Impression of five fingers and five toes of an Amphibian of the Lower Carboniferous Age, from the lowest Carboniferous beds in Nova Scotia—an evidence of the fact that the number five was already selected for the hands and feet of the earliest known land vertebrates, and that the decimal system of notation, with all that it involves to man, was determined in the Palæozoic Age. The upper figure natural size, the lower reduced.
The difficulties above referred to relate to the introduction of life and of new species on the monistic view. Others might be referred to in connection with the production of new organs. An illustration is afforded, among others, by the discussion of the introduction of the five fingers and toes of man, which appear to descend to us unchanged from the amphibians or batrachians of the Carboniferous period. In this ancient age of the earth's geological history, feet with five toes appear in numerous species of reptilians of various grades (Fig. 2). They are preceded by no other vertebrates than fishes, and these have numerous fin-rays instead of toes. There are no properly transitional forms either fossil or recent. How were the five-fingered limbs acquired in this abrupt way? Why were they five rather than any other number? Why, when once introduced, have they continued unchanged up to the present day? Haeckel's answer is a curious example of his method: "The great significance of the five digits depends on the fact that this number has been transmitted from the Amphibia to all higher vertebrates. It would be impossible to discover any reason why in the lowest Amphibia, as well as in reptiles and in higher vertebrates up to man, there should always originally be five digits on each of the anterior and posterior limbs, if we denied that heredity from a common five-fingered parent-form is the efficient cause of this phenomenon; heredity can alone account for it. In many Amphibia certainly, as well as in many higher vertebrates, we find less than five digits. But in all these cases it can be shown that separate digits have retrograded, and have finally been completely lost. The causes which affected the development of the five-fingered foot of the higher vertebrates in this amphibian form from the many-fingered foot (or properly fin), must certainly be found in the adaptation to the totally altered functions which the limbs had to discharge during the transition from an exclusively aquatic life to one which was partially terrestrial. While the many-fingered fins of the fish had previously served almost exclusively to propel the body through the water, they had now also to afford support to the animal when creeping on the land. This effected a modification both of the skeleton and of the muscles of the limbs. The number of fin-rays was gradually lessened, and was finally reduced to five. These five remaining rays were, however, developed more vigorously. The soft cartilaginous rays became hard bones. The rest of the skeleton also became considerably more firm. The movements of the body became not only more vigorous, but also more varied;" and the paragraph proceeds to state other ameliorations of muscular and nervous system supposed to be related to or caused by the improvement of the limbs.
It will be observed that in the above extract, under the formula "the causes which affected the development of the five-fingered foot ... must certainly be found," all that other men would regard as demanding proof is quietly assumed, and the animal grows before our eyes from a fish to a reptile as under the wand of a conjurer. Further, the transmission of the five toes is attributed to heredity or unchanged reproduction, but this, of course, gives no explanation of the original formation of the structure, nor of the causes which prevented heredity from applying to the fishes which became amphibians and acquired five toes, or to the amphibians which faithfully transmitted their five toes, but not their other characteristics.
It is perhaps scarcely profitable to follow further the criticism of this extraordinary book. It may be necessary, however, to repeat that it contains clear, and in the main accurate, sketches of the embryology of a number of animals, only slightly colored by the tendency to minimize differences. It may also be necessary to say that in criticising Haeckel we take him on his own ground—that of a monist—and have no special reference to those many phases which the philosophy of evolution assumes in the minds of other naturalists, many of whom accept it only partially or as a form of mediate creation more or less reconcilable with theism. To these more moderate views no reference has been made, though there can be no doubt that many of them are quite as assailable as the position of Haeckel in point of argument. It may also be observed that Haeckel's argument is almost exclusively biological and confined to the animal kingdom, and to the special line of descent attributed to man. The monistic hypothesis becomes, as already stated, still less tenable when tested by the facts of palæontology. Hence most of the palæontologists who favor evolution appear to shrink from the extreme position of Haeckel. Gaudry, one of the ablest of this school, in his recent work on the development of the Mammalia, candidly admits the multitude of facts for which derivation will not account, and perceives in the grand succession of animals in time the evidence of a wise and far-reaching creative plan, concluding with the words: "We may still leave out of the question the processes by which the Author of the world has produced the changes of which palæontology presents the picture." In like manner, the Count de Saporta in his World of Plants closes his summary of the periods of vegetation with the words: "But if we ascend from one phenomenon to another, beyond the sphere of contingent and changeable appearance, we find ourselves arrested by a Being unchangeable and supreme, the first expression and absolute cause of all existence, in whom diversity unites with unity, an eternal problem, insoluble to science, but ever present to the human consciousness. Here we reach the true source of the idea of religion, and there presents itself distinctly to the mind that conception to which we apply instinctively the name of God."
