Chap. V. DESCRIPTION OF BREEDS. 139 



collection of the Columbidee in the British Museum, and, 

 with the exception of a few forms (such as the Didunculus, 

 Calsenas, Guura, &c), I do not hesitate to affirm that some 

 domestic races of the rock-pigeon differ fully as much from 

 each other in external characters as do the most distinct 

 natural genera. AVe may look in vain through the 288 

 known species 4 for a beak so small and conical as that of the 

 short-faced tumbler ; for one so broad and short as that of 

 the barb ; for one so long, straight, and narrow, with its 

 enormous wattles, as that of the English carrier ; for an ex- 

 panded upraised tail like that of the fantail ; or for an oeso- 

 phagus like that of the pouter. I do not for a moment pretend 

 that the domestic races diifer from each other in their whole 

 organisation as much as the more distinct natural genera. ] 

 refer only to external characters, on which, however, it must 

 be confessed that most genera of birds have been founded. 

 When, in a future chapter, we discuss the principle of selection 

 as followed by man, we shall clearly see why the differences 

 between the domestic races are almost always confined to 

 external,* or at least to externally visible, characters. 



Owing to the amount and gradations of difference between 

 the several breeds, I have found it indispensable in the follow- 

 ing classification to rank them under Groups, Eaces, and Sub- 

 races ; to which varieties and sub - varieties, all strictly 

 inheriting their proper characters, must often be added. 

 Even with the individuals of the same sub-variety, when 

 long kept by different fanciers, different strains can sometimes 

 be recognised. There can be no doubt that, if well-charac- 

 terized forms of the several races had been found wild, all 

 would have been ranked as distinct species, and several of 

 them would certainly have been placed by ornithologists in 

 distinct genera. A good classification of the various domestic 

 breeds is extremely difficult, owing to the manner in which 

 many of the forms graduate into each other ; but it is curious 

 how exactly the same difficulties are encountered, and the 

 same rules have to be followed, as in the classification of any 

 natural but difficult group of organic beings. An " artificial 



4 'Coup d'Oeil sur POrdre des Paris, 1855. This author makes 288 

 Pigeons,' par Prince ~. L. Bonaparte, species, ranked under 85 genera. 



