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BIOLOGY AND ITS MAKERS 



checks' described by Alalthus 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 hke — must, it occurred 

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



Fig, 120. — Alfred Russel Wallace, born 1823. 



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 bv these checks must be on the 



