THE ARGUMENT FROM EMBRYOLOGY.
Evolution derives its greatest argument from the study of the embryo. It makes three claims. First, that the germ of everything, plant and animal, is the same, neither chemical analysis nor the microscope showing any difference. If therefore, such vast variety could come from origins so alike, why could not all we see come from a similar origin, the primitive animal, which was also such a simple cell? Second, in the growth of the embryo it recapitulates the ancestral history of that particular organism. Third, all this when compared with the geologic record, and the present orders of living things as classified, presents the full succession of the forms of life, the one supplying what the other lacks.
These claims must be examined separately.
1. The claim that the germs of all living things are alike is not true. The resemblance is only superficial. Protoplasm, of which the germ is composed, differs and is not homogeneous material. That which builds the muscles is one kind, and that which builds brain and nerves is entirely different. Prof. Clodd tells us it is not a chemical compound but a mechanism. Nor could the germs be alike. For the plant breathes carbon, the animal oxygen. The one oxidizes, the other deoxidizes. There are still greater and deeper differences.
Tyndall says, "Under the most homogeneous material, there lie structural energies of such complexity, that we must question whether we have the mental elements with which to grapple with them.... The most trained and disciplined imagination retires in bewilderment from the problem. In that realm, inaccessible to everything but mind, the wonders of Creation are wrought out.... Here is determined the germ and afterwards the complete organization." (Fragments of Science, p. 153.) So that these cells or germs, which appear so alike, contain each in itself the entire plan and life of the coming creature, to the color of a feather, the trick of a hunting dog and the smile and dimples of a child.
2. The second claim that the course of each embryo traverses its ancestral history, is not nearly so vociferously made as some years ago. Prof. A. Agassiz writes, "Anything beyond a general parallelism is hopeless." Prof. Conn admits "Embryology alone is not a safe guide, and only when verified by the fossils can it be relied upon. It seldom gives a true history.... The parallel is largely a delusion.... It often gives a false history." (Evolution of To-day, pp. 125, 134, 137, 150.) Prof. Thomson writes, "Recapitulation is due to no dead hands of the past, but to physiological conditions which we are unable to discover." (Outline of Zoology, p. 63.) He also says that the young mammal was never like a worm, a fish, or reptile. It was at the most like the young of these in their various stages. So far from the course of all being alike, Baer says he can tell the difference between the embryo of the common fowl and duck on the second day. (Principles of Biology, p. 1.) So far as this claim holds good, it forms an argument against evolution. For here is a goal or ideal to which all things strive. This is intention, and plan and purpose, all of which is opposed to the main idea of Evolution. It is in line with Creation.
3. The culminating argument for Evolution is given by arranging in ascending classification the geologic orders of life (which we have seen do not appear as Evolution demands), and placing alongside of these the classification of present animals (which we have seen is not agreed upon, and is as diverse as the writers themselves), and then laying alongside of these two artificial arrangements, the embryonic recital (which is now doubted and is often false to the past history), and triumphantly pointing to the three-fold combination. The gaps geology shows are thus filled by present forms and what both lack, by the embryonic recital.
Here are compared three things which radically differ. The geologic record shows progress from lower to higher, although not that complete nor unvarying record necessary to the theory, while the present orders of life exist simultaneously. Both show the existence of separate things having no individual connection. The embryo is a single individual, designed from its conception on a predetermined plan, animated by internal forces, and limited to a certain end and life. It is as Dawson says, a "closed series." The worlds of living and fossil creatures consist of myriads of individuals, under many widely different conditions, and aimed at widely different ends and lives. The two are contradictory for the uses of Evolution.
What we do see in these three facts are three marks of personal intelligence. In embryonic growth we see the plan of production. In the coming of the fossil creatures we see the progress of the plan in historical appearance. In the present display of nature we see the ultimate purpose of the whole. It all forms one great consistent plan and bears all the marks of personal and creative work.
So that summing up the argument from comparison of the three facts, the geologic order, the present classification, and the embryonic growth, we find in the first absolute separation of species, in the second no genetic connection as already shown under that argument, and in the third different phenomena having no points in common with the other two. The whole argument then fails of conclusion and reverts as the former do, to proof against Evolution.