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HISTORY OF THE DARWINIAN THEORIES.

§ 1. Darwin.

In order to explain the development of higher species from lower ones in a natural way, Darwin starts from two facts. The first fact is, that all individuals of the same species show, besides their specific similarity, individual differences: a fact which we call the law of individual variability. The other fact is, that each individual inclines to transmit to his offspring all his qualities—not only the characteristics of the species, but also those of the individual: a fact which we call the law of heredity.

To show how the whole basis of explanation of the evolution of one species from another is given in these two facts, Darwin calls attention to the rules according to which the often extraordinarily great varieties of domestic animals and cultivated plants are obtained and preserved; namely, the rules of artificial breeding. The breeder simply selects from a species those individuals having such individual qualities as he wishes to preserve and to increase, and refrains from breeding those individuals which do not possess the characteristics he wants or which possess them only in a small degree. He continues the same process with the next generation; and by the constant and effectual agency of the two before-mentioned laws, he will, after the lapse of a few generations, have breeded a variety in which the characteristics originally belonging only to a single individual have become common and permanent.

It is now important to consider whether nature, in natural selection (whence the name "Selection Theory") does not act unconsciously according to the same rules, and attain the same results, as man with his artificial and intentional selection; and, furthermore, whether she does not reach results which, according to that principle of natural selection, finally explain the origin of all, even of the highest and most complicated organisms, from one single original form or a few original and simplest forms. Darwin finds these questions answered in the affirmative; and arrives at this answer through the following conclusions.

The English political economist Malthus (1766–1834), in his "Essay on the Principles of Population," established a law in regard to the growth of the human race, which may be applied just as well to all the species of the entire organic world: that population tends to increase in a geometrical ratio, although the conditions of life for the individual remain the same or at most increase in an arithmetical ratio. The consequence is that if the species is to be preserved and the individuals of future generations are to continue to find sufficient food and other means for sustaining life, a great many individuals of each generation must perish very early, and even as germ and seed, and only a minority will be preserved and reproduced. This exuberant prodigality of life-germs, of which proportionately only a few are preserved and reproduced, takes place in the plant and animal world in a very marked degree. There a continual struggle for existence prevails; each individual has to get access to his conditions of life by wresting them from a whole series of other individuals of his own or other species; and now the question arises: which individuals will survive in this struggle? which will more probably be preserved and procreate offspring? Evidently, the answer is, those individuals which possess individual characteristics more favorable to the preservation of the individual than those possessed by other individuals. These individual characteristics are transmitted to the next generation. In this there will be again individuals that have in a still higher degree the characteristics thus transmitted and favorable for the preservation of the individual, or that add to these favorable characteristics new characteristics favorable in another direction to the survival of the individual in the struggle for existence. While these individuals, with more probability than the others, are thus preserved and reproduced, they transmit to their offspring not only the old favorable characteristics increased, but also those newly added. Among the favorable individual qualities, Darwin reckons the divergence of character, the perfection of organization, and the law of correlation; the latter, however, can not be explained by natural selection, since according to this law a variation in an organ brings about a corresponding variation in entirely different organs (e.g., cats with white fur and blue eyes are also deaf).

This is natural selection by means of the survival of the fittest in the struggle for existence. Changes in the conditions and surroundings of life, and more or less perfect adaptation of the organisms to the new conditions of form, color, food and habit, are the main causes of those individual variations, the accumulation of which through many generations produces so great effects. If we only have behind us periods long enough to permit us to imagine each step in the development as an extremely small and hardly appreciable one, natural selection offers us not the exclusive but the main means of explaining the evolution of the whole animal and plant world out of one or a few simple organized original forms.

This is the outline of the selection theory, as given by Darwin in 1859, and still retained in all its essentials. It is true, in his work on the origin of man he added as supplemental the sexual to the common natural selection, and made it of special importance for the presentation of the beautiful in nature—for the production of beautiful forms, colors, and tones, and for the development of power and intelligence. And in the same work he said that there are many circumstances of structure which seem to be neither beneficial nor detrimental to the individual, and that to have overlooked this fact was one of his greatest mistakes in his former publications. But for the rest, he maintains the selection theory unchanged, with the single modification that it explains, if not the whole development of the species through descent, at least that which is of most importance in it.

