CHAPTER IV 



SELECTION AND EVOLUTION 



Darwin's Theory of Natural Selection still 

 holds today first place in every discussion of 

 evolution, and for this very reason the theory 

 calls for careful scrutiny; for it is not difficult 

 to show that the expression "natural selection" 

 is to many men a metaphor that carries many 

 meanings, and sometimes different meanings to 

 different men. While I heartily agree with my 

 fellow biologists in ascribing to Darwin him- 

 self, and to his work, the first place in biological 

 philosophy, yet recognition of this claim should 

 not deter us from a careful analysis of the situ- 

 ation in the light of work that has been done 

 since Darwin's time. 



THE THEORY or NATURAL SELECTION 



In his great book on the Origin of Species, 

 Darwin tried to do two things: first, to show 

 that the evidence bearing on evolution makes 



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