OF EVOLUTION. 37 



which the geological evidence amply and fully 

 confirms. 



Were the Mammalia in any way specially 

 connected in their zoological relationship with 

 birds, we should naturally expect to find them 

 appear in succession to the birds. The vertebrate 

 line would then be an absolutely successive one. 

 But this relationship does not exist. For a 

 long time zoologists have held to the opinion 

 that these highest animals were more nearly 

 related to the reptiles than to any other class 

 of the Vertebrata, but the evidence supporting 

 this conclusion was all but the very weakest. 

 The fundamental conception of a mammalian de- 

 parts so widely from that of any other repre- 

 sentative of the great series to which it belongs, 

 that an actual comparison between it and the 

 nearest forms appears almost impossible. But 

 recent researches have thrown new light upon 

 the problem. That most obvious distinction 

 separating the Mammalia from all other animals 

 namely, that they bring forth their young 



