Whether this genealogy of the primordial cells found any followers, we do not know. None of the hypotheses thus far mentioned are so very far from having analogies in experience. The idea of a first development of the higher organisms out of their specific primordial cell, through all kinds of conditions of larvae up to the finished form, demands of us the acceptance of monstrous improbabilities—(think, for example, of the first men, who, originating from a human primordial cell, grow in different metamorphoses of larvae, first in the water and then on the land, until they appear as finished men). Moreover, the hypothesis, in claiming that a heterogenetic generation of one species from another must necessarily nullify all similarity between the organism of the child and that of the mother, is so little convincing, and shows—in the necessity of conceiving the universal type of organisms, the type of kingdoms, of main types, of classes, of orders, of families, of genera, and of species, as but individual existences which, in the form of cells and before the existence of the developed species, partly through many thousands of years, lead a real empiric and concrete life—such an abstract synthetical construction of nature, that {60} we are not astonished that the theory of the genealogy of primordial cells stands almost alone. On the other hand, Wigand's larger critical work rendered great service in clearing up the problems. It is true, his judgment appears in many single cases not at all convincing, since he often enough fights his adversaries with sophisms and deduces from the views of Darwin and Haeckel conclusions to which they certainly do not lead. But in the majority of cases, his work is full of real convincing power, and with the breadth of its philosophical view and with the sharpness of its definitions, as well as with its abundance of philosophic and especially botanical teachings and their ingenious application, it is directly destructive to the use of the selection theory as the principal key to the solution of the problems. Eduard von Hartmann describes the work in his publication, "Wahrheit und Irrthum im Darwinismus," ("Truth and Error in Darwinism"), as a mile-stone which marks the limits where Darwinism as such passed the summit of its influence in Germany.

* * * * * {61}

CHAPTER III.

PRESENT STATE OF THE DARWINIAN THEORIES.

Sec. 1. The Theory of Descent.

The historical retrospect of the Darwinian theories, from their purely scientific side, leads us of itself to a critical review of their present state. We can briefly indicate in advance the result to which it will lead us, viz.: that the descent theory has gained, the selection theory has lost ground, the theory of development oscillates between both; but that all three theories have not yet passed beyond the rank of hypotheses, although they have very unequal hypothetical value. We can best arrange our review by beginning with that theory which is the most common, and which perhaps may still have value when both the others find their value diminished or lost: the theory of descent. From that we proceed to the theory of evolution, and from this to that of selection.

The theory of descent is indeed at first sight exceedingly plausible, and will probably always be the directive for all future investigations as to the origin of species. The organic species show, besides the great variety of their characteristics and the unchangeable nature of these characteristics, many other qualities which are common to them; and these common characteristics are precisely those which are most essential. {62} Moreover the higher the structure of the organisms which are differentiated, the more numerous and more valuable will become the evidences of similarity, and the greater also will be their distance from the inorganic and from the lowest organisms of their class, their type, or their kingdom. For instance, rose and apple-tree, elder and ash, wolf and dog, goat and sheep, ape and man, are not only a great deal farther removed from the mode of existence of inorganic bodies than the algae, the monera, and other low organisms, but they have also, in spite of the great interval which separates them from one another and especially which separates man from every animal, much more numerous and important points of contact than, for instance, two families or genera of algae or of mosses, of polyps or of infusoria, have among one another. Now our imagination refuses to accept the theory that the Creator, or nature, or whatever we wish to call the principle generating the species, in producing the new species, laid aside all those points of contact which are continually becoming more numerous and more important, and produced instead, by ever widening leaps, the new and higher species from the inorganic, which lies farther and farther from them. On the other hand, the theory appears to us all the more plausible, that every new species came into existence on that stage which is the most nearly related to it, and which was already in existence. If we add further, that the two old maxims of the natural scientists, omne vivum ex ovo and omne ovum ex ovario, have not been invalidated, in spite of all the searching for a generatio aequivoca, and that, even if the origination of the lowest organisms out of the inorganic could in future be {63} proved, yet the truth of these maxims for all the higher organized individuals is established as a fact without exception. Moreover, if we take into consideration the fact that we can not at all imagine either the origin or the first development of a higher animal or a human organism without the protecting integument and the nourishing help of a mother's womb, we may venture to say that each and every attempt to render the origin of the first individuals of the higher species conceivable, leads of necessity to the descent theory. We have either to reject, once for all, such an attempt, as an unscientific playing with impossibilities, or to accept the idea of descent. It is certainly the lasting merit of Darwin, even if his whole structure of proofs should in the course of time show itself weak, that he not only had the courage (as others had before him), but also inspired scientists with the courage to trace the idea of a descent of species in a scientific way.

To be sure, so long as we have no other proof of the descent theory than the circumstance that we can imagine it, it will continue to be nothing more than an ingenious hypothesis. We have, therefore, to look to the realm of nature for more direct proofs; and we are there furnished with them. They are presented to us by geology in connection with the botanical and zooelogical systems, by geology in connection with vegetable and animal geography, by comparative anatomy, and by the history of the embryonic development of animals.

Geology finds in the strata of the crust of the globe a large number of extinct plants and animals of extraordinary variety; but all of them, however much they {64} may differ from the organisms of to-day, are completely in harmony with the botanical and zooelogical systems in which we divide the still living organisms. Not only have by far the most of the now extinct genera and species their family and stem-companions, and many even their genera and species companions, in the living world, but also those genera whose nearer relations are now extinct—as, for instance, the club-moss-trees, the trilobites, the ammonites, the belemnites, the sauria, the nummulites,—show still a very perceptible relationship with living genera, and can be quite accurately included in the botanical and zooelogical systems; nay, they even fill up gaps in it. The anatomical, morphological, and, so far as we can judge, the physiological and biological relationship of the fossil with living organisms, is so great and comprehensive that in the present state of science a systematic botany or zooelogy, that should only treat of the fossils or of living organisms alone, would be imperfect. But the relationship of the fossil organisms with the natural systems of botany and zooelogy is apparent not only in this respect, but also in the fact that the single species during the long periods of time which are shown by geology to have elapsed, came into existence in a series, which again pretty closely corresponds to the natural system of the organic kingdoms; and that the fossil representatives of all classes and families, the nearer they come to the present world, appear the more nearly related to the living organisms, so that the fauna and flora of the ante-human time are lost in those of the human period by transitions gliding from the one to the other. For instance, in the Miocene formation of the tertiary epoch {65} we find thirty per cent. of species still living to-day; in the Pliocene, even sixty to eighty per cent., and toward its end even about ninety-six per cent. of species which are identical with those now living.

