152 LAMARCK, HIS [LIFE AND WORK 
in organized bodies, and think that during a succes- 
sion 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 sys- 
tem: If the species have changed by degrees, as they 
assume, we ought to find traces of this gradual modi- 
fication. Thus, between the Palwotherium and the 
species of our own days, we should be able to dis- 
cover 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 perma- 
nent 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. 
“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 es- 
tablished among extraneous fossils, such as the pa/@o- 
therium, anaplotherium, megalonynx, mastodon, ptero- 
dactylis, 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 Iam 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 
