170 FROM THE GREEKS TO DARTVTN 



we see at the present time. The modifications arising 

 from different habits cause the varieties thus formed 

 to be sterile inter se; thus these new species are kept 

 separate. 



Evolution, according to this hypothesis, ad- 

 vances by fortuity, by the chance combinations 

 of hereditary elements which produce new char- 

 acters. Divergence is continued and fostered by 

 physiological isolation. 



Diderot (1713-1784) 



Denis Diderot must also be ranked as one of 

 the speculative contributors to the theory of the 

 origin of species. This famous man of letters of 

 the middle of the eighteenth century became an 

 opponent of the teleological teaching of the day. 

 He is believed to have contributed to D'Hol- 

 bach's Systeme de la Nature^ which was charac- 

 terized as the Bible of Atheism. The passages 

 quoted below, however, indicate that Diderot was 

 a theist. 



Perrier points out {loc. cit.) that it was an 

 essay published in 1751 by de Maupertuis, under 

 an assumed name, which called forth Diderot's 

 Pensees sur V Interpretation de la Nature, pub- 

 lished in 1754. He leaves aside the question of 

 the nature of inorganic material particles, and 

 begins his system by endowing all organic parti- 



