Until this common sense view was adopted there was no science of palaeontology. Cuvier was the first great naturalist to devote particular attention to the mainly unrelated and unverified facts that had been discovered before his time. He was truly the originator of this branch of zooelogy, for he brought together the observations of earlier men and extended his own studies widely and surely, emphasizing particularly the necessity for noting carefully the geological situation of a fossil in rocks of an older or later period of formation. His great result was the demonstration that many groups of animals existed in earlier ages that seem to have no descendants of the same nature to-day, and also that many or most of our modern groups are not represented in the earliest formed sedimentary rocks, although these recent forms possess hard parts which would surely be present somewhere in these levels if the animals actually existed in those times. But the meaning of these facts escaped Cuvier's mind. He was a believer in special creation, like Linnaeus and all but a few among his predecessors, and he explained the diversity of the faunas of different geological times in what seems to us a very simple and naive way. In the beginning, he held, when the world was created, it was furnished with a complete set of animals and plants. Then some great upheaval of nature occurred which overwhelmed and destroyed all living creatures. The Creator then, in Cuvier's view, proceeded to construct a new series of animals and plants, which were not identical with those of the former time, but were created according to the same general working plans or architectural schemes employed before. Another cataclysm was supposed to have occurred, which destroyed the second series of organisms and laid a new covering of rocks over the earth's surface for a subsequent period of relative quiet; and so the process was continued. By this account, Cuvier endeavored to reconcile the doctrine of supernatural creation and intervention with the obvious facts that organisms have differed at various times in the earth's history. Although he saw that animals of successive periods displayed similar structures, like the skeleton of vertebrates, which testified to some connection, Cuvier could not bring himself to believe that this connection was a genealogical one.