THEORY OF EVOLUTION 87 



species appears 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- 

 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. 



Such a view gives us a somewhat different 

 picture of the process of evolution from the old 

 idea of a ferocious struggle between the indi- 

 viduals of a species with the survival of the 

 fittest and the annihilation of the less fit. Evo- 

 lution assumes a more peaceful aspect. New 

 and advantageous characters survive by incor- 

 porating themselves into the race, improving it 

 and opening to it new opportunities. 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 