A brief glance may still more closely illustrate this analogy between the geological series and the organic systems. Plants and animals seem to have appeared nearly at the same time, and at first in the form of the very lowest organisms. The earliest plants found by geology belong also to the lowest stage of the vegetable kingdom; they are the algae. They are followed again by higher cryptogamous plants, especially ferns and club-mosses. Only at a later period flowering plants appear, among them being first the plants with naked seeds standing lower in the systems, as the cycad-trees and pine-forests; later, those with enclosed seeds, among them being again first the monocotyledons, last the dicotyledons,—all of them precisely corresponding to the botanical system. The same thing is true in the animal kingdom. If the eozoon Canadense, found in the laurentian slate of the Cambrian formation in North America, is really an organism and not an inorganic form, the earliest vestiges of animal life we can find are the rhizopodes or foraminifera; and these organisms belong to the lowest stage of life—to that stage which forms a kind of undeveloped intermediate member between the vegetable and animal kingdom, Haeckel's kingdom of the protista. The next oldest animal organisms found in the Cambrian formation are the zooephytes, and immediately above them the mollusca and the crustacea. In the following Silurian period we find corals, radiata, worms, mollusca, and crustacea, in {66} great number, also all the main-types of the invertebrates; and in the highest Silurian strata there are also to be found representatives of the lowest class of vertebrates, of fish, but still of very low organization and little differentiated. That the five main-types of the invertebrates seem to have appeared quite contemporaneously, yet that the zooephytes really appeared first, does not contradict the before-mentioned law of a progress in the appearance of the organisms from the lower to the higher. For in the zooelogical system also these main-types of the invertebrates do not stand one above the other, but by the side of each other: at most, the radiata, the worms, the mollusca, and the articulata, take their places above the zooephytes. Only within the main-types, in the classes, orders, etc., do differences in rank take effect; and even here, not without exception. What difference in rank, for instance, is there between an oyster and a cuttle-fish? between a cochineal and a bee or ant? and yet the first two belong to one and the same type—the type of mollusca; and the last three to one and the same class—the class of insects. The vertebrates rank decidedly above the invertebrates; and in a manner wholly corresponding to this, the vertebrates also appear after the invertebrates. Just as decidedly as to their rank, the main classes of the vertebrates do not stand beside, but above one another: above the fish stand the amphibia, above them the reptiles, next the birds, and above them the mammalia. To this series of succession also the geological facts seem to correspond pretty closely; only long after the fish do the first amphibia and reptilia appear—although it can not yet be decided which of these {67} two classes has left its earliest traces. If the interpretation of the gigantic foot-steps in the colored sandstone of North America, as belonging to the cursorial birds, is correct, the first appearance of birds falls in the time between the reptilia and mammalia; otherwise the first mammalia would have appeared before the first birds. For if we find the first real bones of birds only in the Jura and in the Chalk-formation, they are birds with tail-spines and with teeth in the beak—hence still related to the reptilia or the sauria. The first traces of mammalia to be found in the Upper Keuper formation, and in the Jura, belong to the order of opossums or marsupialia; i.e., to that order which (excepting the echidna and the ornithorhynchus that, as so-called monotremeta, stand the very lowest in the class of the mammalia, but are very scarce) occupies the lowest stage among the multitude of mammalia. Only after them do the higher orders of mammalia appear; and last of all organisms, man.

If we follow more in detail the appearance of the single organisms, some remarkable modifications show themselves in the course of their appearance and growth. We have heretofore mentioned the possibility of the appearance of the mammalia before the bird. Another fact which deserves attention is, that frequently the lowest representatives of a class or an order do not at first appear where the highest representatives of the next lower class or order are in existence, but with lower representatives of a preceding class or order, viz.: such representatives of the same as are still less differentiated and unite in themselves comparatively still more generic and less specific characteristics—as for instance, the lowest and {68} earliest amphibia, which do not appear at the same time and place with the most highly organized fishes, but with fishes of still lower organization. Moreover many groups of organisms show in earlier geological periods a richness of development from which they have now fallen far away. For instance, among the mammalia the pachydermata, among the reptilia the salamander and newt, among the articulata the cephalopoda, are at present remarkably reduced;—compare with the legions of ammonites and belemnites of the secondary period the small number of nautilus and cuttle-fish of the seas at the present day. A similar fortune was experienced by the ferns and club-mosses which formed whole forests in the carboniferous period. Other groups which once played a great role, are now wholly extinct; for instance, the trilobites of the primary, the sauria of the secondary, the nummulites of the tertiary periods. Now, all these modifications of geological progress would entirely correspond to the idea of a pedigree to which the descent theory traces back the whole abundance of forms of organisms. As soon as we seriously accept the idea of a pedigree, each of the two organic kingdoms would throughout form for its classes and species not only one single straight line of descent, but a tree, the branches of which are again ramified in a manifold way; a tree on which single branches—as perhaps that of the class of birds—may leave the main-stem or a main-branch, possibly being a branch destined to a higher development, and on that account held back in the process of development; a tree, finally, on which also branches and twigs can wholly or partly die off, as those of the extinct or reduced groups of organisms. {69}

From the point where the geological formations approach the present time, plant and animal geography also assists geology in increasing the weight of the reasons for an origin of organisms through descent. With the tertiary period, the fauna and flora of the globe, which in former periods had a nearly uniform character all over the earth and showed no climatic differences, begin to separate according to climate, zones, and greater continents. This separation becomes distinctly evident in the middle tertiary formations, the Miocene, and much more distinctly in the higher tertiary formations, the Pliocene. The animals, especially the higher vertebrates, of the Pliocene formation on each continent or each larger group of islands, correspond very closely to the now living animals of the same geographical limit, with the exception of being generally of a much larger size. The Pliocene animal world of mammalia of the three old continents, for instance, corresponds exactly, through all its orders, to the present fauna of Europe, Asia and Africa; and that on an average it was built up more stupendously than that of to-day, we can see from the cave-bear and the mammoth. South America is the home of a peculiar order of mammalia—of the edentata, to which belong the sloth, the armadillo, and the like. All its predecessors are to be found also in the Pliocene strata of South America, and only there; and mostly in gigantic, but otherwise completely related, forms. New Zealand has no indigenous mammalia, but in their place great cursorial birds with but rudimentary wings. Exactly the same thing is found by geology in its tertiary and post-tertiary strata: nowhere a mammal, but gigantic birds with rudimentary {70} wings, down to the dinornis, which probably died out in man's time. New Holland has merely marsupial and some monotrematous, but no placental, mammalia; even its tertiary strata give no placental mammalia, but marsupialia, in analogy with all living genera, herbivorous, and carnivorous. Indeed, the analogy goes so far that the same line which through the Indian Archipelago separates the present Australian animal and plant world from the Asiatic, forms also the separating line for the geological zones of the Pliocene epoch. All these are facts which render quite inevitable the idea of an origin of the higher organic species of to-day through descent.

But still, from another side, animal geography, though it does not yet speak for a common pedigree of the whole animal world, as the facts just mentioned also do not, still at least speaks for a descent of related, though at present separated, genera and species from common forefathers. The continents of the Old and New World are so constructed that toward the North Pole they approach one another very closely, and toward the South Pole they withdraw from one another. Without doubt there existed in the North, through long periods of time, a land-connection of America with Asia and with Europe. Now, both continents have their more or less characteristic animal world, and these characteristics are distributed over the two halves of the globe in the following extremely remarkable way: The fauna of the Old and the New World, in those groups of animal genera which live only in the warmer or tropic zones or only south of the equator, and have no associates of genera or families in the higher North, is in each hemisphere entirely characteristic, and differs in a {71} marked way from the fauna of the other half of the globe. For instance, the rhinoceros, the hippopotamus, the giraffe, the antelope with undivided horns, the hedgehog, the mole proper, are only inhabitants of the Old World, whence also the horse originally came, the striped ones in Africa and the non-striped in Asia; on the other hand, the lemur, the ant-eater, the armadillo, and others, are limited to South America. The apes of the Old World have five molar teeth on each side of the jaw, narrow noses, tails usually short and never prehensile, and fleshy protuberances for sitting; the apes of the New World have six molar teeth, flat noses, and long prehensile tails. And on the contrary, where closely related species are found on both parts of the globe, they belong only to genera of which single species live or have lived in the far North; as, for instance, the rein-deer, still common to the Old and the New World in this very North which once formed a bridge between the two halves of the earth. The same is true in regard to cattle, the deer, the cat, the dog, the hare. Similar facts can also be shown of other animal classes. The farther the different species of these genera withdraw from the North Pole, the greater become the differences between the species on the one half of the globe and the analogous species of the other. Compare on this point K. E. von Baer's "Studien aus dem Gebiete der Naturwissenchaften, ueber Darwin's Lehre," ("Studies from the Realm of Natural Science upon Darwin's Teachings"), p. 356 f. If we add, further, the before mentioned fact, that those genera which are exclusively peculiar to one or the other continent, have their related predecessors in the tertiary strata of these continents, {72} the hypothesis of a separate origin for each single species, without genealogical connection with the anatomically and physiologically related species, becomes neither more nor less than a scientific impossibility.

