Man and Evolution; The Advance in Scientific Knowledge Since Darwin's Day - Prof. Ernst Haeckel's Recent Books

by Joseph Jacobs

MAN AND EVOLUTION

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The Advance in Scientific Knowledge Since Darwin's Day - Prof. Ernst Haeckel's Recent Books

Written forThe New York Times Saturday Review of Books by

JOSEPH JACOBS

It is close on fifty years since Charles Darwin turned the thought of the world toward the problems of life in the stricter sense of the term. His "Origin of Species" was, as he called it, merely a sketch of the very complicated problem, which he, following his grandfather's example, set out to solve. The successive chapters dealt with the different aspects of the problem of biological evolution, and so closely knit was his reasoning, so wide the basis on which his inductions were based, that each of them might have by itself formed the subject of a special treatise. As a matter of face, several of these treatises were afterward written, one notably by Darwin himself, "Animals and Plants Under Domestication," which really expands the reasoning of his second chapter, and Dr. A. R. Wallace's "Geographical Distribution of Animals," which on an equally formidable scale deals with the topic which Darwin touched upon in his seventh chapter.

So, too, Lyell dealt with the imperfections of the geological record which Darwin utilized to account for the non-appearance of missing links, whereas nowadays Prof. De Vries has shown that nature itself makes jumps in forming species. One of the most suggestive hints thrown out by Darwin in his general treatment of the problem was the light that comparative embryology would throw upon the development of species, the underlying assumption being that the embryo passes successively through all the stages of development which the race to which it belongs had traversed. The idea was to a certain extent carried out in the work of F.M. Balfour, whose "Comparative Embryology" is perhaps the most important contribution to biology made by any Englishman, and was conscientiously adopted as the matrix idea in Prof. Haeckel's "Anthropogenie," an English version of which has just appeared in two volumes, the first dealing with human embryology, the second with human "stem-history," as the translator calls it, or what is generally known as phylogeny. The earlier English version translated the second: this is a version of the fifth and much enlarged edition of the original.

The subject is rather gruesome, and is not best adapted for public discussion, but its importance and significance for the theory of evolution can scarcely be overrated. Almost all the speculative work of the last twenty years has clustered around it, in particular the researches of Weismann, whose ingenious views are almost entirely concerned with the distinction between that part of the human body which subserves the individual interests, and that which goes toward continuing the race. As is well known, he contends that there is no means by which the germplasm or reproductive element can be influenced by the experience of the individual, so that we get the paradoxical result that the race must always remain the same, since no means is provided for passing on any change. It is not surprising to find Prof Haeckel somewhat superciliously disregarding the possibilities of such an unevolutional view of evolution. He sturdily declares himself on the side of Lamarck and Darwin in regarding the possibility of the inheritance of acquired characteristics, but is seemingly ignorant that it was rather Erasmus Darwin that held this view. The innovation that Charles Darwin made on his grandfather's theories was rather to give emphasis to the influence of casual advantages than to allow for that of acquired characteristics. In the view of many, Erasmus Darwin was more in the right than his grandson, and certainly recent investigation has trended more in the direction of his thought than that of Charles Darwin. Yet it must always be allowed that it was the latter that convinced the world, whereas Erasmus Darwin only made it laugh at him with his "Loves of the Plants."

Prof. Haeckel is concerned throughout his two massive volumes to prove what he terms the biogenetic law that ontogeny is a brief and condensed recapitulation of phylogeny. By these somewhat repellant technical terms he means to say that the development of the ovum to maturity is a short epitome of the development of the race. In other words, if this contention were exactly true, a life history of one of the higher vertebrates should repeat the whole biological history of the organic world since life began upon the globe. This is obviously a large order. In the first place, marvelous as has been the progress of microscopy during the nineteenth century, even the minutest of organisms evades any complete analysis owing to its very minuteness. Then, if the whole life history of the branch of the race to which an animal belongs could be traced in its embryology, it would only be one branch of the wide-spreading tree of life that would thus be elucidated. But beyond this lies the fact that the biogenetic law only claims that embryology gives merely an "epitome" of the racial development, and it is easy for the evolutional biologist to get over the missing links in the way by dragging in the principle of condensation. If a certain linkage is not there, it is easy to say that they have been skipped in the process of condensation. When to all these difficulties is added the very rapid processes by which the ovum is segmented into very definite organs, it should not be wondered at that the science of comparative embryology is still in a very embryological condition, and that these volumes of Prof. Haeckel are filled with hypotheses which may or may not be verified as further knowledge comes to the student of biology.

