l6 THE EVOLUTION OF LIVING BEINGS. 



constitute a group of individuals of really identical 

 constitutions. As a matter of fact, one has believed 

 this to be the case for a considerable time. 



Linnaeus himself thought so, or at least, doubted 

 it only occasionally and then set his doubts aside ; yet 

 he already was convinced himself, that the checking 

 of his conclusions, based on visible differences, necessi- 

 tated experiments. 



Many before him had felt this : John Ray had said 

 already in the 17th Century, that there was no better 

 criterium to distinguish species, than the fact that true 

 species faithfully reproduce their kind by seeds : nulla 

 certior .... quam distincta propagatio ex semine. 



This test was frequently, though not under all the 

 necessary precautions, resorted to by Linnaeus who, 

 by applying it, saw that the reproduction was not 

 faithfull, that, on the contrary, the different indivi- 

 duals obtained from seeds, supposed to belong to the 

 same species, showed visible differences. Of some of 

 these differences, he could demonstrate the dependency 

 on external conditions and show that they were not 

 transmitted to the offspring, so that they could be 

 neglected. 



Such differences he called varietates minores, and in 

 order to call the attention of his students to the rela- 

 tive unimportance of such differences, he characterised 

 them as: varietates minores non curat botanicus. 

 Unfortunately, Linnaeus drew from a few experiments 

 and observations the conclusion, that all small diffe- 

 rences between individuals should he considered to be 

 such uninheritable differences, and that consequently 



