Varieties and Elementary Species 



As we have seen, De Vries does not believe 

 that new species can arise by the accumulation 

 of fluctuating variations. By means of these 

 the race may be greatly improved, but nothing 

 more can be accomplished. These variations 

 follow Quetelet's law, which says that, for 

 biological phenomena, deviations from the aver- 

 age comply with the same laws as the devia- 

 tions from the average in any other case, if ruled 

 by chance alone. 



Very different in character are mutations. By 

 means of these, new forms, quite unlike the 

 parent species, suddenly spring into being. 

 Mutations are said by De Vries to be of two 

 kinds those that produce varieties and those 

 which result in new elementary species. 



According to De Vries, those species of plants 

 which are in a state of mutation (he refers to the 

 species of the systematic botanists) are of a com- 

 posite nature, being made up of a collection of 

 varieties and elementary species. His concep- 

 tion of a variety is a plant that differs from the 

 parent plant in the loss or suppression of one or 

 more characters, while an elementary species 

 differs from the parent form in the possession of 

 some new and additional character. But we will 

 allow him to speak for himself: "We can con- 

 sider (page 141 Species and Varieties) the follow- 

 ing as the principal difference between elementary 

 species and varieties : that the first arise by the 



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