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PROF. HAECKEL is probably aware of the very hypothetical basis on which his science is at present founded, but he scarcely leaves the impression of doubt as to fundamentals in the minds of his readers. In particular he has a large number of illustrations which at first seem to base his theories on the widest form of induction, but more carefully examined, a good many of these are rather diagramatic than photographic. The discriminations made by the injection of coloring matter into semi-liquid objects are a very precarious basis on which to found such a large and wide-varying induction.

It is only by means of such simplification through diagram and hypothesis that Prof. Haeckel succeeds in putting before his reader a very plausible, and in many ways very clear account of the development of all organic life from a single cell. By their aid he shows how the impregnated ovum divides up into an outer and an inner skin, ectoderm and entoderm, which in their turn give rise to an outer and inner and middle layer, ectoblast, entoblast, and mesoblast. From the former is derived the sense organs, from the second the mucous membrane, and from the last the muscles and the vascular system. From these comparatively simple elements he traces the whole complex of the animal organism, and having thus clear the way by an account of human ontogeny, he proceeds in the second volume to give an account of human phylogeny, or what Darwin called "the Descent of Man." Here he traces the line of development from the Amphioxus and the Ascidia up to man dealing in successive chapters with "our protist ancestors," "our wormlike ancestors," "our fishlike ancestors," and "our ape ancestors." In all this Prof Haeckel is plunging into lines of investigation which simple bristle with difficulties in comparative anatomy but he has the courage of his convictions, and settles the most complex problems off-hand and with the utmost confidence. While there can be no doubt as to the general validity of the scheme of development thus laid down Prof Haeckel would probably be the first to own the probability of envisioning in detail throughout the line of development. In particular, the position of the montremes is very doubtful, the duck-bill platypus being quite off the main line of ascent. The work concludes with a series of chapters on the evolution of the nervous system, sense organs, the motor organs, the elementary organs, the vascular system, & all treated from the standpoint of embryological development.

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Taken with this warning, the book may be recommended as giving a very clear - in fact, a too clear account of our present knowledge book of the development of the individual and that of the race. Much is guess work, a good deal is scarcely to be qualified even by that name, but the bro fact of development and the main details of the process are undeniably given by Prof. Haeckel with a wealth of illustration and a positiveness of statement which aids both understanding and memory, even if it somewhat obscures the complexity of the problem and the insecurity of the conclusions to which one is led.

The final chapter connects this rather specialist book with the more general philosophic position which Prof. Haeckel has expounded as being the root idea of the problem of evolution. He is a monist - that is, he regards the whole universe as the expression of one substance or unifying principles which finds its expression either in matter or in thought, each of which is the aspect of the other. This was the point of view which he took in his lecture on "Monism" some twenty-five years ago, and in his book on "The Riddle of the Universe," which has had an extraordinary success in Germany, for 150,000 copies have been sold, and of the English version of which no less than 100,000 have been distributed. he now follows this up with "The Wonders of Life," which he regards as supplementary to the "The Riddle of the Universe." It is scarcely likely that it will be so popular. Curiously enough when dealing with general physics and psychology, on which he is not an expert, Prof. Haeckel was clear, if somewhat superficial, but in dealing with purely biological problems, on which he is one of the greatest living masters, he is not superficial, but he is also not clear. The puzzle of life remains a puzzle, even after his elaborate explanation of it.

This obscurity is no doubt due to Prof. Haeckel's continual endeavor to make out that he has anticipated all the most important of the theories on the nature of life which have been put forth during the last thirty years. he is perpetually reminding the reader that this is what he said in his "Generelle Morphologie" or in his "Plastitude Seele," or in one of the many works on the philosophy of biology with which he has instructed the world during the last third of a century. As he is naturally concerned to point out the differences between his view and that of the person who has gained credit for it, a considerable amount of space and time is wasted over details that to the readers of the book are somewhat minute, and, to tell the truth, wearisome. One would have preferred to have had a view discussed without the exact amount of credit being apportioned between Prof. Haeckel and his successors. Still, the tendency is a natural one. We all feel inclined to curse those who, as the Irishman said, "break two of the Commandments upon us; first steal our theories, and then adulterate them."

