46 THE EVOLUTION OF LIVING BEINGS. 



while a Linneon or a genus is a group of individuals of 

 different constitutions. 



And when we have once grasped this fundamental 

 difference, we can easily demonstrate that Jordan was 

 perfectly right when he said that I'espece est ind6- 

 pendante du nombre, while the genus is not. If we 

 reduce a species to one single individual, by extermi- 

 nating all others, that species stiU remains in existence, 

 but when we reduce a Linneon or a genus to one spe- 

 cies, that Linneon or that genus disappejirs, because a 

 mixture of different types is no longer a mixture after 

 its reduction to one type. 



While thus Jordan is perfectly right, when he states that 

 a genus is a grou^p made by us, it is not certain yet, that he 

 is right also when he continues to say that the Linneon or 

 the genus n'a la veritd que par les conceptions de notre 

 esprit, because it is possible that groupings, such as we 

 make, coincide with similar groupings made by na- 

 ture. 



Because nature primarily can make nothing but 

 individuals, it does not follow that it cannot se- 

 condarily group such individuals in various ways ; as a 

 matter of fact we know that it does, by the fact of the 

 existence of different plant-societies, different flora's 

 and fauna's in different countries etc. 



Now if our Linneons, obtained by grouping together 

 morphologically similar individuals, happened to co- 

 ver the groupings made by nature, such Linneons would 

 be something more than mere conceptions of our mind 

 and therefore be well worth investigating. 



If nature makes groupings more or less coinciding 



