52 THE ORIGIN OF SPECIES 



unknown. So many sa'ange contingencies are improballe 

 in the highest degree. 



Some facts in regard to the coloring of pigeons well 

 deserve consideration. The rock-pigeon is of a slaty- 

 blue, with white loins; but the Indian sub-species, C. in- 

 termedia of Strickland, has this part bluish. The tail 

 has a terminal dark bar, with the outer feathers exter- 

 nally edged at the base with white. The wings have two 

 black bars. Some semi-domestic breeds, and some truly 

 wild breeds, have, besides the two black bars, the wings 

 checkered with black. These several marks do not occur 

 together in any other species of the whole family. Now, 

 in every one of the domestic breeds, taking thoroughly 

 well-bred birds, all the above marks, even to the white 

 edging of the outer tail-feathers, sometimes concur per- 

 fectly developed. Moreover, when birds belonging to 

 two or more distinct breeds are crossed, none of which 

 are blue or have any of the above-specified marks, the 

 mongrel offspring are very apt suddenly to acquire these 

 characters. To give one instance out of several which I 

 have observed: I crossed some white fantails, which breed 

 very true, with some black barbs — and it so happens that 

 blue varieties of barbs are so rare that I never heard of 

 an instance in England; and the mongrels were black, 

 brown, and mottled. I also crossed a barb with a spot, 

 which is a white bird with a red tail and red spot on 

 the forehead, and which notoriously breeds very true; 

 the mongrels were dusky and mottled. I then crossed 

 one of the mongrel barb-fantails with a mongrel barb- 

 spot, and they produced a bird of as beautiful a blue 

 color, with the white loins, double black wing-bar, and 

 barred and white- edged tail-feathers, as any wild rock- 