Moreover, there are several facts of comparative anatomy which have long been the joy of all zooelogists and have rewarded the toilsome labors of detailed investigations by a delightful view over the whole realm of the organic world, but which find a scientific explanation only in the descent theory. They are the homology of the organs, and to a certain degree also the so-called rudimentary organs. By homology of organs we mean the fact that within one and the same class-group of organisms all the organs, and especially the organs in their most solid constituents, in the skeleton, are built after one and the same fundamental plan, and therefore are even in their most widely separated modifications varied after this one and the same plan. This is especially true of the vertebrae and the limbs. This homology goes so far within one class, particularly within the class of mammalia, that, for instance, the hands and feet of man, the hands of the ape, the paws of the beast of prey, the hoof of the horse and of the ox, the paws of the mole, the fins of the seal and of the whale, the wing-membranes of the flying-squirrel, correspond to one another in their smallest parts and ossicles, and can all be registered with the same numbers and letters; i.e., they are homologous to one another even to the minutest detail. The ideal plan and connection in the organisms, disclosed by these facts, and long ago acknowledged and admired, receives at the same time its simple material basis through the acceptance of a common descent. {73}

A similar relation is observed in rudimentary organs.

Many of them, as the nipples of males, point, if not to a common descent from a lower form, at least to a common plan of the sexes. But when the embryo of the whale still has its teeth in the jaw, the grown up whale its hip-bones, when the eye of man still has its winking membrane, the ear and many portions of the skin their rudimentary muscles of motion, the end of the vertebral column its rudimentary tail, the intestinal canal its blind intestine; when sightless animals, living in the dark, still have their rudimentary eyes, blind worms their shoulder-blades; when in like manner the plants, especially in their parts of fecundation, show in great number such rudimentary organs as are entirely useless for the functions of life, but which are never misleading in determining their relationship with other plants:—how simply are all these facts explained by the descent theory, how not at all without it!

Finally, if we now mention the history of the development of animals, we shall have to postpone to the next section the consideration of the most essential facts furnished by this science; for the individual development of animals is a process which could speak not only for a descent of the species, but also for a descent of them through gradual development. But where, as in the present section, we treat the descent theory apart from the evolution theory, we have also to think of the possibility that the species or groups of species are not originated through gradual development, but nevertheless do originate through descent—namely, in leaps through metamorphosis of germs or a heterogenetic generation; and for such an idea we find confirmation in the {74} observation of the history of development of animals, which we call change of generation or metagenesis.[4] By this is meant the following phenomenon: Certain animals, as the salpa and doliolum of the order of the tunicata, as well as certain mites and many tape-worms, produce offspring which are wholly dissimilar to the mother stock. These offspring have the capacity of reproducing themselves—if not by sexual means, as at the first generation, still by the formation of sprouts; and it is only the animals originated by the second generation (with many species, even those by the third) which return again to the form of the first generation. The plant-lice transmit themselves through six, seven, even ten generations by means of sprouts, until a generation appears which lays eggs. Now it is indeed true that the change of generation forms a circle in which the form of the last generation always returns to that of the first, and therefore leaves the species, as species, wholly unchanged. But it is nevertheless a process which shows that the natural law of an identity between generator and product, observed in other relations, is not without exception; and if we once have reason to suppose that the generation of new species took place in past periods of the globe, but has ceased in the present, such processes in the single period open to our direct observation—namely, the present (in which, however, according to our knowledge, the species remain constant)—are {75} nevertheless hints worthy of notice. For they refer us to ways in which in those former times, when certainly new species did originate, this formation of species might possibly have taken place.

This consideration leads us to treat of the main objection raised to every descent theory: namely, that never yet has the origin of one species from another been observed, but that, on the contrary, all species—so far as our experience goes, stretching over thousands of years—remain constant. We will give no weight to the fact that the constancy of species seems by no means to be absolutely without exception; for on the whole, they certainly remain constant. The only example which goes to prove such an evolution of species as taking place to-day—viz: the natural history of sponges—seems not to have this bearing. The transitions of form, proven by O. Schmidt in the siliceous sponges and by Haeckel in the chalk-sponges, seem to show, not the genetic coming forth of a new species out of another, and especially not the evolution of a higher species out of a lower, but rather the uncertainty of the idea of species in general and the worthlessness of the skeleton-forms, for this idea, in such low organizations as the sponges. But that objection already loses its chief force from the consideration that we have not only never observed the origin of one species from another, but never even the origin of a species itself; and that nevertheless all species have successively originated in time. If we, therefore, are not able to observe directly their origination, we have a right to make all possible attempts at approaching the knowledge of it in an indirect way. But we see this objection invalidated by still another {76} fact. From all observations, it seems to be evident that those agencies which originated the species in general have ceased since man appeared. Now this fact is inconvenient for all those who, on metaphysical grounds, reject aim and purpose in the world and accept an aimless motion in the universe, a circle in which only identical powers are ever active to all eternity. From this standpoint, the scientists cannot, except by very artificial hypotheses, escape the conclusion that, if new species once originated through descent, new species ought still to originate through descent. In like manner, it is true, they are also obliged to accept the other conclusion: that if new species once originated through primitive generation, new species ought still to originate through primitive generation. On the other hand, those scientists who recognize aims in the world for which the world and each part of it is destined, and which are attained in the world through the processes of coming into existence, have to expect in advance that the organic kingdoms are also planned with reference to those aims. They naturally see the aim of the origin of species attained, where in the organic world beings appear who combine with the highest physical organization a self-conscious and responsible spiritual life, and who are capable of conceiving the ideal, even the idea of God. For, with the appearance of these beings, there enter upon the theatre of the world beings who go beyond the value of a purely physical organism and of a purely somato-psychical life, and in like manner represent again a higher order of beings; just as the first appearance of organic life on earth once introduced a new and higher stage of {77} existence in contrast to the inorganic world. Scientists who take this standpoint can readily adopt the fact that we do not now observe the origination of new species; for it is in full harmony with their metaphysical doctrines, without the same being on that account essentially dependent upon the confirmation or rejection of the hypothesis of the present constancy of species. With this very fact, the maxim that if new species once originated through descent, new species must still originate through descent, has lost for them its truth, and therefore its power of demonstration. So we see even here, while in the midst of the discussion of a purely scientific problem, in what close correlation metaphysics and natural science stand, and moreover—since the metaphysical view is most closely connected with the religious—in what close relationship religion and natural science stand. At the same time we also see how little the metaphysical interest, and much more how little the religious interest, has reason to avoid the investigation of facts in nature.

Sec. 4. The Theory of Evolution—Archaeology, Ethnography, Philology.

The evolution theory teaches that the species have developed themselves one from another in gradual transitions, each of which was as small as the individual differences still observed to-day among the individuals of the same species. It is not without support, especially in the history of the development of plants and animals.

Each organic being becomes what it is by means of organic development. Each plant, even the highest organized, begins in its seed-germ with a simple cell, {78} and is differentiated in constant development up to the fully perfected individual. Each animal, even the most highly organized (man included), begins the course of its existence as an egg; and each egg has no greater value of form than that of a single cell. This egg-cell is differentiated, after fecundation, in gradual and imperceptible transitions, farther and farther, higher and higher, until the individual has reached its perfect organization. No organ, no function of the body, no power or function of the soul or of the mind, appears suddenly, but all in gradual development. Since we see all individuals thus originating by means of gradual development, the possibility lies very near that the different organic formations of all the organic kingdoms could also have been originated by the same means.

