270 FOWLS. Chap. VII. 



Cochins and Silk-fowls. The colour of the plumage and the form 

 of the comb are in most breeds, or even sub-breeds, eminently 

 fixed characters ; but in Dorkings these points have not been 

 attended to, and are variable. When any modification in the 

 skeleton is related to some external character which man values, 

 it has been, unintentionally on his part, acted on by selection, 

 and has become more or less fixed. We see this in the wonderful 

 protuberance of the skull, which supports the crest of feathers in 

 Polish fowls, and which by correlation has affected other parts 

 of the skull. We see the same result in the two protuberances 

 which support the horns in the horned fowl, and in the flat- 

 tened shape of the front of the skull in Hamburghs consequent 

 on their flattened and broad " rose-combs." We know not in 

 the least whether additional ribs, or the changed outline of the 

 occipital foramen, or the changed form of the scapula, or of 

 the extremity of the furcula, are in any way correlated with other 

 structures, or have arisen from the changed conditions and habits 

 of life to which our fowls have been subjected ; but there is no 

 reason to doubt that these various modifications in the skeleton 

 could be rendered, either by direct selection, or by the selection 

 of correlated structures, as constant and as characteristic of each 

 breed, as are the size and shape of the body, the colour of the 

 plumage, and the form of the comb. 



Effects of the Disuse of Parts. 



Judging from the habits of our European gallinaceous birds, Oallus 

 lankiva in its native haunts would use its legs and wings more than do 

 our domestic fowls, which rarely fly except to their roosts. The Silk and 

 the Frizzled fowls, from having imperfect wing-feathers, cannot fly at all ; 

 and there is reason to believe that both these breeds are ancient, so that 

 their progenitors during many generations cannot have flown. The 

 Cochins, also, from their short wings and heavy bodies, can hardly fly up 

 to a low perch. Therefore in these breeds, especially in the two first, 

 a considerable diminution in the wing-bones might have been expected, 

 but this is not the case. In every specimen, after disarticulating and 

 cleaning the bones, I carefully compared the relative length of the two 

 main bones of the wing to each other, and of the two main bones of 

 the leg to each other, with those of G. lankiva ; and it was surprising 

 to see (except in the case of the tarsi) how exactly the same relative 

 length had been retained. This fact is curious, from showing how truly 

 the proportions of an organ may be inherited, although not fully exer- 

 cised during many generations. I then compared in several breeds the 



