XI PALAEONTOLOGY AND EVOLUTION 375 



Now, on the hypothesis of evolution, there is no 

 sort of difficulty in admitting that the differences 

 between the Miocene forms of the mammalian 

 Fauna and those which exist at present are the 

 results of gradual modification; and, since such 

 differences in distribution as obtain are readily 

 explained by the changes which have taken place 

 in the physical geography of the world since the 

 Miocene epoch, it is clear that the result of the 

 comparison of the Miocene and present Faunae is 

 distinctly in favour of evolution. Indeed I may 

 go further. I may say that the hypothesis of 

 evolution explains the facts of Miocene, Pliocene, 

 and Recent distribution, and that no other sup- 

 position even pretends to account for them. It is, 

 indeed, a conceivable supposition that every species 

 of Rhinoceros and every species of Hyaena, in the 

 long succession of forms between the Miocene and 

 the present species, was separately constructed out 

 of dust, or out of nothing, by supernatural power ; 

 but until I receive distinct evidence of the fact, I 

 refuse to run the risk of insulting any sane man 

 by supposing that he seriously holds such a 

 notion. 



Let us now take a step further back in time, 

 and inquire into the relations between the Miocene 

 Fauna and its predecessor of the Upper Eocene 

 formation. 



Here it is to be regretted that our materials for 

 forming a judgment are nothing to be compared 



