Chapter IV. Darwinism In General.

Chapter IV. Darwinism In General.Darwinism, which was originally a technical theory of the biological schools, has long since become a veritable tangle of the most diverse problems and opinions, and seems to press hardly upon the religious conception of the world from many different sides. In its theory of blind“natural selection”and the fortuitous play of the factors in the struggle for existence, it appears to surrender the whole of this wonderful world of life to the rough and ready grip of a process without method or plan. In the general theory of evolution and the doctrine of the descent of even the highest from the lowest, it seems to take away all special dignity from the human mind and spirit, all the freedom and all the nobility of pure reason and free will; it seems to reduce the higher products of religion, morality, poetry, and the æsthetic sense to the level of an ignoble tumult of animal impulses, desires and sensations. Purely speculative questions relative to the evolution theory, psychological and metaphysical, logical and epistemological, ethical, æsthetic, and finally even historical and politico-economical questions have been drawn into the[pg 086]coil, and usually receive from the Darwinians an answer at once robust and self-assured. A zoological theory seems suddenly to have thrown light and intelligibility into the most diverse provinces of knowledge.But in point of fact it can be shown that Darwinism has not really done this and cannot do it. It leaves unaffected the problem of the mind with its peculiar and underivable laws, from the logical to the ethical. Whether it be right or wrong in its physiological theories, its genealogical trees and fortuitous factors, preoccupation with this theory is a task of the second order. Nevertheless it is necessary to study it, because the chief objections to the religious interpretation of the world have come from it.The Development of Darwinism.In studying it we should like to follow a method somewhat different from that usually observed in apologetic writings.“Darwinism,”even in its technical, biological form, never was quite, and is to-day not at all a unified and consistent system. It has been modified in so many ways and presented in such different colours, that we must either refrain altogether from attempting to get into close quarters with it, or we must make ourselves acquainted to some extent with the phases of the theory as it has gradually developed up to the present day. This is the more necessary and useful since it is precisely within the circle of technical experts that revolts from and criticisms of the Darwinian theory[pg 087]have in recent years arisen; and these are so incisive, so varied, and so instructive, that through them we can adjust our standpoint in relation to the theory better than in any other way. And in thus letting the biologists speak for themselves, we are spared the fatal task of entering into the discussion of questions belonging to a region outside our own particular studies.We cannot, however, give more than a short sketch. But even such a sketch may do more towards giving us a general knowledge of the question and showing us a way out of the difficulties it raises than any of the current“refutations.”To supplement this sketch, and facilitate a thorough understanding of the problem, we shall give somewhat fuller references than are usual to the relevant literature. And the same method will be pursued in the following chapter, which deals with the mechanical theory of life. This method throws more upon the reader, but it is probably the most satisfactory one for the serious student.The reactions from the Darwinism of the schools which we have just referred to, and to which the second half of this chapter is devoted, are, of course, of a purely scientific kind. And while we are devoting our attention to them, we must not be unfaithful to the canon laid down in the previous chapter, namely that with reference to the question of teleology in the religious sense no real answer can be looked for from scientific study, not even if it be anti-Darwinian. In this case, too, it is impossible to read the convictions[pg 088]and intuitions of the religious conception of the world out of a scientific study of nature: they precede it. But here, too, we may find some accessory support and indirect corroboration more or less strong and secure. This may be illustrated by a single example. It will be shown that, on closer study, it is not impossible to subordinate even the apparently confused tangle of naturalistic factors of evolution which are summed up in the phrase“struggle for existence”to interpretation from the religious point of view. But matters will be in quite a different position if the whole theory collapses, and instead of evolution and its paths being given over to confusion and chance, it appears that from the very beginning and at every point there is a predetermination of fixed and inevitable lines along and up which it must advance. In many other connections considerations of a like nature will reveal themselves to us in the course of our study.Darwinism, as popularly understood, is the theory that“men are descended from monkeys,”and in general that the higher forms of life are descended from the lower, and it is regarded as Darwin's epoch-making work and his chief merit—or fault according to the point of view—that he established the Theory of Descent. This is only half correct, and it leaves out the real point of Darwinism altogether. The Theory of Descent had its way prepared by the evolutionist ideas and the speculative nature-philosophy of Goethe, Schelling, Hegel and Oken; by the suggestions and glimmerings of the[pg 089]nature-mysticism of the romanticists; by the results of comparative anatomy and physiology; was already hinted at, at least as far as derivation of species was concerned, in the works of Linné himself; was worked out in the“zoological philosophies,”by the elder Darwin, by Lamarck, Etienne Geoffrey St. Hilaire and Buffon; was in the field long before Charles Darwin's time; was already in active conflict with the antagonistic theory of the“constancy of species,”and had its more or less decided adherents. Yet undoubtedly it was through and after Darwin that the theory grew so much more powerful and gained general acceptance.Darwinism and Teleology.But the essential and most characteristic importance of Darwin and his work, the reason for which he was called the Newton of biology, and which makes Darwinism at once interesting and dangerous to the religious conception of the world, is something quite special and new. It is its radical opposition to teleology. Du Bois-Reymond, in his witty lecture“Darwin versus Galiani,”4explains the gist of the matter.“Les dés de la nature sont pipés”(nature's dice are loaded). Nature is almost always throwing aces. She brings forth not what is meaningless and purposeless, but in great preponderance what is full of meaning and purpose. What“loaded”her dice like this? Even if the theory of descent be true, in what way does it directly[pg 090]help the purely scientific interpretation of the world? Would not this evolution from the lowest to the highest simply be a series of the most astonishing lucky throws of the dice by which in perplexing“endeavour after an aim,”the increasingly perfect, and ultimately the most perfect is produced? And, on the other hand, every individual organism, from the Amœba up to the most complex vertebrate, is, in its structure, its form, its functions, a stupendous marvel of adaptation to its end and of co-ordination of the parts to the whole, and of the whole and its parts to the functions of the organism, the functions of nutrition, self-maintenance, reproduction, maintenance of the species, and so on. How account for the adaptiveness, both general and special, withoutcausæ finales, without intention and purposes, without guidance towards a conscious aim? How can it be explained as the necessary result solely ofcausæ efficientes, of blindly working causes without a definite aim? Darwinism attempts to answer this question. And its answer is:“What appears to us‘purposeful’and‘perfect’is in truth only the manifold adaptation of the forms of life to the conditions of their existence. And this adaptation is brought about solely by means of these conditions themselves. Without choice, without aim, without conscious purpose nature offers a wealth of possibilities. The conditions of existence act as a sieve. What chances to correspond to them maintains itself, gliding through the meshes of the sieve, what does not perishes.”It is an old idea of the[pg 091]naturalistic philosophies, dating from Empedocles, which Darwin worked up into the theory of“natural selection”through“the survival of the fittest”“in the struggle for existence.”Of course the assumption necessary to his idea is that the forms of life are capable of variation, and of continually offering in ceaseless flux new properties and characters to the sieve of selection, and of being raised thereby from the originally homogeneous to the heterogeneous, from the simple to the complex, from the lower to the higher. This is the theory of descent, and it is, of course, an essential part and the very foundation of Darwin's theory. But it isthe doctrine of descent based upon natural selectionthat is Darwinism itself.The Characteristic Features of Darwinism.We do not propose to expound the Darwinian theory for the hundredth time; a knowledge of it must be taken for granted. We need only briefly call to mind the characteristic features and catchwords of the theory as Darwin founded it, which have also been the starting points of subsequent modifications and controversies.All living creatures are bound together in genetic solidarity. Everything has evolved through endless deviations, gradations, and differentiations, but at the same time by a perfectly continuous process. Variation continually produced a crop of heterogeneous novelties. The struggle for existence sifted these out. Heredity[pg 092]fixed and established them. Without method or plan variations continue to occur (indefinite variations). They manifest themselves in all manner of minute changes (“fluctuating”variations). Every part, every function of an organism may be subject individually to variation and selection. The world is strictly governed by what is useful. The whole organisation as well as the individual organs and functions bear the stamp of utility, at least, they must bear it if the theory is correct. In the general continuity the transitions are always easy; there are no fundamentally distinct“types,”architectural plans, or groups of forms. Where gaps yawn the intermediate links have gone amissing. There is no fundamental difference betweengenus,species, andvariety. Even the most complicated organ such as the eye, the most puzzling function such as the instinct of the bee, may be explained as the outcome of many more primitive stages.The chief evidences of the theory of descent are to be found in homologies, in the correspondences of organs and functions, as revealed by comparative anatomy and physiology, in the recapitulation revealed by embryology, in the structure of parasites, in rudimentary organs and reversions to earlier stages, in the distribution of animals and plants, and in the possibility of still transforming, at least to a slight extent, one species into another, by experimental breeding.Transformation and differentiation go on in nature as a vast, ceaseless, but blind process of selection. In[pg 093]artificial selection evolution is secured by choosing the most fit for breeding purposes; so it is secured in natural selection by the favouring and survival of those forms which are the most fit among the many unfit or less fit, which happened to be exposed to the struggle for existence, that is, to the competition for the means of subsistence, to the struggle with enemies, to hostile environment, and to dangers of every kind. The adaptation thus brought about is of a purely“passive”kind. The variations arise fortuitously out of the organism, and present themselves for selection in the struggle for existence; they are not actively acquired by means of the struggle. The secondary factors of evolution recognised are: correlation in the growth and in the development of parts, the origin of new characters through use, their disappearance through disuse (Lamarck), the transmission of characters thus acquired, the influence of environment and sexual selection.5The Darwinian theory, the interpretation of the teleological in the animate world by means of the theory of descent based upon natural selection, entered like a ferment into the scientific thought-movement, and in a space of forty years it has itself passed through a series of stages, differentiations, and transformations which have in part resulted in the present state of the theory, and have in part anticipated it. These are represented[pg 094]by the names of workers belonging to a generation which has for the most part already passed away: Darwin's collaborateurs, such as Alfred Russel Wallace, who independently and simultaneously expounded the theory of natural selection, Haeckel and Fritz Müller, Nägeli and Askenasy, von Kölliker, Mivart, Romanes and others. The differentiation and elaboration of Darwin's theories has gone ever farther and farther; the grades and shades of doctrine held by his disciples are now almost beyond reckoning.Various Forms of Darwinism.The great majority of these express what may be called popular Darwinism [“Darwinismus vulgaris”], theoretically worthless, but practically possessed of great powers of attraction and propagandism. It expresses in the main a conviction, usually left unexplained, that everything“happens naturally,”that man is really descended from monkeys, and that life has“evolved from lower stages”of itself, that dualism is wrong, and that monism is the truth. It is exactly the standpoint of the popular naturalism we have already described, which here mingles unsuspectingly and without scruple Lamarckian and other principles with the Darwinian, which is enthusiastic on the one hand over the“purely mechanical”interpretation of nature, and on the other drags in directly psychical motives, unconscious consciousness, impulses, spontaneous self-differentiation of organisms, which nevertheless adheres to“monism”[pg 095]and possibly even professes to share Goethe's conception of nature!Above this stratum we come to that of the real experts, the only one which concerns us in the least. Here too we find an ever-growing distance between divergent views, the most manifold differences amounting sometimes to mutual exclusion. These differences occur even with reference to the fundamental doctrine generally adhered to, the doctrine of descent. To one party it is a proved fact, to another a probable, scientific working hypothesis, to a third a“rescuing plank.”One party is always finding fresh corroborations, another new difficulties. And within the same group we find the contrasts of believers in monophyletic and believers in polyphyletic evolution, the mechanists and the half-confessed or thoroughgoing vitalists, the preformationists and the believers in epigenesis. Opinions differ even more widely in regard to therôleof the“struggle for existence”in the production of species. On the one hand we have the Darwinism of Darwin freed from inconsequent additions and formulated as orthodox“neo-Darwinism”; on the other hand we have heterodox Lamarckism. The“all-sufficiency”of natural selection is proclaimed by some, its impotence by others. Indefinite variation is opposed by orthogenesis, fluctuating variation by saltatory mutation (Halmatogenesis in“Greek”), passive adaptation by the spontaneous activity and self-regulation of the living organism. The struggle for existence is variously regarded as the[pg 096]chief factor, or as a co-operating factor, or as an indifferent, or even an inimical factor in the origination of new species.And among the representatives of these different standpoints there are most interesting personal differences: in some, like Weismann, we find a great loyalty to, and persistence in the position once arrived at, in others the most surprising transitions and changes of opinion. Thus Fleischmann, a pupil of Selenka's, after illustrating during many years of personal research the orthodox Darwinian standpoint, finally developed into an outspoken opponent not only of the theory of selection but of the doctrine of descent. So also Friedmann.6Driesch started from the mechanical theory of life and advanced through the connected series of his own biological essays to vitalism. Romanes, a prominent disciple of Darwin, ended in Christian theism, and Wallace, the discoverer of“the struggle for existence,”landed in spiritualism.Nothing like an exhaustive view of the present state of Darwinism and its many champions can here be attempted. But it will be necessary to get to know what we may call its possibilities by a study of typical and leading examples. In the course of our study many of the problems to which the theory gives rise will reveal themselves, and their orientation will be possible.This task falls naturally into two subdivisions: (1) the[pg 097]present state of the theory of Evolution and Descent, and how far the religious conception of the world is or is not affected by it; (2) the truth as to the originative and directive factors of Evolution, especially as to“natural selection in the struggle for existence,”whether they are tenable and sufficient, and what attitude religion must take towards them. These two problems must be kept distinct throughout, and must be discussed in order. For the validity of what is characteristicallyDarwinismis in no way decided by proving descent and evolution, although it appears so in most popular expositions.7The Theory of Descent.Again and again we hear and read, even in scientific circles and journals, that Darwinism breaks down at many points, that it is insufficient, and even that it has quite collapsed. Even the assurances of its most convinced champions are rather forced, and are somewhat suggestive of bills payable in the future.8But here again it is obvious that we must distinguish clearly between the Theory of Descent and Darwinism. Of the Theory of Descent it is by no means true that it has“broken down.”With a slight exaggeration, but on the whole with justice, Weismann has asserted that the[pg 098]Theory of Descent is to-day a“generally accepted truth.”Even Weismann's most pronounced opponents, such as Eimer, Wolff, Reinke, and others, are at one with him in this, that there has been evolution in some form; that there has been a progressive transformation of species; that there is real (not merely ideal) relationship or affiliation connecting our modern forms of life, up to and including man, with the lower and lowest forms of bygone æons.The evidences are the same as those adduced by Darwin and before his time, but they have been multiplied and more sharply defined:—namely, that the forms of life can be arranged in an ascending scale of evolution, both in their morphological and their physiological aspects, both as regards the general type and the differentiation of individual organs and particular characters, bodily and mental. All the rubrics used by Darwin in this connection, from comparative anatomy, from the palæontological record itself, and so on, have been filled out with ever-increasing detail. Palæontology, in particular, is continually furnishing new illustrations of descent and new evidence of its probability, more telling perhaps in respect of general features and particular groups than in regard to the historical process in detail. For certain species and genera palæontology discloses the primitive forms, discovers“synthetic types”which were the starting-point for diverging branches of evolution, bridges over or narrows the yawning gulfs in evolution by the discovery of[pg 099]“intermediate forms”; and, in the case of certain species, furnishes complete genealogical trees. The same holds true of the facts of comparative anatomy, embryology, and so on. In all detailed investigations into an animal type, in the study of the structure, functions, or the instincts of an ant, or of a whale or of a tape-worm, the standpoint of the theory of descent is assumed, and it proves a useful clue for further investigation.In regard to man—so we are assured—the theory finds confirmation through the discovery of the Neanderthal, Spy, Schipka, La Naulette skulls and bones—the remains of a prehistoric human race, with“pithecoid”(ape-like) characters. And the theory reaches its climax in Dubois' discovery of the remains of“Pithecanthropus,”the upright ape-man, in Java, 1891-92, the long sought-for Missing Link between animals and man;9and in the still more recent proofs of“affinity of blood”between man and ape, furnished by experiments in transfusion. Friedenthal has revived the older experiments of transfusing the blood of one animal into another, the blood of an animal of one species into that of another, of related species into related species, more remote into more remote, and finally even from animals into man. The further apart the two species are, the more different are the physiological[pg 100]characters of the blood, and the more difficult does a mingling of the two become. Blood of a too distantly related form does not unite with that of the animal into which it is transfused, but the red corpuscles of the former are destroyed by the serum of the latter, break up and are eliminated. In nearly related species or races, however, the two kinds of blood unite, as in the case of horse and ass, or of hare and rabbit. Human blood serum behaves in a hostile fashion to the blood of eel, pigeon, horse, dog, cat, and even to that of Lemuroids, or that of the more remotely related“non-anthropoid”monkey; human blood transfused from a negro into a white unites readily, as does also that of orang-utan transfused into a gibbon. But human blood also unites without any breaking-up or disturbance with the blood of a chimpanzee; from which the inference is that man is not to be placed in a separate sub-order beside the other sub-orders of the Primates, the platyrrhine and catarrhine monkeys, not even in a distinct sub order beside the catarrhines; but is to be included with them in one zoological sub-order. This classification was previously suggested by Selenka on other grounds, namely, because of the points in common in the embryonic development of the catarrhine monkeys and of man, and their common distinctiveness as contrasted with the platyrrhines.10[pg 101]Haeckel's Evolutionist Position.The average type of the Theory of Descent of the older or orthodox school, which still lingers in the background with its Darwinism unshaken, is that set forth by Haeckel, scientifically in his“Generelle Morphologie der Organismen”(1866), and“Systematische Phylogenie”(1896), and popularly in his“Natural History of Creation”and“Riddles of the Universe,”with their many editions. We may assume that it is well known, and need only briefly recall its chief characteristics. The“inestimable value,”the“incomparable significance,”the“immeasurable importance”of the Theory of Descent lies, according to Haeckel, in the fact that by means of it we can explain the origin of the forms of life“in a mechanical manner.”The theory, especially in regard to the descent of man from the apes, is to him not a working hypothesis or tentative mode of representation; it is a result comparable to Newton's law of gravitation or the Kant-Laplace cosmogony. It is“a certain historical fact.”The proofs of it are those already mentioned.What is especially Haeckelian is the“fundamental biogenetic law,”“ontogeny resembles phylogeny,”that is to say, in development, especially in embryonic development, the individual recapitulates the history of the race. Through“palingenesis,”man, for instance, recapitulates his ancestral stages (protist, gastræad, vermine, piscine, and simian). This recapitulation is condensed,[pg 102]disarranged, or obscured in detail by“cenogenesis”or“cænogenesis.”The groups and types of organisms exhibit the closest genetic solidarity. The genealogical tree of man in particular runs directly through a whole series. From the realm of the protists it leads to that of the gastræadæ (nowadays represented by the Cœlentera), thence into the domain of the worms, touches the hypothetical“primitive chordates”(for the necessary existence of which“certain proofs”can be given), the class of tunicates, ascends through the fishes, amphibians and reptiles to forms parallel to the modern monotremes, then directly through the marsupials to the placentals, through lemuroids and baboons to the anthropoid apes, from them to the“famous Pithecanthropus”discovered in Java, out of whichhomo sapiensarose. (The easy transition from one group of forms to another is to be noted. For it is against this point that most of the opposition has been directed, whether from“grumbling”critics, or thoroughgoing opponents of the Theory of Descent.)Haeckel's facile method of constructing genealogical trees, which ignores difficulties and discrepant facts, has met with much criticism and ridicule even among Darwinians. The“orator of Berlin,”Du Bois-Reymond, declared that if he must read romances he would prefer to read them in some other form than that of genealogical trees. But they have at least the merit that they give a vivid impression of what is most plausible and attractive in the idea of descent, and moreover[pg 103]they have helped towards orientation in the discussion. Nor can we ignore the very marked taxonomic and architectonic talent which their construction displays.Weismann's Evolutionist Position.The most characteristic representative, however, of the modern school of unified and purified Darwinism is not Haeckel, but the Freiburg zoologist, Weismann. Through a long series of writings he has carried on the conflict against heterodox, and especially Lamarckian theories of evolution, and has developed his theories of heredity and the causes of variation, of the non-transmissibility of acquired characters, and the all-sufficiency of natural selection. In his latest great work, in two volumes,“Lectures on the Theory of Descent,”11he has definitely summed up and systematised his views. These will interest us when we come to inquire into the problem of the factors operative in evolution. For the moment we are only concerned with his attitude to the Theory of Descent as such. It is precisely the same as Haeckel's, although he is opposed to Haeckel in regard to the strictly Darwinian standpoint. The Theory of Descent has conquered, and it may be said with assurance, for ever. That is the firm conviction on which the whole work is based, and it is really rather treated as a self-evident axiom than as a statement to be proved. Weismann takes little trouble to[pg 104]prove it. All the well-known, usually very clear proofs from palæontology, comparative anatomy, &c., which we are accustomed to meet with in evolutionist books are wanting here, the genealogical trees of the Equidæ, with the gradually diminishing number of toes and the varying teeth, ofPlanorbis multiformis, of the ammonites, the graduated series of stages exhibited by individual organs, for instance, from the ganglion merely sensitive to light up to the intricate eye, or from the rayed skeleton of the paired fins in fishes up to the five-fingered hands and feet of the higher vertebrates, &c. These are only briefly touched upon in the terse“Introduction,”and the whole of the comprehensive work is then directed to showing what factors can have been operative, and to proving that they must have been“Darwinian”(selection in the struggle for existence), and not Lamarckian or any other. This is shown in regard to the coloration of animals, the phenomena of mimicry, the protective arrangements of plants, the development of instinct in animals, and the origin of flowers.In reality Weismann only adducesonestrict proof, and even that is only laying special stress on what is well known in comparative embryology; namely, the possibility of“predicting”on the basis of the theory of descent, as Leverrier“predicted”Neptune. For instance, in the lower vertebrates from amphibians upwards there is anos centralein the skeleton of wrist, but there is none in man. Now if man be descended[pg 105]from lower vertebrates, and if the fundamental biogenetic law be true (that every form of life recapitulates in its own development, especially in its embryonic development, the evolution of its race, though with abbreviations and condensations), it may be predicted that theos centraleis to be found in the early embryonic stages of man. And Rosenberg found it. In the same way the“gill-clefts”of the fish-like ancestors have long since been discovered in the embryo of the higher vertebrates and of man. Weismann himself“predicted”that the markings of the youngest stage of the caterpillars of the Sphingidæ (hawk-moths) would be found to be not oblique but longitudinal stripes, and ten years later a fortunate observation verified the prediction. Because of the abundance of evidential facts Weismann does not go into any detailed proof of evolution.