That it was only one step in the course of reasoning to extend the selection theory to the descent of man, was seen by many as soon as Darwin's work on the origin of species was published and began to attract attention; although not a syllable upon this question was presented in this work. Various persons manifested their presentiment or perception according to their point of view—partly by the most violent opposition to the new doctrine, partly by scientific development or modification of their anthropogonic views, partly also by revelling in imagination in the consequences hostile to religious faith which they thought could be drawn from this doctrine. We remind the reader of the itinerant lectures of Karl Vogt about the ape-pedigree of man, and of the echo they found by assent or dissent in press and public; also of Huxley in England, Karl Snell, Schleiden, Reichenbach, and others; of the materialists, L. Büchuer and Moleschott, and of the publications of Ernst Häckel. Finally, Darwin himself made us fully certain of the importance which from the beginning he had attributed to his theory, by publishing his work on the "Descent of Man," in the year 1870.

In this work he explained the descent of man fully from the before-named principles of the descent, evolution, and selection theories, of which we have given all the essentials in the foregoing presentation. He carefully enumerates everything in the structure of the human body that reminds us of our relationship with the animals—especially those embryonic phenomena and rudimentary organs in man which are still to be found in use and in a more developed state in different animal species, and which led him to imagine our ancestors now with a tail, then with sharp ears, now living in the water, then being hermaphrodites. He reviews the spiritual qualities of man, and finds for them all analogous qualities in the animal world. He finds in his work on "Expression of the Emotions in Man and Animals," published in 1872, new confirmation of the genealogical relationship of both. He looks over the whole course of the zoölogical system and of palæontological discoveries, and searches for the points where the branches and twigs of the animal pedigree of man must have diverged. To begin with the lowest branches, he thinks the most important divergence took place where the series of vertebrates may have been developed out of the invertebrates. Here he adopts the investigations of A. Kowalewsky, and the deductions of Häckel founded upon them, concerning the larva of the ascidiæ, a genus of marine mollusca of the order tunicata, and sees in a cord, to be found in this larva, most decided relationship to the spine of the lancelet fish or amphioxus, the lowest of all the vertebrates, it being yet doubtful whether it belongs at all to the vertebrates. In the transition that once took place from one species of ascidian larva to a form similar to the lancelet fish, he sees the new branch diverging in the series of vertebrates. Out of the fish he concludes that the amphibia were developed, and out of those the reptilia, out of one of them the marsupialia, and from them the lemurs or half-apes, the representatives of which yet live in Madagascar and the southern part of Asia. From these there branched off on the one side the platyrrhini, or apes with a flat nose, on the new continent; on the other, the catarrhini, or apes with a narrow nose, on the old. Among the ancestor of the last, he searches for the common progenitors, from which again two branches started—on the one hand the ignoble branches of the catarrhine species of apes, always remaining lower in development, to which also belong the anthropomorphous apes, like the orang outang and gibbon in Asia, the gorilla and chimpanzee in Africa; on the other hand, that branch which represents the ascent of animals to man.

The refining agencies which finally raise the animal up to the man are essentially the same that on the lowest scales of the pedigree have caused the development of the lower organisms into the higher, namely: favorable individual variations, inheritance, acclimatization, survival of the fittest in the struggle for existence, natural, and especially, sexual selection. These are, if not the exclusive, still the main agencies which finally led the primate of the earthly creation upon the stage and furnished him with his superior faculties. But it is particularly by means of his social life, and of the forces which determine, transmit, increase and ennoble the various impulses and instincts promoting it, that man has become what he is. Through the need and faculty of reciprocal help, through sexual selection—which of course is a very essential factor of social life—there originated language, and reflection, and all the intellectual qualities; and through these again originated the moral qualities, which are most important in constituting the specific worth of man, and which were finally developed into self-consciousness and free moral responsibility.

But with the description of this attempt to explain more in detail these specific characteristics of man, we leave the ground of pure natural science and enter the region of philosophy, in which we have to take up the question again (in Book II, Ch. I) at the same point where we here leave it.

§ 2. The Followers of Darwin.—Ernst Häckel.

Darwin's theory soon found an enthusiastic corps of followers—on the continent, and especially in Germany, almost more than in his own country. The outlook into an entirely new explanation of the origin of man, and the probable use of this theory for attacks upon faith in a Creator and Master of the world, called wide-spread attention to it; and the theory opened to natural science itself entirely new impulses and paths, and promised the solution of many problems before which it had hitherto been compelled to stand in silence. To be sure, it threatened likewise to allure the mind from the slow but sure ways of solid study to the entertaining but insecure and aimless paths of imagination and hypothesis.

