43^ 



BIOLOGY AND ITS MAKERS 



checks' described by ^lalthus in his Essay on PopulatioUj 

 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 hke — must, it occurred 

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



Fig. 1 20. — 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 Avhile pondering vaguely on this fact, there sud- 

 denly flashed uj^on me the idea of the survival of the fittest — 

 that the individuals removed bv these checks must be on the 