“One can hardly take up any work, large or small, on the finer or more general structural relations, or on the development of any animal, without finding in it proofs for the evolution theory.”But assured as the doctrine of descent appears,12and certain as it is that it has not only maintained its hold since Darwin's day, but has strengthened it and has gained adherents, this foundation of Darwinism is[pg 106]nevertheless not the unanimous and inevitable conclusion of all scientific men in the sense and to the extent that the utterances of Weismann and others would lead us to suppose. Apart from all apologetic attempts either in religious, ethical, or æsthetic interests, apart, too, from the superior standpoint of the philosophers, who have not, so to speak, taken the theory very seriously, but regard it as a provisional theory, as a more or less necessary and useful method of grouping our ideas in regard to the organic world, there are even among the biologists themselves some who, indifferent towards religious or philosophical or naturalistic dogma, hold strictly to fact, and renounce with nonchalance any pretensions at completeness of knowledge if the data do not admit of it, and on these grounds hold themselves aloof from evolutionist generalisation. From among these come the counsels of“caution,”admissions that the theory is a scientific hypothesis and a guide to research, but not knowledge, and confessions that the Theory of Descent as a whole is verifiable rather as a general impression than in detail.Virchow's Position.Warnings of this kind have come occasionally from Du Bois-Reymond, but the true type of this group, and its mode of thought, is Virchow. It will repay us and suffice us to make acquaintance with it through him. His opposition to Darwinism and the theory of descent was directed at its most salient point: the[pg 107]descent of man from the apes. In lectures and treatises, at zoological and anthropological congresses, especially at the meetings of his own Anthropological-Ethnological Society in Berlin, from his“Vorträge über Menschen-und Affen-Schädel”(Lectures on the Skulls of Man and Apes, 1869), to the disputes over Dubois'Pithecanthropus erectusin the middle of the nineties, he threw the whole weight of his immense learning—ethnological and anthropological, osteological, and above all“craniological”—into the scale against the Theory of Descent and its supporters. Virchow has therefore been reckoned often enough among the anti-Darwinians, and has been quoted by apologists and others as against Darwinism, and he has given reason for this, since he has often taken the field against“the Darwinists”or has scoffed at their“longing for a pro-anthropos.”13Sometimes even it has been suggested that he was actuated by religious motives, as when he occasionally championed not only freedom for science, but, incidentally, the right of existence for“the churches,”leaving, for instance, in his theory of psychical life, gaps in knowledge which faith might occupy in moderation and modesty. But this last proves nothing. With Virchow's altogether unemotional nature it is unlikely that religious or spiritual motives had any rôle in the establishment of his convictions, and in Haeckel's naïve blustering at religion, there is, so to speak, more[pg 108]religion than in the cold-blooded connivance with which Virchow leaves a few openings in otherwise frozen ponds for the ducks of faith to swim in! And he has nothing of the pathos of Du Bois-Reymond's“ignorabimus.”He is the neutral, prosaic scientist, who will let nothing“tempt him to a transcendental consideration,”14either theological or naturalistic, who holds tenaciously to matters of fact, who, without absolutely rejecting a general theory, will not concern himself about it, except to point out every difficulty in the way of it; in short, he is the representative of a mood that is the ideal of every investigator and the despair of every theoriser.His lecture of 1869 already indicates his subsequent attitude.“Considered logically and speculatively”the Theory of Descent seems to him“excellent,”15indeed a logical moral(!) hypothesis, but unproved in itself, and erroneous in many of its particular propositions. As far back as 1858, before the publication of Darwin's great work, he stated at the Naturalists' Congress in Carlsruhe, that the origin of one species out of another appeared to him a necessary scientific inference, but——And throughout the whole lecture he alternates between favourable recognition of the theory in general, and emphasis of the difficulties which confront it in detail. The skull, which, according to Goethe's theory, has[pg 109]evolved from three modified vertebræ, is fundamentally different in man and monkeys, both in regard to its externals, crests, ridges and shape, and especially in regard to the nature of the cavity which it forms for the brain. Specifically distinctive differences in the development and structure of the rest of the body must also be taken into account. The so-called ape-like structures in the skull and the rest of the body, which occasionally occur in man (idiots, microcephaloids, &c.) cannot be regarded as atavisms and therefore as proofs of the Theory of Descent; they are of a pathological nature, entirely factssui generis, and“not to be placed in a series with the normal results of evolution.”A man modified by disease“is still thoroughly a man, not a monkey.”Virchow continued to maintain this attitude and persisted in this kind of argument. He energetically rejected all attempts to find“pithecoid”characters in the prehistoric remains of man. He declared the narrow and less arched forehead, the elliptical form, and the unusually large frontal cavities of the“Neanderthal skull”found in the Wupperthal in 1856, to be simply pathological features, which occur as such in certain examples ofhomo sapiens.16He explained the abnormal appearance of the jaw from the Moravian cave of Schipka as a result of the retention of teeth,17accompanied by directly“antipithecoid”characters.[pg 110]The proceedings at the meetings of the Ethnological Society in 1895, at which Dubois was present, had an almost dramatic character.18In the diverse opinions of Dubois, Virchow, Nehring, Kollmann, Krause and others, we have almost an epitome of the present state of the Darwinian question. Virchow doubted whether the parts put together by Dubois (the head of a femur, two molar teeth, and the top of a skull) belonged to the same individual at all, disputed the calculations as to the large capacity of the skull, placed against Dubois' very striking and clever drawing of the curves of the skull-outline, which illustrated, with the help of the Pithecanthropus, the gradual transition from the skull of a monkey to that of man, his own drawing, according to which the Pithecanthropus curve simply coincides with that of a gibbon (Hylobates), and asserted that the remains discovered were those of a species of gibbon, refusing even to admit that they represented a new genus of monkeys. He held fast to hisceterum censeo:“As yet no diluvial discovery has been made which can be referred to a man of a pithecoid type.”Indeed, his polemic or“caution”in regard to the Theory of Descent went even further. He not only refused to admit the proof of the descent of man from monkey, he would not even allow that the descent of one race from another has been demonstrated.19[pg 111]In spite of all the plausible hypotheses it remains“so far only apium desiderium.”The race obstinately maintains its specific distinctness, and resists variation, or gradual transformation into another. The negro remains a negro in America, and the European colonist of Australia remains a European.Yet all Virchow's opposition may be summed up in the characteristic words, which might almost be called his motto,“I warn you of the need for caution,”and it is not a seriously-meant rejection of the Theory of Descent. In reality he holds the evolution-idea as an axiom, and in the last-named treatise he shows distinctly how he conceives of the process. He starts with variation (presumably“kaleidoscopic”), which comes about as a“pathological”phenomenon, that is to say, not spontaneously, but as the result of environmental stimulus, as the organism's reaction to climatic and other conditions of life. The result is an alteration of previous characteristics, and a new stable race is established by an“acquired anomaly.”20Other Instances of Dissatisfaction with the Theory of Descent.What was with Virchow only a suggestion of the[pg 112]need for caution, or controversial matter to be subsequently allowed for or contradicted, had more serious consequences to others, and led to still greater hesitancy as regards evolutionist generalisations and speculations, and sometimes to sharp antagonism to them.One of the best known of the earlier examples of this mood is Kerner von Marilaun's large and beautiful work on“Plant Life.”21He does, indeed, admit that our species are variations of antecedent forms, but only in a very limited sense. Within the stocks or grades of organisation which have always existed, variations have come about, through“hybridisation,”through the crossing of similar, but relatively different forms; these variations alter the configuration and appearance in detail, but neither affect the general character nor cause any transition from“lower”to“higher.”Kerner disposes of the chief argument in favour of the theory of descent, the homology of individual organs, by explaining that the homology is due to the similarity of function in the different organisms. A similar argument is used in regard to“ontogeny recapitulating phylogeny.”Palæontology does not disclose in the plant-world any“synthetic types,”which might have been the common primitive stock from which many now divergent branches have sprung, nor does it disclose any“transition links”really intermediate,[pg 113]for instance, between cryptogams and gymnosperms, or between gymnosperms and angiosperms. That the higher races are apparently absent from the earlier strata is not a proof that they have never existed. The peat-bog flora must have involved the existence of a large companion-flora, without which the peat could not have been formed, but all trace of this is absent in the still persistent vestiges of these times.22Life, with energy and matter, has existed as a phenomenon of the universe from all eternity, and thus its chief forms and manifestations have not“arisen,”but have always been. If facts such as these contradict the Kant-Laplace theory of the universe, then the latter must be corrected in the light of them, not conversely. The extreme isolation of Kerner and his theory is probably due especially to this corollary of his views.Among the most recent examples of antagonism to the Evolution-Theory, the most interesting is a book by Fleischmann, professor of zoology in Erlangen, published in 1901, and entitled,“The Theory of Descent.”It consists of“popular lectures on the rise and decline of a scientific hypothesis”(namely, the Theory of Descent), and it is a complete recantation by a quondam Darwinian of the doctrine of his school, even of its fundamental proposition, the concept of evolution itself. For Fleischmann is not guilty, like Weismann, of the inaccuracy of using“Theory of[pg 114]Descent”as equivalent to Darwinism; he is absolutely indifferent to the theory of natural selection. His book keeps strictly to matters of fact, and rejects as speculation everything in the least beyond these; it does not express even an opinion on the question of the origin of species, but merely criticises and analyses.It does not bring forward any new and overwhelming arguments in refutation of the Theory of Descent, but strongly emphasises difficulties that have always beset it, and discusses these in detail. The old dispute which interested Goethe, Geoffroy St. Hilaire, and Cuvier, as to the unity or the fundamental heterogeneity of the“architectural plan”in nature is revived. Modern zoology recognises not merely the four types of Cuvier, but seventeen different styles,“phyla,”or groups of forms, to derive one of which from another is hopeless. And what is true of the whole is true also of the subdivisions within each phylum;e.g., within the vertebrate phylum with its fishes, amphibians, reptiles, birds and mammals. No bridge leads from one to the other. This is proved particularly by the very instance which is the favourite illustration in support of the Theory of Descent—the fin of fishes and its relation to the five-fingered hand of vertebrates. The so-called transition forms (Archæopteryx, monotremes, &c.) are discredited. So with the“stalking-horse”of evolutionists—the genealogical tree of the Equidæ, which is said to be traceable palæontologically right back, without a break, from the one-toed horses of the present day to[pg 115]the normal five-toed ancestry; and so with another favourite instance of evolution, the history of the pond-snails (Planorbis multiformis), the numerous varieties of which occur with transitions between them in actual contiguity in the Steinheim beds, and thus seem to afford an obvious example of the transformation of species. Against these cases, and against using the palæontological archives as a basis for the construction of genealogical trees in general, the weighty and apparently decisive objection is urged, that nowhere are the soft parts of the earlier forms of life preserved, and that it is impossible to establish relationships with any certainty on the basis of hard parts only, such as bones, teeth and shells. Even Haeckel admits that snails of very different bodily structure may form very similar and even hardly distinguishable shells.Fleischmann further asserts that Haeckel's“fundamental biogenetic law”has utterly collapsed.“Recapitulation”does not occur. Selenka's figures of ovum-segmentation show that there are specific differences in the individual groups. The origin and development of the blastoderm or germinal disc has nothing to do with recapitulation of the phylogeny. It is not the case that the embryos of higher vertebrates are indistinguishable from one another. Even the egg-cell has a specific character, and is totally different from any unicellular organism at the Protistan level. The much-cited“gill-clefts”of higher vertebrates in the embryonic stage are not persistent reminiscences of[pg 116]earlier lower stages; they are rudiments or primordia shared by all vertebrates, and developing differently at the different levels; (thus in fishes they become breathing organs, and in the higher vertebrates they become in part associated with the organs of hearing, or in part disappear again).Though Fleischmann's vigorous protest against over-hastiness in construction and over-confidence on the part of the adherents of the doctrine of descent is very interesting, and may often be justified in detail, it is difficult to resist the impression that the wheat has been rejected with the chaff.23Even a layman may raise the following objections: Admitting that the great groups of forms cannot be traced back to one another, the palæontological record still proves, though it may be only in general outline, that within each phylum there has been a gradual succession and ascent of forms. How is the origin of what is new to be accounted for? Without doing violence to our thinking, without a sort of intellectual autonomy, we cannot rest content with the mere fact that new elements occur. So, in spite of all“difficulties,”the assumption ofan actual descentquietly forces itself upon us as the only satisfactory clue. And the fact, which Fleischmann does not discuss, that even at present we may observe the establishment of what are at least new breeds, impels us to accept an analogous[pg 117]origin of new species. Even if the biogenetic law really“finds its chief confirmation in its exceptions,”even if we cannot speak of a strict recapitulation of earlier stages of evolution, there are indisputable facts which are most readily interpreted as reminiscences, as due to affiliation (ideal or hereditary), with ancestral forms. (Note, for instance, Weismann's“prediction,”&c.24) Even if Archæopteryx and other intermediate forms cannot be regarded as connecting links in the strict sense,i.e., as being stages in the actual pedigree, yet the occurrence of reptilian and avian peculiarities side by side in one organism, goes far to prove the close relationship of the two classes.Fleischmann's book strengthens the impression gained elsewhere, that a general survey of the domain of life as a whole gives force and convincingness to the Theory of Descent, while a study of details often results in breaking the threads and bringing the difficulties into prominence. But the same holds true of many other theoretical constructions, and yet we do not seriously doubt their validity. (Take, for instance, the Kant-Laplace theory, and theories of ethnology, of the history of religion, of the history of language, and so on.) And it is quite commonly to be observed that those who have an expert and specialist knowledge, who are aware of the refractoriness of detailed facts, often take up a sceptical attitude towards every comprehensive[pg 118]theory, though the ultimate use of detailed investigation is to make the construction of general theories possible. Fleischmann does exactly what, say, an anthropologist would do if, under the impression of the constancy and distinctiveness of the human races, which would become stronger the more deeply he penetrated, he should resignedly renounce all possibility of affiliating them, and should rest content with the facts as he found them. Similarly, those who are most intimately acquainted with the races of domesticated animals often resist most strenuously all attempts, although these seem to others a matter of course, to derive our“tame”forms from“wild”species living in freedom.But to return. Even where the Theory of Descent is recognised, whether fully or only half-heartedly, the recognition does not always mean the same thing. Even the adherents of the general, but in itself quite vague view that a transformation from lower forms to higher, and from similar to different forms, has taken place, may present so many points of disagreement, and may even stand in such antagonism to one another, that onlookers are apt to receive the impression that they occupy quite different standpoints, and are no longer at one even in the fundamentals of their hypotheses.The most diverse questions and answers crop up; whether evolution has been brought about“monophyletically”or“polyphyletically,”i.e., through one or many genealogical trees; whether it has taken place in[pg 119]a continuous easy transition from one type to another, or by leaps and bounds; whether through a gradual transformation of all organs, each varying individually, or through correlated“kaleidoscopic”variations of many kinds throughout the whole system; whether it is essentially asymptotic, or whether organisms pass from“labile”phases of vital equilibrium by various halting-places to stable states, which are definitive, and are, so to speak, the blind alleys and terminal points of evolutionary possibilities,e.g., the extinct gigantic saurians, and perhaps also man. And to these problems must be added the various answers to the question, What precedes, or may have preceded, the earliest stages of life of which we know? Whence came the first cell? Whence the first living protoplasm? and How did the living arise from the inorganic? These deeper questions will occupy us in our chapter on the theory of life. Some of the former, in certain of their aspects, will be considered in the sixth chapter, which deals with factors in evolution.The Theory of Descent itself and the differences that obtain even among its adherents can best be studied by considering for a little the works of Reinke and of Hamann.Reinke, Professor of Botany in Kiel, has set forth his views in his book,“Die Welt als Tat,”25and more recently in his“Einleitung in die theoretische Biologie”(1901). Both books are addressed to a wide[pg 120]circle of readers. Reinke and Hamann both revive some of the arguments and opinions set forth in the early days of Darwinism by Wigand,26an author whose works are gradually gaining increased appreciation.It is Reinke's“unalterable conviction”that organisms have evolved, and that they have done so after the manner of fan-shaped genealogical trees. The Theory of Descent is to him an axiom of modern biology, though as a matter of fact the circumstantial evidence in favour of it is extremely fragmentary. The main arguments in favour of it appear to him to be the general ones; the homologies and analogies revealed by comparative morphology and physiology, the ascending series in the palæontological record, vestigial organs, parasitic degeneration, the origin of those vital associations which we call consortism and symbiosis. These he illustrates mainly by examples from his own special domain and personal observation.The simplest unicellular forms of life are to be thought of as at the beginning of evolution; and, since mechanical causes cannot explain their ascent, it must be assumed that they have an inherent“phylogenetic potential of development,”which, working epigenetically, results in ascending evolution. He leaves us to choose between monophyletic and polyphyletic evolution, but himself inclines towards the latter, associating with it a[pg 121]rehabilitation of Wigand's theory of the primitive cells. If, in the beginning, primitive forms of life arose (probably as unicellulars) from the not-living, it is not obvious why we need think of only one so arising, and, if many did so, why they should not have inherent differences which would at once result in typically different evolutionary series and groups of forms. But evolution does not go onad libitumorad infinitum, for the capacity for differentiation and transformation gradually diminishes. The organisation passes from a labile state of equilibrium to an increasingly stable state, and at many points it may reach a terminus where it comes to a standstill. Man, the dog, the horse, the cereals, and fruit trees appear to Reinke to have reached their goal. The preliminary stages he calls“Phylembryos,”because they bear to the possible outcome of their evolution the same relation that the embryo does to the perfect individual. Thus,Phenacodusmay be regarded as the Phylembryo of the modern horse. It is quite conceivable that each of our modern species may have had an independent series of Phylembryos reaching back to the primitive cells. But the palæontological record, and especially its synthetic types, lead Reinke rather to assume that instead of innumerable series, there have been branching genealogical trees, not one, however, but several.These views, together or separately, which are characterised chiefly by the catch-words“polyphyletic descent,”“labile and stable equilibrium,”and so on, crop[pg 122]up together or separately in the writings of various evolutionists belonging to the opposition wing. They are usually associated with a denial of the theory of natural selection, and with theories of“Orthogenesis,”“Heterogenesis,”and“Epigenesis.”We shall discuss them later when we are considering the factors in evolution. But we must first take notice of a work in which the theories opposed to Darwinian orthodoxy have been most decisively and aggressively set forth. As far back as 1892 O. Hamann, then a lecturer on zoology in Göttingen, gathered these together and brought them into the field, against Haeckel in particular, in his book“Entwicklungslehre und Darwinismus.”27Hamann's main theme is that Darwinism overlooks the fact that“there cannot have been an origin of higher types from types already finished.”For this“unfortunate and unsupported assumption”there are no proofs in embryology, palæontology, or anatomy. He adopts and expands the arguments and anti-Haeckelian deliverances of His in embryology, of Snell and Heer in palæontology, of Kölliker and von Baer in their special interpretation of evolution, of Snell particularly as regards the descent of man. It is impossible to derive Metazoa from Protozoa in their present finished state of evolution; even the Amoeba is so exactly adapted in organisation and functional activity[pg 123]to the conditions of its existence that it is a“finished”type. It is only by a stretch of fancy that fishes can be derived from worms, or higher vertebrates from fishes. One of his favourite arguments—and it is a weighty one, though neglected by the orthodox Darwinians—is that living substance is capable, under similar stimuli, of developing spontaneously and afresh, at quite different points and in different groups, similar organs, such as spots sensitive to light, accumulations of pigment, eye-spots, lenses, complete eyes, and similarly with the notochord, the excretory organs, and the like. Therefore homology of organs is no proof of their hereditary affiliation.28They rather illustrate“iterative evolution.”Another favourite argument is the fact of“Pædogenesis.”Certain animals, such asAmphioxus lanceolatus,Peripatus, and certain Medusæ, are very frequently brought forward as examples of persistent primitive stages and“transitional connecting links.”But considered from the point of view of Pædogenesis, they all assume quite a different aspect, and seem rather to represent very highly evolved species, and to be, not primitive forms, but conservative and regressive forms. Pædogenesis is the phenomenon exhibited by a number of species, which may stop short at one of the stages of their embryonic or larval development, become sexually mature, and produce[pg 124]offspring without having attained their own fully developed form.Another argument is the old, suggestive, and really important one urged by Kölliker, that“inorganic nature shows a natural system among minerals (crystals) just as much as animals and plants do, yet in the former there can be no question of any genetic connection in the production of forms.”Yet another argument is found in the occurrence of“inversions”and anomalies in the palæontological succession of forms, which to some extent upsets the Darwinian-Haeckelian genealogical trees. (Thus there are forms in the Cambrian whose alleged ancestors do not appear till the Silurian. Foraminifera and other Protozoa do not appear till the Silurian.)From embryology in particular, as elsewhere in general, we read the“fundamental biogenetic law,”that evolution is from the general to the special, from the imperfect to the more perfect, from what is still indefinite and exuberant to the well-defined and precise, but never from the special to the special. According to Hamann's hypothesis we must think of evolution as going on, so to speak, not about the top but about the bottom. The phyla or groups of forms are great trunks bearing many branches and twigs, but not giving rise to one another. Still less do the little side branches of one trunk bear the whole great trunk of another animal or plant phylum. But they all grow from the same roots among the primitive forms of life. Unicellulars these must[pg 125]have been, but not like our“Protists.”They should be thought of as primitive forms having within themselves the potentialities of the most diverse and widely separate evolution-series to which they gave rise, as it were, along diverging fan-like rays.It would be instructive to follow some naturalist into his own particular domain, for instance a palæontologist into the detailed facts of palæontology, or an embryologist into those of embryology, in order to learn whether these corroborate the assumptions of the Theory of Descent or not. It is just in relation to these detailed facts that criticisms or even denials of the theory have been most frequent. Koken, otherwise a convinced supporter of the theory, inquires in his“Vorwelt,”aproposof the tortoises, what has become of the genealogical trees that were scattered abroad in the world as proved facts in the early days of Darwinism. He asserts, in regard toArchæopteryx, the instance which is always put forward as the intermediate link in the evolution of birds, that it does not show in any of its characters a fundamental difference from any of the birds of to-day, and further, that, through convergent development under similar influences, similar organs and structural relations result, iterative arrangements which come about quite independently of descent. He maintains, too, that the principle of the struggle for existence is rather disproved than corroborated by the palæontological record.In embryology, so competent an authority as[pg 126]O. Hertwig—himself a former pupil of Haeckel's—has reacted from the“fundamental biogenetic law.”His theory of the matter is very much that of Hamann which we have already discussed; development is not so much a recapitulation of finished ancestral types as the laying down of foundations after the pattern of generalised simple forms, not yet specialised; and from these foundations the special organs rise to different levels and grades of differentiation according to the type.29But we must not lose ourselves in details.Looking back over the whole field once more, we feel that we are justified in maintaining with some confidence that the different pronouncements in regard to the detailed application and particular features of the Theory of Descent, and the different standpoints that are occupied even by evolutionists, are at least sufficient to make it obvious that, even if evolution and descent have actually taken place, they have not run so simple and smooth a course as the over-confident would have us believe; that the Theory of Descent rather emphasises than clears away the riddles and difficulties of the case, and that with the mere corroboration of the theory we shall have gained only something relatively external, a clue to creation, which does not so much solve its problems as restate them. The whole criticism of the“right wing,”from captious objections to actual denials, proves this indisputably. And it seems likely that in the course of time a sharpening of[pg 127]the critical insight and temper will give rise to further reactions from the academic theory as we have come to know it.30On the other hand, it may be assumed with even greater certainty that the general evolutionist point of view and the great arguments for descent in some form or other will ultimately be victorious if they are not so already, and that, sooner or later, we shall take the Theory of Descent in its most general form as a matter of course, just as we now do the Kant-Laplace theory.[pg 128]

