"From all these well-established facts, there does not seem to be the smallest foundation for supposing that the new genera which I have discovered or established among extraneous fossils, such as the _palæotherium_, _anaplotherium_, _megalonynx_, _mastodon_, _pterodactylis_, etc., have ever been the sources of any of our present animals, which only differ as far as they are influenced by time or climate. Even if it should prove true, which I am far from believing to be the case, that the fossil elephants, rhinoceroses, elks, and bears do not differ further from the present existing species of the same genera than the present races of dogs differ among themselves, this would by no means be a sufficient reason to conclude that they were of the same species; since the races or varieties of dogs have been influenced by the trammels of domestication, which these other animals never did and indeed never could experience."[102] The extreme views of Cuvier as to the frequent renewal and extinction of life were afterward (in 1850) carried out to an exaggerated extent by D'Orbigny, who maintained that the life of the earth must have become extinct and again renewed twenty-seven times. Similar views were held by Agassiz, who, however, maintained the geological succession of animals and the parallelism between their embryonic development and geological succession, the two foundation stones of the biogenetic law of Haeckel. But immediately after the publication of Cuvier's _Ossemens fossiles_, as early as 1813, Von Schlotheim, the founder of vegetable palæontology, refused to admit that each set of beds was the result of such a thoroughgoing revolution.[103] At a later date Bronn "demonstrated that certain species indeed really passed from one formation to another, and though stratigraphic boundaries are often barriers confining the persistence of some form, still this is not an absolute rule, since the species in nowise appear in their entirety."[104] At present the persistence of genera like Saccamina, Lingula, Ceratodus, etc., from one age to another, or even through two or more geological ages, is well known, while _Atrypa reticulatus_, a species of world-wide distribution, lived from near the beginning of the Upper Silurian to the Waverly or beginning of the Carboniferous age. Such were the views of the distinguished founder of vertebrate palæontology. When we compare the _Hydrogéologie_ of Lamarck with Cuvier's _Discours_, we see, though some erroneous views, some very fantastic conceptions are held, in common with others of his time, in regard to changes of level of the land and the origin of the crystalline rocks, that it did contain the principles upon which modern palæontology is founded, while those of Cuvier are now in the limbo--so densely populated--of exploded, ill-founded theories.