In still another direction does the history of the development of single plants and animals make this possibility plausible to us. In the animal world, and partly also in the plant world, the single individuals of higher species in their embryonic development pass through states of development, in the former stages of which not only the individuals of the most different species look confusingly similar to one another, but also the embryos in their organization remind us of the perfected state of much lower classes of beings. In order to give a clear idea of the first mentioned facts, Haeckel, for instance, in his "Natural History of Creation" and in his "Anthropogeny," represents by engravings the embryos of different vertebrates and also of man; representations which—although, according to the judgment of competent scientists, unfortunately not exact, but modified, after the manner of stencil plates, in favor of {79} greater similarity—yet make it quite clear that the similarity of the different embryos must be very great. We see, for instance, on one table the embryos of a fish, a salamander, a turtle, a fowl; on a second, those of a pig, an ox, a rabbit, a man; on a third, those of a turtle, a fowl, a man; and we find the similarity really great. Examples of the second fact—that individuals of higher classes or orders in former states of their embryonic development represent an organization which corresponds to the full-grown individuals of the lower classes—are: the tail of the human embryo, the gill-arches of the embryos of reptilia, of birds, of mammalia, and of man. Now Haeckel here takes up again an idea first suggested by Fritz Mueller, and derives from these observations the "biogenetic maxim," as he calls it: "The history of the germ is an epitome of the history of the descent; or, in other words, ontogeny (the history of the germs or the individuals) is a recapitulation of phylogeny (the history of the tribe); or, somewhat more explicitly: that the series of forms through which the individual organism passes during its progress from the egg-cell to its fully developed state, is a brief, compressed reproduction of the long series of forms through which the animal ancestors of that organism (or the ancestral forms of its species) have passed from the earliest periods of so-called organic creation down to the present time." In his latest publication, "Ziele und Wege der heutigen Entwicklungsgeschichte," ("Aims and Methods of the Present History of Evolution"), he admits into the formulation of his biogenetic maxim also the consideration of those phenomena in the ontogenetic development which are no recapitulation of the history {80} of the stem, but originated by adapting the embryo to its surroundings. In the description and explanation of this theory, he uses a term which throws upon nature a peculiar reproach, never before made, namely: cenogeny, or history of falsifications, in contrast to palingeny, or history of abridgments. This amended formula now reads: The development of germs is an abridgment of the development of stems, and is the more complete according as the development of the abridgment is continued by inheritance, the less complete according as the development of the false is introduced by adaptation.

Now, we ask: Is this biogenetic maxim correct? and moreover, from the fact of the organic individuals originating through development, are we entitled to draw the conclusion that even the species must have originated through development? To this question we can no longer get an answer from the life-processes of living organisms; for we have already mentioned the fact that, according to the present state of our knowledge, we can no longer observe the origination of a new species. Moreover, the embryonic states of development show also, in all their similarity, even in the very first stages, and with especial distinctness in these first stages, many differences between the single species; and this is true especially of those species which, according to the followers of this so-called biogenetic maxim, should lie in the same stem-line,—so that the direct scientific value of the embryological results to the palaeontological investigation, or of the latter to the former, is so far very slight. Such a problem, however, as the one contained in that biogenetic maxim, which only gives to investigators the direction in which possibly an {81} interesting and profitable path can be opened, does not at all deserve the name of a "law." K. E. von Baer, the founder of the whole present science of the history of development, has certainly a most competent judgment of the correctness of this so-called biogenetic maxim; and he convincingly shows, in his essay on "Darwin's Doctrine," that the embryos never represent a former animalic form, but that their development follows the principle of representing first the common characteristics of the class, then those of the order, etc., until finally the individual characteristics appear in the formation. Those who wish more information about embryology can find it in Heinrich Rathke's "Entwicklungsgeschichte der Wirbelthiere" ("History of the Development of Vertebrates"), edited by A. Koelliker, Leipzig, Engelmann, 1861; and those who wish to inform themselves as to the influence of the ontogenetic results of the solution of the phylogenetic problems, will find, besides the before-mentioned work of Wigand, rich and clearly elaborated material in the publication of Wilhelm His—"Unsere Koerperform und das physiologische Problem ihrer Entstehung, Briefe an einen befreundeten Naturforscher" ("The Form of our Body and the Physiological Problem of its Origin; Letters to an Associate Scientist"), Leipzig, Vogel, 1875. The latter writer, although he advocates the descent theory, rejects the hasty assertions of Haeckel with direct and convincing arguments.

Thus embryology, having from the simple fact of an origin of single plants and animals through descent at least confirmed the idea of the possibility of an origin also of species through development, forsakes us in the {82} inquiry as to the reality of such a genealogy of development, and refers us to other sciences.

Such a science, from which we certainly are entitled to expect a decided answer, is geology. For if the evolution theory is right, those periods of the history of our globe in which new species originated—namely, the periods of geology—must show us also the forms of transition between the different species. And, indeed, geology gives us an answer; but it reads contradictorily: It says yes, and it says no.

Geology does show us forms of transition, and, indeed, most frequently in the lower classes of animals. Who that has once studied petrifactions, does not know the mass of forms of the terebratulae, the belemnites, and the ammonites, in the Jura formation? Wuertemberger has brought light into the perplexing division of species of the ammonites by simply showing their temporary and systematic transitions into one another. In the fresh water chalk formation of Steinheim, near Heidenheim, in Wuertemberg, scientists have found, on the same place, in an uninterrupted series of strata, the snail valvata or paludina multiformis in all imaginable transitions—from the flat winding, showing the form of a chess-board, up to the sharp form of a tower. And it was not, as Hilgendorf thought, in a series which can be traced in the strata according to time, but, as Sandberger says, in quite a varied mixture, yet in all imaginable modifications. But even among the higher and the highest classes of animals, we can trace the transitions. The flying sauria, if not in their organs of flying, which remind us more of the bat, at least in head, neck, and toes, are closely connected with the {83} birds—the oldest birds of the Jura and chalk formations, with their tail-spines similar to the reptilia and their teeth in the beak to the sauria. The tertiary formations especially show the primitive history of many vertebrates in very instructive forms of transitions—which, for instance, Ruetimeyer, a scientist who is very cautious in his conclusions, very distinctly traced to the horse, to the ruminating animals, and lately also to the turtles. Still more in detail, W. Kowalewsky has lately shown us the primitive history of the horse, and Leidy and Marsh have further completed it by the addition of American forms, the former having at the same time described the forms which have led to the tapir.

