THEORY OF THE EABTH. 103 



climate ; and carried to the extreme difference 

 which they now present, during a long succession 

 of ages ? 



This objection must appear strong to those 

 especially who believe in the possibility of indefi- 

 nite alteration of forms in organised bodies ; and 

 who think that, during a succession of ages, and 

 by repeated changes of habitudes, all the species 

 might be changed into one another, or might re- 

 sult from a single species. 



Yet to these persons an answer may be given 

 from their own system. If the species have chang- 

 ed by degrees, we ought to find traces of these 

 gradual modifications. Thus, between the palaeo- 

 theria and our present species, we should be able 

 to discover some intermediate forms ; and yet no 

 such discovery has ever been made. 



Why have not the bowels of the earth preser- 

 ved the monuments of so strange a genealogy, if 

 it be not because the species of former times were 

 as constant as ours ; or, at least, because the ca- 

 tastrophe which destroyed them, had not left 

 them sufficient time for undergoing the variation 

 alleged ? 



In order to reply to those naturalists who ac- 

 knowledge that the varieties of animals are re- 

 strained within certain limits fixed by nature, it 

 would be necessary to examine how far these li- 

 mits extend. This is a very curious inquiry, 



