CONCLL SIGNS. 239 



must be a necessary relation between the races of ani 

 mals and the epoch at which they appear. It is necessary, 

 therefore, in order to comprehend Creation, that we com- 

 bine the study of extinct species with that of those now 

 living, since one is the natural complement of the other. A 

 system of Zoology will consequently be true, in proportion 

 as it corresponds with the order of succession among ani- 

 mals. 



