing that is real is unimportant. The "failures" are not mere
mistakes. We see them, in St. Augustine's words, as "scholar's faults
which men praise in hope of fruit."

We cannot safely trace the origin of the evolutionistic method to the
influence of natural science. The view is tenable that theology led
the way. Probably this is a case of alternate and reciprocal debt.
Quite certainly the evolutionist method in theology, in Christian
history and in the estimate of scripture, has received vast
reinforcement from biology, in which evolution has been the ever
present and ever victorious conception.

(2) The second effect named is the new willingness of Christian
thinkers to take definite account of religious experience. This is
related to Darwin through the general pressure upon religious faith of
scientific criticism. The great advance of our knowledge of organisms
has been an important element in the general advance of science. It
has acted, by the varied requirements of the theory of organisms, upon
all other branches of natural inquiry, and it held for a long time
that leading place in public attention which is now occupied by
speculative physics. Consequently it contributed largely to our
present estimation of science as the supreme judge in all matters of
inquiry,[218] to the supposed destruction of mystery and the
disparagement of metaphysics which marked the last age, as well as to
the just recommendation of scientific method in branches of learning
where the direct acquisitions of natural science had no place.

Besides this, the new application of the idea of law and mechanical
regularity to the organic world seemed to rob faith of a kind of
refuge. The romantics had, as Berthelot[219] shows, appealed to life
to redress the judgments drawn from mechanism. Now, in Spencer,
evolution gave us a vitalist mechanic or mechanical vitalism, and the
appeal seemed cut off. We may return to this point later when we
consider evolution; at present I only endeavour to indicate that
general pressure of scientific criticism which drove men of faith to
seek the grounds of reassurance in a science of their own; in a method
of experiment, of observation, of hypothesis checked by known facts.
It is impossible for me to do more than glance across the threshold of
this subject. But it is necessary to say that the method is in an
elementary stage of revival. The imposing success that belongs to
natural science is absent: we fall short of the unchallengeable
unanimity of the Biologists on fundamentals. The experimental method
with its sure repetitions cannot be applied to our subject-matter. But
we have something like the observational method of palaeontology and
geographical distribution; and in biology there are still men who
think that the large examination of varieties by way of geography and
the search of strata is as truly scientific, uses as genuinely the
logical method of difference, and is as fruitful in sure conclusions
as the quasi-chemical analysis of Mendelian laboratory work, of which
last I desire to express my humble admiration. Religion also has its
observational work in the larger and possibly more arduous manner.

But the scientific work in religion makes its way through difficulties
and dangers. We are far from having found the formula of its
combination with the historical elements of our apologetic. It is
exposed, therefore, to a damaging fire not only from unspiritualist
psychology and pathology but also from the side of scholastic dogma.
It is hard to admit on equal terms a partner to the old undivided rule
of books and learning. With Charles Lamb, we cry in some distress,
"must knowledge come to me, if it come at all, by some awkward
experiment of intuition, and no longer by this familiar process of
reading?"[220] and we are answered that the old process has an
imperishable value, only we have not yet made clear its connection
with other contributions. And all the work is young, liable to be
drawn into unprofitable excursions, side-tracked by self-deceit and
pretence; and it fatally attracts, like the older mysticism, the
curiosity and the expository powers of those least in sympathy with
it, ready writers who, with all the air of extended research, have
been content with narrow grounds for induction. There is a danger,
besides, which accompanies even the most genuine work of this science
and must be provided against by all its serious students. I mean the
danger of unbalanced introspection both for individuals and for
societies; of a preoccupation comparable to our modern social
preoccupation with bodily health; of reflexion upon mental states not
accompanied by exercise and growth of the mental powers; the danger of
contemplating will and neglecting work, of analysing conviction and
not criticising evidence.

Still, in spite of dangers and mistakes, the work remains full of
hopeful indications, and, in the best examples,[221] it is truly
scientific in its determination to know the very truth, to tell what
we think, not what we think we ought to think,[222] truly scientific
in its employment of hypothesis and verification, and in growing
conviction of the reality of its subject-matter through the repeated
victories of a mastery which advances, like science, in the Baconian
road of obedience. It is reasonable to hope that progress in this
respect will be more rapid and sure when religious study enlists more
men affected by scientific desire and endowed with scientific

The class of investigating minds is a small one, possibly even smaller
than that of reflecting minds. Very few persons at any period are able
to find out anything whatever. There are few observers, few
discoverers, few who even wish to discover truth. In how many
societies the problems of philology which face every person who speaks
English are left unattempted! And if the inquiring or the successfully
inquiring class of minds is small, much smaller, of course, is the
class of those possessing the scientific aptitude in an eminent
degree. During the last age this most distinguished class was to a
very great extent absorbed in the study of phenomena, a study which
had fallen into arrears. For we stood possessed, in rudiment, of means
of observation, means for travelling and acquisition, qualifying men
for a larger knowledge than had yet been attempted. These were now to
be directed with new accuracy and ardour upon the fabric and behaviour
of the world of sense. Our debt to the great masters in physical
science who overtook and almost outstripped the task cannot be
measured; and, under the honourable leadership of Ruskin, we may all
well do penance if we have failed "in the respect due to their great
powers of thought, or in the admiration due to the far scope of their
discovery."[223] With what miraculous mental energy and divine good
fortune--as Romans said of their soldiers--did our men of curiosity
face the apparently impenetrable mysteries of nature! And how natural
it was that immense accessions of knowledge, unrelated to the
spiritual facts of life, should discredit Christian faith, by the
apparent superiority of the new work to the feeble and unprogressive
knowledge of Christian believers! The day is coming when men of this
mental character and rank, of this curiosity, this energy and this
good fortune in investigation, will be employed in opening mysteries
of a spiritual nature. They will silence with masterful witness the
over-confident denials of naturalism. They will be in danger of the
widespread recognition which thirty years ago accompanied every
utterance of Huxley, Tyndall, Spencer. They will contribute, in spite
of adulation, to the advance of sober religious and moral science.

And this result will be due to Darwin, first because by raising the
dignity of natural science, he encouraged the development of the
scientific mind; secondly because he gave to religious students the
example of patient and ardent investigation; and thirdly because by
the pressure of naturalistic criticism the religious have been driven
to ascertain the causes of their own convictions, a work in which they
were not without the sympathy of men of science.[224]

In leaving the subject of scientific religious inquiry, I will only
add that I do not believe it receives any important help--and
certainly it suffers incidentally much damaging interruption--from the
study of abnormal manifestations or abnormal conditions of

(3) Both of the above effects seem to me of high, perhaps the very
highest, importance to faith and to thought. But, under the third
head, I name two which are more directly traceable to the personal
work of Darwin, and more definitely characteristic of the age in which
his influence was paramount: viz. the influence of the two conceptions
of evolution and natural selection upon the doctrine of creation and
of design respectively.

It is impossible here, though it is necessary for a complete sketch of
the matter, to distinguish the different elements and channels of this
Darwinian influence; in Darwin's own writings, in the vigourous
polemic of Huxley, and strangely enough, but very actually for popular
thought, in the teaching of the definitely anti-Darwinian evolutionist

Under the head of the directly and purely Darwinian elements I should
class as preeminent the work of Wallace and of Bates; for no two sets
of facts have done more to fix in ordinary intelligent minds a belief
in organic evolution and in natural selection as its guiding factor
than the facts of geographical distribution and of protective colour
and mimicry. The facts of geology were difficult to grasp and the
public and theologians heard more often of the imperfection than of
the extent of the geological record. The witness of embryology,
depending to a great extent upon microscopic work, was and is beyond
the appreciation of persons occupied in fields of work other than


From the influence in religion of scientific modes of thought we pass
to the influence of particular biological conceptions. The former
effect comes by way of analogy, example, encouragement and challenge;
inspiring or provoking kindred or similar modes of thought in the
field of theology; the latter by a collision of opinions upon matters
of fact or conjecture which seem to concern both science and religion.

In the case of Darwinism the story of this collision is familiar, and
falls under the heads of evolution and natural selection, the doctrine
of descent with modification, and the doctrine of its guidance or
determination by the struggle for existence between related varieties.
These doctrines, though associated and interdependent, and in popular
thought not only combined but confused, must be considered separately.
It is true that the ancient doctrine of Evolution, in spite of the
ingenuity and ardour of Lamarck, remained a dream tantalising the
intellectual ambition of naturalists, until the day when Darwin made
it conceivable by suggesting the machinery of its guidance. And,
further, the idea of natural selection has so effectively opened the
door of research and stimulated observation in a score of principal
directions that, even if the Darwinian explanation became one day much
less convincing than, in spite of recent criticism, it now is, yet its
passing, supposing it to pass, would leave the doctrine of Evolution
immeasurably and permanently strengthened. For in the interests of the
theory of selection, "Für Darwin," as Müller wrote, facts have been
collected which remain in any case evidence of the reality of descent
with modification.

But still, though thus united in the modern history of convictions,
though united and confused in the collision of biological and
traditional opinion, yet evolution and natural selection must be
separated in theological no less than in biological estimation.
Evolution seemed inconsistent with Creation; natural selection with
Providence and Divine design.

Discussion was maintained about these points for many years and with
much dark heat. It ranged over many particular topics and engaged
minds different in tone, in quality, and in accomplishment. There was
at most times a degree of misconception. Some naturalists attributed
to theologians in general a poverty of thought which belonged really
to men of a particular temper or training. The "timid theism"
discerned in Darwin by so cautious a theologian as Liddon[225] was
supposed by many biologists to be the necessary foundation of an
honest Christianity. It was really more characteristic of devout
_naturalists_ like Philip Henry Gosse, than of religious believers as
such.[226] The study of theologians more considerable and even more
typically conservative than Liddon does not confirm the description of
religious intolerance given in good faith, but in serious ignorance,
by a disputant so acute, so observant and so candid as Huxley.
Something hid from each other's knowledge the devoted pilgrims in two
great ways of thought. The truth may be, that naturalists took their
view of what creation was from Christian men of science who naturally
looked in their own special studies for the supports and illustrations
of their religious belief. Of almost every labourious student it may
be said: "_Hic ab arte sua non recessit_." And both the believing and
the denying naturalists, confining habitual attention to a part of
experience, are apt to affirm and deny with trenchant vigour and
something of a narrow clearness "_Qui respiciunt ad pauca, de facili

Newman says of some secular teachers that "they persuade the world of
what is false by urging upon it what is true." Of some early opponents
of Darwin it might be said by a candid friend that, in all sincerity
of devotion to truth, they tried to persuade the world of what is true
by urging upon it what is false. If naturalists took their version of
orthodoxy from amateurs in theology, some conservative Christians,
instead of learning what evolution meant to its regular exponents,
took their view of it from celebrated persons, not of the front rank
in theology or in thought, but eager to take account of public
movements and able to arrest public attention.

Cleverness and eloquence on both sides certainly had their share in
producing the very great and general disturbance of men's minds in the
early days of Darwinian teaching. But by far the greater part of that
disturbance was due to the practical novelty and the profound
importance of the teaching itself, and to the fact that the
controversy about evolution quickly became much more public than any
controversy of equal seriousness had been for many generations.

We must not think lightly of that great disturbance because it has, in
some real sense, done its work, and because it is impossible in days
of more coolness and light, to recover a full sense of its very real

Those who would know them better should add to the calm records of
Darwin[228] and to the story of Huxley's impassioned championship, all
that they can learn of George Romanes.[229] For his life was absorbed
in this very struggle and reproduced its stages. It began in a certain
assured simplicity of biblical interpretation; it went on, through the
glories and adventures of a paladin in Darwin's train, to the darkness
and dismay of a man who saw all his most cherished beliefs rendered,
as he thought, incredible.[230] He lived to find the freer faith for
which process and purpose are not irreconcilable, but necessary to one
another. His development, scientific, intellectual and moral, was
itself of high significance; and its record is of unique value to our
own generation, so near the age of that doubt and yet so far from it;
certainly still much in need of the caution and courage by which past
endurance prepares men for new emergencies. We have little enough
reason to be sure that in the discussions awaiting us we shall do as
well as our predecessors in theirs. Remembering their endurance of
mental pain, their ardour in mental labour, the heroic temper and the
high sincerity of controversialists on either side, we may well speak
of our fathers in such words of modesty and self-judgment as Drayton
used when he sang the victors of Agincourt. The progress of biblical
study, in the departments of Introduction and Exegesis, resulting in
the recovery of a point of view anciently tolerated if not prevalent,
has altered some of the conditions of that discussion. In the years
near 1858, the witness of Scripture was adduced both by Christian
advocates and their critics as if unmistakably irreconcilable with

Huxley[231] found the path of the blameless naturalist everywhere
blocked by "Moses": the believer in revelation was generally held to
be forced to a choice between revealed cosmogony and the scientific
account of origins. It is not clear how far the change in Biblical
interpretation is due to natural science, and how far to the vital
movements of theological study which have been quite independent of
the controversy about species. It belongs to a general renewal of
Christian movement, the recovery of a heritage. "Special
Creation"--really a biological rather than a theological
conception,--seems in its rigid form to have been a recent element
even in English biblical orthodoxy.