Chapter IV. Darwinism In General.Darwinism, which was originally a technical theory of the biological schools, has long since become a veritable tangle of the most diverse problems and opinions, and seems to press hardly upon the religious conception of the world from many different sides. In its theory of blind“natural selection”and the fortuitous play of the factors in the struggle for existence, it appears to surrender the whole of this wonderful world of life to the rough and ready grip of a process without method or plan. In the general theory of evolution and the doctrine of the descent of even the highest from the lowest, it seems to take away all special dignity from the human mind and spirit, all the freedom and all the nobility of pure reason and free will; it seems to reduce the higher products of religion, morality, poetry, and the æsthetic sense to the level of an ignoble tumult of animal impulses, desires and sensations. Purely speculative questions relative to the evolution theory, psychological and metaphysical, logical and epistemological, ethical, æsthetic, and finally even historical and politico-economical questions have been drawn into the[pg 086]coil, and usually receive from the Darwinians an answer at once robust and self-assured. A zoological theory seems suddenly to have thrown light and intelligibility into the most diverse provinces of knowledge.But in point of fact it can be shown that Darwinism has not really done this and cannot do it. It leaves unaffected the problem of the mind with its peculiar and underivable laws, from the logical to the ethical. Whether it be right or wrong in its physiological theories, its genealogical trees and fortuitous factors, preoccupation with this theory is a task of the second order. Nevertheless it is necessary to study it, because the chief objections to the religious interpretation of the world have come from it.The Development of Darwinism.In studying it we should like to follow a method somewhat different from that usually observed in apologetic writings.“Darwinism,”even in its technical, biological form, never was quite, and is to-day not at all a unified and consistent system. It has been modified in so many ways and presented in such different colours, that we must either refrain altogether from attempting to get into close quarters with it, or we must make ourselves acquainted to some extent with the phases of the theory as it has gradually developed up to the present day. This is the more necessary and useful since it is precisely within the circle of technical experts that revolts from and criticisms of the Darwinian theory[pg 087]have in recent years arisen; and these are so incisive, so varied, and so instructive, that through them we can adjust our standpoint in relation to the theory better than in any other way. And in thus letting the biologists speak for themselves, we are spared the fatal task of entering into the discussion of questions belonging to a region outside our own particular studies.We cannot, however, give more than a short sketch. But even such a sketch may do more towards giving us a general knowledge of the question and showing us a way out of the difficulties it raises than any of the current“refutations.”To supplement this sketch, and facilitate a thorough understanding of the problem, we shall give somewhat fuller references than are usual to the relevant literature. And the same method will be pursued in the following chapter, which deals with the mechanical theory of life. This method throws more upon the reader, but it is probably the most satisfactory one for the serious student.The reactions from the Darwinism of the schools which we have just referred to, and to which the second half of this chapter is devoted, are, of course, of a purely scientific kind. And while we are devoting our attention to them, we must not be unfaithful to the canon laid down in the previous chapter, namely that with reference to the question of teleology in the religious sense no real answer can be looked for from scientific study, not even if it be anti-Darwinian. In this case, too, it is impossible to read the convictions[pg 088]and intuitions of the religious conception of the world out of a scientific study of nature: they precede it. But here, too, we may find some accessory support and indirect corroboration more or less strong and secure. This may be illustrated by a single example. It will be shown that, on closer study, it is not impossible to subordinate even the apparently confused tangle of naturalistic factors of evolution which are summed up in the phrase“struggle for existence”to interpretation from the religious point of view. But matters will be in quite a different position if the whole theory collapses, and instead of evolution and its paths being given over to confusion and chance, it appears that from the very beginning and at every point there is a predetermination of fixed and inevitable lines along and up which it must advance. In many other connections considerations of a like nature will reveal themselves to us in the course of our study.Darwinism, as popularly understood, is the theory that“men are descended from monkeys,”and in general that the higher forms of life are descended from the lower, and it is regarded as Darwin's epoch-making work and his chief merit—or fault according to the point of view—that he established the Theory of Descent. This is only half correct, and it leaves out the real point of Darwinism altogether. The Theory of Descent had its way prepared by the evolutionist ideas and the speculative nature-philosophy of Goethe, Schelling, Hegel and Oken; by the suggestions and glimmerings of the[pg 089]nature-mysticism of the romanticists; by the results of comparative anatomy and physiology; was already hinted at, at least as far as derivation of species was concerned, in the works of Linné himself; was worked out in the“zoological philosophies,”by the elder Darwin, by Lamarck, Etienne Geoffrey St. Hilaire and Buffon; was in the field long before Charles Darwin's time; was already in active conflict with the antagonistic theory of the“constancy of species,”and had its more or less decided adherents. Yet undoubtedly it was through and after Darwin that the theory grew so much more powerful and gained general acceptance.Darwinism and Teleology.But the essential and most characteristic importance of Darwin and his work, the reason for which he was called the Newton of biology, and which makes Darwinism at once interesting and dangerous to the religious conception of the world, is something quite special and new. It is its radical opposition to teleology. Du Bois-Reymond, in his witty lecture“Darwin versus Galiani,”4explains the gist of the matter.“Les dés de la nature sont pipés”(nature's dice are loaded). Nature is almost always throwing aces. She brings forth not what is meaningless and purposeless, but in great preponderance what is full of meaning and purpose. What“loaded”her dice like this? Even if the theory of descent be true, in what way does it directly[pg 090]help the purely scientific interpretation of the world? Would not this evolution from the lowest to the highest simply be a series of the most astonishing lucky throws of the dice by which in perplexing“endeavour after an aim,”the increasingly perfect, and ultimately the most perfect is produced? And, on the other hand, every individual organism, from the Amœba up to the most complex vertebrate, is, in its structure, its form, its functions, a stupendous marvel of adaptation to its end and of co-ordination of the parts to the whole, and of the whole and its parts to the functions of the organism, the functions of nutrition, self-maintenance, reproduction, maintenance of the species, and so on. How account for the adaptiveness, both general and special, withoutcausæ finales, without intention and purposes, without guidance towards a conscious aim? How can it be explained as the necessary result solely ofcausæ efficientes, of blindly working causes without a definite aim? Darwinism attempts to answer this question. And its answer is:“What appears to us‘purposeful’and‘perfect’is in truth only the manifold adaptation of the forms of life to the conditions of their existence. And this adaptation is brought about solely by means of these conditions themselves. Without choice, without aim, without conscious purpose nature offers a wealth of possibilities. The conditions of existence act as a sieve. What chances to correspond to them maintains itself, gliding through the meshes of the sieve, what does not perishes.”It is an old idea of the[pg 091]naturalistic philosophies, dating from Empedocles, which Darwin worked up into the theory of“natural selection”through“the survival of the fittest”“in the struggle for existence.”Of course the assumption necessary to his idea is that the forms of life are capable of variation, and of continually offering in ceaseless flux new properties and characters to the sieve of selection, and of being raised thereby from the originally homogeneous to the heterogeneous, from the simple to the complex, from the lower to the higher. This is the theory of descent, and it is, of course, an essential part and the very foundation of Darwin's theory. But it isthe doctrine of descent based upon natural selectionthat is Darwinism itself.The Characteristic Features of Darwinism.We do not propose to expound the Darwinian theory for the hundredth time; a knowledge of it must be taken for granted. We need only briefly call to mind the characteristic features and catchwords of the theory as Darwin founded it, which have also been the starting points of subsequent modifications and controversies.All living creatures are bound together in genetic solidarity. Everything has evolved through endless deviations, gradations, and differentiations, but at the same time by a perfectly continuous process. Variation continually produced a crop of heterogeneous novelties. The struggle for existence sifted these out. Heredity[pg 092]fixed and established them. Without method or plan variations continue to occur (indefinite variations). They manifest themselves in all manner of minute changes (“fluctuating”variations). Every part, every function of an organism may be subject individually to variation and selection. The world is strictly governed by what is useful. The whole organisation as well as the individual organs and functions bear the stamp of utility, at least, they must bear it if the theory is correct. In the general continuity the transitions are always easy; there are no fundamentally distinct“types,”architectural plans, or groups of forms. Where gaps yawn the intermediate links have gone amissing. There is no fundamental difference betweengenus,species, andvariety. Even the most complicated organ such as the eye, the most puzzling function such as the instinct of the bee, may be explained as the outcome of many more primitive stages.The chief evidences of the theory of descent are to be found in homologies, in the correspondences of organs and functions, as revealed by comparative anatomy and physiology, in the recapitulation revealed by embryology, in the structure of parasites, in rudimentary organs and reversions to earlier stages, in the distribution of animals and plants, and in the possibility of still transforming, at least to a slight extent, one species into another, by experimental breeding.Transformation and differentiation go on in nature as a vast, ceaseless, but blind process of selection. In[pg 093]artificial selection evolution is secured by choosing the most fit for breeding purposes; so it is secured in natural selection by the favouring and survival of those forms which are the most fit among the many unfit or less fit, which happened to be exposed to the struggle for existence, that is, to the competition for the means of subsistence, to the struggle with enemies, to hostile environment, and to dangers of every kind. The adaptation thus brought about is of a purely“passive”kind. The variations arise fortuitously out of the organism, and present themselves for selection in the struggle for existence; they are not actively acquired by means of the struggle. The secondary factors of evolution recognised are: correlation in the growth and in the development of parts, the origin of new characters through use, their disappearance through disuse (Lamarck), the transmission of characters thus acquired, the influence of environment and sexual selection.5The Darwinian theory, the interpretation of the teleological in the animate world by means of the theory of descent based upon natural selection, entered like a ferment into the scientific thought-movement, and in a space of forty years it has itself passed through a series of stages, differentiations, and transformations which have in part resulted in the present state of the theory, and have in part anticipated it. These are represented[pg 094]by the names of workers belonging to a generation which has for the most part already passed away: Darwin's collaborateurs, such as Alfred Russel Wallace, who independently and simultaneously expounded the theory of natural selection, Haeckel and Fritz Müller, Nägeli and Askenasy, von Kölliker, Mivart, Romanes and others. The differentiation and elaboration of Darwin's theories has gone ever farther and farther; the grades and shades of doctrine held by his disciples are now almost beyond reckoning.Various Forms of Darwinism.The great majority of these express what may be called popular Darwinism [“Darwinismus vulgaris”], theoretically worthless, but practically possessed of great powers of attraction and propagandism. It expresses in the main a conviction, usually left unexplained, that everything“happens naturally,”that man is really descended from monkeys, and that life has“evolved from lower stages”of itself, that dualism is wrong, and that monism is the truth. It is exactly the standpoint of the popular naturalism we have already described, which here mingles unsuspectingly and without scruple Lamarckian and other principles with the Darwinian, which is enthusiastic on the one hand over the“purely mechanical”interpretation of nature, and on the other drags in directly psychical motives, unconscious consciousness, impulses, spontaneous self-differentiation of organisms, which nevertheless adheres to“monism”[pg 095]and possibly even professes to share Goethe's conception of nature!Above this stratum we come to that of the real experts, the only one which concerns us in the least. Here too we find an ever-growing distance between divergent views, the most manifold differences amounting sometimes to mutual exclusion. These differences occur even with reference to the fundamental doctrine generally adhered to, the doctrine of descent. To one party it is a proved fact, to another a probable, scientific working hypothesis, to a third a“rescuing plank.”One party is always finding fresh corroborations, another new difficulties. And within the same group we find the contrasts of believers in monophyletic and believers in polyphyletic evolution, the mechanists and the half-confessed or thoroughgoing vitalists, the preformationists and the believers in epigenesis. Opinions differ even more widely in regard to therôleof the“struggle for existence”in the production of species. On the one hand we have the Darwinism of Darwin freed from inconsequent additions and formulated as orthodox“neo-Darwinism”; on the other hand we have heterodox Lamarckism. The“all-sufficiency”of natural selection is proclaimed by some, its impotence by others. Indefinite variation is opposed by orthogenesis, fluctuating variation by saltatory mutation (Halmatogenesis in“Greek”), passive adaptation by the spontaneous activity and self-regulation of the living organism. The struggle for existence is variously regarded as the[pg 096]chief factor, or as a co-operating factor, or as an indifferent, or even an inimical factor in the origination of new species.And among the representatives of these different standpoints there are most interesting personal differences: in some, like Weismann, we find a great loyalty to, and persistence in the position once arrived at, in others the most surprising transitions and changes of opinion. Thus Fleischmann, a pupil of Selenka's, after illustrating during many years of personal research the orthodox Darwinian standpoint, finally developed into an outspoken opponent not only of the theory of selection but of the doctrine of descent. So also Friedmann.6Driesch started from the mechanical theory of life and advanced through the connected series of his own biological essays to vitalism. Romanes, a prominent disciple of Darwin, ended in Christian theism, and Wallace, the discoverer of“the struggle for existence,”landed in spiritualism.Nothing like an exhaustive view of the present state of Darwinism and its many champions can here be attempted. But it will be necessary to get to know what we may call its possibilities by a study of typical and leading examples. In the course of our study many of the problems to which the theory gives rise will reveal themselves, and their orientation will be possible.This task falls naturally into two subdivisions: (1) the[pg 097]present state of the theory of Evolution and Descent, and how far the religious conception of the world is or is not affected by it; (2) the truth as to the originative and directive factors of Evolution, especially as to“natural selection in the struggle for existence,”whether they are tenable and sufficient, and what attitude religion must take towards them. These two problems must be kept distinct throughout, and must be discussed in order. For the validity of what is characteristicallyDarwinismis in no way decided by proving descent and evolution, although it appears so in most popular expositions.7The Theory of Descent.Again and again we hear and read, even in scientific circles and journals, that Darwinism breaks down at many points, that it is insufficient, and even that it has quite collapsed. Even the assurances of its most convinced champions are rather forced, and are somewhat suggestive of bills payable in the future.8But here again it is obvious that we must distinguish clearly between the Theory of Descent and Darwinism. Of the Theory of Descent it is by no means true that it has“broken down.”With a slight exaggeration, but on the whole with justice, Weismann has asserted that the[pg 098]Theory of Descent is to-day a“generally accepted truth.”Even Weismann's most pronounced opponents, such as Eimer, Wolff, Reinke, and others, are at one with him in this, that there has been evolution in some form; that there has been a progressive transformation of species; that there is real (not merely ideal) relationship or affiliation connecting our modern forms of life, up to and including man, with the lower and lowest forms of bygone æons.The evidences are the same as those adduced by Darwin and before his time, but they have been multiplied and more sharply defined:—namely, that the forms of life can be arranged in an ascending scale of evolution, both in their morphological and their physiological aspects, both as regards the general type and the differentiation of individual organs and particular characters, bodily and mental. All the rubrics used by Darwin in this connection, from comparative anatomy, from the palæontological record itself, and so on, have been filled out with ever-increasing detail. Palæontology, in particular, is continually furnishing new illustrations of descent and new evidence of its probability, more telling perhaps in respect of general features and particular groups than in regard to the historical process in detail. For certain species and genera palæontology discloses the primitive forms, discovers“synthetic types”which were the starting-point for diverging branches of evolution, bridges over or narrows the yawning gulfs in evolution by the discovery of[pg 099]“intermediate forms”; and, in the case of certain species, furnishes complete genealogical trees. The same holds true of the facts of comparative anatomy, embryology, and so on. In all detailed investigations into an animal type, in the study of the structure, functions, or the instincts of an ant, or of a whale or of a tape-worm, the standpoint of the theory of descent is assumed, and it proves a useful clue for further investigation.In regard to man—so we are assured—the theory finds confirmation through the discovery of the Neanderthal, Spy, Schipka, La Naulette skulls and bones—the remains of a prehistoric human race, with“pithecoid”(ape-like) characters. And the theory reaches its climax in Dubois' discovery of the remains of“Pithecanthropus,”the upright ape-man, in Java, 1891-92, the long sought-for Missing Link between animals and man;9and in the still more recent proofs of“affinity of blood”between man and ape, furnished by experiments in transfusion. Friedenthal has revived the older experiments of transfusing the blood of one animal into another, the blood of an animal of one species into that of another, of related species into related species, more remote into more remote, and finally even from animals into man. The further apart the two species are, the more different are the physiological[pg 100]characters of the blood, and the more difficult does a mingling of the two become. Blood of a too distantly related form does not unite with that of the animal into which it is transfused, but the red corpuscles of the former are destroyed by the serum of the latter, break up and are eliminated. In nearly related species or races, however, the two kinds of blood unite, as in the case of horse and ass, or of hare and rabbit. Human blood serum behaves in a hostile fashion to the blood of eel, pigeon, horse, dog, cat, and even to that of Lemuroids, or that of the more remotely related“non-anthropoid”monkey; human blood transfused from a negro into a white unites readily, as does also that of orang-utan transfused into a gibbon. But human blood also unites without any breaking-up or disturbance with the blood of a chimpanzee; from which the inference is that man is not to be placed in a separate sub-order beside the other sub-orders of the Primates, the platyrrhine and catarrhine monkeys, not even in a distinct sub order beside the catarrhines; but is to be included with them in one zoological sub-order. This classification was previously suggested by Selenka on other grounds, namely, because of the points in common in the embryonic development of the catarrhine monkeys and of man, and their common distinctiveness as contrasted with the platyrrhines.10[pg 101]Haeckel's Evolutionist Position.The average type of the Theory of Descent of the older or orthodox school, which still lingers in the background with its Darwinism unshaken, is that set forth by Haeckel, scientifically in his“Generelle Morphologie der Organismen”(1866), and“Systematische Phylogenie”(1896), and popularly in his“Natural History of Creation”and“Riddles of the Universe,”with their many editions. We may assume that it is well known, and need only briefly recall its chief characteristics. The“inestimable value,”the“incomparable significance,”the“immeasurable importance”of the Theory of Descent lies, according to Haeckel, in the fact that by means of it we can explain the origin of the forms of life“in a mechanical manner.”The theory, especially in regard to the descent of man from the apes, is to him not a working hypothesis or tentative mode of representation; it is a result comparable to Newton's law of gravitation or the Kant-Laplace cosmogony. It is“a certain historical fact.”The proofs of it are those already mentioned.What is especially Haeckelian is the“fundamental biogenetic law,”“ontogeny resembles phylogeny,”that is to say, in development, especially in embryonic development, the individual recapitulates the history of the race. Through“palingenesis,”man, for instance, recapitulates his ancestral stages (protist, gastræad, vermine, piscine, and simian). This recapitulation is condensed,[pg 102]disarranged, or obscured in detail by“cenogenesis”or“cænogenesis.”The groups and types of organisms exhibit the closest genetic solidarity. The genealogical tree of man in particular runs directly through a whole series. From the realm of the protists it leads to that of the gastræadæ (nowadays represented by the Cœlentera), thence into the domain of the worms, touches the hypothetical“primitive chordates”(for the necessary existence of which“certain proofs”can be given), the class of tunicates, ascends through the fishes, amphibians and reptiles to forms parallel to the modern monotremes, then directly through the marsupials to the placentals, through lemuroids and baboons to the anthropoid apes, from them to the“famous Pithecanthropus”discovered in Java, out of whichhomo sapiensarose. (The easy transition from one group of forms to another is to be noted. For it is against this point that most of the opposition has been directed, whether from“grumbling”critics, or thoroughgoing opponents of the Theory of Descent.)Haeckel's facile method of constructing genealogical trees, which ignores difficulties and discrepant facts, has met with much criticism and ridicule even among Darwinians. The“orator of Berlin,”Du Bois-Reymond, declared that if he must read romances he would prefer to read them in some other form than that of genealogical trees. But they have at least the merit that they give a vivid impression of what is most plausible and attractive in the idea of descent, and moreover[pg 103]they have helped towards orientation in the discussion. Nor can we ignore the very marked taxonomic and architectonic talent which their construction displays.Weismann's Evolutionist Position.The most characteristic representative, however, of the modern school of unified and purified Darwinism is not Haeckel, but the Freiburg zoologist, Weismann. Through a long series of writings he has carried on the conflict against heterodox, and especially Lamarckian theories of evolution, and has developed his theories of heredity and the causes of variation, of the non-transmissibility of acquired characters, and the all-sufficiency of natural selection. In his latest great work, in two volumes,“Lectures on the Theory of Descent,”11he has definitely summed up and systematised his views. These will interest us when we come to inquire into the problem of the factors operative in evolution. For the moment we are only concerned with his attitude to the Theory of Descent as such. It is precisely the same as Haeckel's, although he is opposed to Haeckel in regard to the strictly Darwinian standpoint. The Theory of Descent has conquered, and it may be said with assurance, for ever. That is the firm conviction on which the whole work is based, and it is really rather treated as a self-evident axiom than as a statement to be proved. Weismann takes little trouble to[pg 104]prove it. All the well-known, usually very clear proofs from palæontology, comparative anatomy, &c., which we are accustomed to meet with in evolutionist books are wanting here, the genealogical trees of the Equidæ, with the gradually diminishing number of toes and the varying teeth, ofPlanorbis multiformis, of the ammonites, the graduated series of stages exhibited by individual organs, for instance, from the ganglion merely sensitive to light up to the intricate eye, or from the rayed skeleton of the paired fins in fishes up to the five-fingered hands and feet of the higher vertebrates, &c. These are only briefly touched upon in the terse“Introduction,”and the whole of the comprehensive work is then directed to showing what factors can have been operative, and to proving that they must have been“Darwinian”(selection in the struggle for existence), and not Lamarckian or any other. This is shown in regard to the coloration of animals, the phenomena of mimicry, the protective arrangements of plants, the development of instinct in animals, and the origin of flowers.In reality Weismann only adducesonestrict proof, and even that is only laying special stress on what is well known in comparative embryology; namely, the possibility of“predicting”on the basis of the theory of descent, as Leverrier“predicted”Neptune. For instance, in the lower vertebrates from amphibians upwards there is anos centralein the skeleton of wrist, but there is none in man. Now if man be descended[pg 105]from lower vertebrates, and if the fundamental biogenetic law be true (that every form of life recapitulates in its own development, especially in its embryonic development, the evolution of its race, though with abbreviations and condensations), it may be predicted that theos centraleis to be found in the early embryonic stages of man. And Rosenberg found it. In the same way the“gill-clefts”of the fish-like ancestors have long since been discovered in the embryo of the higher vertebrates and of man. Weismann himself“predicted”that the markings of the youngest stage of the caterpillars of the Sphingidæ (hawk-moths) would be found to be not oblique but longitudinal stripes, and ten years later a fortunate observation verified the prediction. Because of the abundance of evidential facts Weismann does not go into any detailed proof of evolution.“One can hardly take up any work, large or small, on the finer or more general structural relations, or on the development of any animal, without finding in it proofs for the evolution theory.”But assured as the doctrine of descent appears,12and certain as it is that it has not only maintained its hold since Darwin's day, but has strengthened it and has gained adherents, this foundation of Darwinism is[pg 106]nevertheless not the unanimous and inevitable conclusion of all scientific men in the sense and to the extent that the utterances of Weismann and others would lead us to suppose. Apart from all apologetic attempts either in religious, ethical, or æsthetic interests, apart, too, from the superior standpoint of the philosophers, who have not, so to speak, taken the theory very seriously, but regard it as a provisional theory, as a more or less necessary and useful method of grouping our ideas in regard to the organic world, there are even among the biologists themselves some who, indifferent towards religious or philosophical or naturalistic dogma, hold strictly to fact, and renounce with nonchalance any pretensions at completeness of knowledge if the data do not admit of it, and on these grounds hold themselves aloof from evolutionist generalisation. From among these come the counsels of“caution,”admissions that the theory is a scientific hypothesis and a guide to research, but not knowledge, and confessions that the Theory of Descent as a whole is verifiable rather as a general impression than in detail.Virchow's Position.Warnings of this kind have come occasionally from Du Bois-Reymond, but the true type of this group, and its mode of thought, is Virchow. It will repay us and suffice us to make acquaintance with it through him. His opposition to Darwinism and the theory of descent was directed at its most salient point: the[pg 107]descent of man from the apes. In lectures and treatises, at zoological and anthropological congresses, especially at the meetings of his own Anthropological-Ethnological Society in Berlin, from his“Vorträge über Menschen-und Affen-Schädel”(Lectures on the Skulls of Man and Apes, 1869), to the disputes over Dubois'Pithecanthropus erectusin the middle of the nineties, he threw the whole weight of his immense learning—ethnological and anthropological, osteological, and above all“craniological”—into the scale against the Theory of Descent and its supporters. Virchow has therefore been reckoned often enough among the anti-Darwinians, and has been quoted by apologists and others as against Darwinism, and he has given reason for this, since he has often taken the field against“the Darwinists”or has scoffed at their“longing for a pro-anthropos.”13Sometimes even it has been suggested that he was actuated by religious motives, as when he occasionally championed not only freedom for science, but, incidentally, the right of existence for“the churches,”leaving, for instance, in his theory of psychical life, gaps in knowledge which faith might occupy in moderation and modesty. But this last proves nothing. With Virchow's altogether unemotional nature it is unlikely that religious or spiritual motives had any rôle in the establishment of his convictions, and in Haeckel's naïve blustering at religion, there is, so to speak, more[pg 108]religion than in the cold-blooded connivance with which Virchow leaves a few openings in otherwise frozen ponds for the ducks of faith to swim in! And he has nothing of the pathos of Du Bois-Reymond's“ignorabimus.”He is the neutral, prosaic scientist, who will let nothing“tempt him to a transcendental consideration,”14either theological or naturalistic, who holds tenaciously to matters of fact, who, without absolutely rejecting a general theory, will not concern himself about it, except to point out every difficulty in the way of it; in short, he is the representative of a mood that is the ideal of every investigator and the despair of every theoriser.His lecture of 1869 already indicates his subsequent attitude.“Considered logically and speculatively”the Theory of Descent seems to him“excellent,”15indeed a logical moral(!) hypothesis, but unproved in itself, and erroneous in many of its particular propositions. As far back as 1858, before the publication of Darwin's great work, he stated at the Naturalists' Congress in Carlsruhe, that the origin of one species out of another appeared to him a necessary scientific inference, but——And throughout the whole lecture he alternates between favourable recognition of the theory in general, and emphasis of the difficulties which confront it in detail. The skull, which, according to Goethe's theory, has[pg 109]evolved from three modified vertebræ, is fundamentally different in man and monkeys, both in regard to its externals, crests, ridges and shape, and especially in regard to the nature of the cavity which it forms for the brain. Specifically distinctive differences in the development and structure of the rest of the body must also be taken into account. The so-called ape-like structures in the skull and the rest of the body, which occasionally occur in man (idiots, microcephaloids, &c.) cannot be regarded as atavisms and therefore as proofs of the Theory of Descent; they are of a pathological nature, entirely factssui generis, and“not to be placed in a series with the normal results of evolution.”A man modified by disease“is still thoroughly a man, not a monkey.”Virchow continued to maintain this attitude and persisted in this kind of argument. He energetically rejected all attempts to find“pithecoid”characters in the prehistoric remains of man. He declared the narrow and less arched forehead, the elliptical form, and the unusually large frontal cavities of the“Neanderthal skull”found in the Wupperthal in 1856, to be simply pathological features, which occur as such in certain examples ofhomo sapiens.16He explained the abnormal appearance of the jaw from the Moravian cave of Schipka as a result of the retention of teeth,17accompanied by directly“antipithecoid”characters.[pg 110]The proceedings at the meetings of the Ethnological Society in 1895, at which Dubois was present, had an almost dramatic character.18In the diverse opinions of Dubois, Virchow, Nehring, Kollmann, Krause and others, we have almost an epitome of the present state of the Darwinian question. Virchow doubted whether the parts put together by Dubois (the head of a femur, two molar teeth, and the top of a skull) belonged to the same individual at all, disputed the calculations as to the large capacity of the skull, placed against Dubois' very striking and clever drawing of the curves of the skull-outline, which illustrated, with the help of the Pithecanthropus, the gradual transition from the skull of a monkey to that of man, his own drawing, according to which the Pithecanthropus curve simply coincides with that of a gibbon (Hylobates), and asserted that the remains discovered were those of a species of gibbon, refusing even to admit that they represented a new genus of monkeys. He held fast to hisceterum censeo:“As yet no diluvial discovery has been made which can be referred to a man of a pithecoid type.”Indeed, his polemic or“caution”in regard to the Theory of Descent went even further. He not only refused to admit the proof of the descent of man from monkey, he would not even allow that the descent of one race from another has been demonstrated.19[pg 111]In spite of all the plausible hypotheses it remains“so far only apium desiderium.”The race obstinately maintains its specific distinctness, and resists variation, or gradual transformation into another. The negro remains a negro in America, and the European colonist of Australia remains a European.Yet all Virchow's opposition may be summed up in the characteristic words, which might almost be called his motto,“I warn you of the need for caution,”and it is not a seriously-meant rejection of the Theory of Descent. In reality he holds the evolution-idea as an axiom, and in the last-named treatise he shows distinctly how he conceives of the process. He starts with variation (presumably“kaleidoscopic”), which comes about as a“pathological”phenomenon, that is to say, not spontaneously, but as the result of environmental stimulus, as the organism's reaction to climatic and other conditions of life. The result is an alteration of previous characteristics, and a new stable race is established by an“acquired anomaly.”20Other Instances of Dissatisfaction with the Theory of Descent.What was with Virchow only a suggestion of the[pg 112]need for caution, or controversial matter to be subsequently allowed for or contradicted, had more serious consequences to others, and led to still greater hesitancy as regards evolutionist generalisations and speculations, and sometimes to sharp antagonism to them.One of the best known of the earlier examples of this mood is Kerner von Marilaun's large and beautiful work on“Plant Life.”21He does, indeed, admit that our species are variations of antecedent forms, but only in a very limited sense. Within the stocks or grades of organisation which have always existed, variations have come about, through“hybridisation,”through the crossing of similar, but relatively different forms; these variations alter the configuration and appearance in detail, but neither affect the general character nor cause any transition from“lower”to“higher.”Kerner disposes of the chief argument in favour of the theory of descent, the homology of individual organs, by explaining that the homology is due to the similarity of function in the different organisms. A similar argument is used in regard to“ontogeny recapitulating phylogeny.”Palæontology does not disclose in the plant-world any“synthetic types,”which might have been the common primitive stock from which many now divergent branches have sprung, nor does it disclose any“transition links”really intermediate,[pg 113]for instance, between cryptogams and gymnosperms, or between gymnosperms and angiosperms. That the higher races are apparently absent from the earlier strata is not a proof that they have never existed. The peat-bog flora must have involved the existence of a large companion-flora, without which the peat could not have been formed, but all trace of this is absent in the still persistent vestiges of these times.22Life, with energy and matter, has existed as a phenomenon of the universe from all eternity, and thus its chief forms and manifestations have not“arisen,”but have always been. If facts such as these contradict the Kant-Laplace theory of the universe, then the latter must be corrected in the light of them, not conversely. The extreme isolation of Kerner and his theory is probably due especially to this corollary of his views.Among the most recent examples of antagonism to the Evolution-Theory, the most interesting is a book by Fleischmann, professor of zoology in Erlangen, published in 1901, and entitled,“The Theory of Descent.”It consists of“popular lectures on the rise and decline of a scientific hypothesis”(namely, the Theory of Descent), and it is a complete recantation by a quondam Darwinian of the doctrine of his school, even of its fundamental proposition, the concept of evolution itself. For Fleischmann is not guilty, like Weismann, of the inaccuracy of using“Theory of[pg 114]Descent”as equivalent to Darwinism; he is absolutely indifferent to the theory of natural selection. His book keeps strictly to matters of fact, and rejects as speculation everything in the least beyond these; it does not express even an opinion on the question of the origin of species, but merely criticises and analyses.It does not bring forward any new and overwhelming arguments in refutation of the Theory of Descent, but strongly emphasises difficulties that have always beset it, and discusses these in detail. The old dispute which interested Goethe, Geoffroy St. Hilaire, and Cuvier, as to the unity or the fundamental heterogeneity of the“architectural plan”in nature is revived. Modern zoology recognises not merely the four types of Cuvier, but seventeen different styles,“phyla,”or groups of forms, to derive one of which from another is hopeless. And what is true of the whole is true also of the subdivisions within each phylum;e.g., within the vertebrate phylum with its fishes, amphibians, reptiles, birds and mammals. No bridge leads from one to the other. This is proved particularly by the very instance which is the favourite illustration in support of the Theory of Descent—the fin of fishes and its relation to the five-fingered hand of vertebrates. The so-called transition forms (Archæopteryx, monotremes, &c.) are discredited. So with the“stalking-horse”of evolutionists—the genealogical tree of the Equidæ, which is said to be traceable palæontologically right back, without a break, from the one-toed horses of the present day to[pg 115]the normal five-toed ancestry; and so with another favourite instance of evolution, the history of the pond-snails (Planorbis multiformis), the numerous varieties of which occur with transitions between them in actual contiguity in the Steinheim beds, and thus seem to afford an obvious example of the transformation of species. Against these cases, and against using the palæontological archives as a basis for the construction of genealogical trees in general, the weighty and apparently decisive objection is urged, that nowhere are the soft parts of the earlier forms of life preserved, and that it is impossible to establish relationships with any certainty on the basis of hard parts only, such as bones, teeth and shells. Even Haeckel admits that snails of very different bodily structure may form very similar and even hardly distinguishable shells.Fleischmann further asserts that Haeckel's“fundamental biogenetic law”has utterly collapsed.“Recapitulation”does not occur. Selenka's figures of ovum-segmentation show that there are specific differences in the individual groups. The origin and development of the blastoderm or germinal disc has nothing to do with recapitulation of the phylogeny. It is not the case that the embryos of higher vertebrates are indistinguishable from one another. Even the egg-cell has a specific character, and is totally different from any unicellular organism at the Protistan level. The much-cited“gill-clefts”of higher vertebrates in the embryonic stage are not persistent reminiscences of[pg 116]earlier lower stages; they are rudiments or primordia shared by all vertebrates, and developing differently at the different levels; (thus in fishes they become breathing organs, and in the higher vertebrates they become in part associated with the organs of hearing, or in part disappear again).Though Fleischmann's vigorous protest against over-hastiness in construction and over-confidence on the part of the adherents of the doctrine of descent is very interesting, and may often be justified in detail, it is difficult to resist the impression that the wheat has been rejected with the chaff.23Even a layman may raise the following objections: Admitting that the great groups of forms cannot be traced back to one another, the palæontological record still proves, though it may be only in general outline, that within each phylum there has been a gradual succession and ascent of forms. How is the origin of what is new to be accounted for? Without doing violence to our thinking, without a sort of intellectual autonomy, we cannot rest content with the mere fact that new elements occur. So, in spite of all“difficulties,”the assumption ofan actual descentquietly forces itself upon us as the only satisfactory clue. And the fact, which Fleischmann does not discuss, that even at present we may observe the establishment of what are at least new breeds, impels us to accept an analogous[pg 117]origin of new species. Even if the biogenetic law really“finds its chief confirmation in its exceptions,”even if we cannot speak of a strict recapitulation of earlier stages of evolution, there are indisputable facts which are most readily interpreted as reminiscences, as due to affiliation (ideal or hereditary), with ancestral forms. (Note, for instance, Weismann's“prediction,”&c.24) Even if Archæopteryx and other intermediate forms cannot be regarded as connecting links in the strict sense,i.e., as being stages in the actual pedigree, yet the occurrence of reptilian and avian peculiarities side by side in one organism, goes far to prove the close relationship of the two classes.Fleischmann's book strengthens the impression gained elsewhere, that a general survey of the domain of life as a whole gives force and convincingness to the Theory of Descent, while a study of details often results in breaking the threads and bringing the difficulties into prominence. But the same holds true of many other theoretical constructions, and yet we do not seriously doubt their validity. (Take, for instance, the Kant-Laplace theory, and theories of ethnology, of the history of religion, of the history of language, and so on.) And it is quite commonly to be observed that those who have an expert and specialist knowledge, who are aware of the refractoriness of detailed facts, often take up a sceptical attitude towards every comprehensive[pg 118]theory, though the ultimate use of detailed investigation is to make the construction of general theories possible. Fleischmann does exactly what, say, an anthropologist would do if, under the impression of the constancy and distinctiveness of the human races, which would become stronger the more deeply he penetrated, he should resignedly renounce all possibility of affiliating them, and should rest content with the facts as he found them. Similarly, those who are most intimately acquainted with the races of domesticated animals often resist most strenuously all attempts, although these seem to others a matter of course, to derive our“tame”forms from“wild”species living in freedom.But to return. Even where the Theory of Descent is recognised, whether fully or only half-heartedly, the recognition does not always mean the same thing. Even the adherents of the general, but in itself quite vague view that a transformation from lower forms to higher, and from similar to different forms, has taken place, may present so many points of disagreement, and may even stand in such antagonism to one another, that onlookers are apt to receive the impression that they occupy quite different standpoints, and are no longer at one even in the fundamentals of their hypotheses.The most diverse questions and answers crop up; whether evolution has been brought about“monophyletically”or“polyphyletically,”i.e., through one or many genealogical trees; whether it has taken place in[pg 119]a continuous easy transition from one type to another, or by leaps and bounds; whether through a gradual transformation of all organs, each varying individually, or through correlated“kaleidoscopic”variations of many kinds throughout the whole system; whether it is essentially asymptotic, or whether organisms pass from“labile”phases of vital equilibrium by various halting-places to stable states, which are definitive, and are, so to speak, the blind alleys and terminal points of evolutionary possibilities,e.g., the extinct gigantic saurians, and perhaps also man. And to these problems must be added the various answers to the question, What precedes, or may have preceded, the earliest stages of life of which we know? Whence came the first cell? Whence the first living protoplasm? and How did the living arise from the inorganic? These deeper questions will occupy us in our chapter on the theory of life. Some of the former, in certain of their aspects, will be considered in the sixth chapter, which deals with factors in evolution.The Theory of Descent itself and the differences that obtain even among its adherents can best be studied by considering for a little the works of Reinke and of Hamann.Reinke, Professor of Botany in Kiel, has set forth his views in his book,“Die Welt als Tat,”25and more recently in his“Einleitung in die theoretische Biologie”(1901). Both books are addressed to a wide[pg 120]circle of readers. Reinke and Hamann both revive some of the arguments and opinions set forth in the early days of Darwinism by Wigand,26an author whose works are gradually gaining increased appreciation.It is Reinke's“unalterable conviction”that organisms have evolved, and that they have done so after the manner of fan-shaped genealogical trees. The Theory of Descent is to him an axiom of modern biology, though as a matter of fact the circumstantial evidence in favour of it is extremely fragmentary. The main arguments in favour of it appear to him to be the general ones; the homologies and analogies revealed by comparative morphology and physiology, the ascending series in the palæontological record, vestigial organs, parasitic degeneration, the origin of those vital associations which we call consortism and symbiosis. These he illustrates mainly by examples from his own special domain and personal observation.The simplest unicellular forms of life are to be thought of as at the beginning of evolution; and, since mechanical causes cannot explain their ascent, it must be assumed that they have an inherent“phylogenetic potential of development,”which, working epigenetically, results in ascending evolution. He leaves us to choose between monophyletic and polyphyletic evolution, but himself inclines towards the latter, associating with it a[pg 121]rehabilitation of Wigand's theory of the primitive cells. If, in the beginning, primitive forms of life arose (probably as unicellulars) from the not-living, it is not obvious why we need think of only one so arising, and, if many did so, why they should not have inherent differences which would at once result in typically different evolutionary series and groups of forms. But evolution does not go onad libitumorad infinitum, for the capacity for differentiation and transformation gradually diminishes. The organisation passes from a labile state of equilibrium to an increasingly stable state, and at many points it may reach a terminus where it comes to a standstill. Man, the dog, the horse, the cereals, and fruit trees appear to Reinke to have reached their goal. The preliminary stages he calls“Phylembryos,”because they bear to the possible outcome of their evolution the same relation that the embryo does to the perfect individual. Thus,Phenacodusmay be regarded as the Phylembryo of the modern horse. It is quite conceivable that each of our modern species may have had an independent series of Phylembryos reaching back to the primitive cells. But the palæontological record, and especially its synthetic types, lead Reinke rather to assume that instead of innumerable series, there have been branching genealogical trees, not one, however, but several.These views, together or separately, which are characterised chiefly by the catch-words“polyphyletic descent,”“labile and stable equilibrium,”and so on, crop[pg 122]up together or separately in the writings of various evolutionists belonging to the opposition wing. They are usually associated with a denial of the theory of natural selection, and with theories of“Orthogenesis,”“Heterogenesis,”and“Epigenesis.”We shall discuss them later when we are considering the factors in evolution. But we must first take notice of a work in which the theories opposed to Darwinian orthodoxy have been most decisively and aggressively set forth. As far back as 1892 O. Hamann, then a lecturer on zoology in Göttingen, gathered these together and brought them into the field, against Haeckel in particular, in his book“Entwicklungslehre und Darwinismus.”27Hamann's main theme is that Darwinism overlooks the fact that“there cannot have been an origin of higher types from types already finished.”For this“unfortunate and unsupported assumption”there are no proofs in embryology, palæontology, or anatomy. He adopts and expands the arguments and anti-Haeckelian deliverances of His in embryology, of Snell and Heer in palæontology, of Kölliker and von Baer in their special interpretation of evolution, of Snell particularly as regards the descent of man. It is impossible to derive Metazoa from Protozoa in their present finished state of evolution; even the Amoeba is so exactly adapted in organisation and functional activity[pg 123]to the conditions of its existence that it is a“finished”type. It is only by a stretch of fancy that fishes can be derived from worms, or higher vertebrates from fishes. One of his favourite arguments—and it is a weighty one, though neglected by the orthodox Darwinians—is that living substance is capable, under similar stimuli, of developing spontaneously and afresh, at quite different points and in different groups, similar organs, such as spots sensitive to light, accumulations of pigment, eye-spots, lenses, complete eyes, and similarly with the notochord, the excretory organs, and the like. Therefore homology of organs is no proof of their hereditary affiliation.28They rather illustrate“iterative evolution.”Another favourite argument is the fact of“Pædogenesis.”Certain animals, such asAmphioxus lanceolatus,Peripatus, and certain Medusæ, are very frequently brought forward as examples of persistent primitive stages and“transitional connecting links.”But considered from the point of view of Pædogenesis, they all assume quite a different aspect, and seem rather to represent very highly evolved species, and to be, not primitive forms, but conservative and regressive forms. Pædogenesis is the phenomenon exhibited by a number of species, which may stop short at one of the stages of their embryonic or larval development, become sexually mature, and produce[pg 124]offspring without having attained their own fully developed form.Another argument is the old, suggestive, and really important one urged by Kölliker, that“inorganic nature shows a natural system among minerals (crystals) just as much as animals and plants do, yet in the former there can be no question of any genetic connection in the production of forms.”Yet another argument is found in the occurrence of“inversions”and anomalies in the palæontological succession of forms, which to some extent upsets the Darwinian-Haeckelian genealogical trees. (Thus there are forms in the Cambrian whose alleged ancestors do not appear till the Silurian. Foraminifera and other Protozoa do not appear till the Silurian.)From embryology in particular, as elsewhere in general, we read the“fundamental biogenetic law,”that evolution is from the general to the special, from the imperfect to the more perfect, from what is still indefinite and exuberant to the well-defined and precise, but never from the special to the special. According to Hamann's hypothesis we must think of evolution as going on, so to speak, not about the top but about the bottom. The phyla or groups of forms are great trunks bearing many branches and twigs, but not giving rise to one another. Still less do the little side branches of one trunk bear the whole great trunk of another animal or plant phylum. But they all grow from the same roots among the primitive forms of life. Unicellulars these must[pg 125]have been, but not like our“Protists.”They should be thought of as primitive forms having within themselves the potentialities of the most diverse and widely separate evolution-series to which they gave rise, as it were, along diverging fan-like rays.It would be instructive to follow some naturalist into his own particular domain, for instance a palæontologist into the detailed facts of palæontology, or an embryologist into those of embryology, in order to learn whether these corroborate the assumptions of the Theory of Descent or not. It is just in relation to these detailed facts that criticisms or even denials of the theory have been most frequent. Koken, otherwise a convinced supporter of the theory, inquires in his“Vorwelt,”aproposof the tortoises, what has become of the genealogical trees that were scattered abroad in the world as proved facts in the early days of Darwinism. He asserts, in regard toArchæopteryx, the instance which is always put forward as the intermediate link in the evolution of birds, that it does not show in any of its characters a fundamental difference from any of the birds of to-day, and further, that, through convergent development under similar influences, similar organs and structural relations result, iterative arrangements which come about quite independently of descent. He maintains, too, that the principle of the struggle for existence is rather disproved than corroborated by the palæontological record.In embryology, so competent an authority as[pg 126]O. Hertwig—himself a former pupil of Haeckel's—has reacted from the“fundamental biogenetic law.”His theory of the matter is very much that of Hamann which we have already discussed; development is not so much a recapitulation of finished ancestral types as the laying down of foundations after the pattern of generalised simple forms, not yet specialised; and from these foundations the special organs rise to different levels and grades of differentiation according to the type.29But we must not lose ourselves in details.Looking back over the whole field once more, we feel that we are justified in maintaining with some confidence that the different pronouncements in regard to the detailed application and particular features of the Theory of Descent, and the different standpoints that are occupied even by evolutionists, are at least sufficient to make it obvious that, even if evolution and descent have actually taken place, they have not run so simple and smooth a course as the over-confident would have us believe; that the Theory of Descent rather emphasises than clears away the riddles and difficulties of the case, and that with the mere corroboration of the theory we shall have gained only something relatively external, a clue to creation, which does not so much solve its problems as restate them. The whole criticism of the“right wing,”from captious objections to actual denials, proves this indisputably. And it seems likely that in the course of time a sharpening of[pg 127]the critical insight and temper will give rise to further reactions from the academic theory as we have come to know it.30On the other hand, it may be assumed with even greater certainty that the general evolutionist point of view and the great arguments for descent in some form or other will ultimately be victorious if they are not so already, and that, sooner or later, we shall take the Theory of Descent in its most general form as a matter of course, just as we now do the Kant-Laplace theory.[pg 128]