But to such facts there are, on the other hand, experiences directly contradictory. Many lower and higher forms of animals and plants appear in the geological strata, so far as they have been explored, in a wholly independent way. We have mentioned, in the foregoing section, that the main types of the invertebrates appear somewhat contemporaneously and without any traceable intermediate form. The trilobites, a quite highly organized order of crustacea, appear in the strata of the silurian epoch almost suddenly, in very many and very distinctly marked species. The uncertainty of our knowledge shows itself most clearly when we ask for the geneologic relationship of the vertebrates. In Chap. II, Sec. 1 and Sec. 2 we have already referred to the value which Darwin, and more especially Haeckel, lays on the relationship of the larva of the ascidia to the lancelet fish. Now the important testimony of K. E. von Baer, in his "Memoires de l'Academie de St. Petersbourg," Ser. vii, Vol. 19, No. 2, tells us that the nerve-ganglion {84} of the ascidia lies on the side of the stomach, and on that account can not be homologous with the spine of the vertebrates, but that the cord in the larva of the ascidia is nothing more than a support for the tail in swimming, which afterwards disappears, as with many other larvae. As to the course of reasoning in reaching these genealogical conclusions, he says: "The hypothesis is indeed flexible. According to common reasoning, that which shows itself early in the development is an inheritance of the first progenitors. Therefore the ascidae ought to descend from the vertebrates, and not the reverse. But it was necessary to show the descent of the vertebrates from the lower forms. In order to respond to such a necessity, men sometimes reverse their conclusions. Although favorably disposed to the doctrine of the transmutation of the animalic forms, I want a complete proof before I can believe in a transformation of the vertebrate type into that of the mollusca." Moreover, the zooelogists Semper and Dohrn find in the embryonic development of the sharks, the scates, and other cartilaginous fishes, organs which would bring them rather into a nearer relationship with the ringed worms than with the crustacea. When, on the other hand, we look around in palaeontology, the oldest fossil fishes remind us neither of the crustacea nor of the ringed worms, but of the crabs: a class of animals which lies entirely outside of Haeckel's stem-line of vertebrates. Also the first appearance of mammalia does not show transitions. Thus far we have not found in the geological strata any vestiges of the half-apes, which, according to the hypothesis of the evolutionists, as a common stem-line for the lines of ape and man development, once played such an {85} important role, and which have quite numerous representatives.

But the answer which geology gives to our questions as to the probable confirmation of the evolution theory, naturally becomes most interesting where the origin of man is treated of. Our attention is, therefore, especially directed to the most recent formations of the globe which show us the oldest remains of man. The most instructive are those parts of the skeleton which allow us to draw the most convincing conclusions as to the degree of mental development of an individual, namely: the parts of the skull. Although human bones seem to have been less easily preserved than those of animals, and are, comparatively speaking, very scarce, especially more so than prehistoric implements, still there are not wanting such remains, which go back far beyond historical time. The oldest known skull is the celebrated one of the Neander cave near Duesseldorf, with its large vault of the forehead, and its low height. Although Virchow finds on it evidences of rachitis in youth and of gout in old age, as well as of injuries, it nevertheless can not have been changed in its fundamental form by any sickness, even according to Virchow. This very skull now indisputably shows a still lower formation, which, although quite essentially different from the type of the ape, stands nearer to it than is the case with the skulls of men in later times. Of a later date, and of a correspondingly higher form, are the skull of Engis, of Cannstatt, the skulls of the Belgian caves (especially Chauvaux), of France, and of Gibraltar. According to the weighty authority of Schaaffhausen (note his opening address at the Wiesbaden Congress of the {86} Anthropological Society, 1873), the skulls and the remaining parts of the skeleton show more indications of a lower formation the older they are. He especially calls attention to a certain bone of the roof of the skull—the Os interparietale or the so-called Os Incae—which has only recently been recognized as a characteristic of a lower formation of skulls, standing nearer to that of animals. As late as the summer of 1873, two human skeletons were found at Coblenz in a volcanic sand, of which Schaaffhausen says: "No less than eight anatomic marks of a lower formation, which probably have not heretofore been found together, indicate the great age of these remains." With all these traces of a difference between the former and the present state of the physical condition of man, the differences between the type of man and that of the animal are still great enough to leave wide open the possibility of the origin of man through some other means than that of gradual development. On the other hand, it is more or less in favor of the evolution idea, that so far such old remains of man have been found in places which certainly can not have been the cradle of mankind, and that those parts of the earth which we would naturally suppose to be the first dwelling place of the earliest human genera have been little or not at all investigated. And also the hypothesis of Haeckel, that the cradle of mankind was a land between Africa and Asia, now sunk in the sea, and called Lemuria, can be neither proved nor denied. Such vague possibilities have indeed not the least scientific value.

In considering these contradictory results of geological investigation, we dare not overlook three points: First, our knowledge of the crust of the globe is still {87} very fragmentary, and does not yet extend over the whole globe. Further, it lies in the nature of the case that the strata in mountain formations can only give a very incomplete picture of the whole variety of the real organic life which may have populated the earth and the sea. What a poor picture of the present plant and animal life would be offered, for instance, by the soil of our continents, the slime, sand, and pebbles of our coasts and of the bottoms of our lakes and seas, if we had to construct from them alone the fauna and flora of the present! A third, but purely hypothetical, consideration is rendered of importance particularly by Darwin and Haeckel; namely, that the forms of transition without doubt existed for a shorter period than those forms whose organization has established itself in fully developed species.

Thus far we have directed our attention to inquiring how the organic individuals were originated—and have throughout observed a successive development; next, we have questioned geology—and here also have observed a progress in the appearance of the species, but have received at the same time contradictory answers to the question whether this progress presents itself as a gradual development of one species from another or as a sudden appearance. So the reasons for and against the evolution theory almost balance one another; and it is not improbable that the hypothesis of an origin of species through development will have to share its authority with the hypothesis of a descent of species through heterogenetic generation, as well as with the hypothesis of a primitive generation of lower organisms, still repeating itself at a later time. Thus for the origination of {88} groups lying nearer together, we have the evolution theory; for the other groups, and especially for the origination of types where no transitions to other types can be traced, the theory of the heterogenetic or primitive generation recommends itself; and both theories thus far are of a purely hypothetical nature.

But there is still a third realm, which is just as open to our observation as the history of the development of organisms and as geology, and of which we can also ask, whether it does not open for us an indirect way to the knowledge of the origin of species, and especially of man—a knowledge which we can no longer approach in the direct way of observation. This realm is natural history and the history of the development of the human race. For mankind also is engaged in a process of development, and its present members do not stand on the same height. Now the question is, to what beginning can we trace backward the development of mankind, and to what succeeding stages of development from this present condition? And do we find in these earliest periods, and on these lowest stages, points that are connected with still earlier conditions and organizations, and especially points which could genealogically join together mankind and the animal kingdom? Three sciences, still young, favorite children of the present generation, participate in investigating this realm, namely, archaeology, comparative ethnology, and comparative philology.

Archaeology leads us back to far-off times. It is a fact that, chronologically speaking, man lived in the glacial period—according to French scientists, even before it; and that, palaeontologically speaking, man and {89} mammoth lived at the same time, and, according to a discovery made some thirty years ago at Denise in Middle France, probably even man and another older and defunct form of pachydermata, the elephas meridionalis, in North America man and the mastodon. The reader may compare the discoveries regarding the age of mankind, as they are described most recently by Sir Charles Lyell in his work upon this subject, in the publications of the Anthropological Congress at Brussels in the year 1873, and in those of the fourth General Assembly of the German Society for Anthropology, Ethnology and Primitive History, at Wiesbaden, in the year 1873.