The Middle Ages had no suspicion that religious faith forbad inquiry
into the natural origination of the different forms of life.
Bartholomaeus Anglicus, an English Franciscan of the thirteenth
century, was a mutationist in his way, as Aristotle, "the Philosopher"
of the Christian Schoolmen, had been in his. So late as the
seventeenth century, as we learn not only from early proceedings of
the Royal Society, but from a writer so homely and so regularly pious
as Walton, the variation of species and "spontaneous" generations had
no theological bearing, except as instances of that various wonder of
the world which in devout minds is food for devotion.

It was in the eighteenth century that the harder statement took shape.
Something in the preciseness of that age, its exaltation of law, its
cold passion for a stable and measured universe, its cold denial, its
cold affirmation of the power of God, a God of ice, is the occasion of
that rigidity of religious thought about the living world which Darwin
by accident challenged, or rather by one of those movements of genius
which, Goethe[232] declares, are "elevated above all earthly control."

If religious thought in the eighteenth century was aimed at a fixed
and nearly finite world of spirit, it followed in all these respects
the secular and critical lead. "La philosophie réformatrice du
XVIII^{e} siècle[233] ramenait la nature et la société à des
mécanismes que la pensée réfléchie peut concevoir et récomposer." In
fact, religion in a mechanical age is condemned if it takes any but a
mechanical tone. Butler's thought was too moving, too vital, too
evolutionary, for the sceptics of his time. In a rationalist,
encyclopaedic period, religion also must give hard outline to its
facts, it must be able to display its secret to any sensible man in
the language used by all sensible men. Milton's prophetic genius
furnished the eighteenth century, out of the depth of the passionate
age before it, with the theological tone it was to need. In spite of
the austere magnificence of his devotion, he gives to smaller souls a
dangerous lead. The rigidity of Scripture exegesis belonged to this
stately but imperfectly sensitive mode of thought. It passed away with
the influence of the older rationalists whose precise denials matched
the precise and limited affirmations of the static orthodoxy.

I shall, then, leave the specially biblical aspect of the
debate--interesting as it is and even useful, as in Huxley's
correspondence with the Duke of Argyll and others in 1892[234]--in
order to consider without complication the permanent elements of
Christian thought brought into question by the teaching of evolution.

Such permanent elements are the doctrine of God as Creator of the
universe, and the doctrine of man as spiritual and unique. Upon both
the doctrine of evolution seemed to fall with crushing force.

With regard to Man I leave out, acknowledging a grave omission, the
doctrine of the Fall and of Sin. And I do so because these have not
yet, as I believe, been adequately treated: here the fruitful reaction
to the stimulus of evolution is yet to come. The doctrine of sin,
indeed, falls principally within the scope of that discussion which
has followed or displaced the Darwinian; and without it the Fall
cannot be usefully considered. For the question about the Fall is a
question not merely of origins, but of the interpretation of moral
facts whose moral reality must first be established.

I confine myself therefore to Creation and the dignity of man.

The meaning of evolution, in the most general terms, is that the
differentiation of forms is not essentially separate from their
behaviour and use; that if these are within the scope of study, that
is also; that the world has taken the form we see by movements not
unlike those we now see in progress; that what may be called proximate
origins are continuous in the way of force and matter, continuous in
the way of life, with actual occurrences and actual characteristics.
All this has no revolutionary bearing upon the question of ultimate
origins. The whole is a statement about process. It says nothing to
metaphysicians about cause. It simply brings within the scope of
observation or conjecture that series of changes which has given their
special characters to the different parts of the world we see. In
particular, evolutionary science aspires to the discovery of the
process or order of the appearance of life itself: if it were to
achieve its aim it could say nothing of the cause of this or indeed of
the most familiar occurrences. We should have become spectators or
convinced historians of an event which, in respect of its cause and
ultimate meaning, would be still impenetrable.

With regard to the origin of species, supposing life already
established, biological science has the well founded hopes and the
measure of success with which we are all familiar. All this has, it
would seem, little chance of collision with a consistent theism, a
doctrine which has its own difficulties unconnected with any
particular view of order or process. But when it was stated that
species had arisen by processes through which new species were still
being made, evolutionism came into collision with a statement,
traditionally religious, that species were formed and fixed once for
all and long ago.

What is the theological import of such a statement when it is regarded
as essential to belief in God? Simply that God's activity, with
respect to the formation of living creatures, ceased at some point in
past time.

"God rested" is made the touchstone of orthodoxy. And when, under the
pressure of the evidences, we found ourselves obliged to acknowledge
and assert the present and persistent power of God, in the maintenance
and in the continued formation of "types," what happened was the
abolition of a time-limit. We were forced only to a bolder claim, to
a theistic language less halting, more consistent, more thorough in
its own line, as well as better qualified to assimilate and modify
such schemes as Von Hartmann's philosophy of the Unconscious--a
philosophy, by the way, quite intolerant of a merely mechanical

Here was not the retrenchment of an extravagant assertion, but the
expansion of one which was faltering and inadequate. The traditional
statement did not need paring down so as to pass the meshes of a new
and exacting criticism. It was itself a net meant to surround and
enclose experience; and we must increase its size and close its mesh
to hold newly disclosed facts of life. The world, which had seemed a
fixed picture or model, gained first perspective and then solidity and
movement. We had a glimpse of organic _history_; and Christian thought
became more living and more assured as it met the larger view of life.

However unsatisfactory the new attitude might be to our critics, to
Christians the reform was positive. What was discarded was a
limitation, a negation. The movement was essentially conservative,
even actually reconstructive. For the language disused was a language
inconsistent with the definitions of orthodoxy; it set bounds to the
infinite, and by implication withdrew from the creative rule all such
processes as could be brought within the descriptions of research. It
ascribed fixity and finality to that "creature" in which an apostle
taught us to recognise the birth-struggles of an unexhausted progress.
It tended to banish mystery from the world we see, and to confine it
to a remote first age.

In the reformed, the restored, language of religion, Creation became
again not a link in a rational series to complete a circle of the
sciences, but the mysterious and permanent relation between the
infinite and the finite, between the moving changes we know in part,
and the Power, after the fashion of that observation, unknown, which
is itself "unmoved all motion's source."[236]

With regard to man it is hardly necessary, even were it possible, to
illustrate the application of this bolder faith. When the record of
his high extraction fell under dispute, we were driven to a
contemplation of the whole of his life, rather than of a part and that
part out of sight. We remembered again, out of Aristotle, that the
result of a process interprets its beginnings. We were obliged to read
the title of such dignity as we may claim, in results and still more
in aspirations.

Some men still measure the value of great present facts in
life--reason and virtue and sacrifice--by what a self-disparaged
reason can collect of the meaner rudiments of these noble gifts. Mr.
Balfour has admirably displayed the discrepancy, in this view, between
the alleged origin and the alleged authority of reason. Such an
argument ought to be used not to discredit the confident reason, but
to illuminate and dignify its dark beginnings, and to show that at
every step in the long course of growth a Power was at work which is
not included in any term or in all the terms of the series.

I submit that the more men know of actual Christian teaching, its
fidelity to the past, and its sincerity in face of discovery, the more
certainly they will judge that the stimulus of the doctrine of
evolution has produced in the long run vigour as well as flexibility
in the doctrine of Creation and of man.

I pass from Evolution in general to Natural Selection.

The character in religious language which I have for short called
mechanical was not absent in the argument from design as stated before
Darwin. It seemed to have reference to a world conceived as fixed. It
pointed, not to the plastic capacity and energy of living matter, but
to the fixed adaptation of this and that organ to an unchanging place
or function.

Mr. Hobhouse has given us the valuable phrase "a niche of organic
opportunity." Such a phrase would have borne a different sense in
non-evolutionary thought. In that thought, the opportunity was an
opportunity for the Creative Power, and Design appeared in the
preparation of the organism to fit the niche. The idea of the niche
and its occupant growing together from simpler to more complex mutual
adjustment was unwelcome to this teleology. If the adaptation was
traced to the influence, through competition, of the environment, the
old teleology lost an illustration and a proof. For the cogency of the
proof in every instance depended upon the absence of explanation.
Where the process of adaptation was discerned, the evidence of Purpose
or Design was weak. It was strong only when the natural antecedents
were not discovered, strongest when they could be declared

Paley's favourite word is "Contrivance"; and for him contrivance is
most certain where production is most obscure. He points out the
physiological advantage of the _valvulae conniventes_ to man, and the
advantage for teleology of the fact that they cannot have been formed
by "action and pressure." What is not due to pressure may be
attributed to design, and when a "mechanical" process more subtle than
pressure was suggested, the case for design was so far weakened. The
cumulative proof from the multitude of instances began to disappear
when, in selection, a natural sequence was suggested in which all the
adaptations might be reached by the motive power of life, and
especially when, as in Darwin's teaching, there was full recognition
of the reactions of life to the stimulus of circumstance. "The
organism fits the niche," said the teleologist, "because the Creator
formed it so as to fit." "The organism fits the niche," said the
naturalist, "because unless it fitted it could not exist." "It was
fitted to survive," said the theologian. "It survives because it
fits," said the selectionist. The two forms of statement are not
incompatible; but the new statement, by provision of an ideally
universal explanation of process, was hostile to a doctrine of purpose
which relied upon evidences always exceptional however numerous.
Science persistently presses on to find the universal machinery of
adaptation in this planet; and whether this be found in selection, or
in direct-effect, or in vital reactions resulting in large changes, or
in a combination of these and other factors, it must always be opposed
to the conception of a Divine Power here and there but not everywhere

For science, the Divine must be constant, operative everywhere and in
every quality and power, in environment and in organism, in stimulus
and in reaction, in variation and in struggle, in hereditary
equilibrium, and in "the unstable state of species"; equally present
on both sides of every strain, in all pressures and in all
resistances, in short in the general wonder of life and the world. And
this is exactly what the Divine Power must be for religious faith.

The point I wish once more to make is that the necessary readjustment
of teleology, so as to make it depend upon the contemplation of the
whole instead of a part, is advantageous quite as much to theology as
to science. For the older view failed in courage. Here again our
theism was not sufficiently theistic.

Where results seemed inevitable, it dared not claim them as God-given.
In the argument from Design it spoke not of God in the sense of
theology, but of a Contriver, immensely, not infinitely wise and good,
working within a world, the scene, rather than the ever dependent
outcome, of His Wisdom; working in such emergencies and opportunities
as occurred, by forces not altogether within His control, towards an
end beyond Himself. It gave us, instead of the awful reverence due to
the Cause of all substance and form, all love and wisdom, a
dangerously detached appreciation of an ingenuity and benevolence
meritorious in aim and often surprisingly successful in contrivance.

The old teleology was more useful to science than to religion, and
the design-naturalists ought to be gratefully remembered by
Biologists. Their search for evidences led them to an eager study of
adaptations and of minute forms, a study such as we have now an
incentive to in the theory of Natural Selection. One hardly meets with
the same ardour in microscopical research until we come to modern
workers. But the argument from Design was never of great importance to
faith. Still, to rid it of this character was worth all the stress and
anxiety of the gallant old war. If Darwin had done nothing else for
us, we are to-day deeply in his debt for this. The world is not less
venerable to us now, not less eloquent of the causing mind, rather
much more eloquent and sacred. But our wonder is not that "the
underjaw of the swine works under the ground" or in any or all of
those particular adaptations which Paley collected with so much skill,
but that a purpose transcending, though resembling, our own purposes,
is everywhere manifest; that what we live in is a whole, mutually
sustaining, eventful and beautiful, where the "dead" forces feed the
energies of life, and life sustains a stranger existence, able in some
real measure to contemplate the whole, of which, mechanically
considered, it is a minor product and a rare ingredient. Here, again,
the change was altogether positive. It was not the escape of a vessel
in a storm with loss of spars and rigging, not a shortening of sail to
save the masts and make a port of refuge. It was rather the emergence
from narrow channels to an open sea. We had propelled the great ship,
finding purchase here and there for slow and uncertain movement. Now,
in deep water, we spread large canvas to a favouring breeze.

The scattered traces of design might be forgotten or obliterated. But
the broad impression of Order became plainer when seen at due distance
and in sufficient range of effect, and the evidence of love and wisdom
in the universe could be trusted more securely for the loss of the
particular calculation of their machinery.

Many other topics of faith are affected by modern biology. In some of
these we have learnt at present only a wise caution, a wise
uncertainty. We stand before the newly unfolded spectacle of
suffering, silenced; with faith not scientifically reassured but still
holding fast certain other clues of conviction. In many important
topics we are at a loss. But in others, and among them those I have
mentioned, we have passed beyond this negative state and find faith
positively strengthened and more fully expressed.

We have gained also a language and a habit of thought more fit for the
great and dark problems that remain, less liable to damaging
conflicts, equipped for more rapid assimilation of knowledge. And by
this change biology itself is a gainer. For, relieved of fruitless
encounters with popular religion, it may advance with surer aim along
the path of really scientific life-study which was reopened for modern
men by the publication of _The Origin of Species_.

