THEORY OF EVOLUTION 87 



species apjjears to have taken place by modify- 

 ing and improving bit by bit the structures 

 and habits that the animal or plant already 

 possessed. We have seen that there are thirty 



■ mutant factors at least that have an influence 

 on eye color, and it is probable that there are 

 at least as many normal factors that are in- 



I volved in the production of the red eye of the 

 wild fly. 



Evolution from this point of view has con- 



' sisted largely in introducing new factors that 

 influence characters already present in the ani- 



' mal or plant. 



Sucli a view gives us a somewhat dift'erent 

 picture of the process of evolution from the old 

 idea of a ferocious struggle between the indi- 

 viduals of a species with the siu-vival of the 

 fittest and the annihilation of the less fit. Evo- 

 lution assumes a more peaceful aspect, Xew 

 and advantageous characters survive by incor- 

 porating themselves into the race, improving it 

 and opening to it new opportmiities. In other 

 words, the emphasis may be placed less on the 

 competition between the individuals of a spe- 

 cies (because the destruction of the less fit does 



