CHAPTER IV. 

 THE ORIGIN OF DIPLOID SPECIES. 



The problem of the species and of its origin is, as was 

 said in the preceding chapter, comparable to that of the 

 pure chemical substance and to its origin. 



Just as we do'nt study the origin of pure chemical 

 substances in nature, but investigate this origin 

 in the laboratory, so the question of the origin of spe- 

 cies cannot be tackled in the field, but must be studied 

 in the experiment garden. 



It is a curious fact that one has pretty generally 

 thought, that the problem of heredity lies at bottom of 

 the question of the origin of species, while heredity 

 of course can only be concerned in the perpetuation 

 of a species once formed, because heredity implies 

 the unchanged transmittal of the properties of the 

 parents to the offspring. 



That this confusion has arisen, is due to the fact 

 that most organisms are not specifically pure, and 

 consequently get children more or less similar to them, 

 but not identical with them. 



This similarity has gradually become looked upon 

 as a sufficient criterium for heredity, just as the simi- 

 larity of the individuals composing a Linneon, has been 

 looked upon as to be sufficiently close to allow one to 

 consider a Linneon as a species. 



In this way, the conception heredity has become as 