Charles Darwin regretted that, in following science, he had not done
"more direct good"[237] to his fellow-creatures. He has, in fact,
rendered substantial service to interests bound up with the daily
conduct and hopes of common men; for his work has led to improvements
in the preaching of the Christian faith.


[Footnote 218: F. R. Tennant: "The Being of God in the light of
Physical Science," in _Essays on some theological questions of the
day_. London, 1905.]

[Footnote 219: _Evolutionisme et Platonisme_, pp. 45, 46, 47. Paris,

[Footnote 220: _Essays of Elia_, "New Year's Eve," p. 41; Ainger's
edition. London, 1899.]

[Footnote 221: Such an example is given in Baron F. von Hügel's
recently finished book, the result of thirty years' research: _The
Mystical Element of Religion, as studied in Saint Catherine of Genoa
and her Friends_. London, 1908.]

[Footnote 222: G. Tyrrell, in _Mediaevalism_, has a chapter which is
full of the important _moral_ element in a scientific attitude. "The
only infallible guardian of truth is the spirit of truthfulness."
_Mediaevalism_, p. 182, London, 1908.]

[Footnote 223: _Queen of the Air_, Preface, p. vii. London, 1906.]

[Footnote 224: The scientific rank of its writer justifies the
insertion of the following letter from the late Sir John
Burdon-Sanderson to me. In the lecture referred to I had described the
methods of Professor Moseley in teaching Biology as affording a
suggestion of the scientific treatment of religion.


_April 30, 1902_.


     I feel that I must express to you my thanks for the
     discourse which I had the pleasure of listening to yesterday

     I do not mean to say that I was able to follow all that you
     said as to the identity of Method in the two fields of
     Science and Religion, but I recognise that the "mysticism"
     of which you spoke gives us the only way by which the two
     fields can be brought into relation.

     Among much that was memorable, nothing interested me more
     than what you said of Moseley.

     No one, I am sure, knew better than you the value of his
     teaching and in what that value consisted.

Yours faithfully,



[Footnote 225: H. P. Liddon, _The Recovery of S. Thomas_; a sermon
preached in St. Paul's, London, on April 23rd, 1882 (the Sunday after
Darwin's death).]

[Footnote 226: Dr. Pusey (_Unscience not Science adverse to Faith_,
1878) writes: "The questions as to 'species,' of what variations the
animal world is capable, whether the species be more or fewer, whether
accidental variations may become hereditary ... and the like,
naturally fall under the province of science. In all these questions
Mr. Darwin's careful observations gained for him a deserved
approbation and confidence."]

[Footnote 227: Aristotle, in Bacon, quoted by Newman in his _Idea of a
University_, p. 78. London, 1873.]

[Footnote 228: _Life and Letters_ and _More Letters of Charles

[Footnote 229: _Life and Letters_, London, 1896. _Thoughts on
Religion_, London, 1895. _Candid Examination of Theism_, London,

[Footnote 230: "Never in the history of man has so terrific a calamity
befallen the race as that which all who look may now (viz. in
consequence of the scientific victory of Darwin) behold advancing as a
deluge black with destruction, resistless in might, uprooting our most
cherished hopes, engulphing our most precious creed, and burying our
highest life in mindless destruction."--_A Candid Examination of
Theism_, p. 51.]

[Footnote 231: _Science and Christian Tradition._ London, 1904.]

[Footnote 232: "No productiveness of the highest kind ... is in the
power of anyone."--_Conversations of Goethe with Eckermann and Soret_.
London, 1850.]

[Footnote 233: Berthelot, _Evolutionisme et Platonisme_, Paris, 1908,
p. 45.]

[Footnote 234: _Times_, 1892, _passim._]

[Footnote 235: See Von Hartmann's _Wahrheit und Irrthum in
Darwinismus_. Berlin, 1875.]

[Footnote 236: Hymn of the Church--

    Rerum Deus tenax vigor,
    Immotus in te permanens.


[Footnote 237: _Life and Letters_, Vol. III. p. 359.]




_Regius Professor of Modern History in the University of Cambridge_

1. Evolution, and the principles associated with the Darwinian theory,
could not fail to exert a considerable influence on the studies
connected with the history of civilised man. The speculations which
are known as "philosophy of history," as well as the sciences of
anthropology, ethnography, and sociology (sciences which though they
stand on their own feet are for the historian auxiliary), have been
deeply affected by these principles. Historiographers, indeed, have
with few exceptions made little attempt to apply them; but the growth
of historical study in the nineteenth century has been determined and
characterised by the same general principle which has underlain the
simultaneous developments of the study of nature, namely the _genetic
idea_. The "historical" conception of nature, which has produced the
history of the solar system, the story of the earth, the genealogies
of telluric organisms, and has revolutionised natural science, belongs
to the same order of thought as the conception of human history as a
continuous, genetic, causal process--a conception which has
revolutionised historical research and made it scientific. Before
proceeding to consider the application of evolutional principles, it
will be pertinent to notice the rise of this new view.

2. With the Greeks and Romans history had been either a descriptive
record or had been written in practical interests. The most eminent
of the ancient historians were pragmatical; that is, they regarded
history as an instructress in statesmanship, or in the art of war, or
in morals. Their records reached back such a short way, their
experience was so brief, that they never attained to the conception of
continuous process, or realised the significance of time; and they
never viewed the history of human societies as a phenomenon to be
investigated for its own sake. In the middle ages there was still less
chance of the emergence of the ideas of progress and development. Such
notions were excluded by the fundamental doctrines of the dominant
religion which bounded and bound men's minds. As the course of history
was held to be determined from hour to hour by the arbitrary will of
an extra cosmic person, there could be no self-contained causal
development, only a dispensation imposed from without. And as it was
believed that the world was within no great distance from the end of
this dispensation, there was no motive to take much interest in
understanding the temporal, which was to be only temporary.

The intellectual movements of the fifteenth and sixteenth centuries
prepared the way for a new conception, but it did not emerge
immediately. The historians of the Renaissance period simply reverted
to the ancient pragmatical view. For Machiavelli, exactly as for
Thucydides and Polybius, the use of studying history was instruction
in the art of politics. The Renaissance itself was the appearance of a
new culture, different from anything that had gone before; but at the
time men were not conscious of this; they saw clearly that the
traditions of classical antiquity had been lost for a long period, and
they were seeking to revive them, but otherwise they did not perceive
that the world had moved, and that their own spirit, culture, and
conditions were entirely unlike those of the thirteenth century. It
was hardly till the seventeenth century that the presence of a new
age, as different from the middle ages as from the ages of Greece and
Rome, was fully realised. It was then that the triple division of
ancient, medieval, and modern was first applied to the history of
western civilisation. Whatever objections may be urged against this
division, which has now become almost a category of thought, it marks
a most significant advance in man's view of his own past. He has
become conscious of the immense changes in civilisation which have
come about slowly in the course of time, and history confronts him
with a new aspect. He has to explain how those changes have been
produced, how the transformations were effected. The appearance of
this problem was almost simultaneous with the rise of rationalism, and
the great historians and thinkers of the eighteenth century, such as
Montesquieu, Voltaire, Gibbon, attempted to explain the movement of
civilisation by purely natural causes. These brilliant writers
prepared the way for the genetic history of the following century. But
in the spirit of the _Aufklärung_, that eighteenth-century
Enlightenment to which they belonged, they were concerned to judge all
phenomena before the tribunal of reason; and the apotheosis of
"reason" tended to foster a certain superior _a priori_ attitude,
which was not favourable to objective treatment and was incompatible
with a "historical sense." Moreover the traditions of pragmatical
historiography had by no means disappeared.

3. In the first quarter of the nineteenth century the meaning of
genetic history was fully realised. "Genetic" perhaps is as good a
word as can be found for the conception which in this century was
applied to so many branches of knowledge in the spheres both of nature
and of mind. It does not commit us to the doctrine proper of
evolution, nor yet to any teleological hypothesis such as is implied
in "progress." For history it meant that the present condition of the
human race is simply and strictly the result of a causal series (or
set of causal series)--a continuous succession of changes, where each
state arises causally out of the preceding; and that the business of
historians is to trace this genetic process, to explain each change,
and ultimately to grasp' the complete development of the life of
humanity. Three influential writers, who appeared at this stage and
helped to initiate a new period of research, may specially be
mentioned. Ranke in 1824 definitely repudiated the pragmatical view
which ascribes to history the duties of an instructress, and with no
less decision renounced the function, assumed by the historians of the
_Aufklärung_, to judge the past; it was his business, he said, merely
to show how things really happened. Niebuhr was already working in the
same spirit and did more than any other writer to establish the
principle that historical transactions must be related to the ideas
and conditions of their age. Savigny about the same time founded the
"historical school" of law. He sought to show that law was not the
creation of an enlightened will, but grew out of custom and was
developed by a series of adaptations and rejections, thus applying the
conception of evolution. He helped to diffuse the notion that all the
institutions of a society or a nation are as closely interconnected as
the parts of a living organism.

4. The conception of the history of man as a causal development meant
the elevation of historical inquiry to the dignity of a science. Just
as the study of bees cannot become scientific so long as the student's
interest in them is only to procure honey or to derive moral lessons
from the labours of "the little busy bee," so the history of human
societies cannot become the object of pure scientific investigation so
long as man estimates its value in pragmatical scales. Nor can it
become a science until it is conceived as lying entirely within a
sphere in which the law of cause and effect has unreserved and
unrestricted dominion. On the other hand, once history is envisaged as
a causal process, which contains within itself the explanation of the
development of man from his primitive state to the point which he has
reached, such a process necessarily becomes the object of scientific
investigation and the interest in it is scientific curiosity.

At the same time, the instruments were sharpened and refined. Here
Wolf, a philologist with historical instinct, was a pioneer. His
_Prolegomena_ to Homer (1795) announced new modes of attack.
Historical investigation was soon transformed by the elaboration of
new methods.

5. "Progress" involves a judgment of value, which is not involved in
the conception of history as a genetic process. It is also an idea
distinct from that of evolution. Nevertheless it is closely related to
the ideas which revolutionised history at the beginning of the last
century; it swam into men's ken simultaneously; and it helped
effectively to establish the notion of history as a continuous process
and to emphasise the significance of time. Passing over earlier
anticipations, I may point to a _Discours_ of Turgot (1750), where
history is presented as a process in which "the total mass of the
human race" "marches continually though sometimes slowly to an ever
increasing perfection." That is a clear statement of the conception
which Turgot's friend Condorcet elaborated in the famous work,
published in 1795, _Esquisse d'un tableau historique des progrès de
l'esprit humain_. This work first treated with explicit fulness the
idea to which a leading role was to fall in the ideology of the
nineteenth century. Condorcet's book reflects the triumphs of the
_Tiers état_, whose growing importance had also inspired Turgot; it
was the political changes in the eighteenth century which led to the
doctrine, emphatically formulated by Condorcet, that the masses are
the most important element in the historical process. I dwell on this
because, though Condorcet had no idea of evolution, the predominant
importance of the masses was the assumption which made it possible to
apply evolutional principles to history. And it enabled Condorcet
himself to maintain that the history of civilisation, a progress still
far from being complete, was a development conditioned by general

6. The assimilation of society to an organism, which was a governing
notion in the school of Savigny, and the conception of progress,
combined to produce the idea of an organic development, in which the
historian has to determine the central principle or leading character.
This is illustrated by the apotheosis of democracy in Tocqueville's
_Démocratie en Amérique_, where the theory is maintained that "the
gradual and progressive development of equality is at once the past
and the future of the history of men." The same two principles are
combined in the doctrine of Spencer (who held that society is an
organism, though he also contemplated its being what he calls a
"super-organic aggregate"),[238] that social evolution is a
progressive change from militarism to industrialism.

7. The idea of development assumed another form in the speculations of
German idealism. Hegel conceived the successive periods of history as
corresponding to the ascending phases or ideas in the self-evolution
of his Absolute Being. His _Lectures on the Philosophy of History_
were published in 1837 after his death. His philosophy had a
considerable effect, direct and indirect, on the treatment of history
by historians, and although he was superficial and unscientific
himself in dealing with historical phenomena, he contributed much
towards making the idea of historical development familiar. Ranke was
influenced, if not by Hegel himself, at least by the Idealistic
philosophies of which Hegel's was the greatest. He was inclined to
conceive the stages in the process of history as marked by
incarnations, as it were, of ideas, and sometimes speaks as if the
ideas were independent forces, with hands and feet. But while Hegel
determined his ideas by _a priori_ logic, Ranke obtained his by
induction--by a strict investigation of the phenomena; so that he was
scientific in his method and work, and was influenced by Hegelian
prepossessions only in the kind of significance which he was disposed
to ascribe to his results. It is to be noted that the theory of Hegel
implied a judgment of value; the movement was a progress towards

8. In France, Comte approached the subject from a different side, and
exercised, outside Germany, a far wider influence than Hegel. The 4th
volume of his _Cours de philosophie positive_, which appeared in 1839,
created sociology and treated history as a part of this new science,
namely as "social dynamics." Comte sought the key for unfolding
historical development, in what he called the social-psychological
point of view, and he worked out the two ideas which had been
enunciated by Condorcet: that the historian's attention should be
directed not, as hitherto, principally to eminent individuals, but to
the collective behaviour of the masses, as being the most important
element in the process; and that, as in nature, so in history, there
are general laws, necessary and constant, which condition the
development. The two points are intimately connected, for it is only
when the masses are moved into the foreground that regularity,
uniformity, and law can be conceived as applicable. To determine the
social-psychological laws which have controlled the development is,
according to Comte, the task of sociologists and historians.

