THE 



POPULAR SCIENCE 



MONTHLY, 



MAY, 1910 



HEREDITY 1 



By Professor W. B. CASTLE 



HARVARD UNIVERSITY 



THE conservation movement now in progress has for its end to pre- 

 serve for future generations of men the natural resources of the 

 earth. But it goes without saying that the movement is useless unless 

 there are to he future generations of men capable of utilizing those 

 resources. Thoughtful persons are beginning to wonder whether this is 

 assured. Man is the product of two sets of agencies which we sum- 

 marize in the terms heredity and environment. The question has often 

 been asked which of these is the more important, but with this we need 

 not concern ourselves. Both are indispensable. Seed and soil com- 

 bined assure a harvest, but if either is lacking no harvest can be 

 expected. 



The public is awakening to the importance of providing mankind 

 with a proper environment through the agencies of sanitation, educa- 

 tion and good government, and this is well. This assures a suitable 

 soil in which a crop of healthy human beings may develop. But what 

 of the seed? This question has not yet been seriously considered. 

 Only in England has it been more than suggested. There Francis 

 Galton and his associates in the eugenics movement have started an 

 inquiry as to why it is that the average physical condition of the 

 English nation is declining although more and more attention is con- 

 stantly being given to improving the environment. Likewise in Ger- 

 many statistics show a steadily declining proportion of the young men 

 fit for military service. There is a suspicion in the minds of many, 

 that these nations are producing the new generation of citizens chiefly 

 from inferior family and racial stocks. If this is so the remedy is 



1 From a lecture delivered before Section F, American Association for the 

 Advancement of Science, December 31, 1909. 



vol. lxxvj.— 29. 