Chapter IV. Darwinism In General.Darwinism, which was originally a technical theory of the biological schools, has long since become a veritable tangle of the most diverse problems and opinions, and seems to press hardly upon the religious conception of the world from many different sides. In its theory of blind“natural selection”and the fortuitous play of the factors in the struggle for existence, it appears to surrender the whole of this wonderful world of life to the rough and ready grip of a process without method or plan. In the general theory of evolution and the doctrine of the descent of even the highest from the lowest, it seems to take away all special dignity from the human mind and spirit, all the freedom and all the nobility of pure reason and free will; it seems to reduce the higher products of religion, morality, poetry, and the æsthetic sense to the level of an ignoble tumult of animal impulses, desires and sensations. Purely speculative questions relative to the evolution theory, psychological and metaphysical, logical and epistemological, ethical, æsthetic, and finally even historical and politico-economical questions have been drawn into the[pg 086]coil, and usually receive from the Darwinians an answer at once robust and self-assured. A zoological theory seems suddenly to have thrown light and intelligibility into the most diverse provinces of knowledge.But in point of fact it can be shown that Darwinism has not really done this and cannot do it. It leaves unaffected the problem of the mind with its peculiar and underivable laws, from the logical to the ethical. Whether it be right or wrong in its physiological theories, its genealogical trees and fortuitous factors, preoccupation with this theory is a task of the second order. Nevertheless it is necessary to study it, because the chief objections to the religious interpretation of the world have come from it.The Development of Darwinism.In studying it we should like to follow a method somewhat different from that usually observed in apologetic writings.“Darwinism,”even in its technical, biological form, never was quite, and is to-day not at all a unified and consistent system. It has been modified in so many ways and presented in such different colours, that we must either refrain altogether from attempting to get into close quarters with it, or we must make ourselves acquainted to some extent with the phases of the theory as it has gradually developed up to the present day. This is the more necessary and useful since it is precisely within the circle of technical experts that revolts from and criticisms of the Darwinian theory[pg 087]have in recent years arisen; and these are so incisive, so varied, and so instructive, that through them we can adjust our standpoint in relation to the theory better than in any other way. And in thus letting the biologists speak for themselves, we are spared the fatal task of entering into the discussion of questions belonging to a region outside our own particular studies.We cannot, however, give more than a short sketch. But even such a sketch may do more towards giving us a general knowledge of the question and showing us a way out of the difficulties it raises than any of the current“refutations.”To supplement this sketch, and facilitate a thorough understanding of the problem, we shall give somewhat fuller references than are usual to the relevant literature. And the same method will be pursued in the following chapter, which deals with the mechanical theory of life. This method throws more upon the reader, but it is probably the most satisfactory one for the serious student.The reactions from the Darwinism of the schools which we have just referred to, and to which the second half of this chapter is devoted, are, of course, of a purely scientific kind. And while we are devoting our attention to them, we must not be unfaithful to the canon laid down in the previous chapter, namely that with reference to the question of teleology in the religious sense no real answer can be looked for from scientific study, not even if it be anti-Darwinian. In this case, too, it is impossible to read the convictions[pg 088]and intuitions of the religious conception of the world out of a scientific study of nature: they precede it. But here, too, we may find some accessory support and indirect corroboration more or less strong and secure. This may be illustrated by a single example. It will be shown that, on closer study, it is not impossible to subordinate even the apparently confused tangle of naturalistic factors of evolution which are summed up in the phrase“struggle for existence”to interpretation from the religious point of view. But matters will be in quite a different position if the whole theory collapses, and instead of evolution and its paths being given over to confusion and chance, it appears that from the very beginning and at every point there is a predetermination of fixed and inevitable lines along and up which it must advance. In many other connections considerations of a like nature will reveal themselves to us in the course of our study.Darwinism, as popularly understood, is the theory that“men are descended from monkeys,”and in general that the higher forms of life are descended from the lower, and it is regarded as Darwin's epoch-making work and his chief merit—or fault according to the point of view—that he established the Theory of Descent. This is only half correct, and it leaves out the real point of Darwinism altogether. The Theory of Descent had its way prepared by the evolutionist ideas and the speculative nature-philosophy of Goethe, Schelling, Hegel and Oken; by the suggestions and glimmerings of the[pg 089]nature-mysticism of the romanticists; by the results of comparative anatomy and physiology; was already hinted at, at least as far as derivation of species was concerned, in the works of Linné himself; was worked out in the“zoological philosophies,”by the elder Darwin, by Lamarck, Etienne Geoffrey St. Hilaire and Buffon; was in the field long before Charles Darwin's time; was already in active conflict with the antagonistic theory of the“constancy of species,”and had its more or less decided adherents. Yet undoubtedly it was through and after Darwin that the theory grew so much more powerful and gained general acceptance.Darwinism and Teleology.But the essential and most characteristic importance of Darwin and his work, the reason for which he was called the Newton of biology, and which makes Darwinism at once interesting and dangerous to the religious conception of the world, is something quite special and new. It is its radical opposition to teleology. Du Bois-Reymond, in his witty lecture“Darwin versus Galiani,”4explains the gist of the matter.“Les dés de la nature sont pipés”(nature's dice are loaded). Nature is almost always throwing aces. She brings forth not what is meaningless and purposeless, but in great preponderance what is full of meaning and purpose. What“loaded”her dice like this? Even if the theory of descent be true, in what way does it directly[pg 090]help the purely scientific interpretation of the world? Would not this evolution from the lowest to the highest simply be a series of the most astonishing lucky throws of the dice by which in perplexing“endeavour after an aim,”the increasingly perfect, and ultimately the most perfect is produced? And, on the other hand, every individual organism, from the Amœba up to the most complex vertebrate, is, in its structure, its form, its functions, a stupendous marvel of adaptation to its end and of co-ordination of the parts to the whole, and of the whole and its parts to the functions of the organism, the functions of nutrition, self-maintenance, reproduction, maintenance of the species, and so on. How account for the adaptiveness, both general and special, withoutcausæ finales, without intention and purposes, without guidance towards a conscious aim? How can it be explained as the necessary result solely ofcausæ efficientes, of blindly working causes without a definite aim? Darwinism attempts to answer this question. And its answer is:“What appears to us‘purposeful’and‘perfect’is in truth only the manifold adaptation of the forms of life to the conditions of their existence. And this adaptation is brought about solely by means of these conditions themselves. Without choice, without aim, without conscious purpose nature offers a wealth of possibilities. The conditions of existence act as a sieve. What chances to correspond to them maintains itself, gliding through the meshes of the sieve, what does not perishes.”It is an old idea of the[pg 091]naturalistic philosophies, dating from Empedocles, which Darwin worked up into the theory of“natural selection”through“the survival of the fittest”“in the struggle for existence.”Of course the assumption necessary to his idea is that the forms of life are capable of variation, and of continually offering in ceaseless flux new properties and characters to the sieve of selection, and of being raised thereby from the originally homogeneous to the heterogeneous, from the simple to the complex, from the lower to the higher. This is the theory of descent, and it is, of course, an essential part and the very foundation of Darwin's theory. But it isthe doctrine of descent based upon natural selectionthat is Darwinism itself.The Characteristic Features of Darwinism.We do not propose to expound the Darwinian theory for the hundredth time; a knowledge of it must be taken for granted. We need only briefly call to mind the characteristic features and catchwords of the theory as Darwin founded it, which have also been the starting points of subsequent modifications and controversies.All living creatures are bound together in genetic solidarity. Everything has evolved through endless deviations, gradations, and differentiations, but at the same time by a perfectly continuous process. Variation continually produced a crop of heterogeneous novelties. The struggle for existence sifted these out. Heredity[pg 092]fixed and established them. Without method or plan variations continue to occur (indefinite variations). They manifest themselves in all manner of minute changes (“fluctuating”variations). Every part, every function of an organism may be subject individually to variation and selection. The world is strictly governed by what is useful. The whole organisation as well as the individual organs and functions bear the stamp of utility, at least, they must bear it if the theory is correct. In the general continuity the transitions are always easy; there are no fundamentally distinct“types,”architectural plans, or groups of forms. Where gaps yawn the intermediate links have gone amissing. There is no fundamental difference betweengenus,species, andvariety. Even the most complicated organ such as the eye, the most puzzling function such as the instinct of the bee, may be explained as the outcome of many more primitive stages.The chief evidences of the theory of descent are to be found in homologies, in the correspondences of organs and functions, as revealed by comparative anatomy and physiology, in the recapitulation revealed by embryology, in the structure of parasites, in rudimentary organs and reversions to earlier stages, in the distribution of animals and plants, and in the possibility of still transforming, at least to a slight extent, one species into another, by experimental breeding.Transformation and differentiation go on in nature as a vast, ceaseless, but blind process of selection. In[pg 093]artificial selection evolution is secured by choosing the most fit for breeding purposes; so it is secured in natural selection by the favouring and survival of those forms which are the most fit among the many unfit or less fit, which happened to be exposed to the struggle for existence, that is, to the competition for the means of subsistence, to the struggle with enemies, to hostile environment, and to dangers of every kind. The adaptation thus brought about is of a purely“passive”kind. The variations arise fortuitously out of the organism, and present themselves for selection in the struggle for existence; they are not actively acquired by means of the struggle. The secondary factors of evolution recognised are: correlation in the growth and in the development of parts, the origin of new characters through use, their disappearance through disuse (Lamarck), the transmission of characters thus acquired, the influence of environment and sexual selection.5The Darwinian theory, the interpretation of the teleological in the animate world by means of the theory of descent based upon natural selection, entered like a ferment into the scientific thought-movement, and in a space of forty years it has itself passed through a series of stages, differentiations, and transformations which have in part resulted in the present state of the theory, and have in part anticipated it. These are represented[pg 094]by the names of workers belonging to a generation which has for the most part already passed away: Darwin's collaborateurs, such as Alfred Russel Wallace, who independently and simultaneously expounded the theory of natural selection, Haeckel and Fritz Müller, Nägeli and Askenasy, von Kölliker, Mivart, Romanes and others. The differentiation and elaboration of Darwin's theories has gone ever farther and farther; the grades and shades of doctrine held by his disciples are now almost beyond reckoning.Various Forms of Darwinism.The great majority of these express what may be called popular Darwinism [“Darwinismus vulgaris”], theoretically worthless, but practically possessed of great powers of attraction and propagandism. It expresses in the main a conviction, usually left unexplained, that everything“happens naturally,”that man is really descended from monkeys, and that life has“evolved from lower stages”of itself, that dualism is wrong, and that monism is the truth. It is exactly the standpoint of the popular naturalism we have already described, which here mingles unsuspectingly and without scruple Lamarckian and other principles with the Darwinian, which is enthusiastic on the one hand over the“purely mechanical”interpretation of nature, and on the other drags in directly psychical motives, unconscious consciousness, impulses, spontaneous self-differentiation of organisms, which nevertheless adheres to“monism”[pg 095]and possibly even professes to share Goethe's conception of nature!Above this stratum we come to that of the real experts, the only one which concerns us in the least. Here too we find an ever-growing distance between divergent views, the most manifold differences amounting sometimes to mutual exclusion. These differences occur even with reference to the fundamental doctrine generally adhered to, the doctrine of descent. To one party it is a proved fact, to another a probable, scientific working hypothesis, to a third a“rescuing plank.”One party is always finding fresh corroborations, another new difficulties. And within the same group we find the contrasts of believers in monophyletic and believers in polyphyletic evolution, the mechanists and the half-confessed or thoroughgoing vitalists, the preformationists and the believers in epigenesis. Opinions differ even more widely in regard to therôleof the“struggle for existence”in the production of species. On the one hand we have the Darwinism of Darwin freed from inconsequent additions and formulated as orthodox“neo-Darwinism”; on the other hand we have heterodox Lamarckism. The“all-sufficiency”of natural selection is proclaimed by some, its impotence by others. Indefinite variation is opposed by orthogenesis, fluctuating variation by saltatory mutation (Halmatogenesis in“Greek”), passive adaptation by the spontaneous activity and self-regulation of the living organism. The struggle for existence is variously regarded as the[pg 096]chief factor, or as a co-operating factor, or as an indifferent, or even an inimical factor in the origination of new species.And among the representatives of these different standpoints there are most interesting personal differences: in some, like Weismann, we find a great loyalty to, and persistence in the position once arrived at, in others the most surprising transitions and changes of opinion. Thus Fleischmann, a pupil of Selenka's, after illustrating during many years of personal research the orthodox Darwinian standpoint, finally developed into an outspoken opponent not only of the theory of selection but of the doctrine of descent. So also Friedmann.6Driesch started from the mechanical theory of life and advanced through the connected series of his own biological essays to vitalism. Romanes, a prominent disciple of Darwin, ended in Christian theism, and Wallace, the discoverer of“the struggle for existence,”landed in spiritualism.Nothing like an exhaustive view of the present state of Darwinism and its many champions can here be attempted. But it will be necessary to get to know what we may call its possibilities by a study of typical and leading examples. In the course of our study many of the problems to which the theory gives rise will reveal themselves, and their orientation will be possible.This task falls naturally into two subdivisions: (1) the[pg 097]present state of the theory of Evolution and Descent, and how far the religious conception of the world is or is not affected by it; (2) the truth as to the originative and directive factors of Evolution, especially as to“natural selection in the struggle for existence,”whether they are tenable and sufficient, and what attitude religion must take towards them. These two problems must be kept distinct throughout, and must be discussed in order. For the validity of what is characteristicallyDarwinismis in no way decided by proving descent and evolution, although it appears so in most popular expositions.7The Theory of Descent.Again and again we hear and read, even in scientific circles and journals, that Darwinism breaks down at many points, that it is insufficient, and even that it has quite collapsed. Even the assurances of its most convinced champions are rather forced, and are somewhat suggestive of bills payable in the future.8But here again it is obvious that we must distinguish clearly between the Theory of Descent and Darwinism. Of the Theory of Descent it is by no means true that it has“broken down.”With a slight exaggeration, but on the whole with justice, Weismann has asserted that the[pg 098]Theory of Descent is to-day a“generally accepted truth.”Even Weismann's most pronounced opponents, such as Eimer, Wolff, Reinke, and others, are at one with him in this, that there has been evolution in some form; that there has been a progressive transformation of species; that there is real (not merely ideal) relationship or affiliation connecting our modern forms of life, up to and including man, with the lower and lowest forms of bygone æons.The evidences are the same as those adduced by Darwin and before his time, but they have been multiplied and more sharply defined:—namely, that the forms of life can be arranged in an ascending scale of evolution, both in their morphological and their physiological aspects, both as regards the general type and the differentiation of individual organs and particular characters, bodily and mental. All the rubrics used by Darwin in this connection, from comparative anatomy, from the palæontological record itself, and so on, have been filled out with ever-increasing detail. Palæontology, in particular, is continually furnishing new illustrations of descent and new evidence of its probability, more telling perhaps in respect of general features and particular groups than in regard to the historical process in detail. For certain species and genera palæontology discloses the primitive forms, discovers“synthetic types”which were the starting-point for diverging branches of evolution, bridges over or narrows the yawning gulfs in evolution by the discovery of[pg 099]“intermediate forms”; and, in the case of certain species, furnishes complete genealogical trees. The same holds true of the facts of comparative anatomy, embryology, and so on. In all detailed investigations into an animal type, in the study of the structure, functions, or the instincts of an ant, or of a whale or of a tape-worm, the standpoint of the theory of descent is assumed, and it proves a useful clue for further investigation.In regard to man—so we are assured—the theory finds confirmation through the discovery of the Neanderthal, Spy, Schipka, La Naulette skulls and bones—the remains of a prehistoric human race, with“pithecoid”(ape-like) characters. And the theory reaches its climax in Dubois' discovery of the remains of“Pithecanthropus,”the upright ape-man, in Java, 1891-92, the long sought-for Missing Link between animals and man;9and in the still more recent proofs of“affinity of blood”between man and ape, furnished by experiments in transfusion. Friedenthal has revived the older experiments of transfusing the blood of one animal into another, the blood of an animal of one species into that of another, of related species into related species, more remote into more remote, and finally even from animals into man. The further apart the two species are, the more different are the physiological[pg 100]characters of the blood, and the more difficult does a mingling of the two become. Blood of a too distantly related form does not unite with that of the animal into which it is transfused, but the red corpuscles of the former are destroyed by the serum of the latter, break up and are eliminated. In nearly related species or races, however, the two kinds of blood unite, as in the case of horse and ass, or of hare and rabbit. Human blood serum behaves in a hostile fashion to the blood of eel, pigeon, horse, dog, cat, and even to that of Lemuroids, or that of the more remotely related“non-anthropoid”monkey; human blood transfused from a negro into a white unites readily, as does also that of orang-utan transfused into a gibbon. But human blood also unites without any breaking-up or disturbance with the blood of a chimpanzee; from which the inference is that man is not to be placed in a separate sub-order beside the other sub-orders of the Primates, the platyrrhine and catarrhine monkeys, not even in a distinct sub order beside the catarrhines; but is to be included with them in one zoological sub-order. This classification was previously suggested by Selenka on other grounds, namely, because of the points in common in the embryonic development of the catarrhine monkeys and of man, and their common distinctiveness as contrasted with the platyrrhines.10[pg 101]Haeckel's Evolutionist Position.The average type of the Theory of Descent of the older or orthodox school, which still lingers in the background with its Darwinism unshaken, is that set forth by Haeckel, scientifically in his“Generelle Morphologie der Organismen”(1866), and“Systematische Phylogenie”(1896), and popularly in his“Natural History of Creation”and“Riddles of the Universe,”with their many editions. We may assume that it is well known, and need only briefly recall its chief characteristics. The“inestimable value,”the“incomparable significance,”the“immeasurable importance”of the Theory of Descent lies, according to Haeckel, in the fact that by means of it we can explain the origin of the forms of life“in a mechanical manner.”The theory, especially in regard to the descent of man from the apes, is to him not a working hypothesis or tentative mode of representation; it is a result comparable to Newton's law of gravitation or the Kant-Laplace cosmogony. It is“a certain historical fact.”The proofs of it are those already mentioned.What is especially Haeckelian is the“fundamental biogenetic law,”“ontogeny resembles phylogeny,”that is to say, in development, especially in embryonic development, the individual recapitulates the history of the race. Through“palingenesis,”man, for instance, recapitulates his ancestral stages (protist, gastræad, vermine, piscine, and simian). This recapitulation is condensed,[pg 102]disarranged, or obscured in detail by“cenogenesis”or“cænogenesis.”The groups and types of organisms exhibit the closest genetic solidarity. The genealogical tree of man in particular runs directly through a whole series. From the realm of the protists it leads to that of the gastræadæ (nowadays represented by the Cœlentera), thence into the domain of the worms, touches the hypothetical“primitive chordates”(for the necessary existence of which“certain proofs”can be given), the class of tunicates, ascends through the fishes, amphibians and reptiles to forms parallel to the modern monotremes, then directly through the marsupials to the placentals, through lemuroids and baboons to the anthropoid apes, from them to the“famous Pithecanthropus”discovered in Java, out of whichhomo sapiensarose. (The easy transition from one group of forms to another is to be noted. For it is against this point that most of the opposition has been directed, whether from“grumbling”critics, or thoroughgoing opponents of the Theory of Descent.)Haeckel's facile method of constructing genealogical trees, which ignores difficulties and discrepant facts, has met with much criticism and ridicule even among Darwinians. The“orator of Berlin,”Du Bois-Reymond, declared that if he must read romances he would prefer to read them in some other form than that of genealogical trees. But they have at least the merit that they give a vivid impression of what is most plausible and attractive in the idea of descent, and moreover[pg 103]they have helped towards orientation in the discussion. Nor can we ignore the very marked taxonomic and architectonic talent which their construction displays.Weismann's Evolutionist Position.The most characteristic representative, however, of the modern school of unified and purified Darwinism is not Haeckel, but the Freiburg zoologist, Weismann. Through a long series of writings he has carried on the conflict against heterodox, and especially Lamarckian theories of evolution, and has developed his theories of heredity and the causes of variation, of the non-transmissibility of acquired characters, and the all-sufficiency of natural selection. In his latest great work, in two volumes,“Lectures on the Theory of Descent,”11he has definitely summed up and systematised his views. These will interest us when we come to inquire into the problem of the factors operative in evolution. For the moment we are only concerned with his attitude to the Theory of Descent as such. It is precisely the same as Haeckel's, although he is opposed to Haeckel in regard to the strictly Darwinian standpoint. The Theory of Descent has conquered, and it may be said with assurance, for ever. That is the firm conviction on which the whole work is based, and it is really rather treated as a self-evident axiom than as a statement to be proved. Weismann takes little trouble to[pg 104]prove it. All the well-known, usually very clear proofs from palæontology, comparative anatomy, &c., which we are accustomed to meet with in evolutionist books are wanting here, the genealogical trees of the Equidæ, with the gradually diminishing number of toes and the varying teeth, ofPlanorbis multiformis, of the ammonites, the graduated series of stages exhibited by individual organs, for instance, from the ganglion merely sensitive to light up to the intricate eye, or from the rayed skeleton of the paired fins in fishes up to the five-fingered hands and feet of the higher vertebrates, &c. These are only briefly touched upon in the terse“Introduction,”and the whole of the comprehensive work is then directed to showing what factors can have been operative, and to proving that they must have been“Darwinian”(selection in the struggle for existence), and not Lamarckian or any other. This is shown in regard to the coloration of animals, the phenomena of mimicry, the protective arrangements of plants, the development of instinct in animals, and the origin of flowers.In reality Weismann only adducesonestrict proof, and even that is only laying special stress on what is well known in comparative embryology; namely, the possibility of“predicting”on the basis of the theory of descent, as Leverrier“predicted”Neptune. For instance, in the lower vertebrates from amphibians upwards there is anos centralein the skeleton of wrist, but there is none in man. Now if man be descended[pg 105]from lower vertebrates, and if the fundamental biogenetic law be true (that every form of life recapitulates in its own development, especially in its embryonic development, the evolution of its race, though with abbreviations and condensations), it may be predicted that theos centraleis to be found in the early embryonic stages of man. And Rosenberg found it. In the same way the“gill-clefts”of the fish-like ancestors have long since been discovered in the embryo of the higher vertebrates and of man. Weismann himself“predicted”that the markings of the youngest stage of the caterpillars of the Sphingidæ (hawk-moths) would be found to be not oblique but longitudinal stripes, and ten years later a fortunate observation verified the prediction. Because of the abundance of evidential facts Weismann does not go into any detailed proof of evolution.“One can hardly take up any work, large or small, on the finer or more general structural relations, or on the development of any animal, without finding in it proofs for the evolution theory.”But assured as the doctrine of descent appears,12and certain as it is that it has not only maintained its hold since Darwin's day, but has strengthened it and has gained adherents, this foundation of Darwinism is[pg 106]nevertheless not the unanimous and inevitable conclusion of all scientific men in the sense and to the extent that the utterances of Weismann and others would lead us to suppose. Apart from all apologetic attempts either in religious, ethical, or æsthetic interests, apart, too, from the superior standpoint of the philosophers, who have not, so to speak, taken the theory very seriously, but regard it as a provisional theory, as a more or less necessary and useful method of grouping our ideas in regard to the organic world, there are even among the biologists themselves some who, indifferent towards religious or philosophical or naturalistic dogma, hold strictly to fact, and renounce with nonchalance any pretensions at completeness of knowledge if the data do not admit of it, and on these grounds hold themselves aloof from evolutionist generalisation. From among these come the counsels of“caution,”admissions that the theory is a scientific hypothesis and a guide to research, but not knowledge, and confessions that the Theory of Descent as a whole is verifiable rather as a general impression than in detail.Virchow's Position.Warnings of this kind have come occasionally from Du Bois-Reymond, but the true type of this group, and its mode of thought, is Virchow. It will repay us and suffice us to make acquaintance with it through him. His opposition to Darwinism and the theory of descent was directed at its most salient point: the[pg 107]descent of man from the apes. In lectures and treatises, at zoological and anthropological congresses, especially at the meetings of his own Anthropological-Ethnological Society in Berlin, from his“Vorträge über Menschen-und Affen-Schädel”(Lectures on the Skulls of Man and Apes, 1869), to the disputes over Dubois'Pithecanthropus erectusin the middle of the nineties, he threw the whole weight of his immense learning—ethnological and anthropological, osteological, and above all“craniological”—into the scale against the Theory of Descent and its supporters. Virchow has therefore been reckoned often enough among the anti-Darwinians, and has been quoted by apologists and others as against Darwinism, and he has given reason for this, since he has often taken the field against“the Darwinists”or has scoffed at their“longing for a pro-anthropos.”13Sometimes even it has been suggested that he was actuated by religious motives, as when he occasionally championed not only freedom for science, but, incidentally, the right of existence for“the churches,”leaving, for instance, in his theory of psychical life, gaps in knowledge which faith might occupy in moderation and modesty. But this last proves nothing. With Virchow's altogether unemotional nature it is unlikely that religious or spiritual motives had any rôle in the establishment of his convictions, and in Haeckel's naïve blustering at religion, there is, so to speak, more[pg 108]religion than in the cold-blooded connivance with which Virchow leaves a few openings in otherwise frozen ponds for the ducks of faith to swim in! And he has nothing of the pathos of Du Bois-Reymond's“ignorabimus.”He is the neutral, prosaic scientist, who will let nothing“tempt him to a transcendental consideration,”14either theological or naturalistic, who holds tenaciously to matters of fact, who, without absolutely rejecting a general theory, will not concern himself about it, except to point out every difficulty in the way of it; in short, he is the representative of a mood that is the ideal of every investigator and the despair of every theoriser.His lecture of 1869 already indicates his subsequent attitude.“Considered logically and speculatively”the Theory of Descent seems to him“excellent,”15indeed a logical moral(!) hypothesis, but unproved in itself, and erroneous in many of its particular propositions. As far back as 1858, before the publication of Darwin's great work, he stated at the Naturalists' Congress in Carlsruhe, that the origin of one species out of another appeared to him a necessary scientific inference, but——And throughout the whole lecture he alternates between favourable recognition of the theory in general, and emphasis of the difficulties which confront it in detail. The skull, which, according to Goethe's theory, has[pg 109]evolved from three modified vertebræ, is fundamentally different in man and monkeys, both in regard to its externals, crests, ridges and shape, and especially in regard to the nature of the cavity which it forms for the brain. Specifically distinctive differences in the development and structure of the rest of the body must also be taken into account. The so-called ape-like structures in the skull and the rest of the body, which occasionally occur in man (idiots, microcephaloids, &c.) cannot be regarded as atavisms and therefore as proofs of the Theory of Descent; they are of a pathological nature, entirely factssui generis, and“not to be placed in a series with the normal results of evolution.”A man modified by disease“is still thoroughly a man, not a monkey.”Virchow continued to maintain this attitude and persisted in this kind of argument. He energetically rejected all attempts to find“pithecoid”characters in the prehistoric remains of man. He declared the narrow and less arched forehead, the elliptical form, and the unusually large frontal cavities of the“Neanderthal skull”found in the Wupperthal in 1856, to be simply pathological features, which occur as such in certain examples ofhomo sapiens.16He explained the abnormal appearance of the jaw from the Moravian cave of Schipka as a result of the retention of teeth,17accompanied by directly“antipithecoid”characters.[pg 110]The proceedings at the meetings of the Ethnological Society in 1895, at which Dubois was present, had an almost dramatic character.18In the diverse opinions of Dubois, Virchow, Nehring, Kollmann, Krause and others, we have almost an epitome of the present state of the Darwinian question. Virchow doubted whether the parts put together by Dubois (the head of a femur, two molar teeth, and the top of a skull) belonged to the same individual at all, disputed the calculations as to the large capacity of the skull, placed against Dubois' very striking and clever drawing of the curves of the skull-outline, which illustrated, with the help of the Pithecanthropus, the gradual transition from the skull of a monkey to that of man, his own drawing, according to which the Pithecanthropus curve simply coincides with that of a gibbon (Hylobates), and asserted that the remains discovered were those of a species of gibbon, refusing even to admit that they represented a new genus of monkeys. He held fast to hisceterum censeo:“As yet no diluvial discovery has been made which can be referred to a man of a pithecoid type.”Indeed, his polemic or“caution”in regard to the Theory of Descent went even further. He not only refused to admit the proof of the descent of man from monkey, he would not even allow that the descent of one race from another has been demonstrated.19[pg 111]In spite of all the plausible hypotheses it remains“so far only apium desiderium.”The race obstinately maintains its specific distinctness, and resists variation, or gradual transformation into another. The negro remains a negro in America, and the European colonist of Australia remains a European.Yet all Virchow's opposition may be summed up in the characteristic words, which might almost be called his motto,“I warn you of the need for caution,”and it is not a seriously-meant rejection of the Theory of Descent. In reality he holds the evolution-idea as an axiom, and in the last-named treatise he shows distinctly how he conceives of the process. He starts with variation (presumably“kaleidoscopic”), which comes about as a“pathological”phenomenon, that is to say, not spontaneously, but as the result of environmental stimulus, as the organism's reaction to climatic and other conditions of life. The result is an alteration of previous characteristics, and a new stable race is established by an“acquired anomaly.”20Other Instances of Dissatisfaction with the Theory of Descent.What was with Virchow only a suggestion of the[pg 112]need for caution, or controversial matter to be subsequently allowed for or contradicted, had more serious consequences to others, and led to still greater hesitancy as regards evolutionist generalisations and speculations, and sometimes to sharp antagonism to them.One of the best known of the earlier examples of this mood is Kerner von Marilaun's large and beautiful work on“Plant Life.”21He does, indeed, admit that our species are variations of antecedent forms, but only in a very limited sense. Within the stocks or grades of organisation which have always existed, variations have come about, through“hybridisation,”through the crossing of similar, but relatively different forms; these variations alter the configuration and appearance in detail, but neither affect the general character nor cause any transition from“lower”to“higher.”Kerner disposes of the chief argument in favour of the theory of descent, the homology of individual organs, by explaining that the homology is due to the similarity of function in the different organisms. A similar argument is used in regard to“ontogeny recapitulating phylogeny.”Palæontology does not disclose in the plant-world any“synthetic types,”which might have been the common primitive stock from which many now divergent branches have sprung, nor does it disclose any“transition links”really intermediate,[pg 113]for instance, between cryptogams and gymnosperms, or between gymnosperms and angiosperms. That the higher races are apparently absent from the earlier strata is not a proof that they have never existed. The peat-bog flora must have involved the existence of a large companion-flora, without which the peat could not have been formed, but all trace of this is absent in the still persistent vestiges of these times.22Life, with energy and matter, has existed as a phenomenon of the universe from all eternity, and thus its chief forms and manifestations have not“arisen,”but have always been. If facts such as these contradict the Kant-Laplace theory of the universe, then the latter must be corrected in the light of them, not conversely. The extreme isolation of Kerner and his theory is probably due especially to this corollary of his views.Among the most recent examples of antagonism to the Evolution-Theory, the most interesting is a book by Fleischmann, professor of zoology in Erlangen, published in 1901, and entitled,“The Theory of Descent.”It consists of“popular lectures on the rise and decline of a scientific hypothesis”(namely, the Theory of Descent), and it is a complete recantation by a quondam Darwinian of the doctrine of his school, even of its fundamental proposition, the concept of evolution itself. For Fleischmann is not guilty, like Weismann, of the inaccuracy of using“Theory of[pg 114]Descent”as equivalent to Darwinism; he is absolutely indifferent to the theory of natural selection. His book keeps strictly to matters of fact, and rejects as speculation everything in the least beyond these; it does not express even an opinion on the question of the origin of species, but merely criticises and analyses.It does not bring forward any new and overwhelming arguments in refutation of the Theory of Descent, but strongly emphasises difficulties that have always beset it, and discusses these in detail. The old dispute which interested Goethe, Geoffroy St. Hilaire, and Cuvier, as to the unity or the fundamental heterogeneity of the“architectural plan”in nature is revived. Modern zoology recognises not merely the four types of Cuvier, but seventeen different styles,“phyla,”or groups of forms, to derive one of which from another is hopeless. And what is true of the whole is true also of the subdivisions within each phylum;e.g., within the vertebrate phylum with its fishes, amphibians, reptiles, birds and mammals. No bridge leads from one to the other. This is proved particularly by the very instance which is the favourite illustration in support of the Theory of Descent—the fin of fishes and its relation to the five-fingered hand of vertebrates. The so-called transition forms (Archæopteryx, monotremes, &c.) are discredited. So with the“stalking-horse”of evolutionists—the genealogical tree of the Equidæ, which is said to be traceable palæontologically right back, without a break, from the one-toed horses of the present day to[pg 115]the normal five-toed ancestry; and so with another favourite instance of evolution, the history of the pond-snails (Planorbis multiformis), the numerous varieties of which occur with transitions between them in actual contiguity in the Steinheim beds, and thus seem to afford an obvious example of the transformation of species. Against these cases, and against using the palæontological archives as a basis for the construction of genealogical trees in general, the weighty and apparently decisive objection is urged, that nowhere are the soft parts of the earlier forms of life preserved, and that it is impossible to establish relationships with any certainty on the basis of hard parts only, such as bones, teeth and shells. Even Haeckel admits that snails of very different bodily structure may form very similar and even hardly distinguishable shells.Fleischmann further asserts that Haeckel's“fundamental biogenetic law”has utterly collapsed.“Recapitulation”does not occur. Selenka's figures of ovum-segmentation show that there are specific differences in the individual groups. The origin and development of the blastoderm or germinal disc has nothing to do with recapitulation of the phylogeny. It is not the case that the embryos of higher vertebrates are indistinguishable from one another. Even the egg-cell has a specific character, and is totally different from any unicellular organism at the Protistan level. The much-cited“gill-clefts”of higher vertebrates in the embryonic stage are not persistent reminiscences of[pg 116]earlier lower stages; they are rudiments or primordia shared by all vertebrates, and developing differently at the different levels; (thus in fishes they become breathing organs, and in the higher vertebrates they become in part associated with the organs of hearing, or in part disappear again).Though Fleischmann's vigorous protest against over-hastiness in construction and over-confidence on the part of the adherents of the doctrine of descent is very interesting, and may often be justified in detail, it is difficult to resist the impression that the wheat has been rejected with the chaff.23Even a layman may raise the following objections: Admitting that the great groups of forms cannot be traced back to one another, the palæontological record still proves, though it may be only in general outline, that within each phylum there has been a gradual succession and ascent of forms. How is the origin of what is new to be accounted for? Without doing violence to our thinking, without a sort of intellectual autonomy, we cannot rest content with the mere fact that new elements occur. So, in spite of all“difficulties,”the assumption ofan actual descentquietly forces itself upon us as the only satisfactory clue. And the fact, which Fleischmann does not discuss, that even at present we may observe the establishment of what are at least new breeds, impels us to accept an analogous[pg 117]origin of new species. Even if the biogenetic law really“finds its chief confirmation in its exceptions,”even if we cannot speak of a strict recapitulation of earlier stages of evolution, there are indisputable facts which are most readily interpreted as reminiscences, as due to affiliation (ideal or hereditary), with ancestral forms. (Note, for instance, Weismann's“prediction,”&c.24) Even if Archæopteryx and other intermediate forms cannot be regarded as connecting links in the strict sense,i.e., as being stages in the actual pedigree, yet the occurrence of reptilian and avian peculiarities side by side in one organism, goes far to prove the close relationship of the two classes.Fleischmann's book strengthens the impression gained elsewhere, that a general survey of the domain of life as a whole gives force and convincingness to the Theory of Descent, while a study of details often results in breaking the threads and bringing the difficulties into prominence. But the same holds true of many other theoretical constructions, and yet we do not seriously doubt their validity. (Take, for instance, the Kant-Laplace theory, and theories of ethnology, of the history of religion, of the history of language, and so on.) And it is quite commonly to be observed that those who have an expert and specialist knowledge, who are aware of the refractoriness of detailed facts, often take up a sceptical attitude towards every comprehensive[pg 118]theory, though the ultimate use of detailed investigation is to make the construction of general theories possible. Fleischmann does exactly what, say, an anthropologist would do if, under the impression of the constancy and distinctiveness of the human races, which would become stronger the more deeply he penetrated, he should resignedly renounce all possibility of affiliating them, and should rest content with the facts as he found them. Similarly, those who are most intimately acquainted with the races of domesticated animals often resist most strenuously all attempts, although these seem to others a matter of course, to derive our“tame”forms from“wild”species living in freedom.But to return. Even where the Theory of Descent is recognised, whether fully or only half-heartedly, the recognition does not always mean the same thing. Even the adherents of the general, but in itself quite vague view that a transformation from lower forms to higher, and from similar to different forms, has taken place, may present so many points of disagreement, and may even stand in such antagonism to one another, that onlookers are apt to receive the impression that they occupy quite different standpoints, and are no longer at one even in the fundamentals of their hypotheses.The most diverse questions and answers crop up; whether evolution has been brought about“monophyletically”or“polyphyletically,”i.e., through one or many genealogical trees; whether it has taken place in[pg 119]a continuous easy transition from one type to another, or by leaps and bounds; whether through a gradual transformation of all organs, each varying individually, or through correlated“kaleidoscopic”variations of many kinds throughout the whole system; whether it is essentially asymptotic, or whether organisms pass from“labile”phases of vital equilibrium by various halting-places to stable states, which are definitive, and are, so to speak, the blind alleys and terminal points of evolutionary possibilities,e.g., the extinct gigantic saurians, and perhaps also man. And to these problems must be added the various answers to the question, What precedes, or may have preceded, the earliest stages of life of which we know? Whence came the first cell? Whence the first living protoplasm? and How did the living arise from the inorganic? These deeper questions will occupy us in our chapter on the theory of life. Some of the former, in certain of their aspects, will be considered in the sixth chapter, which deals with factors in evolution.The Theory of Descent itself and the differences that obtain even among its adherents can best be studied by considering for a little the works of Reinke and of Hamann.Reinke, Professor of Botany in Kiel, has set forth his views in his book,“Die Welt als Tat,”25and more recently in his“Einleitung in die theoretische Biologie”(1901). Both books are addressed to a wide[pg 120]circle of readers. Reinke and Hamann both revive some of the arguments and opinions set forth in the early days of Darwinism by Wigand,26an author whose works are gradually gaining increased appreciation.It is Reinke's“unalterable conviction”that organisms have evolved, and that they have done so after the manner of fan-shaped genealogical trees. The Theory of Descent is to him an axiom of modern biology, though as a matter of fact the circumstantial evidence in favour of it is extremely fragmentary. The main arguments in favour of it appear to him to be the general ones; the homologies and analogies revealed by comparative morphology and physiology, the ascending series in the palæontological record, vestigial organs, parasitic degeneration, the origin of those vital associations which we call consortism and symbiosis. These he illustrates mainly by examples from his own special domain and personal observation.The simplest unicellular forms of life are to be thought of as at the beginning of evolution; and, since mechanical causes cannot explain their ascent, it must be assumed that they have an inherent“phylogenetic potential of development,”which, working epigenetically, results in ascending evolution. He leaves us to choose between monophyletic and polyphyletic evolution, but himself inclines towards the latter, associating with it a[pg 121]rehabilitation of Wigand's theory of the primitive cells. If, in the beginning, primitive forms of life arose (probably as unicellulars) from the not-living, it is not obvious why we need think of only one so arising, and, if many did so, why they should not have inherent differences which would at once result in typically different evolutionary series and groups of forms. But evolution does not go onad libitumorad infinitum, for the capacity for differentiation and transformation gradually diminishes. The organisation passes from a labile state of equilibrium to an increasingly stable state, and at many points it may reach a terminus where it comes to a standstill. Man, the dog, the horse, the cereals, and fruit trees appear to Reinke to have reached their goal. The preliminary stages he calls“Phylembryos,”because they bear to the possible outcome of their evolution the same relation that the embryo does to the perfect individual. Thus,Phenacodusmay be regarded as the Phylembryo of the modern horse. It is quite conceivable that each of our modern species may have had an independent series of Phylembryos reaching back to the primitive cells. But the palæontological record, and especially its synthetic types, lead Reinke rather to assume that instead of innumerable series, there have been branching genealogical trees, not one, however, but several.These views, together or separately, which are characterised chiefly by the catch-words“polyphyletic descent,”“labile and stable equilibrium,”and so on, crop[pg 122]up together or separately in the writings of various evolutionists belonging to the opposition wing. They are usually associated with a denial of the theory of natural selection, and with theories of“Orthogenesis,”“Heterogenesis,”and“Epigenesis.”We shall discuss them later when we are considering the factors in evolution. But we must first take notice of a work in which the theories opposed to Darwinian orthodoxy have been most decisively and aggressively set forth. As far back as 1892 O. Hamann, then a lecturer on zoology in Göttingen, gathered these together and brought them into the field, against Haeckel in particular, in his book“Entwicklungslehre und Darwinismus.”27Hamann's main theme is that Darwinism overlooks the fact that“there cannot have been an origin of higher types from types already finished.”For this“unfortunate and unsupported assumption”there are no proofs in embryology, palæontology, or anatomy. He adopts and expands the arguments and anti-Haeckelian deliverances of His in embryology, of Snell and Heer in palæontology, of Kölliker and von Baer in their special interpretation of evolution, of Snell particularly as regards the descent of man. It is impossible to derive Metazoa from Protozoa in their present finished state of evolution; even the Amoeba is so exactly adapted in organisation and functional activity[pg 123]to the conditions of its existence that it is a“finished”type. It is only by a stretch of fancy that fishes can be derived from worms, or higher vertebrates from fishes. One of his favourite arguments—and it is a weighty one, though neglected by the orthodox Darwinians—is that living substance is capable, under similar stimuli, of developing spontaneously and afresh, at quite different points and in different groups, similar organs, such as spots sensitive to light, accumulations of pigment, eye-spots, lenses, complete eyes, and similarly with the notochord, the excretory organs, and the like. Therefore homology of organs is no proof of their hereditary affiliation.28They rather illustrate“iterative evolution.”Another favourite argument is the fact of“Pædogenesis.”Certain animals, such asAmphioxus lanceolatus,Peripatus, and certain Medusæ, are very frequently brought forward as examples of persistent primitive stages and“transitional connecting links.”But considered from the point of view of Pædogenesis, they all assume quite a different aspect, and seem rather to represent very highly evolved species, and to be, not primitive forms, but conservative and regressive forms. Pædogenesis is the phenomenon exhibited by a number of species, which may stop short at one of the stages of their embryonic or larval development, become sexually mature, and produce[pg 124]offspring without having attained their own fully developed form.Another argument is the old, suggestive, and really important one urged by Kölliker, that“inorganic nature shows a natural system among minerals (crystals) just as much as animals and plants do, yet in the former there can be no question of any genetic connection in the production of forms.”Yet another argument is found in the occurrence of“inversions”and anomalies in the palæontological succession of forms, which to some extent upsets the Darwinian-Haeckelian genealogical trees. (Thus there are forms in the Cambrian whose alleged ancestors do not appear till the Silurian. Foraminifera and other Protozoa do not appear till the Silurian.)From embryology in particular, as elsewhere in general, we read the“fundamental biogenetic law,”that evolution is from the general to the special, from the imperfect to the more perfect, from what is still indefinite and exuberant to the well-defined and precise, but never from the special to the special. According to Hamann's hypothesis we must think of evolution as going on, so to speak, not about the top but about the bottom. The phyla or groups of forms are great trunks bearing many branches and twigs, but not giving rise to one another. Still less do the little side branches of one trunk bear the whole great trunk of another animal or plant phylum. But they all grow from the same roots among the primitive forms of life. Unicellulars these must[pg 125]have been, but not like our“Protists.”They should be thought of as primitive forms having within themselves the potentialities of the most diverse and widely separate evolution-series to which they gave rise, as it were, along diverging fan-like rays.It would be instructive to follow some naturalist into his own particular domain, for instance a palæontologist into the detailed facts of palæontology, or an embryologist into those of embryology, in order to learn whether these corroborate the assumptions of the Theory of Descent or not. It is just in relation to these detailed facts that criticisms or even denials of the theory have been most frequent. Koken, otherwise a convinced supporter of the theory, inquires in his“Vorwelt,”aproposof the tortoises, what has become of the genealogical trees that were scattered abroad in the world as proved facts in the early days of Darwinism. He asserts, in regard toArchæopteryx, the instance which is always put forward as the intermediate link in the evolution of birds, that it does not show in any of its characters a fundamental difference from any of the birds of to-day, and further, that, through convergent development under similar influences, similar organs and structural relations result, iterative arrangements which come about quite independently of descent. He maintains, too, that the principle of the struggle for existence is rather disproved than corroborated by the palæontological record.In embryology, so competent an authority as[pg 126]O. Hertwig—himself a former pupil of Haeckel's—has reacted from the“fundamental biogenetic law.”His theory of the matter is very much that of Hamann which we have already discussed; development is not so much a recapitulation of finished ancestral types as the laying down of foundations after the pattern of generalised simple forms, not yet specialised; and from these foundations the special organs rise to different levels and grades of differentiation according to the type.29But we must not lose ourselves in details.Looking back over the whole field once more, we feel that we are justified in maintaining with some confidence that the different pronouncements in regard to the detailed application and particular features of the Theory of Descent, and the different standpoints that are occupied even by evolutionists, are at least sufficient to make it obvious that, even if evolution and descent have actually taken place, they have not run so simple and smooth a course as the over-confident would have us believe; that the Theory of Descent rather emphasises than clears away the riddles and difficulties of the case, and that with the mere corroboration of the theory we shall have gained only something relatively external, a clue to creation, which does not so much solve its problems as restate them. The whole criticism of the“right wing,”from captious objections to actual denials, proves this indisputably. And it seems likely that in the course of time a sharpening of[pg 127]the critical insight and temper will give rise to further reactions from the academic theory as we have come to know it.30On the other hand, it may be assumed with even greater certainty that the general evolutionist point of view and the great arguments for descent in some form or other will ultimately be victorious if they are not so already, and that, sooner or later, we shall take the Theory of Descent in its most general form as a matter of course, just as we now do the Kant-Laplace theory.

