My second example from geology to disprove the notion of an eternal series of animals and plants on the globe, is derived from the history of organic remains. That history shows us clearly, that the earth, since its creation, has been the seat of several distinct economies of life, each occupying long periods, and successively passing away. During each of these periods, distinct groups of animals and plants have occupied the earth, the air, and the waters. Each successive group has been entirely distinct from that which preceded it, though each group was exactly adapted to the existing state of the climate and the food provided; so that, had the different groups changed places with one another, they must have perished, because their constitutions were adapted only to the state of things during the period in which they actually lived. A distinguished naturalist has recently declared that "he has discovered, in surveying the entire series of fossil animal remains, five great groups, so completely independent that no species whatever is found in more than one of them."--_Deshayes._ Including the existing races, this would give us six entirely distinct groups of organic beings that have lived in succession upon this globe since it became a habitable world. But even if it should be found that a few species are common to adjoining groups, the great truth would still remain, that the different groups were too much unlike to be contemporaries, and that consequently a new creation must have taken place whenever each new group commenced its course. It is probable the earth has changed its inhabitants more than the six times that have been mentioned; some think as many as twelve times. But a larger number cannot yet be proved so clearly; and could they be, they would add nothing to this argument; for it rests mainly on the fact that this change of organic life has even once been complete. We may, however, very safely assume that the present animals and plants are the sixth group that have occupied the globe.[12]