9. The hypothesis of general laws operative in history was carried
further in a book which appeared in England twenty years later and
exercised an influence in Europe far beyond its intrinsic merit,
Buckle's _History of Civilisation in England_ (1857-61). Buckle owed
much to Comte, and followed him, or rather outdid him, in regarding
intellect as the most important factor conditioning the upward
development of man, so that progress, according to him, consisted in
the victory of the intellectual over the moral laws.

10. The tendency of Comte and Buckle to assimilate history to the
sciences of nature by reducing it to general "laws," derived stimulus
and plausibility from the vista offered by the study of statistics,
in which the Belgian Quetelet, whose book _Sur l'homme_ appeared in
1835, discerned endless possibilities. The astonishing uniformities
which statistical inquiry disclosed led to the belief that it was only
a question of collecting a sufficient amount of statistical material,
to enable us to predict how a given social group will act in a
particular case. Bourdeau, a disciple of this school, looks forward to
the time when historical science will become entirely quantitative.
The actions of prominent individuals, which are generally considered
to have altered or determined the course of things, are obviously not
amenable to statistical computation or explicable by general laws.
Thinkers like Buckle sought to minimise their importance or explain
them away.

11. These indications may suffice to show that the new efforts to
interpret history which marked the first half of the nineteenth
century were governed by conceptions closely related to those which
were current in the field of natural science and which resulted in the
doctrine of evolution. The genetic principle, progressive development,
general laws, the significance of time, the conception of society as
an organic aggregate, the metaphysical theory of history as the
self-evolution of spirit,--all these ideas show that historical
inquiry had been advancing independently on somewhat parallel lines to
the sciences of nature. It was necessary to bring this out in order to
appreciate the influence of Darwinism.

12. In the course of the dozen years which elapsed between the
appearances of _The Origin of Species_ (observe that the first volume
of Buckle's work was published just two years before) and of _The
Descent of Man_ (1871), the hypothesis of Lamarck that man is the
co-descendant with other species of some lower extinct form was
admitted to have been raised to the rank of an established fact by
most thinkers whose brains were not working under the constraint of
theological authority.

One important effect of the discovery of this fact (I am not speaking
now of the Darwinian explanation) was to assign to history a definite
place in the coordinated whole of knowledge, and relate it more
closely to other sciences. It had indeed a defined logical place in
systems such as Hegel's and Comte's; but Darwinism certified its
standing convincingly and without more ado. The prevailing doctrine
that man was created _ex abrupto_ had placed history in an isolated
position, disconnected with the sciences of nature. Anthropology,
which deals with the animal _anthropos_, now comes into line with
zoology, and brings it into relation with history.[239] Man's
condition at the present day is the result of a series of
transformations, going back to the most primitive phase of society,
which is the ideal (unattainable) beginning of history. But that
beginning had emerged without any breach of continuity from a
development which carries us back to a quadrimane ancestor, still
further back (according to Darwin's conjecture) to a marine animal of
the ascidian type, and then through remoter periods to the lowest form
of organism. It is essential in this theory that though links have
been lost there was no break in the gradual development; and this
conception of a continuous progress in the evolution of life,
resulting in the appearance of uncivilised Anthropos, helped to
reinforce, and increase a belief in, the conception of the history of
civilised Anthropos as itself also a continuous progressive

13. Thus the diffusion of the Darwinian theory of the origin of man,
by emphasising the idea of continuity and breaking down the barriers
between the human and animal kingdoms, has had an important effect in
establishing the position of history among the sciences which deal
with telluric development. The perspective of history is merged in a
larger perspective of development. As one of the objects of biology is
to find the exact steps in the genealogy of man from the lowest
organic form, so the scope of history is to determine the stages in
the unique causal series from the most rudimentary to the present
state of human civilisation.

It is to be observed that the interest in historical research implied
by this conception need not be that of Comte. In the Positive
Philosophy history is part of sociology; the interest in it is to
discover the sociological laws. In the view of which I have just
spoken, history is permitted to be an end in itself; the
reconstruction of the genetic process is an independent interest. For
the purpose of the reconstruction, sociology, as well as physical
geography, biology, psychology, is necessary; the sociologist and the
historian play into each other's hands; but the object of the former
is to establish generalisations; the aim of the latter is to trace in
detail a singular causal sequence.

14. The success of the evolutional theory helped to discredit the
assumption or at least the invocation of transcendent causes.
Philosophically of course it is compatible with theism, but historians
have for the most part desisted from invoking the naive conception of
a "god in history" to explain historical movements. A historian may be
a theist; but, so far as his work is concerned, this particular belief
is otiose. Otherwise indeed (as was remarked above) history could not
be a science; for with a _deus ex machina_ who can be brought on the
stage to solve difficulties scientific treatment is a farce. The
transcendent element had appeared in a more subtle form through the
influence of German philosophy. I noticed how Ranke is prone to refer
to ideas as if they were transcendent existences manifesting
themselves in the successive movements of history. It is intelligible
to speak of certain ideas as controlling, in a given period,--for
instance, the idea of nationality; but from the scientific point of
view, such ideas have no existence outside the minds of individuals
and are purely psychical forces; and a historical "idea," if it does
not exist in this form, is merely a way of expressing a synthesis of
the historian himself.

15. From the more general influence of Darwinism on the place of
history in the system of human knowledge, we may turn to the influence
of the principles and methods by which Darwin explained development.
It had been recognised even by ancient writers (such as Aristotle and
Polybius) that physical circumstances (geography, climate) were
factors conditioning the character and history of a race or society.
In the sixteenth century Bodin emphasised these factors, and many
subsequent writers took them into account. The investigations of
Darwin, which brought them into the foreground, naturally promoted
attempts to discover in them the chief key to the growth of
civilisation. Comte had expressly denounced the notion that the
biological methods of Lamarck could be applied to social man. Buckle
had taken account of natural influences, but had relegated them to a
secondary plane, compared with psychological factors. But the
Darwinian theory made it tempting to explain the development of
civilisation in terms of "adaptation to environment," "struggle for
existence," "natural selection," "survival of the fittest," etc.[240]

The operation of these principles cannot be denied. Man is still an
animal, subject to zoological as well as mechanical laws. The dark
influence of heredity continues to be effective; and psychical
development had begun in lower organic forms,--perhaps with life
itself. The organic and the social struggles for existence are
manifestations of the same principle. Environment and climatic
influence must be called in to explain not only the differentiation of
the great racial sections of humanity, but also the varieties within
these sub-species and, it may be, the assimilation of distinct
varieties. Ritter's _Anthropogeography_ has opened a useful line of
research. But on the other hand, it is urged that, in explaining the
course of history, these principles do not take us very far, and that
it is chiefly for the primitive ultra-prehistoric period that they can
account for human development. It may be said that, so far as concerns
the actions and movements of men which are the subject of recorded
history, physical environment has ceased to act mechanically, and in
order to affect their actions must affect their wills first; and that
this psychical character of the causal relations substantially alters
the problem. The development of human societies, it may be argued,
derives a completely new character from the dominance of the conscious
psychical element, creating as it does new conditions (inventions,
social institutions, etc.) which limit and counteract the operation of
natural selection, and control and modify the influence of physical
environment. Most thinkers agree now that the chief clews to the
growth of civilisation must be sought in the psychological sphere.
Imitation, for instance, is a principle which is probably more
significant for the explanation of human development than natural
selection. Darwin himself was conscious that his principles had only a
very restricted application in this sphere, as is evident from his
cautious and tentative remarks in the 5th chapter of his _Descent of
Man_. He applied natural selection to the growth of the intellectual
faculties and of the fundamental social instincts, and also to the
differentiation of the great races or "sub-species" (Caucasian,
African, etc.) which differ in anthropological character.[241]

16. But if it is admitted that the governing factors which concern the
student of social development are of the psychical order, the
preliminary success of natural science in explaining organic evolution
by general principles encouraged sociologists to hope that social
evolution could be explained on general principles also. The idea of
Condorcet, Buckle, and others, that history could be assimilated to
the natural sciences was powerfully reinforced, and the notion that
the actual historical process, and every social movement involved in
it, can be accounted for by sociological generalisations, so-called
"laws," is still entertained by many, in one form or another.
Dissentients from this view do not deny that the generalisations at
which the sociologist arrives by the comparative method, by the
analysis of social factors, and by psychological deduction may be an
aid to the historian; but they deny that such uniformities are laws or
contain an explanation of the phenomena. They can point to the element
of chance coincidence. This element must have played a part in the
events of organic evolution, but it has probably in a larger measure
helped to determine events in social evolution. The collision of two
unconnected sequences may be fraught with great results. The sudden
death of a leader or a marriage without issue, to take simple cases,
has again and again led to permanent political consequences. More
emphasis is laid on the decisive actions of individuals, which cannot
be reduced under generalisations and which deflect the course of
events. If the significance of the individual will had been
exaggerated to the neglect of the collective activity of the social
aggregate before Condorcet, his doctrine tended to eliminate as
unimportant the roles of prominent men, and by means of this
elimination it was possible to found sociology. But it may be urged
that it is patent on the face of history that its course has
constantly been shaped and modified by the wills of individuals,[242]
which are by no means always the expression of the collective will;
and that the appearance of such personalities at the given moments is
not a necessary outcome of the conditions and cannot be deduced. Nor
is there any proof that, if such and such an individual had not been
born, some one else would have arisen to do what he did. In some cases
there is no reason to think that what happened need ever have come to
pass. In other cases, it seems evident that the actual change was
inevitable, but in default of the man who initiated and guided it, it
might have been postponed, and, postponed or not, might have borne a
different cachet. I may illustrate by an instance which has just come
under my notice. Modern painting was founded by Giotto, and the
Italian expedition of Charles VIII, near the close of the sixteenth
century, introduced into France the fashion of imitating Italian
painters. But for Giotto and Charles VIII, French painting might have
been very different. It may be said that "if Giotto had not appeared,
some other great imitator would have played a role analogous to his,
and that without Charles VIII there would have been the commerce with
Italy, which in the long run would have sufficed to place France in
relation with Italian artists. But the equivalent of Giotto might have
been deferred for a century and probably would have been different;
and commercial relations would have required ages to produce the
_rayonnement imitatif_ of Italian art in France, which the expedition
of the royal adventurer provoked in a few years."[243] Instances
furnished by political history are simply endless. Can we conjecture
how events would have moved if the son of Philip of Macedon had been
an incompetent? The aggressive action of Prussia which astonished
Europe in 1740 determined the subsequent history of Germany; but that
action was anything but inevitable; it depended entirely on the
personality of Frederick the Great.

Hence it may be argued that the action of individual wills is a
determining and disturbing factor, too significant and effective to
allow history to be grasped by sociological formulae. The types and
general forms of development which the sociologist attempts to
disengage can only assist the historian in understanding the actual
course of events. It is in the special domains of economic history and
_Culturgeschichte_ which have come to the front in modern times that
generalisation is most fruitful, but even in these it may be contended
that it furnishes only partial explanations.

17. The truth is that Darwinism itself offers the best illustration of
the insufficiency of general laws to account for historical
development. The part played by coincidence, and the part played by
individuals--limited by, and related to, general social
conditions--render it impossible to deduce the course of the past
history of man or to predict the future. But it is just the same with
organic development. Darwin (or any other zoologist) could not deduce
the actual course of evolution from general principles. Given an
organism and its environment, he could not show that it must evolve
into a more complex organism of a definite predetermined type; knowing
what it has evolved into, he could attempt to discover and assign the
determining causes. General principles do not account for a particular
sequence; they embody necessary conditions; but there is a chapter of
accidents too. It is the same in the case of history.