Darwinism, which was originally a technical theory of the biological schools, has long since become a veritable tangle of the most diverse problems and opinions, and seems to press hardly upon the religious conception of the world from many different sides. In its theory of blind“natural selection”and the fortuitous play of the factors in the struggle for existence, it appears to surrender the whole of this wonderful world of life to the rough and ready grip of a process without method or plan. In the general theory of evolution and the doctrine of the descent of even the highest from the lowest, it seems to take away all special dignity from the human mind and spirit, all the freedom and all the nobility of pure reason and free will; it seems to reduce the higher products of religion, morality, poetry, and the æsthetic sense to the level of an ignoble tumult of animal impulses, desires and sensations. Purely speculative questions relative to the evolution theory, psychological and metaphysical, logical and epistemological, ethical, æsthetic, and finally even historical and politico-economical questions have been drawn into the[pg 086]coil, and usually receive from the Darwinians an answer at once robust and self-assured. A zoological theory seems suddenly to have thrown light and intelligibility into the most diverse provinces of knowledge.

But in point of fact it can be shown that Darwinism has not really done this and cannot do it. It leaves unaffected the problem of the mind with its peculiar and underivable laws, from the logical to the ethical. Whether it be right or wrong in its physiological theories, its genealogical trees and fortuitous factors, preoccupation with this theory is a task of the second order. Nevertheless it is necessary to study it, because the chief objections to the religious interpretation of the world have come from it.

The Development of Darwinism.In studying it we should like to follow a method somewhat different from that usually observed in apologetic writings.“Darwinism,”even in its technical, biological form, never was quite, and is to-day not at all a unified and consistent system. It has been modified in so many ways and presented in such different colours, that we must either refrain altogether from attempting to get into close quarters with it, or we must make ourselves acquainted to some extent with the phases of the theory as it has gradually developed up to the present day. This is the more necessary and useful since it is precisely within the circle of technical experts that revolts from and criticisms of the Darwinian theory[pg 087]have in recent years arisen; and these are so incisive, so varied, and so instructive, that through them we can adjust our standpoint in relation to the theory better than in any other way. And in thus letting the biologists speak for themselves, we are spared the fatal task of entering into the discussion of questions belonging to a region outside our own particular studies.We cannot, however, give more than a short sketch. But even such a sketch may do more towards giving us a general knowledge of the question and showing us a way out of the difficulties it raises than any of the current“refutations.”To supplement this sketch, and facilitate a thorough understanding of the problem, we shall give somewhat fuller references than are usual to the relevant literature. And the same method will be pursued in the following chapter, which deals with the mechanical theory of life. This method throws more upon the reader, but it is probably the most satisfactory one for the serious student.The reactions from the Darwinism of the schools which we have just referred to, and to which the second half of this chapter is devoted, are, of course, of a purely scientific kind. And while we are devoting our attention to them, we must not be unfaithful to the canon laid down in the previous chapter, namely that with reference to the question of teleology in the religious sense no real answer can be looked for from scientific study, not even if it be anti-Darwinian. In this case, too, it is impossible to read the convictions[pg 088]and intuitions of the religious conception of the world out of a scientific study of nature: they precede it. But here, too, we may find some accessory support and indirect corroboration more or less strong and secure. This may be illustrated by a single example. It will be shown that, on closer study, it is not impossible to subordinate even the apparently confused tangle of naturalistic factors of evolution which are summed up in the phrase“struggle for existence”to interpretation from the religious point of view. But matters will be in quite a different position if the whole theory collapses, and instead of evolution and its paths being given over to confusion and chance, it appears that from the very beginning and at every point there is a predetermination of fixed and inevitable lines along and up which it must advance. In many other connections considerations of a like nature will reveal themselves to us in the course of our study.Darwinism, as popularly understood, is the theory that“men are descended from monkeys,”and in general that the higher forms of life are descended from the lower, and it is regarded as Darwin's epoch-making work and his chief merit—or fault according to the point of view—that he established the Theory of Descent. This is only half correct, and it leaves out the real point of Darwinism altogether. The Theory of Descent had its way prepared by the evolutionist ideas and the speculative nature-philosophy of Goethe, Schelling, Hegel and Oken; by the suggestions and glimmerings of the[pg 089]nature-mysticism of the romanticists; by the results of comparative anatomy and physiology; was already hinted at, at least as far as derivation of species was concerned, in the works of Linné himself; was worked out in the“zoological philosophies,”by the elder Darwin, by Lamarck, Etienne Geoffrey St. Hilaire and Buffon; was in the field long before Charles Darwin's time; was already in active conflict with the antagonistic theory of the“constancy of species,”and had its more or less decided adherents. Yet undoubtedly it was through and after Darwin that the theory grew so much more powerful and gained general acceptance.