Now, to be sure, from the oldest human tools and utensils that are found, we can expect still less than from the oldest human bones that they will throw direct light upon the answer to the question of the origin of man. For where man not only uses tools, but manufactures the same for use, a wide breach already exists between man and animal. Manufactured articles, therefore, can only throw some light on the history of the development of the already existing human race. And even this light is less clear than we perhaps expected in view of the first interesting prehistorical discoveries. It is true, all these discoveries show us an ascent from the simplest and roughest forms to the more perfect; from the split but unpolished stone to the polished, and from stone to bronze and iron. But a progress of the human races in manufacturing and using articles, from the simple and rough form to the more artificial, lies so much in the nature of the case, and is so taken for granted with every conception of the origin of man, even with that contradictory to Darwinism, that from this simplicity of {90} the earliest tools we can not at all conclude that there was a condition of mankind lying near that of animals; and especially we can draw only general and uncertain conclusions as to that which makes man man, as to the spiritual and moral qualities of those prehistoric men. Moreover, in discoveries belonging to the very oldest, we come upon drawings and engravings from which we recognize the man of those primitive times as a creature whose life was not entirely taken up in the animalic struggle for existence, but was already adorned with those ideal pursuits and enjoyments which we are accustomed to ascribe to the height of civilization. Examine, for instance, the drawing of a mammoth on a mammoth tooth of Dordogne, which the French scientists Lartet and Christy have reprinted in their Reliquiae Aquitanicae (1868), and which Sir Charles Lyell has copied in his "Age of the Human Race." How much spirit and life in this primitive work of art! Or read what Fraas, in the "Journal of the German Society for Anthropology," March, 1874, reports about the picture of a grazing reindeer, engraved on a knife handle made of the horns of a reindeer, which was lately found in the cave of Thayngen near Schaffhausen, and which surpasses in beauty all rough drawings thus far found. The whole bearing of the animal—the muscles of the legs and the head, the form of the many-branched antlers, with the wide-spread eyes, the representation of the hair upon the body and under-jaw—all disclose a real artist among those savages.

This is also to be taken into consideration: that those men, whose traces we find, could possibly have been the descendants of more noble predecessors, driven {91} off and degenerated, just as well as they could have been representatives of the whole former condition of culture of mankind. In England, where the questions of the first condition of culture of mankind are very warmly discussed, the Duke of Argyll particularly, in his "Primeval Man," advocates these views, and very forcibly calls attention to the fact that thus far the places of the discovery of the earliest traces of man undoubtedly lie very far from the original home of the human race; while Sir John Lubbock, in his "Origin of Civilization" and in his "Prehistoric Times," and also Tylor in his "Beginning of Culture" and in his "Early History of Mankind," take the opposite view of a progress of mankind from the most uncultivated beginnings.

Archaeology, as a whole, seems to do no more than admit that its results can be incorporated into the theory of an origin of the human race through gradual development, if this theory can be shown to be correct in some other way, and that its results can just as well be brought into harmony with a contradictory theory.

Comparative ethnology gives us quite a similar result. It is true, there are races of mankind in the lowest grades of human existence. It is well known how Darwin, in his voyage on board the "Beagle," got one of his first vivid impressions of the possibility of an evolution of man from the animal world, by seeing the inhabitants of Tierra del Fuego; and it is remarkable that the arms, tools, and furniture, used by the lowest savages, are very similar to the earliest remains of civilized races found on earth. The conclusion lies extremely near, that the savages simply remained in earlier stages of human culture; and an ethnographic picture of mankind {92} at present would in a similar way give an approximately correct view of its former development, as the natural zooelogical and botanical system of the present fauna and flora must give us at the same time the key to their pedigree; supposing the Darwinian theory to be correct.

If it were so, ethnology would be an altogether inestimable help for the exploration of the descent and development of the human race. For the extremely few and rare fossil remains of man—which, moreover, do not give us any answer to the most important questions in regard to the mental and moral quality of the primitive man—would be rendered complete by living examples of the kind, which remained at the old stages of development.

But much is still wanting, before the followers of an evolution theory dare to use ethnology directly as a primitive history of the development of mankind, prepared and preserved for them. Especially the before-mentioned objection of the Duke of Argyll—that the lowest savages of our time can just as well be depraved as be men who remained stationary in the process of development—has here increased weight. Moreover, even with the savages of to-day, a rude state of their tools and a low condition of their mental and moral life are not so nearly parallel as to allow unrestricted conclusions to be drawn. Finally, we still know too little about the state of culture of the savages; and the deeper and higher the intellectual and ethical possessions of mankind are, the presence of which among the savages is in question, the more uncertain is our knowledge.

This is especially true of the most important question in this connection—the question as to the existence {93} or absence of an idea of God, and the different stages of development of religious ideas. While some assume as an established fact, that there are savage tribes without any idea of God or any religion, and even give the names of these tribes, especially of some from the interior of South America; while Sir John Lubbock systematically enumerates seven stages of religious development, from atheism to the connection of religious with moral conceptions, and lets each single race run through these stages in an identical series until it either remains on one of the seven stages or arrives at the highest: yet, on the contrary, other equally trustworthy scientists assert that there is not a single human race without some idea of religion and of a God—indeed, not a single race without a monotheistic presentiment—and that all heathenism, down to its most degenerate stages, consists not so much in a non-recognition of a God as in ignoring him. They call especial attention to the difficulty of getting acquainted with the ideas of a savage tribe without living with it through many years and being intimate with its language and customs, and especially without enjoying the unrestricted confidence of the tribe. Mutual misunderstandings, a suspicious reserve, evasive and untrue answers to questions, are entirely unavoidable without those conditions. At any rate, the fact deserves attention, that those who have been longest and most active among savages, and who enjoyed their confidence to the fullest extent, all reached this result: they found them not only not without religion, but also not without a presentiment of the monotheistic idea of God. Livingstone, for instance, expressed this idea decidedly of all the African tribes {94} with which he became acquainted; and Jellinghaus gives the same evidence in regard to the Kols in South Asia.

The anatomic results of ethnology are more favorable to the descent theory, although they too lead no farther than to the conclusion that the skull-forms of the lowest tribes represent a lower stage of formation than those of the higher, and that these lower skull-forms are relatively nearer to the ape-form than the higher, but that they are still separated from it by a wide interval.

It appears, then, that even ethnology does not lead us essentially nearer the solution of the question than archaeology and geological anthropology.

The relatively strongest support to the evolution theory is given by comparative philology; and since language is the most important and most decisive of all the distinctive characteristics which separate man and animal[5], this science deserves especial consideration.

In the realm of the natural sciences, the enormous progress of palaeontology on the one hand and of systematic zooelogy and botany on the other took place step by step together, and thus prepared the way for Darwin's idea—which, from the rich material of analytical investigations, only tries to draw the simple synthesis, and to show at the same time in the zooelogical and botanical system a representation of the zooelogical and botanical history of development. In quite an analogous way, a process took place in the linguistic realm which in independent investigations prepared the way for Darwinism, and now, since Darwin's theory has sought {95} acknowledgment in the realm of natural history, brings again Darwin's ideas to the support of philology.

Linguistic and ethnographic investigations, especially the linguistic works of the missionaries, long ago resulted in gathering rich material from the storehouse of the language of races now living, and the latest works in the realm of historical, etymological, and comparative philology had traced the branches and twigs of the better known languages to stems and roots lying far back. The result of the comparison soon became the same as in the realm of the organic world: what presented itself in the system of the living languages as a lower form, seemed to represent itself as the older and more original form also in the history of languages. Therefore, all the prominent linguistic investigators found themselves more and more urged to accept a theory which declares language, this entirely specific characteristic of man, to be subject to the same laws of development from the simpler and most simple forms as the world of the organic. Long ago so celebrated a man as Jacob Grimm,—"Ueber den Ursprung der Sprache" ("The Origin of Language"), Berlin, Duemmler—following the footsteps of Wilhelm von Humboldt, had established a theory, according to which language is "not created, but produced by the liberty of the human will;" and judging from many of his Darwinistic utterances concerning the origin and development of language, he had traced its development in such a way as to arrive at the conclusion that artless simplicity in the unfolding of the senses is the first period of its appearance.

The scientists divide all the languages of the earth into three great groups: first, the monosyllabic, {96} isolating, radical, or asynthetic languages; second, the agglutinant, terminational, or polysynthetic languages; third, the inflectional languages. They are of the opinion that even the languages of highest rank—the inflectional—very probably took a starting-point from the asynthetic languages, and a course of development through the agglutinants, and that in like manner the agglutinants have behind them an asynthetic period. Thus they trace all the languages back to certain roots, which are more or less common to the different groups of languages.