18. Among the evolutional attempts to subsume the course of history under
general syntheses, perhaps the most important is that of Lamprecht, whose
"kulturhistorische" attempt to discover and assign the determining causes.
German history, exhibits the (indirect) influence of the Comtist school. It
is based upon psychology, which, in his views, holds among the sciences of
mind (_Geisteswissenschaften_) the same place (that of a
_Grundwissenschaft_) which mechanics holds among the sciences of nature.
History, by the same comparison, corresponds to biology, and, according to
him, it can only become scientific if it is reduced to general concepts
(_Begriffe_). Historical movements and events are of a psychical character,
and Lamprecht conceives a given phase of civilisation as "a collective
psychical condition (_seelischer Gesamtzustand_)" controlling the period,
"a diapason which penetrates all psychical phenomena and thereby all
historical events of the time."[244] He has worked out a series of such
phases, "ages of changing psychical diapason," in his _Deutsche
Geschichte_, with the aim of showing that all the feelings and actions of
each age can be explained by the diapason; and has attempted to prove that
these diapasons are exhibited in other social developments, and are
consequently not singular but typical. He maintains further that these ages
succeed each other in a definite order; the principle being that the
collective psychical development begins with the homogeneity of all the
individual members of a society and, through heightened psychical activity,
advances in the form of a continually increasing differentiation of the
individuals (this is akin to the Spencerian formula). This process,
evolving psychical freedom from psychical constraint, exhibits a series of
psychical phenomena which define successive periods of civilisation. The
process depends on two simple principles, that no idea can disappear
without leaving behind it an effect or influence, and that all psychical
life, whether in a person or a society, means change, the acquisition of
new mental contents. It follows that the new have to come to terms with the
old, and this leads to a synthesis which determines the character of a new
age. Hence the ages of civilisation are defined as the "highest concepts
for subsuming without exception all psychical phenomena of the development
of human societies, that is, of all historical events."[245] Lamprecht
deduces the idea of a special historical science, which might be called
"historical ethnology," dealing with the ages of civilisation, and bearing
the same relation to (descriptive or narrative) history as ethnology to
ethnography. Such a science obviously corresponds to Comte's social
dynamics, and the comparative method, on which Comte laid so much emphasis,
is the principal instrument of Lamprecht.

19. I have dwelt on the fundamental ideas of Lamprecht, because they
are not yet widely known in England, and because his system is the
ablest product of the sociological school of historians. It carries
the more weight as its author himself is a historical specialist, and
his historical syntheses deserve the most careful consideration. But
there is much in the process of development which on such assumptions
is not explained, especially the initiative of individuals. Historical
development does not proceed in a right line, without the choice of
diverging. Again and again, several roads are open to it, of which it
chooses one--why? On Lamprecht's method, we may be able to assign the
conditions which limit the psychical activity of men at a particular
stage of evolution, but within those limits the individual has so many
options, such a wide room for moving, that the definition of those
conditions, the "psychical diapasons," is only part of the explanation
of the particular development. The heel of Achilles in all historical
speculations of this class has been the role of the individual.

The increasing prominence of economic history has tended to encourage
the view that history can be explained in terms of general concepts or
types. Marx and his school based their theory of human development on
the conditions of production, by which, according to them, all social
movements and historical changes are entirely controlled. The leading
part which economic factors play in Lamprecht's system is significant,
illustrating the fact that economic changes admit most readily this
kind of treatment, because they have been less subject to direction or
interference by individual pioneers.

Perhaps it may be thought that the conception of _social environment_
(essentially psychical), on which Lamprecht's "psychical diapasons"
depend, is the most valuable and fertile conception that the historian
owes to the suggestion of the science of biology--the conception of
all particular historical actions and movements as (1) related to and
conditioned by the social environment, and (2) gradually bringing
about a transformation of that environment. But no given
transformation can be proved to be necessary (predetermined). And
types of development do not represent laws; their meaning and value
lie in the help they may give to the historian, in investigating a
certain period of civilisation, to enable him to discover the
inter-relations among the diverse features which it presents. They
are, as some one has said, an instrument of heuretic method.

20. The man engaged in special historical researches--which have been
pursued unremittingly for a century past, according to scientific
methods of investigating evidence (initiated by Wolf, Niebuhr,
Ranke)--have for the most part worked on the assumptions of genetic
history or at least followed in the footsteps of those who fully
grasped the genetic point of view. But their aim has been to collect
and sift evidence, and determine particular facts; comparatively few
have given serious thought to the lines of research and the
speculations which have been considered in this paper. They have been
reasonably shy of compromising their work by applying theories which
are still much debated and immature. But historiography cannot
permanently evade the questions raised by these theories. One may
venture to say that no historical change or transformation will be
fully understood until it is explained how social environment acted on
the individual components of the society (both immediately and by
heredity), and how the individuals reacted upon their environment. The
problem is psychical, but it is analogous to the main problem of the


[Footnote 238: A society presents suggestive analogies with an
organism, but it certainly is not an organism, and sociologists who
draw inferences from the assumption of its organic nature must fall
into error. A vital organism and a society are radically distinguished
by the fact that the individual components of the former, namely the
cells, are morphologically as well as functionally differentiated,
whereas the individuals which compose a society are morphologically
homogeneous and only functionally differentiated. The resemblances and
the differences are worked out in E. de Majewski's striking book, _La
Science de la Civilisation_. Paris. 1908.]

[Footnote 239: It is to be observed that history is (not only
different in scope but) not co-extensive with anthropology _in time_.
For it deals only with the development of man in societies, whereas
anthropology includes in its definition the proto-anthropic period
when _anthropos_ was still non-social, whether he lived in herds like
the chimpanzee, or alone like the male ourang-outang. (It has been
well shown by Majewski that congregations--herds, flocks, packs,
&c.--of animals are not _societies_; the characteristic of a society
is differentiation of function. Bee hives, ant hills, may be called
quasi-societies; but in their case the classes which perform distinct
functions are morphologically different.)]

[Footnote 240: Recently O. Seeck has applied these principles to the
decline of Graeco-Roman civilisation in his _Untergang der antiken
Welt_, 2 vols., Berlin, 1895, 1901.]

[Footnote 241: Darwinian formulae may be suggestive by way of analogy.
For instance, it is characteristic of social advance that a multitude
of inventions, schemes and plans are framed which are never carried
out, similar to, or designed for the same end as, an invention or plan
which is actually adopted because it has chanced to suit better the
particular conditions of the hour (just as the works accomplished by
an individual statesman, artist or savant are usually only a residue
of the numerous projects conceived by his brain). This process in
which so much abortive production occurs is analogous to elimination
by natural selection.]

[Footnote 242: We can ignore here the metaphysical question of
freewill and determinism. For the character of the individual's brain
depends in any case on ante-natal accidents and coincidences, and so
it may be said that the role of individuals ultimately depends on
chance,--the accidental coincidence of independent sequences.]

[Footnote 243: I have taken this example from G. Tarde's _La logique
sociale_ (p. 403), Paris, 1904, where it is used for quite a different

[Footnote 244: _Die kulturhistorische Methode_, Berlin, 1900, p. 26.]

[Footnote 245: _Ibid._ pp. 28, 29.]




_Professor of Social Philosophy in the University of Toulouse and
Deputy-Professor at the Sorbonne, Paris_

How has our conception of social phenomena, and of their history, been
affected by Darwin's conception of Nature and the laws of its
transformation? To what extent and in what particular respects have
the discoveries and hypotheses of the author of _The Origin of
Species_ aided the efforts of those who have sought to construct a
science of society?

To such a question it is certainly not easy to give any brief or
precise answer. We find traces of Darwinism almost everywhere.
Sociological systems differing widely from each other have laid claim
to its authority; while, on the other hand, its influence has often
made itself felt only in combination with other influences. The
Darwinian thread is worked into a hundred patterns along with other

To deal with the problem, we must, it seems, first of all distinguish
the more general conclusions in regard to the evolution of living
beings, which are the outcome of Darwinism, from the particular
explanations it offers of the ways and means by which that evolution
is effected. That is to say, we must, as far as possible, estimate
separately the influence of Darwin as an evolutionist and Darwin as a

The nineteenth century, said Cournot, has witnessed a mighty effort to
"réintégrer l'homme dans la nature." From divers quarters there has
been a methodical reaction against the persistent dualism of the
Cartesian tradition, which was itself the unconscious heir of the
Christian tradition. Even the philosophy of the eighteenth century,
materialistic as were for the most part the tendencies of its leaders,
seemed to revere man as a being apart, concerning whom laws might be
formulated _à priori_. To bring him down from his pedestal there was
needed the marked predominance of positive researches wherein no
account was taken of the "pride of man." There can be no doubt that
Darwin has done much to familiarise us with this attitude. Take for
instance the first part of _The Descent of Man_: it is an accumulation
of typical facts, all tending to diminish the distance between us and
our brothers, the lower animals. One might say that the naturalist had
here taken as his motto, "Whosoever shall exalt himself shall be
abased; and he that shall humble himself shall be exalted." Homologous
structures, the survival in man of certain organs of animals, the
rudiments in the animal of certain human faculties, a multitude of
facts of this sort, led Darwin to the conclusion that there is no
ground for supposing that the "king of the universe" is exempt from
universal laws. Thus belief in the _imperium in imperio_ has been, as
it were, whittled away by the progress of the naturalistic spirit,
itself continually strengthened by the conquests of the natural
sciences. The tendency may, indeed, drag the social sciences into
overstrained analogies, such, for instance, as the assimilation of
societies to organisms. But it will, at least, have had the merit of
helping sociology to shake off the pre-conception that the groups
formed by men are artificial, and that history is completely at the
mercy of chance. Some years before the appearance of _The Origin of
Species_, August Comte had pointed out the importance, as regards the
unification of positive knowledge, of the conviction that the social
world, the last refuge of spiritualism, is itself subject to
determinism. It cannot be doubted that the movement of thought which
Darwin's discoveries promoted contributed to the spread of this
conviction, by breaking down the traditional barrier which cut man off
from Nature.

But Nature, according to modern naturalists, is no immutable thing: it
is rather perpetual movement, continual progression. Their discoveries
batter a breach directly into the Aristotelian notion of species; they
refuse to see in the animal world a collection of immutable types,
distinct from all eternity, and corresponding, as Cuvier said, to so
many particular thoughts of the Creator. Darwin especially
congratulated himself upon having been able to deal this doctrine the
_coup de grâce_: immutability is, he says, his chief enemy; and he is
concerned to show--therein following up Lyell's work--that everything
in the organic world, as in the inorganic, is explained by insensible
but incessant transformations. "Nature makes no leaps"--"Nature knows
no gaps": these two _dicta_ form, as it were, the two landmarks
between which Darwin's idea of transformation is worked out. That is
to say, the development of Darwinism is calculated to further the
application of the philosophy of Becoming to the study of human

The progress of the natural sciences thus brings unexpected
reinforcements to the revolution which the progress of historical
discipline had begun. The first attempt to constitute an actual
science of social phenomena--that, namely, of the economists--had
resulted in laws which were called natural, and which were believed to
be eternal and universal, valid for all times and all places. But this
perpetuality, brother, as Knies said, of the immutability of the old
zoology, did not long hold out against the ever-swelling tide of the
historical movement. Knowledge of the transformations that had taken
place in language, of the early phases of the family, of religion, of
property, had all favoured the revival of the Heraclitean view:
πἁντα ρει̃. As to the categories of political economy, it was
soon to be recognised, as by Lasalle, that they too are only
historical. The philosophy of history, moreover, gave expression
under various forms to the same tendency. Hegel declares that "all
that is real is rational," but at the same time he shows that all that
is real is ephemeral, and that for history there is nothing fixed
beneath the sun. It is this sense of universal evolution that Darwin
came with fresh authority to enlarge. It was in the name of biological
facts themselves that he taught us to see only slow metamorphoses in
the history of institutions, and to be always on the outlook for
survivals side by side with rudimentary forms. Anyone who reads
_Primitive Culture_, by Tylor,--a writer closely connected with
Darwin--will be able to estimate the services which these cardinal
ideas were to render to the social sciences when the age of
comparative research had succeeded to that of _à priori_ construction.

Let us note, moreover, that the philosophy of Becoming in passing through
the Darwinian biology became, as it were, filtered; it got rid of those
traces of finalism, which, under different forms, it had preserved through
all the systems of German Romanticism. Even in Herbert Spencer, it has been
plausibly argued, one can detect something of that sort of mystic
confidence in forces spontaneously directing life, which forms the very
essence of those systems. But Darwin's observations were precisely
calculated to render such an hypothesis futile. At first people may have
failed to see this; and we call to mind the ponderous sarcasms of Flourens
when he objected to the theory of Natural Selection that it attributed to
nature a power of free choice. "Nature endowed with will! That was the
final error of last century; but the nineteenth no longer deals in
personifications."[246] In fact Darwin himself put his readers on their
guard against the metaphors he was obliged to use. The processes by which
he explains the survival of the fittest are far from affording any
indication of the design of some transcendent breeder. Nor, if we look
closely, do they even imply immanent effort in the animal; the sorting out
can be brought about mechanically, simply by the action of the environment.
In this connection Huxley could with good reason maintain that Darwin's
originality consisted in showing how harmonies which hitherto had been
taken to imply the agency of intelligence and will could be explained
without any such intervention. So, when later on, objective sociology
declares that, even when social phenomena are in question, all finalist
preconceptions must be distrusted if a science is to be constituted, it is
to Darwin that its thanks are due; he had long been clearing paths for it
which lay well away from the old familiar road trodden by so many theories
of evolution.