Thus these evolutionists, like many others in this country and in England, find a modus vivendi between evolution and theism. They have committed themselves to an interpretation of nature which may prove fanciful and evanescent, and which certainly up to this time remains an hypothesis, ingenious and captivating, but not fortified by the evidence of facts. But in doing so they are not prepared to accept the purely mechanical creed of the monist, or to separate themselves from those ideas of morality, of religion, and of sonship to God which have hitherto been the brightest gems in the crown of man as the lord of this lower world. Whether they can maintain this position against the monists, and whether they will be able in the end to retain any practical form of religion along with the doctrine of the derivation of man from the lower animals, remains to be seen. Possibly before these questions come to a final issue the philosophy of evolution may itself have been "modified" or have given place to some new phase of thought.
One curious point in this connection, to which little attention has been given by evolutionists, is that to which Herbert Spencer has given the name of "direct equilibration," though he is sufficiently wise not to invite too much attention to it. This is the balance of parts and forces within the organism itself. The organism is a complex machine; and if its parts have been put together by chance and are drifting onward in the path of evolution, there must of necessity be a continual struggle going on between the different organs and functions, each tending to swallow up the others and each struggling for its own existence. This resolution of the body of each animal into a house divided against itself is at first sight so revolting to common sense and right feeling that few like to contemplate it. Roux and other recent writers, however, especially in Germany, have brought it into prominence, and it is no doubt a necessary consequence of the evolutionary idea, though altogether at variance with the theory of intelligent design, which supposes the animal machine put together with care and for a purpose, and properly adjusted in all its parts. On the hypothesis of evolution, the animal thus ceases to be, in the proper sense of the term, even a machine, and becomes a mere mass of conflicting parts depending for any constancy they may have on a chance balancing of hostile forces, without any compelling power to bring them together at first, or any means to bind them to joint action in the system. The more such a doctrine is considered, the more difficult does it seem to believe in the possibility of its truth. Evolution has already reduced the cosmos into chaos, the harmony of the universe into discord; but it seems past belief to introduce this into the microcosm itself, and to see nothing in its exquisite adjustments except the momentary equilibrium of a well-balanced fight. Geological history also adds to the absurdity of such a view by showing the marvellous permanence of many forms of life which have continued to perpetuate themselves through almost immeasurable ages without material changes, thus proving unanswerably the perfect adjustment of their parts.
Viewed rightly, this direct equilibration of the parts of the animal seems to throw the greatest possible doubt on the capacity of any form of evolution to produce new species. It is certain, from the facts collected by Mr. Darwin himself in his work on animals under domestication, that when man disturbs the balance of any organism by changing in any way the relations of its parts, he introduces elements of instability and weakness, which, despite the efforts of nature to correct the evils resulting, speedily lead to degeneracy, infertility, and extinction. Mr. T. Warren O'Neil of Philadelphia has recently argued this point with much ability,[4] and has shown, on the testimony of Darwin's facts, that unless "natural selection" is a much more skilful breeder than man, and possesses some secrets not yet discovered by us, the effects of this imaginary power would lead, not to the production of new species, but merely to the extinction of those already existing. In short, all the evidence goes to show that—so beautifully balanced are the parts of the organism—any excess or deficiency in any of them, when artificially or accidentally introduced, brings in elements not only of instability, but of decay and destruction. This subject is deserving of a more full treatment than it can receive here, but enough has been said to show that in this evolutionists have unwittingly furnished us with a new confirmation of the theory of intelligent design.
In some places there are in Haeckel's book touches of a grim humor which are not without interest, as showing the subjective side of the monistic theory and illustrating the attitude of its professors to things held sacred by other men. For example, the following is the introduction to the chapter headed "From the Primitive Worm to the Skulled Animal," and which has for its motto the lines of Goethe beginning:
"Not like the gods am I! full well I know;
But like the worms which in the dust must go."
"Both in prose and poetry man is very often compared to a worm; 'a miserable worm,' 'a poor worm,' are common and almost compassionate phrases. If we cannot detect any deep phylogenetic reference in this zoological metaphor, we might at least safely assert that it contains an unconscious comparison with a low condition of animal development which is interesting in its bearing on the pedigree of the human race."