The result is, therefore, that the new book is by no means so easy reading as "The Riddle of the Universe." Here we come at close grips with specific details of a special science, rather than with vague generalities about the universe in general, and Haeckel's own scientific instinct causes him to go into fuller details than the ordinary layman can follow. His chapter on the forms of life, for example, is practically a short summary of his work on morphology. For instance, the following quotation is not altogether to be "understanded of the vulgar" with out an amount of technical knowledge which cannot be usual:

The distinction between protists and histons is much more important than the familiar division of organisms into plants and animals, in respect of the fundamental forms and their configuration. For the protists, the unicellular organisms (without tissue) exhibit a much greater freedom and variety than the development of their fundamental forms that the histons, the multicellular tissue-forming organisms. In the protists (both protophyta and protozoa the constructive force of the elemental organism, the individual cell, determines the symmetry of the typical form and the special form of its supplementation; but in the histons (both metaphyta and metazoa) it is the plasticity of the tissue, made up of a number of social combined cells, that determines this. On the ground of this techtological distinction we may divide the whole organic world into four kingdoms, (or sub-kingdoms,) as the morphological system in the seventh table shows.

The point is well taken, but not well put. This same chapter, by the way deals partly with one of the most remarkable of Haeckel's productions. In "Kunst-Formen der Natur," in which he gives illustrations of the lower order of animals as instances of pattern in artistic form in nature. So, too, in the chapter on reproduction, he summarizes much that is given in his greater work on anthrogeny, but the summary is so condensed that it is by no means easy to follow his argument.

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NOTWITHSTANDING this obscurity in parts, the whole book is fairly clear as to its tendency, which, as is well known, is opposed to the claims of any recognition of any supernatural element in the universe. Haeckel is for the moment a representative of the opposition of science to religion. But when one examines into the philosophical basis of his anti-religious attitude, it is somewhat curious to find antiquated views and methods of science made the basis of its opposition to religion. Thus, the essence of his contention about the mental life, as based on the parallelism between the body and the mind, was originally started by Spinoza and adopted by most psychologists until within the last fifteen years or so. As a matter of fact, the two most eminent psychologists of the English-speaking world, James Ward and William James, reject this parallelism and regard the possible influence of body on mind and mind on body as being by no means disproved, and indeed as being the most probably hypothesis to explain various psycho-physical phenomena. Similarly Prof. Haeckel's contention that science deals with causes and is indeed the only source from which we can get any explanation of the causes of things has been somewhat rudely disturbed by the views of Mach and Ostwald, Kirchhoff and Pearson, all eminent physicists, who are one in declaring that science can only give changes of configuration, rather than explain the causes of such changes. It is rather the modern view that science can only describe, but cannot explain.

Certainly the explanations which Prof. Haeckel gives of the wonders of answer more to descriptions than explanations. When he is asked the blunt question: "What is life?" he described the typical organism, but does not for a moment profess to explain what is the real difference between that organism while alive and when it has suffered somatic death. Similarly, when he comes to the next wonder of life, sensation or the elements of mentality, he has a most ingenious scale of development from the sensation which he assumes that an atom has up to the highest flights of imagination of the poet and thinker. Further on Prof. Haeckel entirely fails to substantiate any claim that he can treat from his scientific standpoint what he calls the value of life. Science, which deals only with the facts, has to accept all facts - good, bad, or indifferent. For instance, the criminal and the sage are each facts in the mental order, and science has no criterion for determining why one should be reprobated and the other admired. The world of values is outside the sphere of science. Here again Prof. Haeckel, the foremost exponent of modern science, is somewhat out of date in not recognizing a distinction which has been since Lotze a commonplace in modern philosophy. In fact, his incursions into the philosophic field strike one as being as amateurish as the excursions philosophers sometimes make into the world of biological science.

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THE fact is that biological science is not old enough or advanced enough to give certain data that science of sciences which men call philosophy. After all, in its modern form, biology is only fifty years old, and its fundamental principles have not yet been established so thoroughly as to form a firm basis for philosophical discussion. As we have seen, the work on which Haeckel's reputation is mainly founded is full of hypothesis and guesswork, and yet it is upon this foundation that he professes to instruct us as to the real meaning of the wonders of life. Theology in the past has been presumptuous enough to found a whole pseudo-science on its guesswork as to the relations of this and the other life. Science as represented by Prof. Haeckel is equally presumptuous in its claims to a solution of the wonders of this life.

JOSEPH JACOBS