THE GROWTH OF GROUPS 171 



evolution appears to be another, the two processes being 

 independent of one another. It is evident, however, that 

 many persons believe the two processes to be dependent ; 

 by them selection is spoken of as the cause of evolution. 

 But there is some reason to believe that the two pro- 

 cesses are independent. Evolution is the arrival of 

 novelties into the world ; each extinct species of animal 

 or plant was in its early days a novelty. It seems that 

 this definition of evolution is sound. If so, it follows 

 that selection is not a cause of evolution since one cannot 

 obtain by means of artificial selection any novelty that 

 may be required ; moreover, novelties often appear without 

 the help of selection. As investigation goes on, more 

 and more cases are brought forward to exemplify (i) 

 selection in a group without effect ; (2) a new group 

 arising from an established group without the help of 

 selection. 



However, the belief that selection is the cause of 

 evolution still holds the field. According to this view, 

 the offspring of animals and plants always show some 

 slight points of difference from their parents. These 

 differences or variations are said to be " in all directions." 

 A species does not change so long as its circumstances 

 remain unchanged. The characteristics of a species are 

 always suited, so it is said, to the particular circumstances 

 in which that species finds itself. Hence, if any indivi- 

 duals should deviate from the standard quality of the 

 species they would be at a disadvantage and die out. 

 Because for the most part the aberrant members die 

 without leaving offspring, the species remains pure and 

 constant in quality always suited to its surroundings. 

 But when the circumstances change, the species as a 



