DEGENERATION. 15 



not got a complete explanation, for we must find a 

 substitute in nature for the Jmman selection exercised 

 by the breeder. The question arises, then, " Is there 

 any necessary selective process in nature which could 

 have operated through untold ages, and so have repre- 

 sented the selective action of the breeder, durinsf an 

 immense period of time ? " Strangely enough, Mr. 

 Darwin was led to the discovery of such a cause 

 existing necessarily in the mechanical arrangements 

 of nature, by reading the celebrated book of an 

 English clergyman, the Rev. Mr. Malthus, On Popula- 

 tion. On happening to read this book, Mr. Darwin 

 himself tells us that the idea of " natural selection " 

 flashed upon him. That idea is as follows. Not 

 only among mankind, but far more largely among 

 other kinds of animals and of plants, the number of 

 offspring produced by every pair is immensely in 

 excess of the available amount of the food appro- 

 priate to the particular species in question. Ac- 

 cordingly, there is necessarily a struggle for existence 

 — a struggle among all those born for the possession 

 of the small quantum of food. The result of this 

 struggle is to pick out, or select, a few who survive 

 and propagate the species, whilst the majority perish 



