42S 



ZOOLOGY 



in the long run, will be the most perfectly fitted to their environ- 

 ment. Darwin, however, did not sufficient!}^ appreciate the 

 process in nature that corresponds to the breeder's preserva- 

 tion of a new peculiarit,y. The Dutch naturalist De Vries 

 has shown that in nature pecuharities, mutatio?is, frequently 



suddenly occur and these may 

 constitute the beginnings of new 

 species. These two processes, 

 the occurrence of variations and 

 the inheritance of them, are 

 sufficient to bring aljout those 

 great changes in organisms which 

 constitute evolution. 



As a concrete illu.stration of 

 the evolution of a domestic race, 

 the fancy mice may lie taken. 

 Fancj' mice have lieen derived 

 from the house mouse. The 

 house mouse is of an ashy gray 

 color. When its hairs are care- 

 fullj' examined, it will be found that they are black at the base 

 and reddish yello-w near the tip. Wild mice, like all other ani- 

 mals belonging to the class of mammals (including man) , some- 

 times produce individuals mthout pigment in the skin, hair, and 

 even the eyes. Such individuals are called albinos, and the 

 peculiarity is designated as albinism. All)ino or white mice with 

 pink eyes have this peculiarity, that when bred together they 

 produce onl}' white mice. But when a white mouse is bred with 

 a house mouse, none of the offs]:>ring are white. However, when 

 the gray descendants of white and house mice are bred together, 

 one-fourth of their offspring will be white. This statement 



Charles Darwin. 



