SEX AND NATURAL SELECTION 207 



which are transmitted in the Mendelian manner, are just 

 as common in one sex as in the other, while others blend, 

 thus behaving in a manner quite different to the secondary 

 sexual characters. 



The evidence then seems to suggest that the secondary 

 sexual characters are dependent for their development upon 

 the presence of the sexual glands in the individual, and that 

 the potentiality of producing them is present in all indi- 

 viduals of both sexes. Whatever is alternative in their 

 appearance is dependent upon the fact that sex is alternative. 



The fundamental difference between the two sexes is that 

 one produces sperms, the other ova. How far any differences 

 beyond this should be regarded as secondary and not primary 

 sexual characters is immaterial to the question now under 

 consideration. It has already been pointed out that, had 

 sex, like other characters that have become racial, ended in 

 blending when crossed, hermaphrodites would have been 

 produced, and sex would have been eliminated. Natural 

 selection has preserved the alternative transmission of sex, 

 and the race thereby gains material advantages through the 

 limitation of inbreeding. The whole usefulness of sex de- 

 pends, therefore, upon its inheritance remaining alternative. 1 

 Hence natural selection would eliminate all variations 

 towards blending, and sex would continue to be trans- 

 mitted in the same manner as an individual character. 

 In fact, it seems that sex ought to be regarded as a character 



1 A certain school of biologists holds that the explanation of the appearance 

 of a character on the grounds of its utility is insufficient, and that such an 

 explanation is unscientific and superficial. Apart from the fact that this con- 

 demns all our greatest biologists, including particularly Darwin, as unscientific 

 and superficial, it is difficult to see, admitting that evolution is a fact, how the 

 existence of the great majority of racial characters is to be accounted for in any 

 other way. Useful variations have given their possessors an advantage over 

 their fellows, and so they have been preserved. It does not matter in this case 

 whether acquired characters are or are not transmitted. Variations have been 

 preserved and have produced characters because they were advantageous to their 

 possessors because they were useful. The critics of this explanation fail to dis- 

 tinguish between the meanings of the words why and how. An explanation 

 that is quite satisfactory as to why a thing has come about, need not attempt to 

 explain the details of how it has done so. 



