io6 WHAT EVOLUTION IS 



nation of the less fit with the result 

 that the fittest survive, leave off- 

 spring, and thus hand on to future 

 generations their peculiar qualities, 

 for the individual differences noted by 

 Darwin are the inborn traits of each 

 individual. Thus a form of natural 

 selection is continually in operation 

 ever moulding plants and animals 

 with great nicety to their fluctu- 

 ating surroundings. This, according 

 to Darwin, is the mainspring that 

 keeps evolution continually moving. 



Survival of the fittest, struggle for 

 existence, and other like expressions 

 have been used as figures of speech 

 with which to make clear what is 

 meant by natural selection. And 

 these expressions do indicate what at 

 times occurs in nature, but anyone 

 who looks upon the world of plant 

 and animal life will not see a field of 

 battle, an arena of combat, with each 



