40 THE THEORIES OF EVOLUTION 



him by paleontology and embryology. A capital 

 datum furnished by paleontology, he said, was the 

 close affinity existing between the fossil remains of 

 two successive formations ; nothing short of direct de- 

 scent could explain it. 



The same applies to the resemblance between rep- 

 resentative specimens of the fauna of a given region, 

 and to the important fact that the more highly or- 

 ganised a form is, the more recent its appearance 

 must have been. This of course does not imply a 

 continuous progress, for, otherwise, the lowest organ- 

 isms would have all disappeared long ago. In re- 

 ality, nothing prevents their survival for they can 

 become adapted to their environment as perfectly as 

 the most highly differentiated beings. 



-It only goes to prove that higher forms of life 

 have developed successively and gradually at the ex- 

 pense of parents having a very close resemblance 

 to them. The geographical distribution of living 

 things points in the same direction. The wide differ- 

 ences observed between the faunas of regions whose/ 

 geographical and climatic conditions do not differ to" 

 my great extent, for instance the fauna of the new 

 and the fauna of the old world, can only be explained 

 by the hypothesis of the local development of those 

 faunae. 



On the other hand, the fact that the presence of 

 certain animal forms presupposes the presence of 



