and historical geology, of the succession of life on the earth, of the unity of organization pervading that life from monad to man all through the ages from the Precambrian to the present age, know that there were vast periods of preparation followed by crises, perhaps geologically brief, when there were widespread changes in physical geography, which reacted on the life-forms, rendering certain ones extinct, and modifying others; but this conception is entirely distinct from the views of Cuvier and his school,[101] which may, in the light of our present knowledge, properly be deemed not only totally inadequate, but childish and fantastic. Cuvier cites the view of Dolomieu, the well-known geologist and mineralogist (1770-1801), only, however, to reject it, who went to the extent of supposing that "tides of seven or eight hundred fathoms have carried off from time to time the bottom of the ocean, throwing it up in mountains and hills on the primitive valleys and plains of the continents" (Dolomieu in _Journal de Physique_). Cuvier met with objections to his extreme views. In his discourse he thus endeavors to answer "the following objection" which "has already been stated against my conclusions": "Why may not the non-existing races of mammiferous land quadrupeds be mere modifications or varieties of those ancient races which we now find in the fossil state, which modifications may have been produced by change of climate and other local circumstances, and since raised to the present excessive differences by the operation of similar causes during a long succession of ages? "This objection may appear strong to those who believe in the indefinite possibility of change of forms in organized bodies, and think that during a succession of ages, and by alternations of habits, all the species may change into each other, or one of them give birth to all the rest. Yet to these persons the following answer may be given from their own system: If the species have changed by degrees, as they assume, we ought to find traces of this gradual modification. Thus, between the Palæotherium and the species of our own days, we should be able to discover some intermediate forms; and yet no such discovery has ever been made. Since the bowels of the earth have not preserved monuments of this strange genealogy, we have a right to conclude that the ancient and now extinct species were as permanent in their forms and characters as those which exist at present; or, at least, that the catastrophe which destroyed them did not have sufficient time for the production of the changes that are alleged to have taken place." Cuvier thus emphatically rejects all idea that any of the tertiary mammals could have been the ancestral forms of those now existing.