Chap. XIV. VARIABILITY. 131 



age marked and coloured almost as symmetrically 

 as in natural species. In laced and spangled fowls 

 the coloured margins of the feathers are abruptly 

 defined ; but in a mongrel raised by me from a black 

 Spanish cock glossed with green and a white game 

 hen, all the feathers were greenish -black, excepting 

 towards their extremities, which were yellowish- white ; 

 but between the white extremities and the black 

 bases, there was on each feather a symmetrical, curved 

 zone of dark-brown. In some instances the shaft of 

 the feather determines the distribution of the tints ; 

 thus with the body-feathers of a mongrel from the 

 same black Spanish cock and a silver-spangled Polish 

 hen, the shaft, together with a narrow space on each 

 side, was greenish-black, and this was surrounded by 

 a reii'ular zone of dark-brown, edf>;ed with brownish- 

 white. In these cases we see feathers becoming sym- 

 metrically shaded, like those which give so much 

 elegance to the plumage of many natural species. I 

 have also noticed a variety of the common pigeon 

 with the wing-bars symmetrically zoned with three 

 bright shades, instead of being simply black on a slaty- 

 blue ground, as in the pareut-species. 



In many large groups of birds it may be observed 

 that the plumage is differently coloured in each species, 

 yet that certain spots, marks, or strij)es, though like- 

 wise differently coloured, are retained by all the species. 

 Analogous cases occur with the breeds of the pigeon, 

 which usually retain the two ^^dng-bars, though they 

 may be coloured red, yellow, white, black, or blue, the 

 rest of the plumage being of some wholly different tint. 

 Here is a more curious case, in which certain marks 

 are retained, though coloured in almost an exactly 

 reversed manner to v/hat is natural ; the aboriginal 

 pigeon has a blue tail, with the terminal halves of the 



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