This anti-finalist doctrine, when fully worked out, was, moreover,
calculated to aid in the needful dissociation of two notions: that of
evolution and that of progress. In application to society these had
long been confounded; and, as a consequence, the general idea seemed
to be that only one type of evolution was here possible. Do we not
detect such a view in Comte's sociology, and perhaps even in Herbert
Spencer's? Whoever, indeed, assumes an end for evolution is naturally
inclined to think that only one road leads to that end. But those
whose minds the Darwinian theory has enlightened are aware that the
transformations of living beings depend primarily upon their
conditions, and that it is these conditions which are the agents of
selection from among individual variations. Hence, it immediately
follows that transformations are not necessarily improvements. Here,
Darwin's thought hesitated. Logically his theory proves, as Ray
Lankester pointed out, that the struggle for existence may have as its
outcome degeneration as well as amelioration: evolution may be
regressive as well as progressive. Then, too--and this is especially
to be borne in mind--each species takes its good where it finds it,
seeks its own path and survives as best it can. Apply this notion to
society and you arrive at the theory of multilinear evolution.
Divergencies will no longer surprise you. You will be forewarned not
to apply to all civilisations the same measure of progress, and you
will recognise that types of evolution may differ just as social
species themselves differ. Have we not here one of the conceptions
which mark off sociology proper from the old philosophy of history?

       *       *       *       *       *

But if we are to estimate the influence of Darwinism upon sociological
conceptions, we must not dwell only upon the way in which Darwin
impressed the general notion of evolution upon the minds of thinkers.
We must go into details. We must consider the influence of the
particular theories by which he explained the mechanism of this
evolution. The name of the author of _The Origin of Species_ has been
especially attached, as everyone knows, to the doctrines of "natural
selection" and of "struggle for existence," completed by the notion of
"individual variation." These doctrines were turned to account by very
different schools of social philosophy. Pessimistic and optimistic,
aristocratic and democratic, individualistic and socialistic systems
were to war with each other for years by casting scraps of Darwinism
at each other's heads.

It was the spectacle of human contrivance that suggested to Darwin his
conception of natural selection. It was in studying the methods of
pigeon breeders that he divined the processes by which nature, in the
absence of design, obtains analogous results in the differentiation of
types. As soon as the importance of artificial selection in the
transformation of species of animals was understood, reflection
naturally turned to the human species, and the question arose, How far
do men observe, in connection with themselves, those laws of which
they make practical application in the case of animals? Here we come
upon one of the ideas which guided the researches of Gallon, Darwin's
cousin. The author of _Inquiries into Human Faculty and its
Development_,[247] has often expressed his surprise that, considering
all the precautions taken, for example, in the breeding of horses,
none whatever are taken in the breeding of the human species. It seems
to be forgotten that the species suffers when the "fittest" are not
able to perpetuate their type. Ritchie, in his _Darwinism and
Politics_[248] reminds us of Darwin's remark that the institution of
the peerage might be defended on the ground that peers, owing to the
prestige they enjoy, are enabled to select as wives "the most
beautiful and charming women out of the lower ranks."[249] But, says
Galton, it is as often as not "heiresses" that they pick out, and
birth statistics seem to show that these are either less robust or
less fecund than others. The truth is that considerations continue to
preside over marriage which are entirely foreign to the improvement of
type, much as this is a condition of general progress. Hence the
importance of completing Odin's and De Candolle's statistics which are
designed to show how characters are incorporated in organisms, how
they are transmitted, how lost, and according to what law eugenic,
elements depart from the mean or return to it.

But thinkers do not always content themselves with undertaking merely
the minute researches which the idea of Selection suggests. They are
eager to defend this or that thesis. In the name of this idea certain
social anthropologists have recast the conception of the process of
civilisation, and have affirmed that Social Selection generally works
against the trend of Natural Selection. Vacher de Lapouge--following
up an observation by Broca on the point--enumerates the various
institutions, or customs, such as the celibacy of priests and military
conscription, which cause elimination or sterilisation of the bearers
of certain superior qualities, intellectual or physical. In a more
general way he attacks the democratic movement, a movement, as P.
Bourget says, which is "anti-physical" and contrary to the natural
laws of progress; though it has been inspired "by the dreams of that
most visionary of all centuries, the eighteenth."[250] The "Equality"
which levels down and mixes (justly condemned, he holds, by the Comte
de Gobineau), prevents the aristocracy of the blond dolichocephales
from holding the position and playing the part which, in the interests
of all, should belong to them. Otto Ammon, in his _Natural Selection
in Man_, and in _The Social Order and its Natural Bases_,[251]
defended analogous doctrines in Germany; setting the curve
representing frequency of talent over against that of income, he
attempted to show that all democratic measures which aim at promoting
the rise in the social scale of the talented are useless, if not
dangerous; that they only increase the panmixia, to the great
detriment of the species and of society.

Among the aristocratic theories which Darwinism has thus inspired we
must reckon that of Nietzsche. It is well known that in order to
complete his philosophy he added biological studies to his
philological; and more than once in his remarks upon the _Wille zur
Macht_ he definitely alludes to Darwin; though it must be confessed
that it is generally in order to proclaim the insufficiency of the
processes by which Darwin seeks to explain the genesis of species.
Nevertheless, Nietzsche's mind is completely possessed by an ideal of
Selection. He, too, has a horror of panmixia. The naturalists'
conception of "the fittest" is joined by him to that of the "hero" of
romance to furnish a basis for his doctrine of the Superman. Let us
hasten to add, moreover, that at the very moment when support was
being sought in the theory of Selection for the various forms of the
aristocratic doctrine, those same forms were being battered down on
another side by means of that very theory. Attention was drawn to the
fact that by virtue of the laws which Darwin himself had discovered
isolation leads to etiolation. There is a risk that the privilege
which withdraws the privileged elements of Society from competition
will cause them to degenerate. In fact, Jacoby in his _Studies in
Selection, in connexion with Heredity in Man_,[252] concludes that
"sterility, mental debility, premature death and, finally, the
extinction of the stock were not specially and exclusively the fate of
sovereign dynasties; all privileged classes, all families in
exclusively elevated positions share the fate of reigning families,
although in a minor degree and in direct proportion to the loftiness
of their social standing. From the mass of human beings spring
individuals, families, races, which tend to raise themselves above the
common level; painfully they climb the rugged heights, attain the
summits of power, of wealth, of intelligence, of talent, and then, no
sooner are they there than they topple down and disappear in gulfs of
mental and physical degeneracy." The demographical researches of
Hansen[253] (following up and completing Dumont's) tended, indeed, to
show that urban as well as feudal aristocracies, burgher classes as
well as noble castes, were liable to become effete. Hence it might
well be concluded that the democratic movement, operating as it does
to break down class barriers, was promoting instead of impeding human

       *       *       *       *       *

So we see that, according to the point of view, very different
conclusions have been drawn from the application of the Darwinian idea
of Selection to human society. Darwin's other central idea, closely
bound up with this, that, namely, of the "struggle for existence" also
has been diversely utilised. But discussion has chiefly centered upon
its signification. And while some endeavour to extend its application
to everything, we find others trying to limit its range. The
conception of a "struggle for existence" has in the present day been
taken up into the social sciences from natural science, and adopted.
But originally it descended from social science to natural. Darwin's
law is, as he himself said, only Malthus' law generalised and extended
to the animal world: a growing disproportion between the supply of
food and the number of the living is the fatal order whence arises the
necessity of universal struggle, a struggle which, to the great
advantage of the species, allows only the best equipped individuals to
survive. Nature is regarded by Huxley as an immense arena where all
living beings are gladiators.[254]

Such a generalisation was well adapted to feed the stream of
pessimistic thought; and it furnished to the apologists of war, in
particular, new arguments, weighted with all the authority which in
these days attaches to scientific deliverances. If people no longer
say, as Bonald did, and Moltke after him, that war is a providential
fact, they yet lay stress on the point that it is a natural fact. To
the peace party Dragomirov's objection is urged that its attempts are
contrary to the fundamental laws of nature, and that no sea wall can
hold against breakers that come with such gathered force.

But in yet another quarter Darwinism was represented as opposed to
philanthropic intervention. The defenders of the orthodox political
economy found in it support for their tenets. Since in the organic
world universal struggle is the condition of progress, it seemed
obvious that free competition must be allowed to reign unchecked in
the economic world. Attempts to curb it were in the highest degree
imprudent. The spirit of Liberalism here seemed in conformity with the
trend of nature: in this respect, at least, contemporary naturalism,
offspring of the discoveries of the nineteenth century, brought
reinforcements to the individualist doctrine, begotten of the
speculations of the eighteenth: but only, it appeared, to turn mankind
away for ever from humanitarian dreams. Would those whom such
conclusions repelled be content to oppose to nature's imperatives
only the protests of the heart? There were some who declared, like
Brunetière, that the laws in question, valid though they might be for
the animal kingdom, were not applicable to the human. And so a return
was made to the classic dualism. This indeed seems to be the line that
Huxley took, when, for instance, he opposed to the cosmic process an
ethical process which was its reverse.

But the number of thinkers whom this antithesis does not satisfy grows
daily. Although the pessimism which claims authorisation from Darwin's
doctrines is repugnant to them, they still are unable to accept the
dualism which leaves a gulf between man and nature. And their
endeavour is to link the two by showing that while Darwin's laws
obtain in both kingdoms, the conditions of their application are not
the same: their forms, and, consequently, their results, vary with the
varying mediums in which the struggle of living beings takes place,
with the means these beings have at disposal, with the ends even which
they propose to themselves.

Here we have the explanation of the fact that among determined
opponents of war partisans of the "struggle for existence" can be
found: there are disciples of Darwin in the peace party. Novicow, for
example, admits the "_combat universel_" of which Le Dantec[255]
speaks; but he remarks that at different stages of evolution, at
different stages of life the same weapons are not necessarily
employed. Struggles of brute force, armed hand to hand conflicts, may
have been a necessity in the early phases of human societies.
Nowadays, although competition may remain inevitable and
indispensable, it can assume milder forms. Economic rivalries,
struggles between intellectual influences, suffice to stimulate
progress: the processes which these admit are, in the actual state of
civilisation, the only ones which attain their end without waste, the
only ones logical. From one end to the other of the ladder of life,
struggle is the order of the day; but more and more as the higher
rungs are reached, it takes on characters which are proportionately
more "humane."

Reflections of this kind permit the introduction into the economic
order of limitations to the doctrine of "laisser faire, laisser
passer." This appeals, it is said, to the example of nature where
creatures, left to themselves, struggle without truce and without
mercy; but the fact is forgotten that upon industrial battlefields the
conditions are different. The competitors here are not left simply to
their natural energies: they are variously handicapped. A rich store
of artificial resources exists in which some participate and others do
not. The sides then are unequal; and as a consequence the result of
the struggle is falsified. "In the animal world," said De
Laveleye,[256] criticising Spencer, "the fate of each creature is
determined by its individual qualities; whereas in civilised societies
a man may obtain the highest position and the most beautiful wife
because he is rich and well-born, although he may be ugly, idle or
improvident; and then it is he who will perpetuate the species. The
wealthy man, ill constituted, incapable, sickly, enjoys his riches and
establishes his stock under the protection of the laws." Haycraft in
England and Jentsch in Germany have strongly emphasised these
"anomalies," which nevertheless are the rule. That is to say that even
from a Darwinian point of view all social reforms can readily be
justified which aim at diminishing, as Wallace said, inequalities at
the start.

But we can go further still. Whence comes the idea that all measures
inspired by the sentiment of solidarity are contrary to Nature's
trend? Observe her carefully, and she will not give lessons only in
individualism. Side by side with the struggle for existence do we not
find in operation what Lanessan calls "association for existence."
Long ago, Espinas had drawn attention to "societies of animals,"
temporary or permanent, and to the kind of morality that arose in
them. Since then, naturalists have often insisted upon the importance
of various forms of symbiosis. Kropotkin in _Mutual Aid_ has chosen
to enumerate many examples of altruism furnished by animals to
mankind. Geddes and Thomson went so far as to maintain that "Each of
the greater steps of progress is in fact associated with an increased
measure of subordination of individual competition to reproductive or
social ends, and of interspecific competition to co-operative,
association."[257] Experience shows, according to Geddes, that the
types which are fittest to surmount great obstacles are not so much
those who engage in the fiercest competitive struggle for existence,
as those who contrive to temper it. From all these observations there
resulted, along with a limitation of Darwinian pessimism, some
encouragement for the aspirations of the collectivists.

And Darwin himself would, doubtless, have subscribed to these
rectifications. He never insisted, like his rival, Wallace, upon the
necessity of the solitary struggle of creatures in a state of nature,
each for himself and against all. On the contrary, in _The Descent of
Man_, he pointed out the serviceableness of the social instincts, and
corroborated Bagehot's statements when the latter, applying laws of
physics to politics, showed the great advantage societies derived from
intercourse and communion. Again, the theory of sexual evolution which
makes the evolution of types depend increasingly upon preferences,
judgments, mental factors, surely offers something to qualify what
seems hard and brutal in the theory of natural selection.

But, as often happens with disciples, the Darwinians had out-Darwined
Darwin. The extravagances of social Darwinism provoked a useful
reaction; and thus people were led to seek, even in the animal
kingdom, for facts of solidarity which would serve to justify humane

       *       *       *       *       *

On quite another line, however, an attempt has been made to connect
socialist tendencies with Darwinian principles. Marx and Darwin have
been confronted; and writers have undertaken to show that the work of
the German philosopher fell readily into line with that of the English
naturalist and was a development of it. Such has been the endeavour of
Ferri in Italy and of Woltmann in Germany, not to mention others. The
founders of "scientific socialism" had, moreover, themselves thought
of this reconciliation. They make more than one allusion to Darwin in
works which appeared after 1859. And sometimes they use his theory to
define by contrast their own ideal. They remark that the capitalist
system, by giving free course to individual competition, ends indeed
in a _bellum omnium contra omnes_; and they make it clear that
Darwinism, thus understood, is as repugnant to them as to Dühring.

