Facts and fancies in modern science / Studies of the relations of science to prevalent speculations and religious belief

by Sir John William Dawson

Thus the utmost value which can be attached to Haeckel's argument from analogy would be that it suggests a possibility that the processes which we see carried on in the evolution of the individual may, in the laws which regulate them, be connected in some way more or less close with those creative processes which on the wider field of geological time have been concerned in the production of the multitudinous forms of animal life. That Haeckel's philosophy goes but a very little way toward any understanding of such relations, and that our present information, even within the more limited scope of biological science, is too meagre to permit of safe generalization, will appear from the consideration of a few facts taken here and there from the multitude employed by him to illustrate the monistic theory.

When we are told that a moner or an embryo-cell is the early stage of all animals alike, we naturally ask, Is it meant that all these cells are really similar, or is it only that they appear similar to us, and may actually be as profoundly unlike as the animals which they are destined to produce? To make this question more plain, let us take the case as formally stated: "From the weighty fact that the egg of the human being, like the egg of all other animals, is a simple cell, it may be quite certainly inferred that a one-celled parent-form once existed, from which all the many-celled animals, man included, developed."

Now, let us suppose that we have under our microscope a one-celled animalcule quite as simple in structure as our supposed ancestor. Along with this we may have on the same slide another cell, which is the embryo of a worm, and a third, which is the embryo of a man. All these, according to the hypothesis, are similar in appearance; so that we can by no means guess which is destined to continue always an animalcule, or which will become a worm or may develop into a poet or a philosopher. Is it meant that the things are actually alike or only apparently so? If they are really alike, then their destinies must depend on external circumstances. Put either of them into a pond, and it will remain a monad. Put either of them into the ovary of a complex animal, and it will develop into the likeness of that animal. But such similarity is altogether improbable, and it would destroy the argument of the evolutionist. In this case he would be hopelessly shut up to the conclusion that "hens were before eggs;" and Haeckel elsewhere informs us that the exactly opposite view is necessarily that of the monistic evolutionist. Thus, though it may often be convenient to speak of these three kinds of cells as if they were perfectly similar, the method of "disappearance" has immediately to be resorted to, and they are shown to be, in fact, quite dissimilar. There is, indeed, the best ground to suppose that the one-celled animals and the embryo-cells referred to, have little in common except their general form. We know that the most minute cell must include a sufficient number of molecules of protoplasm to admit of great varieties of possible arrangement, and that these may be connected with most varied possibilities as to the action of forces. Further, the embryo-cell which is produced by a particular kind of animal, and whose development results in the reproduction of a similar animal, must contain potentially the parts and structures which are evolved from it; and fact shows that this may be affirmed of both the embryo and the sperm-cells where there are two sexes. Therefore it is in the highest degree probable that the eggs of a worm and those of man, though possibly alike to our coarse methods of investigation, are as dissimilar as the animals that result from them. If so, the "egg may be before the hen;" but it is as difficult to imagine the spontaneous production of the egg which is potentially the hen as of the hen itself. Thus the similarity of the eggs and early embryos of animals of different grades is apparent only; and this fact, which embodies a great, and perhaps insoluble, mystery, invalidates the whole of Haeckel's reasoning on the alleged resemblances of different kinds of animals in their early stages.

A second difficulty arises from the fact that the simple embryo-cell of any of the higher animals rapidly produces various kinds of specialized cells different in structure and appearance and capable of performing different functions, whereas in the lower forms of life such cells may remain simple or may merely produce several similar cells little or not at all differentiated. This objection, whenever it occurs, Haeckel endeavors to turn by the assertion that a complex animal is merely an aggregate of independent cells, each of which is a sort of individual. He thus tries to break up the integrity of the complex organism and to reduce it to a mere swarm of monads. He compares the cells of an organism to the "individuals of a savage community," who, at first separate and all alike in their habits and occupations, at length organize themselves into a community and assume different avocations. Single cells, he says, at first were alike, and each performed the same simple offices of all the others. "At a later period isolated cells gathered into communities; groups of simple cells which had arisen from the continued division of a single cell remained together, and now began gradually to perform different offices of life."

But this is a mere vague analogy. It does not represent anything actually occurring in nature, except in the case of an embryo produced by some animal which already shows all the tissues which its embryo is destined to reproduce. Thus it establishes no probability of the evolution of complex tissues from simple cells, and leaves altogether unexplained that wonderful process by which the embryo-cell not only divides into many cells, but becomes developed into all the variety of dissimilar tissues evolved from the homogeneous egg; but evolved from it, as we naturally suppose, because of the fact that the egg represents potentially all these tissues as existing previously in the parent organism.

But if we are content to waive these objections or to accept the solutions given of them by the "appearance-and-disappearance" argument, we still find that the phylogeny, unlike the ontogenesis, is full of wide gaps only to be passed per saltum or to be accounted for by the disappearance of a vast number of connecting-links. Of course, it is easy to suppose that these intermediate forms have been lost through time and accident, but why this has happened to some rather than to others cannot be explained. In the phylogeny of man, for example, what a vast hiatus yawns between the ascidian and the lancelet, and another between the lancelet and the lamprey! It is true that the missing links may have consisted of animals little likely to be preserved as fossils; but why, if they ever existed, do not some of them remain in the modern seas? Again, when we have so many species of apes and so many races of men, why can we find no trace, recent or fossil, of that "missing link" which we are told must have existed, the "ape-like men," known to Haeckel as the "Alali," or speechless men?

A further question which should receive consideration from the monist school is that very serious one, Why, if all is "mechanical" in the development and actions of living beings, should there be any progress whatever? Ordinary people fail to understand why a world of mere dead matter should not go on to all eternity obeying physical and chemical laws without developing life; or why, if some low form of life were introduced capable of reproducing simple one-celled organisms, it should not go on doing so.

Further, even if some chance deviations should occur, we fail to perceive why these should go on in a definite manner producing not only the most complex machines, but many kinds of such machines—on different plans, but each perfect in its way. Haeckel is never weary of telling us that to monists organisms are mere machines. Even his own mental work is merely the grinding of a cerebral machine. But he seems not to perceive that to such a philosophy the homely argument which Paley derived from the structure of a watch would be fatal: "The question is whether machines (which monists consider all animals to be, including themselves) infinitely more complicated than watches could come into existence without design somewhere"[3] —that is, by mere chance. Common sense is not likely to admit that this is possible.

Fig. 2.