118 BIOLOGY AND SOCIAL PROBLEMS 



process to include the mental growth of man, 

 Lamarckism affords an accurate statement of 

 the way by which much of our mental equip- 

 ment has come to us, though this statement, 

 as compared with that advanced by Lamarck 

 and his followers, is figurative rather than 

 real. What we do not get by social inherit- 

 ance, however, we obtain by the strictest kind 

 of organic transmission. Thus our personal- 

 ity is in part an organic and in pai;t a social 

 heritage. 



With the evidence so preponderatingly 

 against Lamarckism as an effective factor in 

 organic evolution, there is left as a guiding 

 principle for the transmutationists little more 

 than Darwin's theory of natural selection. 

 This theory is so well known in its general 

 outlines as to require no special exposition. 

 Every species, according to Darwin, produces 

 many more offspring than can possibly reach 

 maturity. These offspring all differ somewhat 

 one from another. In consequence, at any pe- 

 riod of stress those individuals whose differ- 

 ences lie in the directions favorable for life 

 are more likely to survive than those that ex- 

 hibit unfavorable differences. Thus the more 

 favored individuals tend to be preserved and 



