THE CROSSING, &C, OP PIGEONS AND FOWES. 251 



reiterated) concerning the evil results of interbreeding 

 the highly improved or fancy birds, and concerning 

 the absolute necessity of crossing them with individ- 

 uals of the other varieties, that this very divergence 

 of character, is in derogation of the fertility and con- 

 stitutional vigor of the individuals of the divergent 

 varieties; — aye, incompatible, when carried to any 

 great extent, with their very existence ; for, he says (p. 

 270, Vol i, Animals and Plants, &c), that : 



" The young of all highly improved fancy breeds, are 

 extremely liable to disease and death /" 



This shows conclusively, that the further that this 

 process of divergence (upon which he counts to evolve 

 the varieties of any species, into distinct species), is 

 carried, the nearer, step by step, do the varieties, so 

 divergent, approximate complete sterility and extinc- 

 tion! 



On the other hand, it is shown, by his remarks, 

 already quoted, and by those quoted below, that the 

 only means, by which such divergent varieties may re- 

 gain their fertility, and retrieve their shattered consti- 

 tutions, is, by undoing the very process which, he would 

 have his readers believe, evolves them into distinct species! 



Even though the phenomena of close-interbreeding, 

 and' of crossing, did not conclusively imply, that the 

 sum of all the positive characters of the respective 

 species, was the only, perfect type; what would be 

 the strength of an argument, favoring the evolution 

 of species, by means of divergence of character, when 

 the individuals of each of the varieties, assumed to be 

 so diverging into distinct species, meets with com- 