Among all the German followers of Darwin who adopted not only the idea of an origin of species through descent and evolution, but also the explanation of evolution by natural selection, and extended it so as to make the principle of selection of exclusive value, Ernst Häckel occupies the most prominent rank.

In his "General Morphology," published in 1866, and in his "Natural History of the Creation," the first edition of which appeared in 1868, and finally in his "Anthropogeny"^[2] (why he does not say Anthropogony, we are nowhere informed), 1874, this scientist brought the new theory, which had been presented by Darwin in an almost bewildering flood of details, into connection and order, and, analyzing the powers active in natural selection, combined them into an entire system of laws. He at once drew the origin of man also into the course of reasoning on the new theory, and sustained the theory by the discovery of the monera and other low organisms of one cell, as well as by special investigations of the calcareous sponges. For these labors, he was rewarded by the warm and unreserved acknowledgment which Darwin made to him in his work upon the origin of man, which was published subsequently to the "Natural History of the Creation." There Darwin says: "If this work had appeared before my essay had been written, I should probably never have completed it. Almost all the conclusions at which I have arrived, I find confirmed by this naturalist, whose knowledge on many points is much fuller than mine." Häckel's labors rendered still greater service to the Darwinian theory by dividing the organic world into three kingdoms: the protista kingdom, the vegetable kingdom, and the animal kingdom—a division which solves in a most simple way the difficulty that was felt more and more of securing for the lowest organisms a place among the animals or plants. He further aided the theory by leaving the choice open to adopt either a uniform or multiform pedigree of the organisms and their kingdoms and classes, and by treating each class under both points of view; and finally, by fascinating experiments to bring before us in detail the hypothetical pedigrees of all classes of organisms from the protista kingdom up to man.

We will try to reproduce briefly the pedigree which is of most interest—the hypothetical pedigree of man. Häckel divides it into twenty-two stages, eight of them belonging to the series of the invertebrates, and fourteen to that of the vertebrates. On this ladder of twenty-two rounds, he leads us from the lowest form of the living being, in slight and mostly plausible transitions, continually higher and higher, up to man; and makes our steps easy by mentioning at each stage, on the one hand the corresponding state in the embryonic development, on the other the still living creature through which, in his opinion, the former organisms of the corresponding round of the ladder are still represented, and which accordingly has been a creature that remained on its round, while other members of its family have been developed up to man and to many other genera and species.

