SEXUAL SELECTION 651 



The structure of each individual feather generally causes 

 any change in its coloring to be symmetrical; we see this 

 in the various laced, spangled, and pencilled breeds of the 

 fowl ; and on the principle of correlation the feathers over 

 the whole body are often colored in the same manner. We 

 are thus enabled without much trouble to rear breeds with 

 their plumage marked almost as symmetrically as in natural 

 species. In laced and spangled fowls the colored 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, ex- 

 cepting toward 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 deter- 

 mines 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 regular zone of dark brown, edged 

 with brownish white. In these cases we have feathers sym- 

 metrically shaded, like those which give so much elegance 

 to the plumage of many natural species. I have also no- 

 ticed a variety of the common pigeon with the wing-bara 

 symmetrically zoned with three bright shades, instead of 

 being simply black on a slaty-blue ground, as in the parent 

 species. 



In many groups of birds the plumage is differently col- 

 ored in the several species, yet certain spots, marks, or 

 stripes are retained by all. Analogous cases occur with the 

 breeds of the pigeon, which usually retain the two wing- 

 bars, though they may be colored red, yellow, white, 

 black, or blue, the rest of the plumage being of some 

 wholly different tint. Here is a more curious case, ia 

 which certain marks are retained, though colored in a 

 manner almost exactly the opposite of what is natural; 

 the aboriginal pigeon has a blue tail, with the terminal 



