io THE GEOLOGICAL EVIDENCES 



discovered. The fact, however, that the Cambrian 

 deposits have been so extensively studied, and that 

 no such remains have yet been found, renders it 

 more than probable that the animals of this class, 

 if they existed at all, existed in very small num- 

 bers ; and there can scarcely be a shadow of doubt 

 that their real development followed that of the 

 animals without backbone, whose remains are so 

 numerously scattered through the rocks. And let 

 me warn you further that the future finding of a few 

 vertebrate remains in the Cambrian deposits will be 

 no evidence against the doctrine of evolution not 

 until these remains will be found very much more 

 numerously than there is a prospect of ever find- 

 ing them. 



In the period succeeding the Cambrian, the Silu- 

 rian, we find the first traces of backboned animals, 

 and what are they ? The lowest members of the 

 series, those which exhibit the least development of 

 the sense organs the fishes. These animals are 

 numerically insignificant during this era, and appear 

 only towards its close ; in the period following, 