He begins with the monera, the organisms of the lowest form, discovered by himself, which have not so much as the organic rank of a cell, but are only corpuscules of mucus, without kernel or external covering, called by him cytod, and arising from an organic carbon formation. The lowest and most formless moneron is the bathybius, discovered by Thomas Huxley, a network of recticular mucus, which in the greatest depths of the sea, as far down as 7,000 metres, covers stone fragments and other objects, but are also found in less depths, in the Mediterranean Sea, for instance. From the moneron he proceeds to the amœba—a simple cell, with a kernel, which still corresponds to the egg of man in its first state. The third stage is formed by the communities of amœbæ (synamœbæ), corresponding to the mulberry-yolk in the first development of the fecundated egg, and to some still living heaps of amœbæ. To the fourth stage he assigns the planæa, corresponding to the embryonic development of an albumen and the planula or ciliated larva. When these ciliated larvæ are developed, they contract themselves so as to form a cavity; and this fifth stage—especially important for his theory—he calls gastræa. In this form, he says, the progaster is already developed, and its wall is differentiated for the first time into an animal or dermal layer (ectoblast), and into a vegetative or intestinal layer (hypoblast). At the sixth stage, there branched off the prothelmis, or worms, with the first formations of a nervous system, the simplest organs of sense, the simplest organs for secretion (kidneys) and generation (sexual organs), represented to-day by the gliding worms or turbellaria; as the seventh stage, the soft worms, as he called them at first—the blood worms, or cœlomati, as he describes them in his "Anthropogeny"—a purely hypothetical stage, on which a true body-cavity and blood were formed; the eighth stage are the chorda-animals with the beginning of a spinal rod, corresponding to the larva of the ascidiæ. At the ninth stage, called the skull-less animals (acrania), and corresponding to the still living lancelet, we enter the series of the vertebrates. The importance of the eighth and ninth stages for the theory, we have already pointed out in our remarks upon Darwin, p. 43. The tenth stage is formed by those low fishes in which the spinal rod is differentiated into the skull—and the vertebral-column, called the single-nostriled animals (monorrhini), and represented by the cyclostoma of today (hag and lampreys). The eleventh stage is formed by the primæval fish or selachii (sharks); the twelfth by the mud fish, of which there still live the protopterus in Africa, the lepidosiren in the tributaries of the Amazon, and the ceratodus in the swamps of Southern Australia. On the thirteenth stage, there are the gilled amphibians (sozobranchia), proteus and axolotl; on the fourteenth, the tailed amphibians (sozura), newt and salamander; on the fifteenth, the purely hypothetical primæval amniota or protamnia (amnion is the name given to the chorion which surrounds the germ-water and embryo of the three higher classes of vertebrates) on the sixteenth, the primary mammals (promammalia), to which the present monotremes (ornithorhynchus and echidna) stand nearest; on the seventeenth, the pouched animals or marsupialia; on the eighteenth, the semi-apes or prosimiæ (loris and maki); on the nineteenth, the tailed apes, or menocerca (nose-apes and slender-apes, or semnopithecus); on the twentieth, the man-like apes (anthropoides) or tail-less catarrhini (gorilla, chimpanzee, orang outang and gibbon). And now we come to twenty-one—ape-like men or speechless primæval men (alali)—of whom we are reminded to-day by the deaf, and dumb, the cretins and the microcephali; and number twenty-two is homo sapiens, the man. The Australians and the Papuans are supposed to be the only remaining representatives of his first stage-development. In like manner, Häckel also gives us the stem-branches of all the types, classes and orders of the organisms, and forms from them a very acceptable hypothetical pedigree; or—if we prefer to suppose a polyphyletic rather than a monophyletic origin of species—hypothetical pedigrees of the whole organic world.

The perspicuity and clearness of Häckel's deductions, the extent of his knowledge, and the singleness of his aim, to which he makes them all subservient, lend to his works a great charm. But on the other hand we dare not conceal that, even on the ground of explanations belonging purely to natural history, the character of hypothesis is often lost in that of arbitrariness and of the undemonstrable. Even the unlearned in natural science often enough get this impression when reading his works, and will find it confirmed by scientists who not only contradict his assertions in many cases, but disclose plain errors in his drawings—errors, indeed, exclusively in favor of the unity-hypothesis; and in other cases they show that drawings which are given as pictures of the real, represent merely hypothetical opinions. There is especially evident in his works an extremely strong tendency to impress on his hypotheses the character of an established and proved fact, by giving them the alluring name of laws. Entire systems of laws of the selection theory are produced, and all imaginable assertions are also immediately called laws. For example, Huxley, in his anatomical investigations of apes and men, arrives at the conclusion that the differences between the highest and the lowest apes are greater than the differences between the highest apes and man. This purely anatomical comparison, Häckel calls repeatedly "Huxley's Law." We are well aware that the idea of law is capable of great extension in meaning, and in that respect we can refer to nothing more instructive than the well-meditated inquiry upon this idea in the "Reign of Law" of the Duke of Argyll (London, Strahan & Co.). But if we may venture to call purely anatomical comparisons of this nature laws, such a use of language destroys all logical reasoning; and this mistake appears again in Häckel's philosophic discussions, of which we shall have to speak hereafter. We shall have to refer also hereafter to an additional embellishment, which Häckel thinks himself obliged to give to his works—namely, that he makes on every occasion the strongest attacks upon faith in a personal God, a Creator and Lord of the world; that he traces all the motives of human action to self-interest; that he denies the liberty of man and the moral system of the world; that he makes consent to his view of things the criterion of the intellectual development of a man; and that he thinks to render a service to civilization by such a view of the world and of ethics.

In the consequent carrying out of the selection principle as the satisfactory key in explaining the origin of all species and also of man, Häckel is indeed, in spite of the approval of his works by the British master, more Darwinian than Darwin himself, who expressly refuses to give exclusive value to this theory of explanation. Hence there are among scientists only a few who go with him to this extent. In Germany, aside from the materialists, we only know of Seidlitz and Oskar Schmidt—who in the thirteenth volume of the "International Scientific Series" treats of "The Theory of Descent and Darwinism," and advocates not only the autocracy of the selection theory, but also all the monistic and atheistic consequences which are deduced from it. Perhaps Gustav Jäger, Schleiden, Bernhard Cotta—at least judging from their earlier publications—should be mentioned as followers of the pure selection theory; although they do not all draw from it the before-mentioned philosophic consequences. On the other hand, the number of those is very great who, although inspired by Darwin to adopt the idea of an origin of species through descent and evolution, yet have more or less modified, laid aside, or entirely refused the very doctrine which is especially new in Darwin's theory—the selection theory. In the following section we shall briefly give an account of them.

