280 THE WHENCE AND THE WHITHER OF MAN 



and plant world there is abundant room and advan- 

 tage at the top. 



Once more, natural selection works as a rule for the 

 survival of individuals, only indirectly for that of 

 organs composing, or of species including, these indi- 

 viduals. It may work for the development of a trait 

 or structure which, while of no immediate advantage 

 to the individual, increases the probability of its rear- 

 ing a larger number of fitter offspring. Thus defence 

 of the young by birds may be a disadvantage to the 

 parent, but this is more than counterbalanced in the 

 life of the species by the number of young coming to 

 maturity and inheriting the trait. Even here natural 

 selection favors the survival of the trait indirectly by 

 sparing the descendants of the individual possessing 

 it. Natural selection may always Avork on and through 

 individuals without always working for their sole and 

 selfish advantage. 



In human society we find the selection of families, 

 societies, nations, and civilizations going on, but mainly 

 as the result of the survival of the fittest individuals. 



There may very probably be a struggle for existence 

 between organs or cells in the body of each individual. 

 The amount of nutriment in the body is a more or less 

 fixed quantity ; and if one organ seizes more than its 

 fair share, others may or must diminish for lack. But 

 the limit to this usurpation must apparently be set by 

 the crowding out of those individuals in which it is 

 carried too far. Natural selection, so to speak, leaves 

 the individual responsible for the distribution of the 

 nutriment among the organs, and spares or destroys 

 the individual as this usurpation proves for its advan- 

 tage or disadvantage. 



