288 FROM THE GREEKS TO DARWIN 



for we find only another proof of the insuperable 

 difficulties under which these early evolutionists 

 labored, in the comparatively limited knowledge 

 they possessed of the forms and successions of 

 life. As soon as Treviranus departs from these 

 first principles of biology and undertakes an ap- 

 plication of these principles to a theory of devel- 

 opment of animal life, he becomes more and more 

 speculative, and shows himself even more fan- 

 tastic than Lamarck in his approach to the truth. 



In his conception of the processes of Evolu- 

 tion, we see him erroneously translating Buf- 

 fon's term 'denaturee,' by ^degeneration' ; for he 

 means by * degeneration' exactly what we now 

 term adaptation or modification, by the action of 

 external formative forces — in other words, both 

 development and degeneration — whereas Buff on 

 in the w^ord denaturee implied modification by 

 climate of an originally perfect type. His theory 

 of the causes of Evolution is very similar to that 

 of Buffon, as he traces degeneration solely to the 

 influences of varying external conditions, and 

 this he believes to be the modifying factor in sin- 

 gle organisms. The perpetual changes in living 

 surroundings bring about constant changes in 

 the organization of the body. 



In the course of these changes old species are 

 destroyed and new ones take their places. He 

 brings out clearly the idea of the direct action of 



