THE EVOLUTION OF SEX 13 



tunate to measure the importance of every result by 

 its relation to the theory of evolution. But with this 

 understanding I may venture upon a few suggestions. 

 If a variation should arise in a hermaphroditic 

 species (already reproducing sexually) that made cross- 

 fertilization more likely than self-fertilization, and if, 

 as a rule, the hybrid condition (however this may be 

 explained) is more vigorous in the sense that it leaves 

 more offspring, such a variation would survive, other 

 things being equal. 



But the estabhshment of the contrivance in the 

 species by means of which it is more likely to cross- 

 fertihze, might in another sense act as a drawback. 

 Should weak individuals appear, they, too, may be 

 perpetuated, for on crossing, their weakness is concealed 

 and their offspring are vigorous owing to their hybrid 

 condition. The race will be the loser in so far as re- 

 cessive or weak combinations will continue to appear, 

 as they do in many small communities that have some 

 deficiency in their race ; but it is a question whether the 

 vigor that comes from mixing may not more than com- 

 pensate for the loss due to the continual appearance of 

 weakened individuals. 



This argument appUes to a supposed advantage 

 within the species. But recombination of what already 

 exists will not lead to the development of anything 

 that is essentially new. Evolution, however, is con- 

 cerned with the appearance and maintenance of new 

 characters. Admitting that sexual reproduction proved 

 an advantage to species, and especially so when com- 

 bined with a better chance of cross-fertilization, the 

 machinery would be at hand by means of which any 