In studying it we should like to follow a method somewhat different from that usually observed in apologetic writings.“Darwinism,”even in its technical, biological form, never was quite, and is to-day not at all a unified and consistent system. It has been modified in so many ways and presented in such different colours, that we must either refrain altogether from attempting to get into close quarters with it, or we must make ourselves acquainted to some extent with the phases of the theory as it has gradually developed up to the present day. This is the more necessary and useful since it is precisely within the circle of technical experts that revolts from and criticisms of the Darwinian theory[pg 087]have in recent years arisen; and these are so incisive, so varied, and so instructive, that through them we can adjust our standpoint in relation to the theory better than in any other way. And in thus letting the biologists speak for themselves, we are spared the fatal task of entering into the discussion of questions belonging to a region outside our own particular studies.

We cannot, however, give more than a short sketch. But even such a sketch may do more towards giving us a general knowledge of the question and showing us a way out of the difficulties it raises than any of the current“refutations.”To supplement this sketch, and facilitate a thorough understanding of the problem, we shall give somewhat fuller references than are usual to the relevant literature. And the same method will be pursued in the following chapter, which deals with the mechanical theory of life. This method throws more upon the reader, but it is probably the most satisfactory one for the serious student.

The reactions from the Darwinism of the schools which we have just referred to, and to which the second half of this chapter is devoted, are, of course, of a purely scientific kind. And while we are devoting our attention to them, we must not be unfaithful to the canon laid down in the previous chapter, namely that with reference to the question of teleology in the religious sense no real answer can be looked for from scientific study, not even if it be anti-Darwinian. In this case, too, it is impossible to read the convictions[pg 088]and intuitions of the religious conception of the world out of a scientific study of nature: they precede it. But here, too, we may find some accessory support and indirect corroboration more or less strong and secure. This may be illustrated by a single example. It will be shown that, on closer study, it is not impossible to subordinate even the apparently confused tangle of naturalistic factors of evolution which are summed up in the phrase“struggle for existence”to interpretation from the religious point of view. But matters will be in quite a different position if the whole theory collapses, and instead of evolution and its paths being given over to confusion and chance, it appears that from the very beginning and at every point there is a predetermination of fixed and inevitable lines along and up which it must advance. In many other connections considerations of a like nature will reveal themselves to us in the course of our study.

Darwinism, as popularly understood, is the theory that“men are descended from monkeys,”and in general that the higher forms of life are descended from the lower, and it is regarded as Darwin's epoch-making work and his chief merit—or fault according to the point of view—that he established the Theory of Descent. This is only half correct, and it leaves out the real point of Darwinism altogether. The Theory of Descent had its way prepared by the evolutionist ideas and the speculative nature-philosophy of Goethe, Schelling, Hegel and Oken; by the suggestions and glimmerings of the[pg 089]nature-mysticism of the romanticists; by the results of comparative anatomy and physiology; was already hinted at, at least as far as derivation of species was concerned, in the works of Linné himself; was worked out in the“zoological philosophies,”by the elder Darwin, by Lamarck, Etienne Geoffrey St. Hilaire and Buffon; was in the field long before Charles Darwin's time; was already in active conflict with the antagonistic theory of the“constancy of species,”and had its more or less decided adherents. Yet undoubtedly it was through and after Darwin that the theory grew so much more powerful and gained general acceptance.

Darwinism and Teleology.But the essential and most characteristic importance of Darwin and his work, the reason for which he was called the Newton of biology, and which makes Darwinism at once interesting and dangerous to the religious conception of the world, is something quite special and new. It is its radical opposition to teleology. Du Bois-Reymond, in his witty lecture“Darwin versus Galiani,”4explains the gist of the matter.“Les dés de la nature sont pipés”(nature's dice are loaded). Nature is almost always throwing aces. She brings forth not what is meaningless and purposeless, but in great preponderance what is full of meaning and purpose. What“loaded”her dice like this? Even if the theory of descent be true, in what way does it directly[pg 090]help the purely scientific interpretation of the world? Would not this evolution from the lowest to the highest simply be a series of the most astonishing lucky throws of the dice by which in perplexing“endeavour after an aim,”the increasingly perfect, and ultimately the most perfect is produced? And, on the other hand, every individual organism, from the Amœba up to the most complex vertebrate, is, in its structure, its form, its functions, a stupendous marvel of adaptation to its end and of co-ordination of the parts to the whole, and of the whole and its parts to the functions of the organism, the functions of nutrition, self-maintenance, reproduction, maintenance of the species, and so on. How account for the adaptiveness, both general and special, withoutcausæ finales, without intention and purposes, without guidance towards a conscious aim? How can it be explained as the necessary result solely ofcausæ efficientes, of blindly working causes without a definite aim? Darwinism attempts to answer this question. And its answer is:“What appears to us‘purposeful’and‘perfect’is in truth only the manifold adaptation of the forms of life to the conditions of their existence. And this adaptation is brought about solely by means of these conditions themselves. Without choice, without aim, without conscious purpose nature offers a wealth of possibilities. The conditions of existence act as a sieve. What chances to correspond to them maintains itself, gliding through the meshes of the sieve, what does not perishes.”It is an old idea of the[pg 091]naturalistic philosophies, dating from Empedocles, which Darwin worked up into the theory of“natural selection”through“the survival of the fittest”“in the struggle for existence.”Of course the assumption necessary to his idea is that the forms of life are capable of variation, and of continually offering in ceaseless flux new properties and characters to the sieve of selection, and of being raised thereby from the originally homogeneous to the heterogeneous, from the simple to the complex, from the lower to the higher. This is the theory of descent, and it is, of course, an essential part and the very foundation of Darwin's theory. But it isthe doctrine of descent based upon natural selectionthat is Darwinism itself.

But the essential and most characteristic importance of Darwin and his work, the reason for which he was called the Newton of biology, and which makes Darwinism at once interesting and dangerous to the religious conception of the world, is something quite special and new. It is its radical opposition to teleology. Du Bois-Reymond, in his witty lecture“Darwin versus Galiani,”4explains the gist of the matter.“Les dés de la nature sont pipés”(nature's dice are loaded). Nature is almost always throwing aces. She brings forth not what is meaningless and purposeless, but in great preponderance what is full of meaning and purpose. What“loaded”her dice like this? Even if the theory of descent be true, in what way does it directly[pg 090]help the purely scientific interpretation of the world? Would not this evolution from the lowest to the highest simply be a series of the most astonishing lucky throws of the dice by which in perplexing“endeavour after an aim,”the increasingly perfect, and ultimately the most perfect is produced? And, on the other hand, every individual organism, from the Amœba up to the most complex vertebrate, is, in its structure, its form, its functions, a stupendous marvel of adaptation to its end and of co-ordination of the parts to the whole, and of the whole and its parts to the functions of the organism, the functions of nutrition, self-maintenance, reproduction, maintenance of the species, and so on. How account for the adaptiveness, both general and special, withoutcausæ finales, without intention and purposes, without guidance towards a conscious aim? How can it be explained as the necessary result solely ofcausæ efficientes, of blindly working causes without a definite aim? Darwinism attempts to answer this question. And its answer is:“What appears to us‘purposeful’and‘perfect’is in truth only the manifold adaptation of the forms of life to the conditions of their existence. And this adaptation is brought about solely by means of these conditions themselves. Without choice, without aim, without conscious purpose nature offers a wealth of possibilities. The conditions of existence act as a sieve. What chances to correspond to them maintains itself, gliding through the meshes of the sieve, what does not perishes.”It is an old idea of the[pg 091]naturalistic philosophies, dating from Empedocles, which Darwin worked up into the theory of“natural selection”through“the survival of the fittest”“in the struggle for existence.”Of course the assumption necessary to his idea is that the forms of life are capable of variation, and of continually offering in ceaseless flux new properties and characters to the sieve of selection, and of being raised thereby from the originally homogeneous to the heterogeneous, from the simple to the complex, from the lower to the higher. This is the theory of descent, and it is, of course, an essential part and the very foundation of Darwin's theory. But it isthe doctrine of descent based upon natural selectionthat is Darwinism itself.

The Characteristic Features of Darwinism.We do not propose to expound the Darwinian theory for the hundredth time; a knowledge of it must be taken for granted. We need only briefly call to mind the characteristic features and catchwords of the theory as Darwin founded it, which have also been the starting points of subsequent modifications and controversies.All living creatures are bound together in genetic solidarity. Everything has evolved through endless deviations, gradations, and differentiations, but at the same time by a perfectly continuous process. Variation continually produced a crop of heterogeneous novelties. The struggle for existence sifted these out. Heredity[pg 092]fixed and established them. Without method or plan variations continue to occur (indefinite variations). They manifest themselves in all manner of minute changes (“fluctuating”variations). Every part, every function of an organism may be subject individually to variation and selection. The world is strictly governed by what is useful. The whole organisation as well as the individual organs and functions bear the stamp of utility, at least, they must bear it if the theory is correct. In the general continuity the transitions are always easy; there are no fundamentally distinct“types,”architectural plans, or groups of forms. Where gaps yawn the intermediate links have gone amissing. There is no fundamental difference betweengenus,species, andvariety. Even the most complicated organ such as the eye, the most puzzling function such as the instinct of the bee, may be explained as the outcome of many more primitive stages.The chief evidences of the theory of descent are to be found in homologies, in the correspondences of organs and functions, as revealed by comparative anatomy and physiology, in the recapitulation revealed by embryology, in the structure of parasites, in rudimentary organs and reversions to earlier stages, in the distribution of animals and plants, and in the possibility of still transforming, at least to a slight extent, one species into another, by experimental breeding.Transformation and differentiation go on in nature as a vast, ceaseless, but blind process of selection. In[pg 093]artificial selection evolution is secured by choosing the most fit for breeding purposes; so it is secured in natural selection by the favouring and survival of those forms which are the most fit among the many unfit or less fit, which happened to be exposed to the struggle for existence, that is, to the competition for the means of subsistence, to the struggle with enemies, to hostile environment, and to dangers of every kind. The adaptation thus brought about is of a purely“passive”kind. The variations arise fortuitously out of the organism, and present themselves for selection in the struggle for existence; they are not actively acquired by means of the struggle. The secondary factors of evolution recognised are: correlation in the growth and in the development of parts, the origin of new characters through use, their disappearance through disuse (Lamarck), the transmission of characters thus acquired, the influence of environment and sexual selection.5The Darwinian theory, the interpretation of the teleological in the animate world by means of the theory of descent based upon natural selection, entered like a ferment into the scientific thought-movement, and in a space of forty years it has itself passed through a series of stages, differentiations, and transformations which have in part resulted in the present state of the theory, and have in part anticipated it. These are represented[pg 094]by the names of workers belonging to a generation which has for the most part already passed away: Darwin's collaborateurs, such as Alfred Russel Wallace, who independently and simultaneously expounded the theory of natural selection, Haeckel and Fritz Müller, Nägeli and Askenasy, von Kölliker, Mivart, Romanes and others. The differentiation and elaboration of Darwin's theories has gone ever farther and farther; the grades and shades of doctrine held by his disciples are now almost beyond reckoning.

We do not propose to expound the Darwinian theory for the hundredth time; a knowledge of it must be taken for granted. We need only briefly call to mind the characteristic features and catchwords of the theory as Darwin founded it, which have also been the starting points of subsequent modifications and controversies.

All living creatures are bound together in genetic solidarity. Everything has evolved through endless deviations, gradations, and differentiations, but at the same time by a perfectly continuous process. Variation continually produced a crop of heterogeneous novelties. The struggle for existence sifted these out. Heredity[pg 092]fixed and established them. Without method or plan variations continue to occur (indefinite variations). They manifest themselves in all manner of minute changes (“fluctuating”variations). Every part, every function of an organism may be subject individually to variation and selection. The world is strictly governed by what is useful. The whole organisation as well as the individual organs and functions bear the stamp of utility, at least, they must bear it if the theory is correct. In the general continuity the transitions are always easy; there are no fundamentally distinct“types,”architectural plans, or groups of forms. Where gaps yawn the intermediate links have gone amissing. There is no fundamental difference betweengenus,species, andvariety. Even the most complicated organ such as the eye, the most puzzling function such as the instinct of the bee, may be explained as the outcome of many more primitive stages.

The chief evidences of the theory of descent are to be found in homologies, in the correspondences of organs and functions, as revealed by comparative anatomy and physiology, in the recapitulation revealed by embryology, in the structure of parasites, in rudimentary organs and reversions to earlier stages, in the distribution of animals and plants, and in the possibility of still transforming, at least to a slight extent, one species into another, by experimental breeding.

Transformation and differentiation go on in nature as a vast, ceaseless, but blind process of selection. In[pg 093]artificial selection evolution is secured by choosing the most fit for breeding purposes; so it is secured in natural selection by the favouring and survival of those forms which are the most fit among the many unfit or less fit, which happened to be exposed to the struggle for existence, that is, to the competition for the means of subsistence, to the struggle with enemies, to hostile environment, and to dangers of every kind. The adaptation thus brought about is of a purely“passive”kind. The variations arise fortuitously out of the organism, and present themselves for selection in the struggle for existence; they are not actively acquired by means of the struggle. The secondary factors of evolution recognised are: correlation in the growth and in the development of parts, the origin of new characters through use, their disappearance through disuse (Lamarck), the transmission of characters thus acquired, the influence of environment and sexual selection.5

The Darwinian theory, the interpretation of the teleological in the animate world by means of the theory of descent based upon natural selection, entered like a ferment into the scientific thought-movement, and in a space of forty years it has itself passed through a series of stages, differentiations, and transformations which have in part resulted in the present state of the theory, and have in part anticipated it. These are represented[pg 094]by the names of workers belonging to a generation which has for the most part already passed away: Darwin's collaborateurs, such as Alfred Russel Wallace, who independently and simultaneously expounded the theory of natural selection, Haeckel and Fritz Müller, Nägeli and Askenasy, von Kölliker, Mivart, Romanes and others. The differentiation and elaboration of Darwin's theories has gone ever farther and farther; the grades and shades of doctrine held by his disciples are now almost beyond reckoning.

Various Forms of Darwinism.The great majority of these express what may be called popular Darwinism [“Darwinismus vulgaris”], theoretically worthless, but practically possessed of great powers of attraction and propagandism. It expresses in the main a conviction, usually left unexplained, that everything“happens naturally,”that man is really descended from monkeys, and that life has“evolved from lower stages”of itself, that dualism is wrong, and that monism is the truth. It is exactly the standpoint of the popular naturalism we have already described, which here mingles unsuspectingly and without scruple Lamarckian and other principles with the Darwinian, which is enthusiastic on the one hand over the“purely mechanical”interpretation of nature, and on the other drags in directly psychical motives, unconscious consciousness, impulses, spontaneous self-differentiation of organisms, which nevertheless adheres to“monism”[pg 095]and possibly even professes to share Goethe's conception of nature!Above this stratum we come to that of the real experts, the only one which concerns us in the least. Here too we find an ever-growing distance between divergent views, the most manifold differences amounting sometimes to mutual exclusion. These differences occur even with reference to the fundamental doctrine generally adhered to, the doctrine of descent. To one party it is a proved fact, to another a probable, scientific working hypothesis, to a third a“rescuing plank.”One party is always finding fresh corroborations, another new difficulties. And within the same group we find the contrasts of believers in monophyletic and believers in polyphyletic evolution, the mechanists and the half-confessed or thoroughgoing vitalists, the preformationists and the believers in epigenesis. Opinions differ even more widely in regard to therôleof the“struggle for existence”in the production of species. On the one hand we have the Darwinism of Darwin freed from inconsequent additions and formulated as orthodox“neo-Darwinism”; on the other hand we have heterodox Lamarckism. The“all-sufficiency”of natural selection is proclaimed by some, its impotence by others. Indefinite variation is opposed by orthogenesis, fluctuating variation by saltatory mutation (Halmatogenesis in“Greek”), passive adaptation by the spontaneous activity and self-regulation of the living organism. The struggle for existence is variously regarded as the[pg 096]chief factor, or as a co-operating factor, or as an indifferent, or even an inimical factor in the origination of new species.And among the representatives of these different standpoints there are most interesting personal differences: in some, like Weismann, we find a great loyalty to, and persistence in the position once arrived at, in others the most surprising transitions and changes of opinion. Thus Fleischmann, a pupil of Selenka's, after illustrating during many years of personal research the orthodox Darwinian standpoint, finally developed into an outspoken opponent not only of the theory of selection but of the doctrine of descent. So also Friedmann.6Driesch started from the mechanical theory of life and advanced through the connected series of his own biological essays to vitalism. Romanes, a prominent disciple of Darwin, ended in Christian theism, and Wallace, the discoverer of“the struggle for existence,”landed in spiritualism.Nothing like an exhaustive view of the present state of Darwinism and its many champions can here be attempted. But it will be necessary to get to know what we may call its possibilities by a study of typical and leading examples. In the course of our study many of the problems to which the theory gives rise will reveal themselves, and their orientation will be possible.This task falls naturally into two subdivisions: (1) the[pg 097]present state of the theory of Evolution and Descent, and how far the religious conception of the world is or is not affected by it; (2) the truth as to the originative and directive factors of Evolution, especially as to“natural selection in the struggle for existence,”whether they are tenable and sufficient, and what attitude religion must take towards them. These two problems must be kept distinct throughout, and must be discussed in order. For the validity of what is characteristicallyDarwinismis in no way decided by proving descent and evolution, although it appears so in most popular expositions.7

The great majority of these express what may be called popular Darwinism [“Darwinismus vulgaris”], theoretically worthless, but practically possessed of great powers of attraction and propagandism. It expresses in the main a conviction, usually left unexplained, that everything“happens naturally,”that man is really descended from monkeys, and that life has“evolved from lower stages”of itself, that dualism is wrong, and that monism is the truth. It is exactly the standpoint of the popular naturalism we have already described, which here mingles unsuspectingly and without scruple Lamarckian and other principles with the Darwinian, which is enthusiastic on the one hand over the“purely mechanical”interpretation of nature, and on the other drags in directly psychical motives, unconscious consciousness, impulses, spontaneous self-differentiation of organisms, which nevertheless adheres to“monism”[pg 095]and possibly even professes to share Goethe's conception of nature!

Above this stratum we come to that of the real experts, the only one which concerns us in the least. Here too we find an ever-growing distance between divergent views, the most manifold differences amounting sometimes to mutual exclusion. These differences occur even with reference to the fundamental doctrine generally adhered to, the doctrine of descent. To one party it is a proved fact, to another a probable, scientific working hypothesis, to a third a“rescuing plank.”One party is always finding fresh corroborations, another new difficulties. And within the same group we find the contrasts of believers in monophyletic and believers in polyphyletic evolution, the mechanists and the half-confessed or thoroughgoing vitalists, the preformationists and the believers in epigenesis. Opinions differ even more widely in regard to therôleof the“struggle for existence”in the production of species. On the one hand we have the Darwinism of Darwin freed from inconsequent additions and formulated as orthodox“neo-Darwinism”; on the other hand we have heterodox Lamarckism. The“all-sufficiency”of natural selection is proclaimed by some, its impotence by others. Indefinite variation is opposed by orthogenesis, fluctuating variation by saltatory mutation (Halmatogenesis in“Greek”), passive adaptation by the spontaneous activity and self-regulation of the living organism. The struggle for existence is variously regarded as the[pg 096]chief factor, or as a co-operating factor, or as an indifferent, or even an inimical factor in the origination of new species.

And among the representatives of these different standpoints there are most interesting personal differences: in some, like Weismann, we find a great loyalty to, and persistence in the position once arrived at, in others the most surprising transitions and changes of opinion. Thus Fleischmann, a pupil of Selenka's, after illustrating during many years of personal research the orthodox Darwinian standpoint, finally developed into an outspoken opponent not only of the theory of selection but of the doctrine of descent. So also Friedmann.6Driesch started from the mechanical theory of life and advanced through the connected series of his own biological essays to vitalism. Romanes, a prominent disciple of Darwin, ended in Christian theism, and Wallace, the discoverer of“the struggle for existence,”landed in spiritualism.

Nothing like an exhaustive view of the present state of Darwinism and its many champions can here be attempted. But it will be necessary to get to know what we may call its possibilities by a study of typical and leading examples. In the course of our study many of the problems to which the theory gives rise will reveal themselves, and their orientation will be possible.

This task falls naturally into two subdivisions: (1) the[pg 097]present state of the theory of Evolution and Descent, and how far the religious conception of the world is or is not affected by it; (2) the truth as to the originative and directive factors of Evolution, especially as to“natural selection in the struggle for existence,”whether they are tenable and sufficient, and what attitude religion must take towards them. These two problems must be kept distinct throughout, and must be discussed in order. For the validity of what is characteristicallyDarwinismis in no way decided by proving descent and evolution, although it appears so in most popular expositions.7

The Theory of Descent.Again and again we hear and read, even in scientific circles and journals, that Darwinism breaks down at many points, that it is insufficient, and even that it has quite collapsed. Even the assurances of its most convinced champions are rather forced, and are somewhat suggestive of bills payable in the future.8But here again it is obvious that we must distinguish clearly between the Theory of Descent and Darwinism. Of the Theory of Descent it is by no means true that it has“broken down.”With a slight exaggeration, but on the whole with justice, Weismann has asserted that the[pg 098]Theory of Descent is to-day a“generally accepted truth.”Even Weismann's most pronounced opponents, such as Eimer, Wolff, Reinke, and others, are at one with him in this, that there has been evolution in some form; that there has been a progressive transformation of species; that there is real (not merely ideal) relationship or affiliation connecting our modern forms of life, up to and including man, with the lower and lowest forms of bygone æons.The evidences are the same as those adduced by Darwin and before his time, but they have been multiplied and more sharply defined:—namely, that the forms of life can be arranged in an ascending scale of evolution, both in their morphological and their physiological aspects, both as regards the general type and the differentiation of individual organs and particular characters, bodily and mental. All the rubrics used by Darwin in this connection, from comparative anatomy, from the palæontological record itself, and so on, have been filled out with ever-increasing detail. Palæontology, in particular, is continually furnishing new illustrations of descent and new evidence of its probability, more telling perhaps in respect of general features and particular groups than in regard to the historical process in detail. For certain species and genera palæontology discloses the primitive forms, discovers“synthetic types”which were the starting-point for diverging branches of evolution, bridges over or narrows the yawning gulfs in evolution by the discovery of[pg 099]“intermediate forms”; and, in the case of certain species, furnishes complete genealogical trees. The same holds true of the facts of comparative anatomy, embryology, and so on. In all detailed investigations into an animal type, in the study of the structure, functions, or the instincts of an ant, or of a whale or of a tape-worm, the standpoint of the theory of descent is assumed, and it proves a useful clue for further investigation.In regard to man—so we are assured—the theory finds confirmation through the discovery of the Neanderthal, Spy, Schipka, La Naulette skulls and bones—the remains of a prehistoric human race, with“pithecoid”(ape-like) characters. And the theory reaches its climax in Dubois' discovery of the remains of“Pithecanthropus,”the upright ape-man, in Java, 1891-92, the long sought-for Missing Link between animals and man;9and in the still more recent proofs of“affinity of blood”between man and ape, furnished by experiments in transfusion. Friedenthal has revived the older experiments of transfusing the blood of one animal into another, the blood of an animal of one species into that of another, of related species into related species, more remote into more remote, and finally even from animals into man. The further apart the two species are, the more different are the physiological[pg 100]characters of the blood, and the more difficult does a mingling of the two become. Blood of a too distantly related form does not unite with that of the animal into which it is transfused, but the red corpuscles of the former are destroyed by the serum of the latter, break up and are eliminated. In nearly related species or races, however, the two kinds of blood unite, as in the case of horse and ass, or of hare and rabbit. Human blood serum behaves in a hostile fashion to the blood of eel, pigeon, horse, dog, cat, and even to that of Lemuroids, or that of the more remotely related“non-anthropoid”monkey; human blood transfused from a negro into a white unites readily, as does also that of orang-utan transfused into a gibbon. But human blood also unites without any breaking-up or disturbance with the blood of a chimpanzee; from which the inference is that man is not to be placed in a separate sub-order beside the other sub-orders of the Primates, the platyrrhine and catarrhine monkeys, not even in a distinct sub order beside the catarrhines; but is to be included with them in one zoological sub-order. This classification was previously suggested by Selenka on other grounds, namely, because of the points in common in the embryonic development of the catarrhine monkeys and of man, and their common distinctiveness as contrasted with the platyrrhines.10

Again and again we hear and read, even in scientific circles and journals, that Darwinism breaks down at many points, that it is insufficient, and even that it has quite collapsed. Even the assurances of its most convinced champions are rather forced, and are somewhat suggestive of bills payable in the future.8But here again it is obvious that we must distinguish clearly between the Theory of Descent and Darwinism. Of the Theory of Descent it is by no means true that it has“broken down.”With a slight exaggeration, but on the whole with justice, Weismann has asserted that the[pg 098]Theory of Descent is to-day a“generally accepted truth.”Even Weismann's most pronounced opponents, such as Eimer, Wolff, Reinke, and others, are at one with him in this, that there has been evolution in some form; that there has been a progressive transformation of species; that there is real (not merely ideal) relationship or affiliation connecting our modern forms of life, up to and including man, with the lower and lowest forms of bygone æons.

The evidences are the same as those adduced by Darwin and before his time, but they have been multiplied and more sharply defined:—namely, that the forms of life can be arranged in an ascending scale of evolution, both in their morphological and their physiological aspects, both as regards the general type and the differentiation of individual organs and particular characters, bodily and mental. All the rubrics used by Darwin in this connection, from comparative anatomy, from the palæontological record itself, and so on, have been filled out with ever-increasing detail. Palæontology, in particular, is continually furnishing new illustrations of descent and new evidence of its probability, more telling perhaps in respect of general features and particular groups than in regard to the historical process in detail. For certain species and genera palæontology discloses the primitive forms, discovers“synthetic types”which were the starting-point for diverging branches of evolution, bridges over or narrows the yawning gulfs in evolution by the discovery of[pg 099]“intermediate forms”; and, in the case of certain species, furnishes complete genealogical trees. The same holds true of the facts of comparative anatomy, embryology, and so on. In all detailed investigations into an animal type, in the study of the structure, functions, or the instincts of an ant, or of a whale or of a tape-worm, the standpoint of the theory of descent is assumed, and it proves a useful clue for further investigation.

In regard to man—so we are assured—the theory finds confirmation through the discovery of the Neanderthal, Spy, Schipka, La Naulette skulls and bones—the remains of a prehistoric human race, with“pithecoid”(ape-like) characters. And the theory reaches its climax in Dubois' discovery of the remains of“Pithecanthropus,”the upright ape-man, in Java, 1891-92, the long sought-for Missing Link between animals and man;9and in the still more recent proofs of“affinity of blood”between man and ape, furnished by experiments in transfusion. Friedenthal has revived the older experiments of transfusing the blood of one animal into another, the blood of an animal of one species into that of another, of related species into related species, more remote into more remote, and finally even from animals into man. The further apart the two species are, the more different are the physiological[pg 100]characters of the blood, and the more difficult does a mingling of the two become. Blood of a too distantly related form does not unite with that of the animal into which it is transfused, but the red corpuscles of the former are destroyed by the serum of the latter, break up and are eliminated. In nearly related species or races, however, the two kinds of blood unite, as in the case of horse and ass, or of hare and rabbit. Human blood serum behaves in a hostile fashion to the blood of eel, pigeon, horse, dog, cat, and even to that of Lemuroids, or that of the more remotely related“non-anthropoid”monkey; human blood transfused from a negro into a white unites readily, as does also that of orang-utan transfused into a gibbon. But human blood also unites without any breaking-up or disturbance with the blood of a chimpanzee; from which the inference is that man is not to be placed in a separate sub-order beside the other sub-orders of the Primates, the platyrrhine and catarrhine monkeys, not even in a distinct sub order beside the catarrhines; but is to be included with them in one zoological sub-order. This classification was previously suggested by Selenka on other grounds, namely, because of the points in common in the embryonic development of the catarrhine monkeys and of man, and their common distinctiveness as contrasted with the platyrrhines.10

Haeckel's Evolutionist Position.The average type of the Theory of Descent of the older or orthodox school, which still lingers in the background with its Darwinism unshaken, is that set forth by Haeckel, scientifically in his“Generelle Morphologie der Organismen”(1866), and“Systematische Phylogenie”(1896), and popularly in his“Natural History of Creation”and“Riddles of the Universe,”with their many editions. We may assume that it is well known, and need only briefly recall its chief characteristics. The“inestimable value,”the“incomparable significance,”the“immeasurable importance”of the Theory of Descent lies, according to Haeckel, in the fact that by means of it we can explain the origin of the forms of life“in a mechanical manner.”The theory, especially in regard to the descent of man from the apes, is to him not a working hypothesis or tentative mode of representation; it is a result comparable to Newton's law of gravitation or the Kant-Laplace cosmogony. It is“a certain historical fact.”The proofs of it are those already mentioned.What is especially Haeckelian is the“fundamental biogenetic law,”“ontogeny resembles phylogeny,”that is to say, in development, especially in embryonic development, the individual recapitulates the history of the race. Through“palingenesis,”man, for instance, recapitulates his ancestral stages (protist, gastræad, vermine, piscine, and simian). This recapitulation is condensed,[pg 102]disarranged, or obscured in detail by“cenogenesis”or“cænogenesis.”The groups and types of organisms exhibit the closest genetic solidarity. The genealogical tree of man in particular runs directly through a whole series. From the realm of the protists it leads to that of the gastræadæ (nowadays represented by the Cœlentera), thence into the domain of the worms, touches the hypothetical“primitive chordates”(for the necessary existence of which“certain proofs”can be given), the class of tunicates, ascends through the fishes, amphibians and reptiles to forms parallel to the modern monotremes, then directly through the marsupials to the placentals, through lemuroids and baboons to the anthropoid apes, from them to the“famous Pithecanthropus”discovered in Java, out of whichhomo sapiensarose. (The easy transition from one group of forms to another is to be noted. For it is against this point that most of the opposition has been directed, whether from“grumbling”critics, or thoroughgoing opponents of the Theory of Descent.)Haeckel's facile method of constructing genealogical trees, which ignores difficulties and discrepant facts, has met with much criticism and ridicule even among Darwinians. The“orator of Berlin,”Du Bois-Reymond, declared that if he must read romances he would prefer to read them in some other form than that of genealogical trees. But they have at least the merit that they give a vivid impression of what is most plausible and attractive in the idea of descent, and moreover[pg 103]they have helped towards orientation in the discussion. Nor can we ignore the very marked taxonomic and architectonic talent which their construction displays.