§ 3. Modifications of the Theory—Moriz Wagner. Wigand.

One of the most prominent objections to the selection theory, which strikes us at once from the standpoint of natural history, is the following: The varieties of a domesticated species, obtained by artificial breeding, are lost, and return to the original wild form of the species as soon as they are crossed long enough with other varieties or are left to themselves and to the crossing with individuals of the original form of their species; and hence we can not see how individual characteristics, even if favorable to the individual, will not be lost again by the crossing which is inevitable in a state of nature, with such individuals as do not possess those characteristics. Besides, it is an established fact, confirmed by all our observations stretching over thousands of years, that the characteristics of species are preserved in spite of all individual modifications, and that this preservation of the characteristics of species has its cause essentially in the free crossing of individuals.

This objection induced Moriz Wagner to take up again an idea already expressed by Leopold von Buch, and to complete the principle of a selection through natural breeding by another, and partly, indeed, to supplant it by the principle of isolation by migration. Isolated individuals, who, from any reason naturally to be accounted for, leave the mass of their fellows, can from the very consequence of this isolation transmit to their offspring common individual characteristics which are not destroyed again by the crossing with other individuals. They will especially fix and transmit these individual characteristics, when they are favorable to them for the conditions of existence in their new place of living, and these individual characteristics will so much the more be increased and developed in a direction favorable to the subsistence of the individuals in their new place of living, as there are more closely connected with this isolation variations in the conditions of existence, in climate, geographical surroundings, food, and so on. He very attractively applies this theory also to the explanation of the origin of man. According to his opinion, even the nearest animal progenitors of man were isolated, and the isolating power was the rise of the great mountains of the Old World, which took place previous to the glacial period. One pair, or perhaps a few pairs, of those progenitors were driven away from the luxurious climate of the torrid zone to the northern half of the globe, and found their return cut off by glaciers and high mountains; in place of a comfortable life on the trees, necessity urged them to gain support from conditions less favorable to existence, and necessity, this mother of so many virtues and achievements, finally made man what he is. In following out these ideas, Moriz Wagner has gradually and more and more decidedly given up the selection theory, and opposed it by sharp criticisms.

This migration or isolation theory also found a degree of favor, but subordinate in its nature. For it can not and will not pretend to solve the main problems. It only tries to explain how the individual variations, already in existence, might have been preserved and perhaps increased, and how new conditions of existence could have roused latent powers; but not how these variations and these powers originated. Just as little is the selection theory able to explain this; but it pretends to do it, and hence we can easily comprehend how during the last few years a constantly increasing number of voices, and more important ones, have been raised against the selection theory. This opposition came not only from those who—like Agassiz, Barrande, Emil Blanchard, Escher von der Linth, Göppert, Giebel, Sir Roderick Murchison, Pfaff, and others—directly reject each and every idea of descent on account of the difficulty in defending the selection theory; or who—like Karl Ernst von Baer,^[3] (the pioneer in the region of the history of individual development), like Oskar Fraas, Griesebach, Sandberger, and others—generally take a more reserved and neutral position, because of the uncertainty of the facts and the inaccessibility of the problems; but it comes especially from those scientists who are inclined to adopt an origin of species through descent and even through development, yet refuse to explain it by the selection principle, and look for the essential cause of the development in the organisms themselves, without claiming to have themselves found these causes. Among the most prominent advocates of this view, we may name the late Sir Charles Lyell, Mivart, and Richard Owen, in England; and in Germany, Alexander Braun, Ecker, Gegenbaur, Oswald Heer, W. His, Nägeli, Rütimeyer, Schaaffhausen, Virchow, Karl Vogt, A. W. Volkmann, Weismann, Zittel, and here also Moriz Wagner, and among the philosophers, Eduard von Hartmann. Many of these men are but little aware of the difference between the two questions: whether, on the one hand, the adoption of the origin of species through descent does not of itself involve the idea of a gradual development of one species from another, almost unobservable in its single steps; or, on the other hand, whether a descent of species through heterogenetic generation in leaps and through a metamorphosis of the germs, could be imagined. They consider descent and evolution as identical; and this identification is explainable so long as we are not in a condition to come nearer to the eventual causes of the supposed variation of species. But men are not wanting who put these questions clearly and plainly, and separate them distinctly from one another. Among them we may mention K. E. von Baer, Ed. von Hartmann and Wigand; of the latter we will have occasion to speak more in detail hereafter. Among them we find also scientists who answer the question in the sense of a new-modeling of the species, of a heterogenetic generation, and of a metamorphosis of germs. To this class belong especially Oswald Heer—"Urwelt der Schweitz" ("Antediluvian World in Switzerland"), Zürich, 1865, p. 590–604; Kölliker—"Ueber die Darwin'sche Schöpfungstheorie," ("Darwin's Theory of Creation"), Leipzig, 1864; "Morphologie und Entwicklungeschichte des Pennatulidenstammes nebst allgemeinen Betrachtungen zur Descendenzlehre," ("Morphology and History of the Development of the Stem of the Pennatulidæ, together with General Remarks on the Descent Theory"), Frankfurt, 1872; and Heinrich Baumgärtner—"Natur und Gott" ("Nature and God"), Leipzig, Brockhaus, 1870. Heer has introduced into scientific language the term "new-modeling of the species," Kölliker that of a "heterogenetic generation," and Baumgärtner that of a "transmutation of the types through a metamorphosis of germs." Baer also is not averse to adopting the latter.

