32 ENGLISH MEN OF SCIENCE. [CHAP. 



been no sexual preference for contrast in height, 

 that we may safely affirm in* this case also, that 

 the love of contrast does not prevail over that of 

 harmony. 1 



It is a question of high importance to specu-' 

 lations on the future of our race, whether the 

 instincts of sexual selection are or are not re- 

 pugnant to an improvement in the human 

 breed. We know perfectly well that they are re- 

 pugnant to unions where the resemblance is very 

 close ; thus near intermarriages shock bur feel- 

 ings, and the maintenance of high-bred artificial 

 varieties in their purity is always effected with 

 difficulty among animals. On the other hand, 

 they are equally repugnant to unions in which 

 there is great contrast ; thus, the intermarriage 

 of white and black races rarely takes place, and 

 animals of different species refuse to cross. 

 Where, then, and how wide, is the belt that lies 



1 The series of facts in (1), (2), and (3), and the correspond- 

 ing figures given by the theory with which they are supposed 

 to conform, are as follows : 