The average type of the Theory of Descent of the older or orthodox school, which still lingers in the background with its Darwinism unshaken, is that set forth by Haeckel, scientifically in his“Generelle Morphologie der Organismen”(1866), and“Systematische Phylogenie”(1896), and popularly in his“Natural History of Creation”and“Riddles of the Universe,”with their many editions. We may assume that it is well known, and need only briefly recall its chief characteristics. The“inestimable value,”the“incomparable significance,”the“immeasurable importance”of the Theory of Descent lies, according to Haeckel, in the fact that by means of it we can explain the origin of the forms of life“in a mechanical manner.”The theory, especially in regard to the descent of man from the apes, is to him not a working hypothesis or tentative mode of representation; it is a result comparable to Newton's law of gravitation or the Kant-Laplace cosmogony. It is“a certain historical fact.”The proofs of it are those already mentioned.

What is especially Haeckelian is the“fundamental biogenetic law,”“ontogeny resembles phylogeny,”that is to say, in development, especially in embryonic development, the individual recapitulates the history of the race. Through“palingenesis,”man, for instance, recapitulates his ancestral stages (protist, gastræad, vermine, piscine, and simian). This recapitulation is condensed,[pg 102]disarranged, or obscured in detail by“cenogenesis”or“cænogenesis.”The groups and types of organisms exhibit the closest genetic solidarity. The genealogical tree of man in particular runs directly through a whole series. From the realm of the protists it leads to that of the gastræadæ (nowadays represented by the Cœlentera), thence into the domain of the worms, touches the hypothetical“primitive chordates”(for the necessary existence of which“certain proofs”can be given), the class of tunicates, ascends through the fishes, amphibians and reptiles to forms parallel to the modern monotremes, then directly through the marsupials to the placentals, through lemuroids and baboons to the anthropoid apes, from them to the“famous Pithecanthropus”discovered in Java, out of whichhomo sapiensarose. (The easy transition from one group of forms to another is to be noted. For it is against this point that most of the opposition has been directed, whether from“grumbling”critics, or thoroughgoing opponents of the Theory of Descent.)

Haeckel's facile method of constructing genealogical trees, which ignores difficulties and discrepant facts, has met with much criticism and ridicule even among Darwinians. The“orator of Berlin,”Du Bois-Reymond, declared that if he must read romances he would prefer to read them in some other form than that of genealogical trees. But they have at least the merit that they give a vivid impression of what is most plausible and attractive in the idea of descent, and moreover[pg 103]they have helped towards orientation in the discussion. Nor can we ignore the very marked taxonomic and architectonic talent which their construction displays.

Weismann's Evolutionist Position.The most characteristic representative, however, of the modern school of unified and purified Darwinism is not Haeckel, but the Freiburg zoologist, Weismann. Through a long series of writings he has carried on the conflict against heterodox, and especially Lamarckian theories of evolution, and has developed his theories of heredity and the causes of variation, of the non-transmissibility of acquired characters, and the all-sufficiency of natural selection. In his latest great work, in two volumes,“Lectures on the Theory of Descent,”11he has definitely summed up and systematised his views. These will interest us when we come to inquire into the problem of the factors operative in evolution. For the moment we are only concerned with his attitude to the Theory of Descent as such. It is precisely the same as Haeckel's, although he is opposed to Haeckel in regard to the strictly Darwinian standpoint. The Theory of Descent has conquered, and it may be said with assurance, for ever. That is the firm conviction on which the whole work is based, and it is really rather treated as a self-evident axiom than as a statement to be proved. Weismann takes little trouble to[pg 104]prove it. All the well-known, usually very clear proofs from palæontology, comparative anatomy, &c., which we are accustomed to meet with in evolutionist books are wanting here, the genealogical trees of the Equidæ, with the gradually diminishing number of toes and the varying teeth, ofPlanorbis multiformis, of the ammonites, the graduated series of stages exhibited by individual organs, for instance, from the ganglion merely sensitive to light up to the intricate eye, or from the rayed skeleton of the paired fins in fishes up to the five-fingered hands and feet of the higher vertebrates, &c. These are only briefly touched upon in the terse“Introduction,”and the whole of the comprehensive work is then directed to showing what factors can have been operative, and to proving that they must have been“Darwinian”(selection in the struggle for existence), and not Lamarckian or any other. This is shown in regard to the coloration of animals, the phenomena of mimicry, the protective arrangements of plants, the development of instinct in animals, and the origin of flowers.In reality Weismann only adducesonestrict proof, and even that is only laying special stress on what is well known in comparative embryology; namely, the possibility of“predicting”on the basis of the theory of descent, as Leverrier“predicted”Neptune. For instance, in the lower vertebrates from amphibians upwards there is anos centralein the skeleton of wrist, but there is none in man. Now if man be descended[pg 105]from lower vertebrates, and if the fundamental biogenetic law be true (that every form of life recapitulates in its own development, especially in its embryonic development, the evolution of its race, though with abbreviations and condensations), it may be predicted that theos centraleis to be found in the early embryonic stages of man. And Rosenberg found it. In the same way the“gill-clefts”of the fish-like ancestors have long since been discovered in the embryo of the higher vertebrates and of man. Weismann himself“predicted”that the markings of the youngest stage of the caterpillars of the Sphingidæ (hawk-moths) would be found to be not oblique but longitudinal stripes, and ten years later a fortunate observation verified the prediction. Because of the abundance of evidential facts Weismann does not go into any detailed proof of evolution.“One can hardly take up any work, large or small, on the finer or more general structural relations, or on the development of any animal, without finding in it proofs for the evolution theory.”But assured as the doctrine of descent appears,12and certain as it is that it has not only maintained its hold since Darwin's day, but has strengthened it and has gained adherents, this foundation of Darwinism is[pg 106]nevertheless not the unanimous and inevitable conclusion of all scientific men in the sense and to the extent that the utterances of Weismann and others would lead us to suppose. Apart from all apologetic attempts either in religious, ethical, or æsthetic interests, apart, too, from the superior standpoint of the philosophers, who have not, so to speak, taken the theory very seriously, but regard it as a provisional theory, as a more or less necessary and useful method of grouping our ideas in regard to the organic world, there are even among the biologists themselves some who, indifferent towards religious or philosophical or naturalistic dogma, hold strictly to fact, and renounce with nonchalance any pretensions at completeness of knowledge if the data do not admit of it, and on these grounds hold themselves aloof from evolutionist generalisation. From among these come the counsels of“caution,”admissions that the theory is a scientific hypothesis and a guide to research, but not knowledge, and confessions that the Theory of Descent as a whole is verifiable rather as a general impression than in detail.

The most characteristic representative, however, of the modern school of unified and purified Darwinism is not Haeckel, but the Freiburg zoologist, Weismann. Through a long series of writings he has carried on the conflict against heterodox, and especially Lamarckian theories of evolution, and has developed his theories of heredity and the causes of variation, of the non-transmissibility of acquired characters, and the all-sufficiency of natural selection. In his latest great work, in two volumes,“Lectures on the Theory of Descent,”11he has definitely summed up and systematised his views. These will interest us when we come to inquire into the problem of the factors operative in evolution. For the moment we are only concerned with his attitude to the Theory of Descent as such. It is precisely the same as Haeckel's, although he is opposed to Haeckel in regard to the strictly Darwinian standpoint. The Theory of Descent has conquered, and it may be said with assurance, for ever. That is the firm conviction on which the whole work is based, and it is really rather treated as a self-evident axiom than as a statement to be proved. Weismann takes little trouble to[pg 104]prove it. All the well-known, usually very clear proofs from palæontology, comparative anatomy, &c., which we are accustomed to meet with in evolutionist books are wanting here, the genealogical trees of the Equidæ, with the gradually diminishing number of toes and the varying teeth, ofPlanorbis multiformis, of the ammonites, the graduated series of stages exhibited by individual organs, for instance, from the ganglion merely sensitive to light up to the intricate eye, or from the rayed skeleton of the paired fins in fishes up to the five-fingered hands and feet of the higher vertebrates, &c. These are only briefly touched upon in the terse“Introduction,”and the whole of the comprehensive work is then directed to showing what factors can have been operative, and to proving that they must have been“Darwinian”(selection in the struggle for existence), and not Lamarckian or any other. This is shown in regard to the coloration of animals, the phenomena of mimicry, the protective arrangements of plants, the development of instinct in animals, and the origin of flowers.

In reality Weismann only adducesonestrict proof, and even that is only laying special stress on what is well known in comparative embryology; namely, the possibility of“predicting”on the basis of the theory of descent, as Leverrier“predicted”Neptune. For instance, in the lower vertebrates from amphibians upwards there is anos centralein the skeleton of wrist, but there is none in man. Now if man be descended[pg 105]from lower vertebrates, and if the fundamental biogenetic law be true (that every form of life recapitulates in its own development, especially in its embryonic development, the evolution of its race, though with abbreviations and condensations), it may be predicted that theos centraleis to be found in the early embryonic stages of man. And Rosenberg found it. In the same way the“gill-clefts”of the fish-like ancestors have long since been discovered in the embryo of the higher vertebrates and of man. Weismann himself“predicted”that the markings of the youngest stage of the caterpillars of the Sphingidæ (hawk-moths) would be found to be not oblique but longitudinal stripes, and ten years later a fortunate observation verified the prediction. Because of the abundance of evidential facts Weismann does not go into any detailed proof of evolution.“One can hardly take up any work, large or small, on the finer or more general structural relations, or on the development of any animal, without finding in it proofs for the evolution theory.”

But assured as the doctrine of descent appears,12and certain as it is that it has not only maintained its hold since Darwin's day, but has strengthened it and has gained adherents, this foundation of Darwinism is[pg 106]nevertheless not the unanimous and inevitable conclusion of all scientific men in the sense and to the extent that the utterances of Weismann and others would lead us to suppose. Apart from all apologetic attempts either in religious, ethical, or æsthetic interests, apart, too, from the superior standpoint of the philosophers, who have not, so to speak, taken the theory very seriously, but regard it as a provisional theory, as a more or less necessary and useful method of grouping our ideas in regard to the organic world, there are even among the biologists themselves some who, indifferent towards religious or philosophical or naturalistic dogma, hold strictly to fact, and renounce with nonchalance any pretensions at completeness of knowledge if the data do not admit of it, and on these grounds hold themselves aloof from evolutionist generalisation. From among these come the counsels of“caution,”admissions that the theory is a scientific hypothesis and a guide to research, but not knowledge, and confessions that the Theory of Descent as a whole is verifiable rather as a general impression than in detail.

Virchow's Position.Warnings of this kind have come occasionally from Du Bois-Reymond, but the true type of this group, and its mode of thought, is Virchow. It will repay us and suffice us to make acquaintance with it through him. His opposition to Darwinism and the theory of descent was directed at its most salient point: the[pg 107]descent of man from the apes. In lectures and treatises, at zoological and anthropological congresses, especially at the meetings of his own Anthropological-Ethnological Society in Berlin, from his“Vorträge über Menschen-und Affen-Schädel”(Lectures on the Skulls of Man and Apes, 1869), to the disputes over Dubois'Pithecanthropus erectusin the middle of the nineties, he threw the whole weight of his immense learning—ethnological and anthropological, osteological, and above all“craniological”—into the scale against the Theory of Descent and its supporters. Virchow has therefore been reckoned often enough among the anti-Darwinians, and has been quoted by apologists and others as against Darwinism, and he has given reason for this, since he has often taken the field against“the Darwinists”or has scoffed at their“longing for a pro-anthropos.”13Sometimes even it has been suggested that he was actuated by religious motives, as when he occasionally championed not only freedom for science, but, incidentally, the right of existence for“the churches,”leaving, for instance, in his theory of psychical life, gaps in knowledge which faith might occupy in moderation and modesty. But this last proves nothing. With Virchow's altogether unemotional nature it is unlikely that religious or spiritual motives had any rôle in the establishment of his convictions, and in Haeckel's naïve blustering at religion, there is, so to speak, more[pg 108]religion than in the cold-blooded connivance with which Virchow leaves a few openings in otherwise frozen ponds for the ducks of faith to swim in! And he has nothing of the pathos of Du Bois-Reymond's“ignorabimus.”He is the neutral, prosaic scientist, who will let nothing“tempt him to a transcendental consideration,”14either theological or naturalistic, who holds tenaciously to matters of fact, who, without absolutely rejecting a general theory, will not concern himself about it, except to point out every difficulty in the way of it; in short, he is the representative of a mood that is the ideal of every investigator and the despair of every theoriser.His lecture of 1869 already indicates his subsequent attitude.“Considered logically and speculatively”the Theory of Descent seems to him“excellent,”15indeed a logical moral(!) hypothesis, but unproved in itself, and erroneous in many of its particular propositions. As far back as 1858, before the publication of Darwin's great work, he stated at the Naturalists' Congress in Carlsruhe, that the origin of one species out of another appeared to him a necessary scientific inference, but——And throughout the whole lecture he alternates between favourable recognition of the theory in general, and emphasis of the difficulties which confront it in detail. The skull, which, according to Goethe's theory, has[pg 109]evolved from three modified vertebræ, is fundamentally different in man and monkeys, both in regard to its externals, crests, ridges and shape, and especially in regard to the nature of the cavity which it forms for the brain. Specifically distinctive differences in the development and structure of the rest of the body must also be taken into account. The so-called ape-like structures in the skull and the rest of the body, which occasionally occur in man (idiots, microcephaloids, &c.) cannot be regarded as atavisms and therefore as proofs of the Theory of Descent; they are of a pathological nature, entirely factssui generis, and“not to be placed in a series with the normal results of evolution.”A man modified by disease“is still thoroughly a man, not a monkey.”Virchow continued to maintain this attitude and persisted in this kind of argument. He energetically rejected all attempts to find“pithecoid”characters in the prehistoric remains of man. He declared the narrow and less arched forehead, the elliptical form, and the unusually large frontal cavities of the“Neanderthal skull”found in the Wupperthal in 1856, to be simply pathological features, which occur as such in certain examples ofhomo sapiens.16He explained the abnormal appearance of the jaw from the Moravian cave of Schipka as a result of the retention of teeth,17accompanied by directly“antipithecoid”characters.[pg 110]The proceedings at the meetings of the Ethnological Society in 1895, at which Dubois was present, had an almost dramatic character.18In the diverse opinions of Dubois, Virchow, Nehring, Kollmann, Krause and others, we have almost an epitome of the present state of the Darwinian question. Virchow doubted whether the parts put together by Dubois (the head of a femur, two molar teeth, and the top of a skull) belonged to the same individual at all, disputed the calculations as to the large capacity of the skull, placed against Dubois' very striking and clever drawing of the curves of the skull-outline, which illustrated, with the help of the Pithecanthropus, the gradual transition from the skull of a monkey to that of man, his own drawing, according to which the Pithecanthropus curve simply coincides with that of a gibbon (Hylobates), and asserted that the remains discovered were those of a species of gibbon, refusing even to admit that they represented a new genus of monkeys. He held fast to hisceterum censeo:“As yet no diluvial discovery has been made which can be referred to a man of a pithecoid type.”Indeed, his polemic or“caution”in regard to the Theory of Descent went even further. He not only refused to admit the proof of the descent of man from monkey, he would not even allow that the descent of one race from another has been demonstrated.19[pg 111]In spite of all the plausible hypotheses it remains“so far only apium desiderium.”The race obstinately maintains its specific distinctness, and resists variation, or gradual transformation into another. The negro remains a negro in America, and the European colonist of Australia remains a European.Yet all Virchow's opposition may be summed up in the characteristic words, which might almost be called his motto,“I warn you of the need for caution,”and it is not a seriously-meant rejection of the Theory of Descent. In reality he holds the evolution-idea as an axiom, and in the last-named treatise he shows distinctly how he conceives of the process. He starts with variation (presumably“kaleidoscopic”), which comes about as a“pathological”phenomenon, that is to say, not spontaneously, but as the result of environmental stimulus, as the organism's reaction to climatic and other conditions of life. The result is an alteration of previous characteristics, and a new stable race is established by an“acquired anomaly.”20

Warnings of this kind have come occasionally from Du Bois-Reymond, but the true type of this group, and its mode of thought, is Virchow. It will repay us and suffice us to make acquaintance with it through him. His opposition to Darwinism and the theory of descent was directed at its most salient point: the[pg 107]descent of man from the apes. In lectures and treatises, at zoological and anthropological congresses, especially at the meetings of his own Anthropological-Ethnological Society in Berlin, from his“Vorträge über Menschen-und Affen-Schädel”(Lectures on the Skulls of Man and Apes, 1869), to the disputes over Dubois'Pithecanthropus erectusin the middle of the nineties, he threw the whole weight of his immense learning—ethnological and anthropological, osteological, and above all“craniological”—into the scale against the Theory of Descent and its supporters. Virchow has therefore been reckoned often enough among the anti-Darwinians, and has been quoted by apologists and others as against Darwinism, and he has given reason for this, since he has often taken the field against“the Darwinists”or has scoffed at their“longing for a pro-anthropos.”13Sometimes even it has been suggested that he was actuated by religious motives, as when he occasionally championed not only freedom for science, but, incidentally, the right of existence for“the churches,”leaving, for instance, in his theory of psychical life, gaps in knowledge which faith might occupy in moderation and modesty. But this last proves nothing. With Virchow's altogether unemotional nature it is unlikely that religious or spiritual motives had any rôle in the establishment of his convictions, and in Haeckel's naïve blustering at religion, there is, so to speak, more[pg 108]religion than in the cold-blooded connivance with which Virchow leaves a few openings in otherwise frozen ponds for the ducks of faith to swim in! And he has nothing of the pathos of Du Bois-Reymond's“ignorabimus.”He is the neutral, prosaic scientist, who will let nothing“tempt him to a transcendental consideration,”14either theological or naturalistic, who holds tenaciously to matters of fact, who, without absolutely rejecting a general theory, will not concern himself about it, except to point out every difficulty in the way of it; in short, he is the representative of a mood that is the ideal of every investigator and the despair of every theoriser.

His lecture of 1869 already indicates his subsequent attitude.“Considered logically and speculatively”the Theory of Descent seems to him“excellent,”15indeed a logical moral(!) hypothesis, but unproved in itself, and erroneous in many of its particular propositions. As far back as 1858, before the publication of Darwin's great work, he stated at the Naturalists' Congress in Carlsruhe, that the origin of one species out of another appeared to him a necessary scientific inference, but——And throughout the whole lecture he alternates between favourable recognition of the theory in general, and emphasis of the difficulties which confront it in detail. The skull, which, according to Goethe's theory, has[pg 109]evolved from three modified vertebræ, is fundamentally different in man and monkeys, both in regard to its externals, crests, ridges and shape, and especially in regard to the nature of the cavity which it forms for the brain. Specifically distinctive differences in the development and structure of the rest of the body must also be taken into account. The so-called ape-like structures in the skull and the rest of the body, which occasionally occur in man (idiots, microcephaloids, &c.) cannot be regarded as atavisms and therefore as proofs of the Theory of Descent; they are of a pathological nature, entirely factssui generis, and“not to be placed in a series with the normal results of evolution.”A man modified by disease“is still thoroughly a man, not a monkey.”

Virchow continued to maintain this attitude and persisted in this kind of argument. He energetically rejected all attempts to find“pithecoid”characters in the prehistoric remains of man. He declared the narrow and less arched forehead, the elliptical form, and the unusually large frontal cavities of the“Neanderthal skull”found in the Wupperthal in 1856, to be simply pathological features, which occur as such in certain examples ofhomo sapiens.16He explained the abnormal appearance of the jaw from the Moravian cave of Schipka as a result of the retention of teeth,17accompanied by directly“antipithecoid”characters.

The proceedings at the meetings of the Ethnological Society in 1895, at which Dubois was present, had an almost dramatic character.18In the diverse opinions of Dubois, Virchow, Nehring, Kollmann, Krause and others, we have almost an epitome of the present state of the Darwinian question. Virchow doubted whether the parts put together by Dubois (the head of a femur, two molar teeth, and the top of a skull) belonged to the same individual at all, disputed the calculations as to the large capacity of the skull, placed against Dubois' very striking and clever drawing of the curves of the skull-outline, which illustrated, with the help of the Pithecanthropus, the gradual transition from the skull of a monkey to that of man, his own drawing, according to which the Pithecanthropus curve simply coincides with that of a gibbon (Hylobates), and asserted that the remains discovered were those of a species of gibbon, refusing even to admit that they represented a new genus of monkeys. He held fast to hisceterum censeo:“As yet no diluvial discovery has been made which can be referred to a man of a pithecoid type.”Indeed, his polemic or“caution”in regard to the Theory of Descent went even further. He not only refused to admit the proof of the descent of man from monkey, he would not even allow that the descent of one race from another has been demonstrated.19[pg 111]In spite of all the plausible hypotheses it remains“so far only apium desiderium.”The race obstinately maintains its specific distinctness, and resists variation, or gradual transformation into another. The negro remains a negro in America, and the European colonist of Australia remains a European.

Yet all Virchow's opposition may be summed up in the characteristic words, which might almost be called his motto,“I warn you of the need for caution,”and it is not a seriously-meant rejection of the Theory of Descent. In reality he holds the evolution-idea as an axiom, and in the last-named treatise he shows distinctly how he conceives of the process. He starts with variation (presumably“kaleidoscopic”), which comes about as a“pathological”phenomenon, that is to say, not spontaneously, but as the result of environmental stimulus, as the organism's reaction to climatic and other conditions of life. The result is an alteration of previous characteristics, and a new stable race is established by an“acquired anomaly.”20

