412 STERILITY OF HYBEIDS. 



of facts he has in hand. His theory requires, that all of 

 the phenomena of Variation, of Reversion, of Correla- 

 tion, of Crossing, of Close-Interbreeding, of Genera- 

 tion, &c, be deemed inscrutable, ultimate in their 

 character, and absolutely inexplicable. True it is, 

 that his theory demands this, not without reason; for, 

 as the reader sees, knowledge of the causes of these 

 phenomena, explodes his theory. 



The answer, to be made to his argument of an 

 appeal to every person's ignorance of the causes of 

 the evil effects of close-interbreeding, and of the good 

 resulting from crossing individuals of the same spe- 

 cies, is, — that there is no such ignorance ! — all of the 

 phenomena, to which he appeals, as being inexplica- 

 ble, are susceptible, as has been fully shown in previ- 

 ous chapters of this book, of a full qualitative and 

 quantitative explanation. Evil effects flow from the 

 interbreeding of individuals of the same species, be- 

 cause such individuals have characters of their species, 

 reduced or suppressed. Those differences in the quan- 

 tity of effects, which make Darwin so confident, that 

 the subject is hopelessly confused, are simply due to 

 corresponding degrees of defective development, in 

 the individuals so interbred. The good resulting from 

 the crossing of varieties, is, as has been shown, due to 

 the fact, that one variety contributes, to the offspring, 

 a character or characters which the other variety 

 lacks; and the physiological gain, evidenced in the 

 fertility resulting, is because, by such contribution of 

 characters, the mongrel offspring has removed the 

 nearer to the perfect type of the species. Those dif- 



