E VWENCES OF E VOL UTION. 95 



ing the nature and signification of species. On 

 the contrary, the divergence of views was rendered 

 greater in proportion to the progress of research and 

 discovery, so that it soon became difficult to find 

 any two persons who could agree on a definition of 

 the term "species." 



Everyone who wrote on zoology, as we have 

 learned, had his own system of classification. In 

 like manner, everyone who had occasion to treat of 

 questions of natural history found himself compelled 

 to define the little word " species," and the defini- 

 tion given usually differed in important respects 

 from those of previous investigators. Indeed, if 

 we compare the definitions of species which have 

 been given since the time of Ray, we shall find that 

 there has been as great a change of opinion respecting 

 its nature, as there has been displayed in the various 

 systems of classification that have been elaborated 

 since the period of Linnaeus. Everywhere there is 

 uncertainty, doubt, nebulosity. 



The learned anthropologist, De Quatrefages, in 

 his interesting work, " Darwin et ses Precurseurs 

 Frangais," gives, besides his own definition of the 

 term, no fewer than twenty definitions of species 

 he might have given many more as proposed by as 

 many eminent naturalists. 1 Some, like Ray and Flou- 

 rens, base their definition on genealogical connection ; 

 others like Tournefort and De Candolle regard like- 

 ness among individuals as the essential thing in a true 

 definition of species, while others still, and these for 



P P . 186, 187. 



