IMPROVING THE HUMAN PLANT 



But in one case, as in the other, such changes 

 are, after all, only matters of minor detail. 



A plum tree transplanted from Japan may put 

 out a somewhat larger growth of twigs and a 

 somewhat larger and more highly flavored fruit 

 than was its wont in its native habitat. But at 

 best it remains unmistakably a Japanese plum. 



The modifications wrought by the environment 

 are matters of detail; the fundamentals of hered- 

 ity, built up by thousands of generations of past 

 environments, are fixed beyond immediate change. 



Nor can we doubt that the same thing is true of 

 the fundamental physical, mental, and moral 

 traits of the alien races that make up the great 

 army of immigrants that come to our ports in such 

 numbers as to make their migration, in all prob- 

 ability, by far the largest and most rapid migra- 

 tion of human races that ever took place in the 

 history of the world. 



The total number of immigrants that have come 

 to America since 1880 — ^vidthin the compass, there- 

 fore, of a single generation — ^is more than twenty 

 million. 



This is a number in excess of the total popula- 

 tion of America at any census prior to 1850. 



Such an influx of new blood must of necessity 

 change in very large measure the aggregate hered- 

 ity of the population of America. Whatever the 



[237] 



