VARIATION UNDER DOMESTICATION 21 



o* the orifice of the nostrils, of the tongue (not always 

 in strict correlation with the length of beak), the size 

 of the crop and of the upper part of the oesophagus ; 

 the development and abortion of the oil-gland ; the 

 number of the primary wing and caudal feathers ; the 

 relative length of wing and tail to each other and to 

 the body ; the relative length of leg and of the feet ; 

 the number of scutellae on the toes, the development 

 of skin between the toes, are all points of structure 

 which are variable. The period at which the perfect 

 plumage is acquired varies, as does the state of the 

 down with which the nestling birds are clothed when 

 hatched. The shape and size of the eggs vary. The 

 manner of flight differs remarkably ; as does in some 

 breeds the voice and disposition. Lastly, in certain 

 breeds, the males and females have come to differ to a 

 slight degree from each other. 



Altogether at least a score of pigeons might be 

 chosen, which if shown to an ornithologist, and he were 

 told that they were wild birds, would certainly, I think, 

 be ranked by him as well-defined species. Moreover, 

 I do not believe that any ornithologist would place the 

 English carrier, the short-faced tumbler, the runt, the 

 barb, pouter, and fantail in the same genus ; more 

 especially as in each of these breeds several truly- 

 inherited sub-breeds, or species as he might have called 

 them, could be shown him. 



Great as the differences are between the breeds of 

 pigeons, I am fully convinced that the common opinion 

 of naturalists is correct, namely, that all have de- 

 scended from the rock-pigeon (Columba livia), including 

 under this term several geographical races or sub- 

 species, which differ from each other in the most trifling 

 respects. As several of the reasons which have led me 

 to this belief are in some degree applicable in other 

 cases, I will here briefly give them. If the several 

 breeds are not varieties, and have not proceeded from 

 the rock-pigeon, they must have descended from at 

 least seven or eight aboriginal stocks ; for it is im- 

 possible to make the present domestic breeds by the 