The botanist, Albert Wigand, of Marburg, takes a peculiar position. On one hand, the observation of the relationship of organic beings with one another leads him to adopt a common genealogy, a descent; on the other, the objections to adopting a descent of the species one from another appear to him insurmountable. In the first place, he sees all the species everywhere strictly limited—although in the second volume of his work, which appeared after the preceding lines were written, he again warns against a one-sided emphasizing of the invariability of species. In the second place, he sees so clearly, through the whole organic world, the differences, nay, the contrasts, of the species, in their building plan, in the numbers and conditions and positions of their parts, and in their mode of development, that it appears to him impossible to assume in the perfected organism a production of germs which in a course of generations, by a process even as gradual as possible, would grow into such an entirely new phenomenon as a new, even closely related, species would be. But if we adopt the theory of a heterogenetic generation, we explain by it the variety but not the similarity of species; for a heterogenetic generation would in the new species make everything different from the old one—a conclusion, the necessity of which it would be difficult to show. For these reasons, he refers the descent of the organic beings, not to the series of the species, with their individuals already specified and defined, but to the series of primordial cells living free in the water. The earliest primordial cells represented only the common character of the whole organic world, and out of them the primordial cells of the animal and those of the vegetable kingdom were produced by dividing the cells; so that the first ones embraced only the general and primitive characteristics of the whole animal, the last ones those of the whole vegetable kingdom. Out of these primordial cells of the two kingdoms, those of the main types proceeded—(for instance, the primordial cells of the radiated animals, the vertebrates, etc., the gymnosperms, the angiosperms, etc.); out of them those of the classes—(for instance, the mammalia, the dicotyledons); out of them those of the orders—(for instance, the beasts of prey, rosifloræ); out of them those of the families (canina, rosaceæ); out of them those of the genus (canis, rosa); and out of them those of the species (canis lupus, rosa canina). Only when the primordial cells of the species had been produced, were they developed into finished representatives of the species; and when once these primordial cells of the species had been developed into finished and full-grown individuals of the species, their transmission took place in the manner well known to us. Wigand published his criticism of the Darwinian Theories in his larger work, "Der Darwinismus und die Naturforschung Newtons und Cuviers," ("Darwinism and the Natural Science of Newton and Cuvier"), Braunschweig, Vieweg, Vol. I, 1874, Vol. II, 1876, and his own attempt at explanation in a smaller book, published at the same place in 1872: "Die Genealogie der Urzellen als Lösung des Descendenzproblems oder die Entstehung der Arten ohne natürliche Zuchtwahl" ("Genealogy of the Primordial Cells as a Solution of the Problem of Descent; or the Origin of Species without Natural Selection").

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 larvæ 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 larvæ, 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 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 Häckel 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.