But it is at the scientific and not at the moral point of view that
they place themselves when they connect their economic history with
Darwin's work. Thanks to this unifying hypothesis, they claim to have
constructed--as Marx does in his preface to _Das Kapital_--a veritable
natural history of social evolution. Engels speaks in praise of his
friend Marx as having discovered the true mainspring of history hidden
under the veil of idealism and sentimentalism, and as having
proclaimed in the _primum vivere_ the inevitableness of the struggle
for existence. Marx himself, in _Das Kapital_, indicated another
analogy when he dwelt upon the importance of a general technology for
the explanation of this psychology:--a history of tools which would be
to social organs what Darwinism is to the organs of animal species.
And the very importance they attach to tools, to apparatus, to
machines, abundantly proves that neither Marx nor Engels were likely
to forget the special characters which mark off the human world from
the animal. The former always remains to a great extent an artificial
world. Inventions change the face of its institutions. New modes of
production revolutionise not only modes of government, but modes even
of collective thought. Therefore it is that the evolution of society
is controlled by laws special to it, of which the spectacle of nature
offers no suggestion.

If, however, even in this special sphere, it can still be urged that
the evolution of the material conditions of society is in accord with
Darwin's theory, it is because the influence of the methods of
production is itself to be explained by the incessant strife of the
various classes with each other. So that in the end Marx, like Darwin,
finds the source of all progress is in struggle. Both are grandsons of
Heraclitus:--πὁλεμος πατἠρ πἁντων. It sometimes happens, in
these days, that the doctrine of revolutionary socialism is contrasted
as rude and healthy with what may seem to be the enervating tendency
of "solidarist" philanthropy: the apologists of the doctrine then
pride themselves above all upon their faithfulness to Darwinian

       *       *       *       *       *

So far we have been mainly concerned to show the use that social
philosophies have made of the Darwinian laws for practical purposes:
in order to orientate society towards their ideals each school tries
to show that the authority of natural science is on its side. But even
in the most objective of theories, those which systematically make
abstraction of all political tendencies in order to study the social
reality in itself, traces of Darwinism are readily to be found.

Let us take for example Durkheim's theory of Division of Labour.[258]
The conclusions he derives from it are that whenever professional
specialisation causes multiplication of distinct branches of activity,
we get organic solidarity--implying differences--substituted for
mechanical solidarity, based upon likenesses. The umbilical cord, as
Marx said, which connects the individual consciousness with the
collective consciousness is cut. The personality becomes more and more
emancipated. But on what does this phenomenon, so big with
consequences, itself depend? The author goes to social morphology for
the answer: it is, he says, the growing density of population which
brings with it this increasing differentiation of activities. But,
again, why? Because the greater density, in thrusting men up against
each other, augments the intensity of their competition for the means
of existence; and for the problems which society thus has to face
differentiation of functions presents itself as the gentlest solution.

Here one sees that the writer borrows directly from Darwin.
Competition is at its maximum between similars, Darwin had declared;
different species, not laying claim to the same food, could more
easily coexist. Here lay the explanation of the fact that upon the
same oak hundreds of different insects might be found. Other things
being equal, the same applies to society. He who finds some unadopted
specialty possesses a means of his own for getting a living. It is by
this division of their manifold tasks that men contrive not to crush
each other. Here we obviously have a Darwinian law serving as
intermediary in the explanation of that progress of division of labour
which itself explains so much in the social evolution.

And we might take another example, at the other end of the series of
sociological systems. G. Tarde is a sociologist with the most
pronounced anti-naturalistic views. He has attempted to show that all
application of the laws of natural science to society is misleading.
In his _Opposition Universelle_ he has directly combatted all forms of
sociological Darwinism. According to him the idea that the evolution
of society can be traced on the same plan as the evolution of species
is chimerical. Social evolution is at the mercy of all kinds of
inventions, which by virtue of the laws of imitation modify, through
individual to individual, through neighbourhood to neighbourhood, the
general state of those beliefs and desires which are the only
"quantities" whose variation matters to the sociologist. But, it may
be rejoined, that however psychical the forces may be, they are none
the less subject to Darwinian laws. They compete with each other; they
struggle for the mastery of minds. Between types of ideas, as between
organic forms, selection operates. And though it may be that these
types are ushered into the arena by unexpected discoveries, we yet
recognise in the psychological accidents, which Tarde places at the
base of everything, near relatives of those small accidental
variations upon which Darwin builds. Thus, accepting Tarde's own
representations, it is quite possible to express in Darwinian terms,
with the necessary transpositions, one of the most idealistic
sociologies that have ever been constructed.

These few examples suffice. They enable us to estimate the extent of
the field of influence of Darwinism. It affects sociology not only
through the agency of its advocates but through that of its opponents.
The questions to which it has given rise have proved no less fruitful
than the solutions it has suggested. In short, few doctrines, in the
history of social philosophy, will have produced on their passage a
finer crop of ideas.


[Footnote 246: P. Flourens, _Examen du Livre de M. Darwin sur
l'Origine des Espèces_, p. 53, Paris, 1864. See also Huxley,
"Criticisms on the _Origin of Species," Collected Essays_, Vol. II, p.
102, London, 1902.]

[Footnote 247: _Inquiries into Human Faculty_, pp. 1, 2, 3 sq.,
London, 1883.]

[Footnote 248: _Darwinism and Politics_, pp. 9, 22, London, 1889.]

[Footnote 249: _Life and Letters of Charles Darwin_, II. p. 385.]

[Footnote 250: V. de Lapouge, _Les Sélections sociales_, p. 259,
Paris, 1896.]

[Footnote 251: _Die natärliche Auslese beim Menschen_, Jena, 1893; _Du
Gesellschaftsordnung und ihre natürlichen Grundlagen. Entwurf einer
Sozialanthropologie_, Jena, 1896.]

[Footnote 252: _Etudes sur la Sélection dans ses rapports avec
l'hérédité chez l'homme_, Paris, p. 481, 1881.]

[Footnote 253: _Die drei Bevölkerungsstufen_, Munich, 1889.]

[Footnote 254: _Evolution and Ethics_, p. 200; _Collected Essays_,
Vol. IX, London, 1894.]

[Footnote 255: _Les Luttes entre Sociétés humaines et leurs phases
successives_, Paris, 1893.]

[Footnote 256: _Le socialisme contemporain_, p. 384 (6th edit.),
Paris, 1891.]

[Footnote 257: Geddes and Thomson, _The Evolution of Sex_, p. 311,
London, 1889.]

[Footnote 258: _De la Division du Travail social_, Paris. 1893.]


_Abraxas grossulariata_, 100

Acquired characters, transmission of, 20, 28, 42, 94, 120, 149, 171, 173

_Acraea johnstoni_, 290
[Transcriber's Note: No such page number or reference seen]

Adaptation, 24, 27, 34, 39, 42-45, 50, 58, 79-86, 106, 107

Adloff, 140

Alexander, 217

Ameghino, 132, 138

Ammon, O., Works of, 271

_Anaea divina_, 69

Anglicus, Bartholomaeus, 237

Ankyroderma, 40

Anomma, 44

Anthropops, 132

Ants, modifications of, 43-46, 51

Ardigò, 207, 208

Argyll, Huxley and the Duke of, 238

Aristotle, 3, 237, 240

Avenarius, 211

Bacon, on mutability of species, 4, 5

Baehr, von, on Cytology, 99

Bain, 194

Baldwin, J. M., 53, Foot Note 165

Balfour, A. J., 241

Barratt, 217

Bates, H. W., on Mimicry, 70, 76

BATESON, W., on _Heredity and
Variation in Modern Lights_, 87-110
  --on discontinuous evolution, 30

Bathmism, 14

Bells (Sir Charles) _Anatomy of Expression_, 177

Bentham, Jeremy, 217, 218

Bergson, H., 208

Berkeley, 200

Berthelot, 228

Bickford, E., experiments on degeneration by, 52

Biophores, 47

Blumenbach, 89

Bodin, 256

Bonald, on war, 273

Bonnet, 6

BOUGLÉ, C., on _Darwinism and Sociology_, 264-280

Bourdeau, 253

Bourget, P., 270

Boutroux, 208

Brassica, hybrids of, 106

_Brassica Napus_, 106

Broca, 137, 270

Brock, on Kant, Foot Note 6

Brunetière, 274

Bruno, on Evolution, 4

Buch, von, 15

Buckle, 252, 253, 256, 258

Buffon, 6-15, 21, 88

Burdon-Sanderson, J., letter from, Foot Note 224

BURY, J. B., on _Darwinism and History_, 246-263

Butler, Samuel, 9, Foot Note 17, Foot Note 57, Foot Note 61, 94, Foot Note 66, 107

Butterflies, mimicry in, 65-83
  --sexual characters in, 59-63

Cabanis, 201

Candolle, de, 270

Carneri, 217

_Castnia linus_, 76

Caterpillars, variation in, 36, 37

Cesnola, experiments on Mantis by, 65

Chaerocampa, colouring of, 68

Chambers, R., _The Vestiges of Creation_ by, 15

Chromosomes and Chromomeres, 47, 96-100

Chun, Foot Note 36

Claus, Foot Note 21

Clodd, E., Foot Note 13

Coadaptation, 41-54

_Colobopsis truncata_, 44

Colour, E. B. Poulton, in relation to Sexual Selection, 61-65

Comte, A., 200-203, 252-255, 262, 265

Condorcet, 221, 250, 252, 258

Cope, 138

Correlation of organisms, Darwin's idea of the, 2

Cournot, 265

Cuvier, 9, 10, 266, 268

Cytology and heredity, 95, 96, 99, 100

_Danaida chrysippus_, 75

_Danaida genutia_, 75

_D. Plexippus_, 75

Dantec, Le, 274

Darwin, Charles, as an Anthropologist, 146-165
  --on ants, 44
  --and S. Butler, Foot Note 61, 94
  --on Cirripedia, 212
  --on the Descent of Man, 111-145
  --evolutionist authors referred to in the _Origin_ by, 9

Darwin, Charles, and Haeckel, 137
  --and History, 246-263
  --and Huxley, 112
  --on Lamarck, 28, 129
  --on Language, 124
  --and Malthus, 16, 24, 91
  --on Patrick Matthew, 19
  --on mental evolution, 166-196
  --on Natural Selection, 21, 41, 54, 55, 122
  --a "Naturalist for Naturalists," 87
  --his personality, 187
  --his influence on Philosophy, 197-222
  --predecessors of, 1-22
  --his views on religion, etc., 115, 116, 219-222
  --his influence on religious thought, 223-245
  --causes of his success, 10, 90

Darwin, Charles, on the _Vestiges of Creation_, 15
  --and Wallace, 23, 183
  --on evolution, 7-15, 88
  --on Lamarckism, 11

Darwin, F., on Prichard's "Anticipations," 21

Darwinism, Sociology, Evolution and, 17-18

Degeneration, 49-51, 93

Deniker, 137

Descartes, 4

Descent, history of doctrine of, 1

_Descent of Man_, G. Schwalbe on _The_, 111-145
  --rejection in Germany of _The_, 156

Diderot, 6, 198

Dimorphism, seasonal, 30

_Dismorphia orise_, 75

Dragomirov, 273

Driesch, Foot Note 67

Dryopithecus, 132

Dubois, E., on Pithecanthropus, 132, 137

Dühring, 214, 277

Duns Scotus, 200

Duret, C., 6

Durkheim, on division of labour, 278

Ecology, Foot Note 205

Eimer, 109

_Elymnias undularis_, 73, 75

Embryology, the Origin of Species and, 154, 155

Empedocles, 3, 27, 151

Engels, 277

Environment, action of, 12, 13, 15

Epicurus, a poet of Evolution, 4

Eristalis, 75

Espinas, 275

Evolution, and creation, 233
  --conception of, 3-5, 9, 148, 151, 198
  --discontinuous, 30
  --experimental, 5, 7
  --factors of, 11-15
  --mental, 194
  --Lloyd Morgan on mental factors in, 166-196
  --Darwinism and Social, 18
  --Saltatory, 29-32
  --Herbert Spencer on, 204-207
  --Philosophers and modern methods of studying, 4

Expression of the Emotions, 177-184

Ferri, 277

Ferrier, his work on the brain, 523
[Transcriber's note: No such page number or reference seen]

Fichte, 222

Flourens, 267

Flowers and Insects, 61, 78

Fouillée, 207, 208

Fraipont, on skulls from Spy, 134

GADOW, 162

_Gallus bankiva_, 102

Gallon, F., 125, 150, 269

Geddes, P., 17, Foot Note 32

Geddes, P. and A. W. Thomson, 276

Gegenbaur, 150, 163

Genetics, 93, 96

_Germ-plasm_, continuity of, 95
--Weismann on, 46-51

Germinal Selection, 36, 37, 46-51, 64

Gibbon, 248

Giuffrida-Ruggeri, 138, 140

Giotto, 259

Gizycki, 217

Goethe and Evolution, 8, 14, 15, 201
--on the relation between Man and Mammals, 161, 163