To the question that now arises—How did these roots originate?—the linguists give us three different answers. The onomatopoetic theory, called by Max Mueller the Wow-Wow Theory, traces them to imitations of the sound (W. Bleek, G. Curtius, Schleicher, Wedgewood, Farrar); the interjectional theory, called by Max Mueller the Pooh-Pooh, or Pah-Pah Theory, traces them to expressions of the senses (Condillac); a third theory declares the roots to be phonetic types (Max Mueller, Lazar Geiger, Heyse, Steinthal); while it is still an open question, whether the attempts at explanation of these types must here come to a stand-still for the present, as Max Mueller thinks, or whether, according to Lazar Geiger, we can trace the first root-expressions especially to impressions of light and color.

The reasons from which Max Mueller, in his "Lectures on the Science of Languages" (Vol. I, Lect. IX), rejects the first two theories and proves the third, are quite convincing. Even if, in a purely hypothetical way, a language could be thought of in abstracto, the roots of which only consist in imitations of sounds or interjections, still in the really existing languages, {97} so far as we can trace back and uncover their roots, the roots imitating sounds and the interjectional roots form only a small and entirely isolated minority, which neither shares in, nor is capable of development; they stand like "dead sticks in a live hedge." By far the greater number of roots, and all which are capable of development, express abstractions from visible objects, conditions and activities, and therefore presume a human intelligence, reflecting with self-consciousness, which formed and used the roots.

Now Max Mueller sees, back of this period, still open to science, in which the root-elements of the human languages were fixed, a long period of exuberant and unhindered growth of the elements of language, in which the roots were separated from the multitude of nascent tones by elimination or natural selection in the struggle for existence. In this realm, which is no longer open to investigation, the naturalistic and the linguistic friends of the evolution theory are now in entire accord. Wilhelm Bleek, in his small, but very noteworthy essay, "Ueber den Ursprung der Sprache" ("Origin of Language"), Weimar, Boehlau, 1868, p. 11, uses this ingenious figure: what the animal world possesses analogous to language, takes about the same position as, in the art of printing, the block-print does in relation to printing with movable types. On page 12, he sees in the communication of the emotions among animals the sources from which under favorable conditions (in consequence of which the separation of language into articulated parts became possible) human language might have originated. This idea, which is closely joined to the interjectional theory, Darwin meets {98} with a related idea, depending upon the onomatopoetical theory, when he says, in his "Descent of Man": "Since monkeys certainly understand much that is said to them by man, and when wild, utter signal-cries of danger to their fellows, may not some unusually wise ape-like animal have imitated the growl of a beast of prey, and thus told his fellow-monkeys the nature of the expected danger? This would have been a first step in the formation of language."

But philology, from the point where it goes farther back in search of the roots of language, leaves the safe ground of knowledge and commits itself to the fluctuating ocean of conjectures; and since also the scientific evolution theory has only a hypothetical value, the support of a hypothesis in the one science by a hypothesis in the other naturally adds no weight to its probability, either for the one or the other. Besides, we must not overlook the fact that the very point in the history of the development of languages on which the investigation, as it looks backwards, must at present pause—namely, the existence of linguistic roots—presumes a faculty of abstraction which can not be thought of without self-consciousness.

Therefore archaeology, comparative ethnography, and comparative philology, show us quite clearly a development, but not an origin of mankind through development. Yet they do show an already existing development of mankind; for all three sciences lead back to starting-points, where mankind already existed with all the essential attributes of mankind, and leave us without answer to our questions as to the conditions lying still farther back. Their results we can {99} without difficulty harmonize with a theory which supposes mankind to have originated by evolution, provided such a theory could be confirmed from another side; but they agree just as well with a contrary theory, which excludes the origin of mankind by gradual development.

Taking, thus, everything into consideration, we come to the conclusion that the evolution theory, like the descent theory, is so far only a hypothesis—and, indeed, a hypothesis which as such has a much more problematical character than the descent theory. For while in regard to the latter we had to say that we have either this explanation or none of the origin of the higher species, with the evolution theory there is not even room for this alternative. For even in case of its failure, a descent of one species from another through heterogenetic generation is certainly very possible. Besides, it is not only possible, but even probable, that both theories—that of heterogenetic generation and that of gradual development—may have to share with one another in the explanation of the origin of species; and even that, especially for the lowest species and for the beginnings of the main types, primitive generation also has its share in the establishment of the paternity.

The evolution theory could only pass beyond the rank of a hypothesis, if we should succeed in showing the impelling forces of such an origin of species through development. Such an attempt can be made in two ways—the metaphysical and the scientific-empirical. The first, the metaphysical, although it may be justified in its general principles, will always, from the point at which it attempts to approach the concrete questions as {100} to the origin of single species, expose itself to the fate of being a priori rejected by science as unjustified, and of being a posteriori confuted by facts—a fate which it has richly and clearly experienced in the first half of our century. But the discussion of the metaphysical way does not belong to the present purely scientific part of our investigation; it will, however, be shortly taken up again in Book II. The other way, the scientific-empirical, will have to be looked upon as correct when it can show the impelling forces of development in such powers and laws as are either still active to-day or at least have their points of connection in powers and laws active to-day. Such an attempt is the selection theory. We have already in Chap. II, Sec. 1 and 2, given an outline of this theory, and have only yet to discuss its present state of tenability.

Sec. 3. The Theory of Selection.

The selection theory also is not entirely without support in the realm of observed facts. How simply it explains the fixedness of the differences of closely related species arising from their geographical and climatical home! how simply the similarity of the color of many animals from the color of their abode, through which they have protection against persecution! how simply the so-called mimicry—i.e., the similarity of certain species in form and color with form and color of entirely different species in the midst of which they live, a similarity which often gives them protection against persecution! The best known examples of this, in our regions, are the spinning caterpillars, which in a state of rest look strikingly like a twig of a tree or a shrub on which {101} they live. In other regions there is a multitude of the most striking freaks of nature of this kind—for instance, butterflies and other insects, which at rest look like the leaves of plants under which they live; butterflies living among other butterflies which, by an offensive odor, are protected against persecution, and although they are themselves a favorite food for birds, carrying the form and color of that badly-smelling family of butterflies. We can also add the orchideae, and their resemblance to bees, flies, butterflies, spiders, etc. A. R. Wallace and Darwin themselves recur often to these striking appearances.

But herewith we have mentioned nearly every support which the selection theory has on the ground of observed facts. More numerous and more weighty are the objections to it. First of all, we have to state that the selection theory no longer enjoys that protection which the descent and evolution theories can justly claim, against the main objection, mentioned in Chap. III, Sec. 1, to all the ideas of descent, development and selection. That main objection is the permanence of species, observed through thousands of years; and the defense with which the descent and evolution theories successfully weaken it, is the statement of the fact that, since man appeared, no new species has originated, and that therefore the principle of the generation of species seems to have come to a stand-still. Now this fact is no longer in favor of the selection theory, but directly repugnant to it. For the selection theory expressly declares the origin of species through agencies that are all active still, and, therefore, if they really suffice to explain the origin of species, would not only have to generate new species, {102} but also to develop all the existing species. All those circumstances which, according to the selection theory, have led to change of species, are just as active to-day as they are supposed to have been from the beginning of organic life; and the effect which we observe is not change but permanence of species. The individuals still have individual qualities; they still have the tendency to inherit, in addition to the qualities of the species, those of the individual; the individuals still change their abode, and therewith also their conditions of life; a natural selection still takes place in the struggle for existence; and what is the result? From an observation stretching over thousands of years, we find nowhere an effect of natural selection going farther than alterations in growth and color and purely external changes in form. All the dispositions of organisms and their reciprocal action aim not at increasing the individual differences, but at reducing them to the average character of the species. When the species change their abode or their conditions of life, they either perish or remain constant; at least, with the exception of the slight modifications before mentioned. Even those alterations which artificial breeding produces, have a tendency to return to the original species: as soon as cultivated plants and domestic animals are left to themselves, they run wild, i.e., they reassume their original qualities. Even the bastard-formations either cease to be fertile, or, remaining fertile, finally return to one or the other stem-form of the originally crossed species. Nor can we oppose to these facts the consideration that the period of time during which mankind has observed the organisms is too short. For the permanence of very many {103} species can be traced through thousands of years, and the shortness of the period of our observations is amply counterbalanced on the one hand by the multitude of species from all parts of the organic systems which come under our notice, on the other by the immense alterations in the conditions of existence to which man submits plants and animals. How great, for instance, are the alterations in the conditions of existence which tropical plants undergo in our hot-houses and gardens! And the only alteration they show is that they are stunted and only bear blossoms with difficulty and fruits with still greater difficulty.[6] Now, if the ever-active selection principle does not produce in thousands of years even minimum alterations which can be observed, science certainly is justified in doubting for the present the asserted effect of that principle.

