TIIK STRUGGLE FOR EXISTENCE 31 



plant and animal use is limited; many more individuals 

 are jjorn than can siu/vivc; the result is a perpetual 

 ^ru,i;i;le for survival, y' 



V (2) The fittest individuals tend to he the ones that 

 survive; the battle is to the strong, the race is to the 

 swift. 



(^ The individuals so selected transmit many of 

 their favorable qualities to their offspring by hereditjy 

 (;(4J But although heredity produces a wonderfully 

 exact copy of the parent in the child, there is never pre- 

 cise reduplication. Tliere is latitude for individual vari- 

 ation. II', among the innumerable multitudes of indi- 

 vidual variations that may occur, one chances to appear 

 which, no matter in how slight a degree, gives the in- 

 dividual possessing it advantage in the struggle, that 

 individual is bound to be favored with longer life^nd 

 larger number of progeny — with survival, in shortJ 



But the theory of natural selection proposes to ex- 

 plain only those characters which give advantage in the 

 struggle for existence. It does not explain the existence 

 of certain characters which do not give definite advan- 

 tage to their possessors and yet tend to persist from 

 generation to generation. Some of these characters, like 

 the brilliant plumage of certain birds (peacock and pea- 

 hen), would seem to bo of positive disadvantage by 

 making them conspicuous to their enemies. To account 

 for these markedly contrasted sex-characters, Darwin 

 advanced the theory of Sexual Selection. He believed 

 that the individuals possessing the brilliant coloring 

 were more attractive to those of the opposite sex and so 

 had a better chance to mate than their fellows of a more 

 sober hue. By the laws of heredity the brilliant plumage 

 was transmitted, and the less attractive individuals, not 



