DIDEROT. 115 



fortuitous variation : We can, he says, thus readily 

 explain how new species are formed, ... by sup- 

 posing that the elementary particles may not always 

 retain the order which they present in the parents, 

 but may fortuitously produce differences, which, 

 multiplying and accumulating, have resulted in the 

 infinite variety of species which 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, advances 

 by fortuity, by the chance combinations of hered- 

 itary elements which produce new characters. 

 Divergence is continued and fostered by physio- 

 logical isolation. 



DENIS DIDEROT l (1713-1784) must also be ranked 

 as one of the speculative contributors to the theory 

 of the origin of species. Perrier points out that it 

 was an essay published in 1751 by Maupertuis, 

 under an assumed name, which called forth Dide- 

 rot's Pens'ees sur ^Interpretation de la Nature, 

 published in 1754. He leaves aside the question 

 of the nature of inorganic material particles, and 

 begins his system by endowing all organic parti- 

 cles with a sort of rudimentary sensibility, which 



1 Denis Diderot, the famous man of letters of the middle of the eighteenth 

 century, became an opponent of the Ideological teaching of the day. He is 

 believed to have contributed to D'Holbach's Systeme de la Nature, which was 

 characterized as the Bible of Atheism. . The passages quoted, however, indicate 

 that Diderot was a theist. 