Thus not only are the facts directly opposed to the autocracy of the selection principle; but logic is also none the less so. For, under the most favorable circumstances, selection would only explain the preservation and perhaps also the increase of useful qualities and organs, if the same are already in existence and have shown themselves useful to the individual; but would not explain their origination. This would rather most emphatically be left to chance. According to the strict selection theory, it would be pure chance that among the thousands and thousands of individual qualities of the individuals of a species, such qualities are always existing as offer advantages to the individual in his struggle for existence. And it would be a second series of chances, which from generation to generation would {104} have to coincide with the first, that among the individual qualities advantageous to the individual and making it victorious in the struggle for existence, there should be found always just those qualities which develop the species and raise it to a higher rank and order in the zooelogical and botanical systems. But the total of improbabilities which would have to be overcome continually in this theatre of chance, would in the course of generations necessarily amount to infinity. Thus, in the very beginning, insuperable doubts arise as to how we can explain from two causes the world of organisms which is so richly, beautifully, and systematically arranged. The first of these causes is the inclination to individual alteration, inherited indeed in the organisms, but in itself absolutely indifferent, for the systematical idea in the framework of the organic systems and for the progressive element in the development. The other is the struggle for existence and natural selection, which approaches the organisms purely from without like individual variability, must as a whole appear a necessity, but in each single case in the concrete mixture of coinciding circumstances, would seem a work of chance for the individual which is to be changed.

Moreover, it is a demonstrable impossibility to explain the origin of just those organs and members in the structure of organisms which are systematically the most significant and functionally the most important, by means of natural selection. It is true that many of these organs and members, in their perfected state, offer to the organism an immense advantage over lower organisms; but if they had been originated through gradual development, they would have been in their first {105} beginnings and earlier stages of development at least quite indifferent, often directly obstructive to the individual in its struggle for existence, and therefore would have been called into existence and developed by agencies which had an effect directly counteracting natural selection. How high, for instance, stand the vertebrates above the invertebrates! Yet how could the first deviation from the ganglionic system of the nerves of the invertebrates to the cerebro-spinal system of the vertebrates have occurred?—and, especially, how could the first deposit of the vertebral column have procured any benefit to the individual in the struggle for existence? We quote this objection from Karl Planck's "Wahrheit und Flachheit des Darwinismus," ("Truth and Platitude of Darwinism"), Noerdlingen, Beck, 1872.

Still more striking is the insufficiency of the selection theory for the explanation of the origin of the organs of motion in the higher classes of vertebrates. A. W. Volkman says of it, in his instructive lecture, "Zur Entwickelung der Organismen," ("Development of the Organisms") Halle, Schmidt, 1875, p. 3 ff.: "Without doubt, animals with extremities will come from animals which lacked extremities. Now if the metamorphosis originated in the course of one generation, the animals with extremities would have an advantage over the rest, which ought to show itself in the natural selection; but if the development of an extremity needs 10,000 generations, the individual in which the process of the development begins produces 1/10000 of the extremity and the advantage, resulting therefrom is reduced to zero. For an organ can only be of advantage when it performs its functions; and on {106} the first of the 10,000 stages of development the extremity can not perform its functions. Just think of the cetacea! Of the hind extremity, only its carrier, the pelvis, has been developed; and even this is only represented by the two hip-bones, hanging in the flesh. As to the python, the hind extremities are more complete, but they lie hidden under the skin, and therefore are of no use for local movement. Such examples show that in the history of the development of an organ thousands of years may pass, and numerous generations may arise and disappear, until it reaches that grade of perfection where it is of use to its owner. How therefore, can we look upon such an organ, when finally it is perfect, as a product of selection in the sense of Darwin?"

We find the scientific objections to the selection theory collected in detail in the before-mentioned works of Wigand, Blanchard, His, von Baer, and especially in Mivart's "Genesis of Species," (London, MacMillan, 1871); and it is a praiseworthy testimony of Darwin's love of truth, that lately he himself, the originator of the selection theory, willingly admits these weak points in his theory,[7] while Haeckel and many of his followers {107} in Germany still stoutly reject every doubt of the autocracy of the selection principle.

In summing up all we have said thus far about the theories of descent, of evolution, and of selection, we still find all three solutions of the scientific problems to be hypotheses, but hypotheses of very different value. The idea of descent has the most scientific ground; it will, as a permanent presupposition, govern all scientific investigations as to the origin of species, even if it does not exclude the idea of an often-repeated primitive generation of organisms—especially of those that stand still lower in development. More uncertain and less comprehensive is the position of the evolution theory; in all likelihood, the idea of an origin through development will have to share the sovereignty with the idea of origin by leaps through metamorphosis of germs. Still more unfavorable is the state of the selection theory. It possesses the merit of having started the whole question as to the origin of species; it may explain subordinary developments; natural selection may have cooeperated as a regulator in the whole progress and the whole preservation of organic life. Ed. von Hartmann, in his essay, "Truth and Error of Darwinism," (Berlin, Duncker, 1875), on page 111, compares its functions with those of the bolt and coupling in a machine; but that the driving principle which called new species into existence lay or originated in the organisms, and did not approach them from without, seems to be confirmed more and more decidedly with every new step of exact investigation as well as of reflection.

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BOOK II.

THE PHILOSOPHIC SUPPLEMENTS AND CONSEQUENCES OF THE DARWINIAN THEORIES.

* * * * *

THE PHILOSOPHIC PROBLEMS.

Although, in accordance with the requirements of the task before us, we have to restrict ourselves to giving the results of natural science only in their general outlines, still we believe that we have not overlooked any essential result which is of importance to the question of the origin of species and of man. We have now finished our scientific review; and the conclusion to which we see ourselves brought is that natural science, in its investigation of the origin of species, has arrived at nothing but problems which it is not able to solve. There is a very great probability of an origin of species, at least of the higher organized species, through descent; but whether through descent by means of gradual development or of metamorphosis of germs, or whether with one group of organisms it is in this way, with another in that, is not yet decided. The attempt to explain their entire origin exclusively by the selection theory, must be regarded as a failure; all indications rather show that, supposing the descent principle correct, the deciding agencies which formed new species did not approach the old species out of which the new ones originated from {109} without, but that they originated or were already in existence within them. But what these agencies were, natural science is at present unable to state; and not only those scientists who reject every idea of a descent, but also those who are favorable to the ideas of descent and of evolution, rejecting only the selection theory, are at one in silent or open acknowledgment of this limit of our knowledge, be it permanent or temporary.