In the second place, where one fact in nature looks favorable to this hypothesis, a thousand facts teach the contrary.
Take for example the reproduction of animals. Out of every thousand individuals we have certain evidence that nine hundred and ninety-nine are brought into existence by the ordinary modes of generation; that is, they depend upon progenitors. Still, if in the thousandth case the animal’s existence was clearly casual, if we could see an elephant, or an ox, start into life without parental agency, that single case would prove the hypothesis. But never do its advocates pretend that any of the larger animals are produced in this way. Nor is it till they get among the smaller and obscure animals, whose habits are very difficult to trace out, that we find any examples where a suspicion even can exist of the communication of vitality irrespective of parental agency. Is not a strong presumption hence produced that further and more scrutinizing observation will show the few excepted cases not to be real exceptions? Does not sound philosophy demand that the proof of the casual production of the thousandth case shall be as decided as that of the normal generation of the nine hundred and ninety-nine? But no one, it seems to me, will pretend that any thing like such certainty exists in a single example throughout all nature. The presumption, then, is really more than a thousand to one against the hypothesis.
Take an example from hybridity. While a thousand species retain from age to age their individuality, not more than one coalesces with its neighbor, and loses its identity. And even here, all admit that there is a constant tendency in the hybrid race to revert to the original stock; and there is strong reason to believe that this will sooner or later take place, and that it would speedily occur in every case, were it not for the influence of domestication. Such facts make the presumption very strong, that species are permanent, and any extensive metamorphosis impossible. Hybridity appears to be in a measure unnatural; and the old proverb true in respect to it—
“Si furca naturam expellas,
Usque recurret.”
By the hypothesis under consideration, we ought to expect at least a few examples of the formation of new organs in animals, in the efforts of nature to advance towards a more perfect state. It has usually been said that the time since animals were first described is too short for such development. But we have examples, from the catacombs of Egypt, of animals and plants that lived in that country three thousand years ago; and yet, according to Cuvier,—and who is a better judge?—they are precisely like the living species. Strange that this great length of time should not have produced even one new organ, or the marks of a conatus to produce one. We are, indeed, pointed to the different varieties of the human species, as examples of this progress. But these diversities, also, can be shown to be the same now as at the earliest date of historical records; and where, then, is the evidence that they ever have undergone, or ever will undergo, any change of importance? There may indeed be examples of amalgamation, but under favorable circumstances the original varieties are again developed.
In the third place, geology contradicts this hypothesis.
We have seen that it offers no satisfactory explanation of the gradual increase of the more perfect animals and plants, as we rise higher in the rocks. That fact is most perfectly explained by supposing that divine wisdom and benevolence adapted the new species, which from time to time were created, to the changing and improving condition of the earth. A multitude of species have been dug from the rocks; but not one exhibits evidence of the development of new organs in the manner described by this hypothesis. New species often appear, but they differ as decidedly from the previous ones as species now do; and at the beginning of each formation there is often a very decided advance in the organic beings from those found in the top of the subjacent formation. How can this hypothesis explain such sudden changes, when its essential principle is, that the progress of the development is uniform? Nothing can explain them surely but special creating interposition.
Geology also shows us that for a vast period the world existed without inhabitants. Now, what was it that gave the laws of nature power, after so long an operation unproductive of vitality, to produce organic natures? Who can conceive of any inherent force that should thus enable them, all at once, to do what true philosophy shows to have demanded infinite skill?
In short, of all the sciences, geology most clearly shows special divine interference to explain its phenomena. It presents us with such stupendous changes, after long periods of repose, such sudden exhibitions of life, springing forth from the bosom of universal death, that nothing but divine, special, miraculous agency can explain the results. And of all the vast domains of nature, it seems to me no part is so barren of facts to sustain this hypothesis as the rocks; nor so full of facts for its refutation. These, however, have been so fully detailed in a previous part of this lecture that they need not be here repeated.
In the fourth place, the prodigious increase of the power and the means of reproduction, which we find among the lower tribes of animals, affords a strong presumption against this hypothesis.