CONTROL OF HEREDITY: EUGENICS 383 



I. The Influence of Environment in Pro- 

 ducing New Races 



There is a popular belief that the value of 

 cultivated races is due to good environment, 

 good food, good soil, protection from enemies, 

 etc., and that if turned out to shift for them- 

 selves they revert at once to the original wild 

 stock. There are two ways in which it is con- 

 ceivable that new races might be produced by 

 environmental influences: 



1. By the direct inheritance of somatic or 

 personal characters acquired under the stimu- 

 lus of the environment. In spite of popular 

 opinion in favor of this view there is no evi- 

 dence that this ever occurs. There is no doubt 

 that environment has much to do with indi- 

 vidual development, but it does not usually 

 modify the hereditary constitution of the race. 



2. It is possible that environmental changes 

 acting upon germ cells at a sensitive period of 

 their development may produce germinal vari- 

 ations or mutations and thus give rise to new 

 races. There is considerable evidence that en- 

 vironment does sometimes act in this way. 



