BIOLOGY AND ITS MAKERS 



checks' described by Malthus in his Essay on Population, 

 a work I had read several years before, and which had made 

 a deep and permanent impression on my mind. These 

 checks war, disease, famine, and the like must, it occurred 

 to me, act on animals as well as man. Then I thought of 



FIG. 120. ALFRED RUSSEL WALLACE, 1823-1913. 



the enormously rapid multiplication of animals, causing these 

 checks to be much more effective in them than in the case of 

 man; and while pondering vaguely on this fact, there sud- 

 denly flashed upon me the idea of the survival of the fittest 

 that the individuals removed by these checks must be on the 



