NATURAL SELECTION IN MAN 203 



have a strong influence on the mortality of later life. And there is 

 another factor which may be operative, and that is the influence 

 of unfavorable surroundings on the germ plasm. It is, of course, 

 possible that many conditions leading to a high infant death 

 rate may affect the germ plasm in such a way as to produce 

 variations of an inferior kind. It is on this point that we are in 

 most urgent need of more light. Selective agencies differ in their 

 effect upon the general vitality of the organisms. The problem of 

 how any agent of elimination may affect the race is complicated 

 by its possible action in producing variations in the germ plasm. 

 A high infant death rate caused by agencies with an injurious 

 effect on the germ plasm instead of being a blessing in disguise 

 might prove to be an index of racial decay. 



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