236 COOK 



Differences resulting from the ability of individual organisms 

 to adjust or accommodate themselves to different environments. 

 These are the variations which have the most intimate connec- 

 tion with the environment, though they have no special signifi- 

 cance as causes of evolution. 



Differences of Deficient Accommodation (Topisni) . — Differ- 

 ences resulting from the inability of organisms to fully adjust 

 themselves to special conditions. The result is a non-hereditary 

 divergence from the normal characters of the species. 



Differences under New Conditions (NeotoJ>ism) . —Vari- 

 ations induced by the transfer of organism to new and unwonted 

 conditions. Three stages of new place effects may be distin- 

 guished, (1) those in which there is merely a stimulation of 

 growth, (2) those in which there is also a definite mutative 

 change of the hereditary characteristics of the variety, (3) those 

 in which the new conditions call forth a promiscuous mutative 

 diversity. 



Differences of Partial or Recent Interruption of Inter- 

 breeding {Porrisni). — Differences arising from the unequal 

 distribution of variations, that is, from a recent or partial inter- 

 ruption of interbreeding. Such are the differences that exist 

 between individuals from the remote parts of the range of a 

 species (geographical differences) and the differences of segre- 

 gated local varieties of domesticated species. The nature of 

 these differences is the same as that of the differences between 

 species. They are the result of divergent tendencies of evolution. 



Differences of New Genetic Variations (Neism). — Prepotent 

 variations which arise under normal conditions of free inter- 

 breeding, without having existed previously among the ancestors 

 of the variant individuals. They can be preserved without 

 isolation, and are the characters which probably contribute most 

 to heterism, and to the normal evolutionary progress of species 

 in nature. There is no evidence that the appearance of such 

 variations has any connection with adjustment or environmental 

 fitness. Their preservation depends, of course, upon their being 

 useful, or at least not positively detrimental. 



Differences of Aberrant Heredity ( Teratism). — Failure of 

 the organism to attain the normal form, structure or size of the 



