CHAPTER XII. 

 Sterility of Hybrids. 



An objection, which has ever obtained, to Darwin's 

 theory, is the fact of the sterility of species, when 

 crossed, or the sterility of the hybrids from a cross be- 

 tween two species. This has ever precluded the idea 

 of the evolution of one species into another. 



Since varieties cross readily, and their offspring are 

 fertile, this feature, of the sterility of hybrids, clearly 

 appears to be a fundamental distinction between varie- 

 ties and species. 



Darwin admits the fact, of the sterility of species 

 when crossed, or of their hybrids, and recognizes the 

 antagonism it bears to his hypothesis. 



He says (p. 293, Origin of Species): 



" Hybrids * * have their reproductive organs 

 functionally impotent, as may be clearly seen in the . 

 state of the male element in both plants and ani- 

 mals ; though their formative organs themselves are 

 perfect in structure, as far as the microscope reveals." 



Again, on p. 299, Origin of Species, he says : 

 " I doubt whether any case of a perfectly fertile 

 hybrid can be considered as thoroughly well authenti- 

 cated." 



On p. 27, Origin of Species, he says : 



" It is difficult, perhaps impossible, to bring forward 

 (408) 



