CHAPTER IV. 



EMBRYOLOGY. 



The Importance of Embryology. 



THE evidence which organic evolution derives 

 from classification and geological succession is as 

 conclusive as could be expected from such data. 

 The genetic connection of animals is, however, only 

 a matter of inference, if this evidence only be con. 

 sidered ; a very strong inference it is to be sure, but 

 one which does not necessarily follow from the facts. 

 It is always possible to say, and frequently has been 

 claimed, that although animals are classified as if 

 genetically -related, and although the fossils appear 

 in order exactly in harmony with the same idea, yet 

 there is no proof that the species thus appearing did 

 develop from each other. It is possible to admit all 

 of the facts which we have hitherto considered, and 

 still to claim that it has only been shown that if 

 evolution were true, classification and paleontology 

 would be as we find them, but that no direct argu- 

 ment has been offered to prove that the species liv- 

 ing to-day have passed through these various early 

 stages. Direct proof of genetic descent of the nature 

 demanded by this claim is impossible, but the infer- 

 ences from the classes of facts considered is the 



