192 FROM LAMARCK TO ST. HfLAIRE. 



f^as essentially modern in his method. We, there- 

 fore, expect to find an equal breadth of view in his 

 treatment of the problem of Evolution. Here we 

 are disappointed, for we find only another proof of 

 the insuperable difficulties under which these early 

 evolutionists laboured, in the comparatively limited 

 knowledge they possessed of the forms and succes- 

 sions of life. As soon as Treviranus departs from 

 these first principles of Biology and undertakes an 

 application of these principles to a theory of devel- 

 opment of animal life, he becomes more and more 

 speculative, and shows himself much inferior to 

 Lamarck in his approach to the truth. 



In his conception of Evolution, we see him trans- 

 lating Buffon's term ' d'cnaturee, ' by ' degeneration ' ; 

 for he means by ' degeneration ' exactly what we 

 now term ' adaptation,' or modification, by the ac- 

 tion of external formative forces; in other words, 

 both development and degeneration. His theory of 

 the Evolution factors is very similar to that of 

 Buffon, as he traces degeneration solely to the influ- 

 ences of varying external conditions, and this he be- 

 lieves to be the modifying factor in single organisms. 

 The perpetual changes in living surroundings bring 

 about constant changes in the organization of the 

 body. 



In course of these changes old species are de- 

 stroyed and new ones take their places. He brings 

 out clearly the idea of the action of environment in 

 the elimination of species, groups, and families, but 



