HYBRIDITY OF THE CERYID^. 



As has been already several times intimated, nature seems to 

 have established a law of sexual aversion not only among the 

 genera, but even among the species of animals and plants, which 

 is more or less intense as the dividing line which separates the 

 species is more or less pronounced. This aversion is more potent 

 with the female than the male, and is more commanding in the 

 wild state than when they are brought together in confinement, 

 and partial or complete domestication. This aversion is sufficient 

 to prevent the commingling of blood of species very nearly 

 allied when unrestrained in the wild state, though inhabiting 

 abundantly the same wild range, and perhaps this law of sexual 

 aversion may furnish as safe a rule as any to distinguish species 

 from varieties. Varieties are never constant and distinguishable 

 in the same district of country, for the simple reason that there 

 is no sexual restraint, which absolutely prevents the maintenance 

 of hereditary distinctions which distinguish varieties, and so would 

 it happen among species, were there no natural restraint to keep 

 them asunder. When such restraint exists which amounts to 

 practical prohibition, nature itself declares a purpose to maintain 

 a specific distinction. 



If we recognize the law of evolution, then the lines of separa- 

 ration of divergent families from an original stock, have become 

 so widely separated as to interpose this law of sexual aversion 

 between them, and we shall be sure to find permanent physical 

 characteristics dependent not upon factitious circumstances, but 

 solely on hereditary influences, which, uniting with the law of 

 sexual aversion, satisfactorily declares distinct species, where, a 

 long time before, when the lines of divergence were less sep- 

 arated, they were but varieties, with scarcely impaired sexual 

 inclinations for each other. 



We may admit that sexual intercourse sometimes occurs be- 

 tween individuals of different species in the wild state, just as 

 we see unnatural impulses manifested sometimes in both man 

 and brute, but they are so exceedingly rare as to be entitled to 

 no influence in the general discussion, and we may if you choose 

 asrree with those who contend that when such intercourse does 



