CHAPTER VII.-NATURAL SELECTION. 



NATURAL SELECTION is the process of dis- 

 crimination of variations, by which those which 

 are most in harmony with the environment survive. It 

 is, in short, as expressed by Spencer, "the survival of 

 the fittest." Fitness is of various kinds, and is only 

 determined by the nature of the environment. The 

 success of a variety which appears in aquatic sur- 

 roundings will depend on characters different from 

 those which bring success in a forest. Variations 

 which favor survival and increase among carnivorous 

 animals differ from those useful to the life of herbivo- 

 rous forms. So survival in human society depends on 

 characters different from those which secure the same 

 result among the lower animals, etc. It is thus evi- 

 dent that natural selection is of many kinds and that 

 forms survive for various reasons ; and it is hence of 

 universal application. The reasons for survival may 

 be divided into those which depend for survival on the 

 relations of a type to the non-living environment, and 

 those which depend on the living. The former may be 

 divided into those which are passive and those which 

 are active. The particular influences may be imper- 

 fectly enumerated as follows : 