Gore, Dr., 226

Gorjanovič-Kramberger, 134

Gosse, P. H., 234

_Grapta C. album_, 69

Groos, 187, 188

Gulick, 15, 53

Guyau, 217

Haberlandt, G., 34

HAECKEL, E., on _Charles Darwin as an Anthropologist_, 146-165
  --and Darwin, 135-151, 137, 146-165
  --on the Descent of Man, 137, 143
  --on Lamarck, 8, Foot Note 21
  --a leader in the Darwinian controversy, 137

Häcker, 33

Hansen, 272

Hartmann, von, 240

Harvey, 4

Haycraft, 275

Hegel, 201, 203, 215, 251, 252, 255

Heraclitus, 278

Herder, 4, 5, 20

Heredity and Cytology, 95, 96
  --Haeckel on, 147, 148, 149, 153
  --and Variation, 87-110
  --219, 224

Hering, E., on Memory, 153

Hertwig, O., 150

History, Darwin and, 246-263

Hobbes, T., 200, 215

Hobhouse, 242

HÖFFDING, H., on _The Influence of the Conception of Evolution
                             on Modern Philosophy_, 197-222

Holothurians, calcareous bodies in skin of, 37-41

_Homo heidelbergensis_, Foot Note 118

_H. neandertalensis_, 138

_H. pampaeus_, 144

_H. primigenius_, 133, 134, 138, 144

_Homunculus_, 132

Hooker, Sir J. D., and Darwin, 23, 116

Huber, 170

Hügel, F. von, Foot Note 221

Hume, 200

Hutcheson, 216

Huxley, T. H., and Darwin, 112, 116, 268
  --and the Duke of Argyll, 238
  --on Lamarck, 89
  --on Man, 111, 112, 137, 146, 156, 160, 163
  --on Selection, 24, 91
  --on transmission of acquired characters, 149
  --14, 24, 104, 231-236, 273, 274

Hybrids, Sterility of, 104, 105, 106

Inheritance of acquired characters, 93, 94

Insects and Flowers, 60, 61, 78, 79

Instinct, 122, 172-175

Irish Elk, an example of coadaptation, 41, 42, 45

Jacoby, _Studies in Selection_ by, 272

James, W., 180, 191, 211

Jentsch, 275

Kallima, protective colouring of, 35, 68, 70

_K. inachis_, 68

Kammerer's experiments on Salamanders, 28

Kant, I., 4, 5, 6, 27, 198, 211, 212, 217, 221, 222

Keane, on the Primates, 138

Keith, on Anthropoid Apes, 138

Kepler, 198

Klaatsch, on Ancestry of Man, 140

Klaatsch and Hauser, 134

Knies, 266

Kölliker, his views on Evolution, 29, 150

Kollmann, on origin of human races, 144

Korschinsky, 31

Krause, E., Foot Note 10, 13

Kropotkin, 214, 275

Lamarck, his division of the Animal Kingdom, 160, 161
  --Darwin's opinion of, 129
  --on Evolution, 9-14, 21, 25, 171, 172, 173, 179, 180, 201, 202, 253
  --on Man, 146, 148, 160, 163
  --89, 109, 201, 202, 233

Lamarckian principle, 28, 41-44, 50-54, 67, 84, 86

Lamb, C., 229

Lamettrie, 198

Lamprecht, 260-263

Lanessan, J. L. de, Foot Note 17, 275

Lang, Foot Note 21

Lange, 180

Language, Darwin on, 123, 124
  --Evolution and the Science of, 178, 179, 188

Lankester, Sir E. Ray, on degeneration, 268
  --on educability, 170, 189

Lankester, Sir E. Ray, on the germ-plasm theory, 150

Lapouge, Vacher de, 270

Lartet, M. E., 189

Lasalle, 266

Laveleye, de, 275

Lawrence, W., 89, Foot Note 65

Lehmann-Nitsche, 138, 144

Leibnitz, 4, 5, 213

Lepidoptera, variation in, 37, 60-63

Lessing, 4, 221

Liddon, H. P., 234

_Limenitis archippus_, 74

Linnaeus, 6

Locy, W. A., Foot Note 15

Lovejoy, Foot Note 56

Lubbock, 125

Lucretius, a poet of Evolution, 4

Lyell, Sir Charles, and Darwin, 23, 116
  --the uniformitarian teaching of, 89

Macacus, ear of, 119

Mach, E., 153, 211

Mahoudeau, 137

Maillet, de, 6

Majewski, Foot Note 238, Foot Note 239

Malthus, his influence on Darwin, 16-18, 21, 24, 91
  --200, 273

Man, Descent of, 126, 127, 128, 131-145, 156-165, 189, 254, 265
  --mental and moral qualities of animals and, 122-126, 164, 188-192
  --pre-Darwinian views on the Descent of, 1

Man, Tertiary flints worked by, 136

_Man_, G. Schwalbe on Darwin's _Descent of_, 111-145

Manouvrier, 137

_Mantis religiosa_, colour experiments on, 65, 68

Marx, 262, 276-278

Matthew, P., and Natural Selection, 18, 19

Maupertuis, 6, 88, 103

Mayer, R., 197

_Mechanitis lysimnia_, 77

_Melinaea ethra_, 77

Mendel, 97-100, 184, 228

Merz, J. T., Foot Note 14

Mesopithecus, 132

Mill, J. S., 193, 200, 202, 218

Mimicry, 70-82

Moltke, on war, 273

Monkeys, fossil, 132

Montesquieu, 248

Monticelli, 155

MORGAN, C. LLOYD, on _Mental Factors in Evolution_, 166-196
  --on Organic Selection, 53

Morgan, T. H., 99

Morselli, 138

Mortillet, 136

Moseley, Foot Note 224

Muller, Fritz, _Für Darwin_ by, 154
  --on Mimicry, 233
  --59, 77

Muller, J., 147

Müller, Max, on language, 124

Mutation, 15, 31, 184, 199, 209

Nägeli, 109, 151, 153

Nathusius, 103

Natural Selection, Darwin's views on, 90, 91, 122, 149
  --Darwin and Wallace on, 2, 163, 183
  --and design, 241, 242
  --and educability, 195
  --and human development, 125, 256, 257
  --16-20, 25, 26, 41, 55-58, 64-86, 87-96, 199, 233

Neandertal skulls, 133, 134

Neodarwinism, 150

Newton, A., Foot Note 59

Newton, I., 197, 198

Niebuhr, 249, 263

Nietzsche, 214, 271

Nitsche, 119

Novicow, 274

Nuttall, G. H. F., 135

Occam, 200

Odin, 270

Oecology, see Ecology

_Oenothera lamarckiana_, 32

Oestergren, on Holothurians, 37-39

Oken, L., 7, 201

Organic Selection, 53, 54, 172, 173

Orthogenesis, 109

Osborn, H. F., 53, Foot Note 165
  --_From the Greeks to Darwin_ by, 3-5, 12, 14, 20

_Ovibos moschatus_, 67

Owen, Sir Richard, 111

Packard, A. S., Foot Note 12, Foot Note 18

Palaeopithecus, 132

Paley, 18, 242, 244

Panmixia, Weismann's principle of, 54

_Papilio dardanus_, 72, 73, 74

_P. meriones_, 73

_P. merope_, 72

Pearson, K., Foot Note 7

Penck, 136

Peridineae, 33

Perrier, E., Foot Note 21, 20

Perthes, B. de, 123

Pfeffer, W., 28

Philosophy, influence of the conception of evolution on modern, 197-222

Pithecanthropus, 133, 134, 138, 143

Pitheculites, 144

Plate, Foot Note 37

Pliopithecus, 132

Pouchet, G., Foot Note 3

POULTON, E. B., experiments on Butterflies by, 65
  --on J. C. Prichard, 20
  --on Mimicry, 69, 71, 75, 78
  --Foot Note 34, Foot Note 43, Foot Note 49, Foot Note 55

Prichard, J. C., 20, 21, 89, Foot Note 65

_Pronuba yuccasella_, 79

Protective resemblance, 65-70

Pusey, 115

Quatrefages, A. de, Foot Note 21, 19

Radiolarians, 33

Ranke, 249, 251, 255, 263

Rau, A., 153

Ray, J., 4

Regeneration, Foot Note 71

Religious thought, Darwin's influence on, 223-245

Reversion, 120, 121

Ridley, H. N., Foot Note 88

Ritchie, 270

Robinet, 6

Rolph, 217

Romanes, G. J., Foot Note 3, 15, 32, 54, 164, 234

Roux, 151, 152

Ruskin, 230

Rutot, 136

Saint-Hilaire, E. G. de, 8, 15, 20

Saltatory Evolution, 29-32 (see also Mutations)

Sanders, experiments on Vanessa by, 65

Savigny, 249

Schelling, 4, 5, 200, 201

Schleiden and Schwann, Cell-theory of, 147

Schoetensack, on _Homo heidelbergensis_, Foot Note 118

Schütt, 23

SCHWALBE, G., on _The Descent of Man_, 111-145

Seeck, O., Foot Note 240

Segregation, 97, 98

Selection, artificial, 24, 25, 26, 41, 45, 120, 269-272
  --germinal, 35, 36, 46-52, 64

Selection, natural (see Natural Selection)
  --organic, 53, 171, 172
  --sexual, 55-64, 117, 118
  --social and natural, 271
  --23-86, 103, 129, 130

Selenka, 131

Semnopithecus, 132

Semon, R., 28, 153

Sergi, 138, 143

Sex, recent investigations on, 99, 100

Sibbern, 201

_Smerinthus ocellata_, 38

_Smerinthus populi_, 38

_S. tiliae_, 38

Smith, A., 200

Sociology,  Darwinism and, 264-280
  --History and, 255

Sollas, W. J., 134

Sorley, W. R., 217

Species and varieties, 100

Spencer, H., on evolution, 204-209
  --on the theory of Selection, 41

Spencer, H., on Sociology, 268
  --on the transmission of acquired characters, 149
  --on Weismann, 41, 150
  --2, 17, 217, 231, 268

Sphingidae, variation in, 37

Spinoza, 153, 206

Standfuss, 82

Stephen, L., 217

Sterility in hybrids, 104-106

Sterne, C, Foot Note 10

Struggle for existence, 25, 26, 272-274

Sutton, A. W., Foot Note 73

Synapta, calcareous bodies in skin of, 38-41

Syrphus, 75

Tarde, G., 279

Tennant, F. R., Foot Note 218

Tetraprothomo, 138, 144

THOMSON, J. A., on _Darwin's Predecessors_, 1-22
  --and P. Geddes, 276

Treschow, 201

Treviranus, 8, 14, 15

Turgot, 249

Turner, Sir W., 150

Tylor, 267

Tyndall, W., 267

Tyrrell, G, Foot Note 222

Uhlenhuth, on blood reactions, 135

Use and disuse, 28, 41-43, 48-54, 94, 95, 119, 149

Vanessa, 63

_V. levana_, 31

_V. polychloros_, 82

_V. urticae_, 65, 82

Variability, Darwin's attention directed to, 24
  --W. Bateson on, 87-110
  --causes of, 200

Variation, Darwin's views as an evolutionist, and as a systematist, on, 212
  --and heredity, 87-110
  --minute, 28-32
  --in relation to species, 100, 101

Varigny, H. de, 6, 19

Verworn, 136

_Vestiges of Creation_, Darwin on _The_, 15

Virchow, his opposition to Darwin, 157, 158
  --on the transmission of acquired characters, 149

Vogt, 137

Voltaire, 248

VRIES, H. de, the Mutation theory of, 31, 101, 151, 213

WAGGETT, Rev. P. N., on _The Influence of Darwin upon Religious
                                    Thought_, 223-245

Wallace, A. R., on Colour, 63, 71
  --and Darwin, Foot Note 7, 23, 183
  --on the Descent of Man, 116
  --on Malthus, 17
  --on Natural Selection, 2, 16, 163, 232

Wallace, A. R., on social reforms, 275, 276
  --on Sexual Selection, 183, 184

Walton, 237

Watt, J., and Natural Selection, 21

WEISMANN, A., on _The Selection Theory_, 23-86
  --his germ-plasm theory, 46-51, 149, 150
  --and Prichard, 20
  --and Spencer, 42

Weismann, A., on the transmission of acquired characters, 93-95

Wells, W. C, and Natural Selection, 18

White, G., 3

Williams, C. M., 217

Wilson, E. B., on cytology, 99

Wolf, 249

Wollaston's, T. V., _Variation of Species_, Foot Note 59

Woltmann, 277

Woolner, 118

Wundt, on language, 207, 208

_Xylina vetusta_, 82

Yucca, fertilisation of, 78, 79

Zeller, E., Foot Note 3

_Zoonomia_, Erasmus Darwin's, 7

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