196 CAUSES OF VARIATION 



take on the secondary sexual characters (those dominant in the 

 other sex) prematurely young. 1 



Many entire individuals never develop strongly the primary 

 characters of their own sex. There are effeminate males and 

 masculine females, those in which the characters of the oppo- 

 site sex are unusually developed. It is needless to say that such 

 individuals are not the best parents. 



II INTERNAL INFLUENCES AFFECTING THE 

 RACE AS A WHOLE 



Over against those causes that may operate in the case of 

 each individual to warp its development are to be considered 

 those that influence the race as a whole, turning the line of 

 descent more or less permanently aside from former channels. 

 Some of these influences are clearly denned and easily recog- 

 nized ; others are problematical, the discussion not having yet 

 passed beyond the stage of a plausible theory. 



The student of thremmatology and the breeder should be 

 always mindful that the purpose of all good breeding is not simply 

 to hold what we already have but to produce new types better 

 adapted than the old to the purposes of man. Accordingly any 

 and all lines that promise any hope of success should be assidu- 

 ously investigated. 



SECTION XI RELATIVE FERTILITY, OR GENETIC 

 SELECTION 2 



The assumption that all members of a race are equally fertile 

 in se and inter se (of themselves and between each other in all 

 directions) is not only hasty but dangerously incorrect. To 

 quote Pearson, " Fertility is not equally distributed among alJ 

 individuals." 



1 The entire animal with increasing age, its own sexual characters abating, 

 begins to take on those of the other sex. Thus the hen grows spurs, the cow 

 bellows and paws the dirt, women grow scanty beards, and old men's voices gro\v 

 light. 



2 Pearson, Grammar of Science, pp. 376, 414, 437-449, 462. 