Other Instances of Dissatisfaction with the Theory of Descent.What was with Virchow only a suggestion of the[pg 112]need for caution, or controversial matter to be subsequently allowed for or contradicted, had more serious consequences to others, and led to still greater hesitancy as regards evolutionist generalisations and speculations, and sometimes to sharp antagonism to them.One of the best known of the earlier examples of this mood is Kerner von Marilaun's large and beautiful work on“Plant Life.”21He does, indeed, admit that our species are variations of antecedent forms, but only in a very limited sense. Within the stocks or grades of organisation which have always existed, variations have come about, through“hybridisation,”through the crossing of similar, but relatively different forms; these variations alter the configuration and appearance in detail, but neither affect the general character nor cause any transition from“lower”to“higher.”Kerner disposes of the chief argument in favour of the theory of descent, the homology of individual organs, by explaining that the homology is due to the similarity of function in the different organisms. A similar argument is used in regard to“ontogeny recapitulating phylogeny.”Palæontology does not disclose in the plant-world any“synthetic types,”which might have been the common primitive stock from which many now divergent branches have sprung, nor does it disclose any“transition links”really intermediate,[pg 113]for instance, between cryptogams and gymnosperms, or between gymnosperms and angiosperms. That the higher races are apparently absent from the earlier strata is not a proof that they have never existed. The peat-bog flora must have involved the existence of a large companion-flora, without which the peat could not have been formed, but all trace of this is absent in the still persistent vestiges of these times.22Life, with energy and matter, has existed as a phenomenon of the universe from all eternity, and thus its chief forms and manifestations have not“arisen,”but have always been. If facts such as these contradict the Kant-Laplace theory of the universe, then the latter must be corrected in the light of them, not conversely. The extreme isolation of Kerner and his theory is probably due especially to this corollary of his views.Among the most recent examples of antagonism to the Evolution-Theory, the most interesting is a book by Fleischmann, professor of zoology in Erlangen, published in 1901, and entitled,“The Theory of Descent.”It consists of“popular lectures on the rise and decline of a scientific hypothesis”(namely, the Theory of Descent), and it is a complete recantation by a quondam Darwinian of the doctrine of his school, even of its fundamental proposition, the concept of evolution itself. For Fleischmann is not guilty, like Weismann, of the inaccuracy of using“Theory of[pg 114]Descent”as equivalent to Darwinism; he is absolutely indifferent to the theory of natural selection. His book keeps strictly to matters of fact, and rejects as speculation everything in the least beyond these; it does not express even an opinion on the question of the origin of species, but merely criticises and analyses.It does not bring forward any new and overwhelming arguments in refutation of the Theory of Descent, but strongly emphasises difficulties that have always beset it, and discusses these in detail. The old dispute which interested Goethe, Geoffroy St. Hilaire, and Cuvier, as to the unity or the fundamental heterogeneity of the“architectural plan”in nature is revived. Modern zoology recognises not merely the four types of Cuvier, but seventeen different styles,“phyla,”or groups of forms, to derive one of which from another is hopeless. And what is true of the whole is true also of the subdivisions within each phylum;e.g., within the vertebrate phylum with its fishes, amphibians, reptiles, birds and mammals. No bridge leads from one to the other. This is proved particularly by the very instance which is the favourite illustration in support of the Theory of Descent—the fin of fishes and its relation to the five-fingered hand of vertebrates. The so-called transition forms (Archæopteryx, monotremes, &c.) are discredited. So with the“stalking-horse”of evolutionists—the genealogical tree of the Equidæ, which is said to be traceable palæontologically right back, without a break, from the one-toed horses of the present day to[pg 115]the normal five-toed ancestry; and so with another favourite instance of evolution, the history of the pond-snails (Planorbis multiformis), the numerous varieties of which occur with transitions between them in actual contiguity in the Steinheim beds, and thus seem to afford an obvious example of the transformation of species. Against these cases, and against using the palæontological archives as a basis for the construction of genealogical trees in general, the weighty and apparently decisive objection is urged, that nowhere are the soft parts of the earlier forms of life preserved, and that it is impossible to establish relationships with any certainty on the basis of hard parts only, such as bones, teeth and shells. Even Haeckel admits that snails of very different bodily structure may form very similar and even hardly distinguishable shells.Fleischmann further asserts that Haeckel's“fundamental biogenetic law”has utterly collapsed.“Recapitulation”does not occur. Selenka's figures of ovum-segmentation show that there are specific differences in the individual groups. The origin and development of the blastoderm or germinal disc has nothing to do with recapitulation of the phylogeny. It is not the case that the embryos of higher vertebrates are indistinguishable from one another. Even the egg-cell has a specific character, and is totally different from any unicellular organism at the Protistan level. The much-cited“gill-clefts”of higher vertebrates in the embryonic stage are not persistent reminiscences of[pg 116]earlier lower stages; they are rudiments or primordia shared by all vertebrates, and developing differently at the different levels; (thus in fishes they become breathing organs, and in the higher vertebrates they become in part associated with the organs of hearing, or in part disappear again).Though Fleischmann's vigorous protest against over-hastiness in construction and over-confidence on the part of the adherents of the doctrine of descent is very interesting, and may often be justified in detail, it is difficult to resist the impression that the wheat has been rejected with the chaff.23Even a layman may raise the following objections: Admitting that the great groups of forms cannot be traced back to one another, the palæontological record still proves, though it may be only in general outline, that within each phylum there has been a gradual succession and ascent of forms. How is the origin of what is new to be accounted for? Without doing violence to our thinking, without a sort of intellectual autonomy, we cannot rest content with the mere fact that new elements occur. So, in spite of all“difficulties,”the assumption ofan actual descentquietly forces itself upon us as the only satisfactory clue. And the fact, which Fleischmann does not discuss, that even at present we may observe the establishment of what are at least new breeds, impels us to accept an analogous[pg 117]origin of new species. Even if the biogenetic law really“finds its chief confirmation in its exceptions,”even if we cannot speak of a strict recapitulation of earlier stages of evolution, there are indisputable facts which are most readily interpreted as reminiscences, as due to affiliation (ideal or hereditary), with ancestral forms. (Note, for instance, Weismann's“prediction,”&c.24) Even if Archæopteryx and other intermediate forms cannot be regarded as connecting links in the strict sense,i.e., as being stages in the actual pedigree, yet the occurrence of reptilian and avian peculiarities side by side in one organism, goes far to prove the close relationship of the two classes.Fleischmann's book strengthens the impression gained elsewhere, that a general survey of the domain of life as a whole gives force and convincingness to the Theory of Descent, while a study of details often results in breaking the threads and bringing the difficulties into prominence. But the same holds true of many other theoretical constructions, and yet we do not seriously doubt their validity. (Take, for instance, the Kant-Laplace theory, and theories of ethnology, of the history of religion, of the history of language, and so on.) And it is quite commonly to be observed that those who have an expert and specialist knowledge, who are aware of the refractoriness of detailed facts, often take up a sceptical attitude towards every comprehensive[pg 118]theory, though the ultimate use of detailed investigation is to make the construction of general theories possible. Fleischmann does exactly what, say, an anthropologist would do if, under the impression of the constancy and distinctiveness of the human races, which would become stronger the more deeply he penetrated, he should resignedly renounce all possibility of affiliating them, and should rest content with the facts as he found them. Similarly, those who are most intimately acquainted with the races of domesticated animals often resist most strenuously all attempts, although these seem to others a matter of course, to derive our“tame”forms from“wild”species living in freedom.But to return. Even where the Theory of Descent is recognised, whether fully or only half-heartedly, the recognition does not always mean the same thing. Even the adherents of the general, but in itself quite vague view that a transformation from lower forms to higher, and from similar to different forms, has taken place, may present so many points of disagreement, and may even stand in such antagonism to one another, that onlookers are apt to receive the impression that they occupy quite different standpoints, and are no longer at one even in the fundamentals of their hypotheses.The most diverse questions and answers crop up; whether evolution has been brought about“monophyletically”or“polyphyletically,”i.e., through one or many genealogical trees; whether it has taken place in[pg 119]a continuous easy transition from one type to another, or by leaps and bounds; whether through a gradual transformation of all organs, each varying individually, or through correlated“kaleidoscopic”variations of many kinds throughout the whole system; whether it is essentially asymptotic, or whether organisms pass from“labile”phases of vital equilibrium by various halting-places to stable states, which are definitive, and are, so to speak, the blind alleys and terminal points of evolutionary possibilities,e.g., the extinct gigantic saurians, and perhaps also man. And to these problems must be added the various answers to the question, What precedes, or may have preceded, the earliest stages of life of which we know? Whence came the first cell? Whence the first living protoplasm? and How did the living arise from the inorganic? These deeper questions will occupy us in our chapter on the theory of life. Some of the former, in certain of their aspects, will be considered in the sixth chapter, which deals with factors in evolution.The Theory of Descent itself and the differences that obtain even among its adherents can best be studied by considering for a little the works of Reinke and of Hamann.Reinke, Professor of Botany in Kiel, has set forth his views in his book,“Die Welt als Tat,”25and more recently in his“Einleitung in die theoretische Biologie”(1901). Both books are addressed to a wide[pg 120]circle of readers. Reinke and Hamann both revive some of the arguments and opinions set forth in the early days of Darwinism by Wigand,26an author whose works are gradually gaining increased appreciation.It is Reinke's“unalterable conviction”that organisms have evolved, and that they have done so after the manner of fan-shaped genealogical trees. The Theory of Descent is to him an axiom of modern biology, though as a matter of fact the circumstantial evidence in favour of it is extremely fragmentary. The main arguments in favour of it appear to him to be the general ones; the homologies and analogies revealed by comparative morphology and physiology, the ascending series in the palæontological record, vestigial organs, parasitic degeneration, the origin of those vital associations which we call consortism and symbiosis. These he illustrates mainly by examples from his own special domain and personal observation.The simplest unicellular forms of life are to be thought of as at the beginning of evolution; and, since mechanical causes cannot explain their ascent, it must be assumed that they have an inherent“phylogenetic potential of development,”which, working epigenetically, results in ascending evolution. He leaves us to choose between monophyletic and polyphyletic evolution, but himself inclines towards the latter, associating with it a[pg 121]rehabilitation of Wigand's theory of the primitive cells. If, in the beginning, primitive forms of life arose (probably as unicellulars) from the not-living, it is not obvious why we need think of only one so arising, and, if many did so, why they should not have inherent differences which would at once result in typically different evolutionary series and groups of forms. But evolution does not go onad libitumorad infinitum, for the capacity for differentiation and transformation gradually diminishes. The organisation passes from a labile state of equilibrium to an increasingly stable state, and at many points it may reach a terminus where it comes to a standstill. Man, the dog, the horse, the cereals, and fruit trees appear to Reinke to have reached their goal. The preliminary stages he calls“Phylembryos,”because they bear to the possible outcome of their evolution the same relation that the embryo does to the perfect individual. Thus,Phenacodusmay be regarded as the Phylembryo of the modern horse. It is quite conceivable that each of our modern species may have had an independent series of Phylembryos reaching back to the primitive cells. But the palæontological record, and especially its synthetic types, lead Reinke rather to assume that instead of innumerable series, there have been branching genealogical trees, not one, however, but several.These views, together or separately, which are characterised chiefly by the catch-words“polyphyletic descent,”“labile and stable equilibrium,”and so on, crop[pg 122]up together or separately in the writings of various evolutionists belonging to the opposition wing. They are usually associated with a denial of the theory of natural selection, and with theories of“Orthogenesis,”“Heterogenesis,”and“Epigenesis.”We shall discuss them later when we are considering the factors in evolution. But we must first take notice of a work in which the theories opposed to Darwinian orthodoxy have been most decisively and aggressively set forth. As far back as 1892 O. Hamann, then a lecturer on zoology in Göttingen, gathered these together and brought them into the field, against Haeckel in particular, in his book“Entwicklungslehre und Darwinismus.”27Hamann's main theme is that Darwinism overlooks the fact that“there cannot have been an origin of higher types from types already finished.”For this“unfortunate and unsupported assumption”there are no proofs in embryology, palæontology, or anatomy. He adopts and expands the arguments and anti-Haeckelian deliverances of His in embryology, of Snell and Heer in palæontology, of Kölliker and von Baer in their special interpretation of evolution, of Snell particularly as regards the descent of man. It is impossible to derive Metazoa from Protozoa in their present finished state of evolution; even the Amoeba is so exactly adapted in organisation and functional activity[pg 123]to the conditions of its existence that it is a“finished”type. It is only by a stretch of fancy that fishes can be derived from worms, or higher vertebrates from fishes. One of his favourite arguments—and it is a weighty one, though neglected by the orthodox Darwinians—is that living substance is capable, under similar stimuli, of developing spontaneously and afresh, at quite different points and in different groups, similar organs, such as spots sensitive to light, accumulations of pigment, eye-spots, lenses, complete eyes, and similarly with the notochord, the excretory organs, and the like. Therefore homology of organs is no proof of their hereditary affiliation.28They rather illustrate“iterative evolution.”Another favourite argument is the fact of“Pædogenesis.”Certain animals, such asAmphioxus lanceolatus,Peripatus, and certain Medusæ, are very frequently brought forward as examples of persistent primitive stages and“transitional connecting links.”But considered from the point of view of Pædogenesis, they all assume quite a different aspect, and seem rather to represent very highly evolved species, and to be, not primitive forms, but conservative and regressive forms. Pædogenesis is the phenomenon exhibited by a number of species, which may stop short at one of the stages of their embryonic or larval development, become sexually mature, and produce[pg 124]offspring without having attained their own fully developed form.Another argument is the old, suggestive, and really important one urged by Kölliker, that“inorganic nature shows a natural system among minerals (crystals) just as much as animals and plants do, yet in the former there can be no question of any genetic connection in the production of forms.”Yet another argument is found in the occurrence of“inversions”and anomalies in the palæontological succession of forms, which to some extent upsets the Darwinian-Haeckelian genealogical trees. (Thus there are forms in the Cambrian whose alleged ancestors do not appear till the Silurian. Foraminifera and other Protozoa do not appear till the Silurian.)From embryology in particular, as elsewhere in general, we read the“fundamental biogenetic law,”that evolution is from the general to the special, from the imperfect to the more perfect, from what is still indefinite and exuberant to the well-defined and precise, but never from the special to the special. According to Hamann's hypothesis we must think of evolution as going on, so to speak, not about the top but about the bottom. The phyla or groups of forms are great trunks bearing many branches and twigs, but not giving rise to one another. Still less do the little side branches of one trunk bear the whole great trunk of another animal or plant phylum. But they all grow from the same roots among the primitive forms of life. Unicellulars these must[pg 125]have been, but not like our“Protists.”They should be thought of as primitive forms having within themselves the potentialities of the most diverse and widely separate evolution-series to which they gave rise, as it were, along diverging fan-like rays.It would be instructive to follow some naturalist into his own particular domain, for instance a palæontologist into the detailed facts of palæontology, or an embryologist into those of embryology, in order to learn whether these corroborate the assumptions of the Theory of Descent or not. It is just in relation to these detailed facts that criticisms or even denials of the theory have been most frequent. Koken, otherwise a convinced supporter of the theory, inquires in his“Vorwelt,”aproposof the tortoises, what has become of the genealogical trees that were scattered abroad in the world as proved facts in the early days of Darwinism. He asserts, in regard toArchæopteryx, the instance which is always put forward as the intermediate link in the evolution of birds, that it does not show in any of its characters a fundamental difference from any of the birds of to-day, and further, that, through convergent development under similar influences, similar organs and structural relations result, iterative arrangements which come about quite independently of descent. He maintains, too, that the principle of the struggle for existence is rather disproved than corroborated by the palæontological record.In embryology, so competent an authority as[pg 126]O. Hertwig—himself a former pupil of Haeckel's—has reacted from the“fundamental biogenetic law.”His theory of the matter is very much that of Hamann which we have already discussed; development is not so much a recapitulation of finished ancestral types as the laying down of foundations after the pattern of generalised simple forms, not yet specialised; and from these foundations the special organs rise to different levels and grades of differentiation according to the type.29But we must not lose ourselves in details.Looking back over the whole field once more, we feel that we are justified in maintaining with some confidence that the different pronouncements in regard to the detailed application and particular features of the Theory of Descent, and the different standpoints that are occupied even by evolutionists, are at least sufficient to make it obvious that, even if evolution and descent have actually taken place, they have not run so simple and smooth a course as the over-confident would have us believe; that the Theory of Descent rather emphasises than clears away the riddles and difficulties of the case, and that with the mere corroboration of the theory we shall have gained only something relatively external, a clue to creation, which does not so much solve its problems as restate them. The whole criticism of the“right wing,”from captious objections to actual denials, proves this indisputably. And it seems likely that in the course of time a sharpening of[pg 127]the critical insight and temper will give rise to further reactions from the academic theory as we have come to know it.30On the other hand, it may be assumed with even greater certainty that the general evolutionist point of view and the great arguments for descent in some form or other will ultimately be victorious if they are not so already, and that, sooner or later, we shall take the Theory of Descent in its most general form as a matter of course, just as we now do the Kant-Laplace theory.

What was with Virchow only a suggestion of the[pg 112]need for caution, or controversial matter to be subsequently allowed for or contradicted, had more serious consequences to others, and led to still greater hesitancy as regards evolutionist generalisations and speculations, and sometimes to sharp antagonism to them.

One of the best known of the earlier examples of this mood is Kerner von Marilaun's large and beautiful work on“Plant Life.”21He does, indeed, admit that our species are variations of antecedent forms, but only in a very limited sense. Within the stocks or grades of organisation which have always existed, variations have come about, through“hybridisation,”through the crossing of similar, but relatively different forms; these variations alter the configuration and appearance in detail, but neither affect the general character nor cause any transition from“lower”to“higher.”

Kerner disposes of the chief argument in favour of the theory of descent, the homology of individual organs, by explaining that the homology is due to the similarity of function in the different organisms. A similar argument is used in regard to“ontogeny recapitulating phylogeny.”Palæontology does not disclose in the plant-world any“synthetic types,”which might have been the common primitive stock from which many now divergent branches have sprung, nor does it disclose any“transition links”really intermediate,[pg 113]for instance, between cryptogams and gymnosperms, or between gymnosperms and angiosperms. That the higher races are apparently absent from the earlier strata is not a proof that they have never existed. The peat-bog flora must have involved the existence of a large companion-flora, without which the peat could not have been formed, but all trace of this is absent in the still persistent vestiges of these times.22Life, with energy and matter, has existed as a phenomenon of the universe from all eternity, and thus its chief forms and manifestations have not“arisen,”but have always been. If facts such as these contradict the Kant-Laplace theory of the universe, then the latter must be corrected in the light of them, not conversely. The extreme isolation of Kerner and his theory is probably due especially to this corollary of his views.

Among the most recent examples of antagonism to the Evolution-Theory, the most interesting is a book by Fleischmann, professor of zoology in Erlangen, published in 1901, and entitled,“The Theory of Descent.”It consists of“popular lectures on the rise and decline of a scientific hypothesis”(namely, the Theory of Descent), and it is a complete recantation by a quondam Darwinian of the doctrine of his school, even of its fundamental proposition, the concept of evolution itself. For Fleischmann is not guilty, like Weismann, of the inaccuracy of using“Theory of[pg 114]Descent”as equivalent to Darwinism; he is absolutely indifferent to the theory of natural selection. His book keeps strictly to matters of fact, and rejects as speculation everything in the least beyond these; it does not express even an opinion on the question of the origin of species, but merely criticises and analyses.

It does not bring forward any new and overwhelming arguments in refutation of the Theory of Descent, but strongly emphasises difficulties that have always beset it, and discusses these in detail. The old dispute which interested Goethe, Geoffroy St. Hilaire, and Cuvier, as to the unity or the fundamental heterogeneity of the“architectural plan”in nature is revived. Modern zoology recognises not merely the four types of Cuvier, but seventeen different styles,“phyla,”or groups of forms, to derive one of which from another is hopeless. And what is true of the whole is true also of the subdivisions within each phylum;e.g., within the vertebrate phylum with its fishes, amphibians, reptiles, birds and mammals. No bridge leads from one to the other. This is proved particularly by the very instance which is the favourite illustration in support of the Theory of Descent—the fin of fishes and its relation to the five-fingered hand of vertebrates. The so-called transition forms (Archæopteryx, monotremes, &c.) are discredited. So with the“stalking-horse”of evolutionists—the genealogical tree of the Equidæ, which is said to be traceable palæontologically right back, without a break, from the one-toed horses of the present day to[pg 115]the normal five-toed ancestry; and so with another favourite instance of evolution, the history of the pond-snails (Planorbis multiformis), the numerous varieties of which occur with transitions between them in actual contiguity in the Steinheim beds, and thus seem to afford an obvious example of the transformation of species. Against these cases, and against using the palæontological archives as a basis for the construction of genealogical trees in general, the weighty and apparently decisive objection is urged, that nowhere are the soft parts of the earlier forms of life preserved, and that it is impossible to establish relationships with any certainty on the basis of hard parts only, such as bones, teeth and shells. Even Haeckel admits that snails of very different bodily structure may form very similar and even hardly distinguishable shells.

Fleischmann further asserts that Haeckel's“fundamental biogenetic law”has utterly collapsed.“Recapitulation”does not occur. Selenka's figures of ovum-segmentation show that there are specific differences in the individual groups. The origin and development of the blastoderm or germinal disc has nothing to do with recapitulation of the phylogeny. It is not the case that the embryos of higher vertebrates are indistinguishable from one another. Even the egg-cell has a specific character, and is totally different from any unicellular organism at the Protistan level. The much-cited“gill-clefts”of higher vertebrates in the embryonic stage are not persistent reminiscences of[pg 116]earlier lower stages; they are rudiments or primordia shared by all vertebrates, and developing differently at the different levels; (thus in fishes they become breathing organs, and in the higher vertebrates they become in part associated with the organs of hearing, or in part disappear again).

Though Fleischmann's vigorous protest against over-hastiness in construction and over-confidence on the part of the adherents of the doctrine of descent is very interesting, and may often be justified in detail, it is difficult to resist the impression that the wheat has been rejected with the chaff.23

Even a layman may raise the following objections: Admitting that the great groups of forms cannot be traced back to one another, the palæontological record still proves, though it may be only in general outline, that within each phylum there has been a gradual succession and ascent of forms. How is the origin of what is new to be accounted for? Without doing violence to our thinking, without a sort of intellectual autonomy, we cannot rest content with the mere fact that new elements occur. So, in spite of all“difficulties,”the assumption ofan actual descentquietly forces itself upon us as the only satisfactory clue. And the fact, which Fleischmann does not discuss, that even at present we may observe the establishment of what are at least new breeds, impels us to accept an analogous[pg 117]origin of new species. Even if the biogenetic law really“finds its chief confirmation in its exceptions,”even if we cannot speak of a strict recapitulation of earlier stages of evolution, there are indisputable facts which are most readily interpreted as reminiscences, as due to affiliation (ideal or hereditary), with ancestral forms. (Note, for instance, Weismann's“prediction,”&c.24) Even if Archæopteryx and other intermediate forms cannot be regarded as connecting links in the strict sense,i.e., as being stages in the actual pedigree, yet the occurrence of reptilian and avian peculiarities side by side in one organism, goes far to prove the close relationship of the two classes.

Fleischmann's book strengthens the impression gained elsewhere, that a general survey of the domain of life as a whole gives force and convincingness to the Theory of Descent, while a study of details often results in breaking the threads and bringing the difficulties into prominence. But the same holds true of many other theoretical constructions, and yet we do not seriously doubt their validity. (Take, for instance, the Kant-Laplace theory, and theories of ethnology, of the history of religion, of the history of language, and so on.) And it is quite commonly to be observed that those who have an expert and specialist knowledge, who are aware of the refractoriness of detailed facts, often take up a sceptical attitude towards every comprehensive[pg 118]theory, though the ultimate use of detailed investigation is to make the construction of general theories possible. Fleischmann does exactly what, say, an anthropologist would do if, under the impression of the constancy and distinctiveness of the human races, which would become stronger the more deeply he penetrated, he should resignedly renounce all possibility of affiliating them, and should rest content with the facts as he found them. Similarly, those who are most intimately acquainted with the races of domesticated animals often resist most strenuously all attempts, although these seem to others a matter of course, to derive our“tame”forms from“wild”species living in freedom.

But to return. Even where the Theory of Descent is recognised, whether fully or only half-heartedly, the recognition does not always mean the same thing. Even the adherents of the general, but in itself quite vague view that a transformation from lower forms to higher, and from similar to different forms, has taken place, may present so many points of disagreement, and may even stand in such antagonism to one another, that onlookers are apt to receive the impression that they occupy quite different standpoints, and are no longer at one even in the fundamentals of their hypotheses.

The most diverse questions and answers crop up; whether evolution has been brought about“monophyletically”or“polyphyletically,”i.e., through one or many genealogical trees; whether it has taken place in[pg 119]a continuous easy transition from one type to another, or by leaps and bounds; whether through a gradual transformation of all organs, each varying individually, or through correlated“kaleidoscopic”variations of many kinds throughout the whole system; whether it is essentially asymptotic, or whether organisms pass from“labile”phases of vital equilibrium by various halting-places to stable states, which are definitive, and are, so to speak, the blind alleys and terminal points of evolutionary possibilities,e.g., the extinct gigantic saurians, and perhaps also man. And to these problems must be added the various answers to the question, What precedes, or may have preceded, the earliest stages of life of which we know? Whence came the first cell? Whence the first living protoplasm? and How did the living arise from the inorganic? These deeper questions will occupy us in our chapter on the theory of life. Some of the former, in certain of their aspects, will be considered in the sixth chapter, which deals with factors in evolution.

The Theory of Descent itself and the differences that obtain even among its adherents can best be studied by considering for a little the works of Reinke and of Hamann.

Reinke, Professor of Botany in Kiel, has set forth his views in his book,“Die Welt als Tat,”25and more recently in his“Einleitung in die theoretische Biologie”(1901). Both books are addressed to a wide[pg 120]circle of readers. Reinke and Hamann both revive some of the arguments and opinions set forth in the early days of Darwinism by Wigand,26an author whose works are gradually gaining increased appreciation.

It is Reinke's“unalterable conviction”that organisms have evolved, and that they have done so after the manner of fan-shaped genealogical trees. The Theory of Descent is to him an axiom of modern biology, though as a matter of fact the circumstantial evidence in favour of it is extremely fragmentary. The main arguments in favour of it appear to him to be the general ones; the homologies and analogies revealed by comparative morphology and physiology, the ascending series in the palæontological record, vestigial organs, parasitic degeneration, the origin of those vital associations which we call consortism and symbiosis. These he illustrates mainly by examples from his own special domain and personal observation.

The simplest unicellular forms of life are to be thought of as at the beginning of evolution; and, since mechanical causes cannot explain their ascent, it must be assumed that they have an inherent“phylogenetic potential of development,”which, working epigenetically, results in ascending evolution. He leaves us to choose between monophyletic and polyphyletic evolution, but himself inclines towards the latter, associating with it a[pg 121]rehabilitation of Wigand's theory of the primitive cells. If, in the beginning, primitive forms of life arose (probably as unicellulars) from the not-living, it is not obvious why we need think of only one so arising, and, if many did so, why they should not have inherent differences which would at once result in typically different evolutionary series and groups of forms. But evolution does not go onad libitumorad infinitum, for the capacity for differentiation and transformation gradually diminishes. The organisation passes from a labile state of equilibrium to an increasingly stable state, and at many points it may reach a terminus where it comes to a standstill. Man, the dog, the horse, the cereals, and fruit trees appear to Reinke to have reached their goal. The preliminary stages he calls“Phylembryos,”because they bear to the possible outcome of their evolution the same relation that the embryo does to the perfect individual. Thus,Phenacodusmay be regarded as the Phylembryo of the modern horse. It is quite conceivable that each of our modern species may have had an independent series of Phylembryos reaching back to the primitive cells. But the palæontological record, and especially its synthetic types, lead Reinke rather to assume that instead of innumerable series, there have been branching genealogical trees, not one, however, but several.

These views, together or separately, which are characterised chiefly by the catch-words“polyphyletic descent,”“labile and stable equilibrium,”and so on, crop[pg 122]up together or separately in the writings of various evolutionists belonging to the opposition wing. They are usually associated with a denial of the theory of natural selection, and with theories of“Orthogenesis,”“Heterogenesis,”and“Epigenesis.”

We shall discuss them later when we are considering the factors in evolution. But we must first take notice of a work in which the theories opposed to Darwinian orthodoxy have been most decisively and aggressively set forth. As far back as 1892 O. Hamann, then a lecturer on zoology in Göttingen, gathered these together and brought them into the field, against Haeckel in particular, in his book“Entwicklungslehre und Darwinismus.”27

Hamann's main theme is that Darwinism overlooks the fact that“there cannot have been an origin of higher types from types already finished.”For this“unfortunate and unsupported assumption”there are no proofs in embryology, palæontology, or anatomy. He adopts and expands the arguments and anti-Haeckelian deliverances of His in embryology, of Snell and Heer in palæontology, of Kölliker and von Baer in their special interpretation of evolution, of Snell particularly as regards the descent of man. It is impossible to derive Metazoa from Protozoa in their present finished state of evolution; even the Amoeba is so exactly adapted in organisation and functional activity[pg 123]to the conditions of its existence that it is a“finished”type. It is only by a stretch of fancy that fishes can be derived from worms, or higher vertebrates from fishes. One of his favourite arguments—and it is a weighty one, though neglected by the orthodox Darwinians—is that living substance is capable, under similar stimuli, of developing spontaneously and afresh, at quite different points and in different groups, similar organs, such as spots sensitive to light, accumulations of pigment, eye-spots, lenses, complete eyes, and similarly with the notochord, the excretory organs, and the like. Therefore homology of organs is no proof of their hereditary affiliation.28They rather illustrate“iterative evolution.”

Another favourite argument is the fact of“Pædogenesis.”Certain animals, such asAmphioxus lanceolatus,Peripatus, and certain Medusæ, are very frequently brought forward as examples of persistent primitive stages and“transitional connecting links.”But considered from the point of view of Pædogenesis, they all assume quite a different aspect, and seem rather to represent very highly evolved species, and to be, not primitive forms, but conservative and regressive forms. Pædogenesis is the phenomenon exhibited by a number of species, which may stop short at one of the stages of their embryonic or larval development, become sexually mature, and produce[pg 124]offspring without having attained their own fully developed form.

Another argument is the old, suggestive, and really important one urged by Kölliker, that“inorganic nature shows a natural system among minerals (crystals) just as much as animals and plants do, yet in the former there can be no question of any genetic connection in the production of forms.”

Yet another argument is found in the occurrence of“inversions”and anomalies in the palæontological succession of forms, which to some extent upsets the Darwinian-Haeckelian genealogical trees. (Thus there are forms in the Cambrian whose alleged ancestors do not appear till the Silurian. Foraminifera and other Protozoa do not appear till the Silurian.)

From embryology in particular, as elsewhere in general, we read the“fundamental biogenetic law,”that evolution is from the general to the special, from the imperfect to the more perfect, from what is still indefinite and exuberant to the well-defined and precise, but never from the special to the special. According to Hamann's hypothesis we must think of evolution as going on, so to speak, not about the top but about the bottom. The phyla or groups of forms are great trunks bearing many branches and twigs, but not giving rise to one another. Still less do the little side branches of one trunk bear the whole great trunk of another animal or plant phylum. But they all grow from the same roots among the primitive forms of life. Unicellulars these must[pg 125]have been, but not like our“Protists.”They should be thought of as primitive forms having within themselves the potentialities of the most diverse and widely separate evolution-series to which they gave rise, as it were, along diverging fan-like rays.

It would be instructive to follow some naturalist into his own particular domain, for instance a palæontologist into the detailed facts of palæontology, or an embryologist into those of embryology, in order to learn whether these corroborate the assumptions of the Theory of Descent or not. It is just in relation to these detailed facts that criticisms or even denials of the theory have been most frequent. Koken, otherwise a convinced supporter of the theory, inquires in his“Vorwelt,”aproposof the tortoises, what has become of the genealogical trees that were scattered abroad in the world as proved facts in the early days of Darwinism. He asserts, in regard toArchæopteryx, the instance which is always put forward as the intermediate link in the evolution of birds, that it does not show in any of its characters a fundamental difference from any of the birds of to-day, and further, that, through convergent development under similar influences, similar organs and structural relations result, iterative arrangements which come about quite independently of descent. He maintains, too, that the principle of the struggle for existence is rather disproved than corroborated by the palæontological record.

In embryology, so competent an authority as[pg 126]O. Hertwig—himself a former pupil of Haeckel's—has reacted from the“fundamental biogenetic law.”His theory of the matter is very much that of Hamann which we have already discussed; development is not so much a recapitulation of finished ancestral types as the laying down of foundations after the pattern of generalised simple forms, not yet specialised; and from these foundations the special organs rise to different levels and grades of differentiation according to the type.29But we must not lose ourselves in details.

Looking back over the whole field once more, we feel that we are justified in maintaining with some confidence that the different pronouncements in regard to the detailed application and particular features of the Theory of Descent, and the different standpoints that are occupied even by evolutionists, are at least sufficient to make it obvious that, even if evolution and descent have actually taken place, they have not run so simple and smooth a course as the over-confident would have us believe; that the Theory of Descent rather emphasises than clears away the riddles and difficulties of the case, and that with the mere corroboration of the theory we shall have gained only something relatively external, a clue to creation, which does not so much solve its problems as restate them. The whole criticism of the“right wing,”from captious objections to actual denials, proves this indisputably. And it seems likely that in the course of time a sharpening of[pg 127]the critical insight and temper will give rise to further reactions from the academic theory as we have come to know it.30On the other hand, it may be assumed with even greater certainty that the general evolutionist point of view and the great arguments for descent in some form or other will ultimately be victorious if they are not so already, and that, sooner or later, we shall take the Theory of Descent in its most general form as a matter of course, just as we now do the Kant-Laplace theory.

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