292 Evolution and Adaptation 



relatives, not in one character only, but in nearly all their 

 characters. There is no ground, De Vries states, for believ- 

 ing them to be varieties. If it is found inconvenient to rank 

 them under the names of the old Linnaean species, it will be 

 better, perhaps, to treat them as subspecies, but De Vries 

 prefers to call them elementary species. 



In regard to the distribution of species in nature, it may be 

 generally stated that the larger the geographical domain so 

 much the larger is the number of elementary species. They 

 are found to be heaped up in the centre of their area of dis- 

 tribution, but are more scattered at the periphery. 



In any one locality each Linnaean species has as a rule 

 only one or a few elementary species. The larger the area 

 the more numerous the forms. From France alone Jordan 

 had brought together in his garden 50 elementary species of 

 Draba vcrna. From England, Italy, and Austria there could 

 be added 1 50 more. This polymorphism is, De Vries thinks, 

 a general phenomenon, although the number of forms is sel- 

 dom so great as in this case. 



Amongst animals this great variety of forms is not often 

 met with, yet amongst the mammalia and birds of North 

 America there are many cases of local forms or races, some 

 of which at least are probably mutations. This can only be 

 proven, however, by actually transferring the forms to new 

 localities in order to find out if they retain their original char- 

 acters, or become changed into another form. It seems not 

 improbable that many of the forms are not the outcome of 

 the external conditions under which the animal now lives, 

 but would perpetuate themselves in a new environment. 



From the evidence that his results have given, De Vries 

 believes it is probable that mutation has occurred in all direc- 

 tions. In the same way that Darwin supposed that individ- 

 ual or fluctuating variations are scattering, so also De Vries 

 believes that the new forms that arise through mutation are 

 scattering. On this point it seems to me that De Vries may 



