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.