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Show 130 fiEXUAL SELECTION: niUDS. PART II. various hideous deformities-deep scars on the face with the flesh raised into protuberances, the septum of tho nose pierced by sticks or bones, holes in t~w cars and lips stretched widely open-arc all admired as ornamental. Whether or not unimportant differences between the sexes, such as those just specified, have been preserved throu()"h sexual selection, these differences, as well as all others, must primarily depend on the laws of variation. On the principle of correlated development, the plumage often varies ou different parts of tho body, or over the whole body, in the same manner. We see this ,vell illustrated in certain breeds of the fowl. In all the breeds the feathers on the neck and loins of the males are elongated, and are called hackles; now when both sexes acquire a top-lmot, which is a new character in the genus, the feathers on the head of the male become hackle-shaped, evidently on the principle of correlation; whilst those on the head of the female are of the ordinary shap . The colour also of the hackl s forming the top-knot of the male, is often ~orrelated with that of the hackles on the neck andloms, as may be seen by comparing these feathers in the Golden and Silver-, pangled Polish, the Houdans, and Crevc-cccur breeds. In some natural species we may observe exactly the same correlation in the colours ?f these same feathers, as in the males of the splendid Golden and Amherst pheasants. 'rhe structure of each individual feather generally causes any change in its colouring 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 oYer the whole body are often modi£od in the same manner. vVe are thus enabled without much trouble to rear breeds with their plum- VA UIABILI'l'Y. 131 age marked and coloured almost as symmetrically as in natural species. In laced and spangled fow Is the coloured margins of the feathers are abruptly do£ned; but in a mongrel raised by me from a black Spanish cock glossed with green and a white game ben, all the feathers were greenish- black, excepting towards their extremities, which were yellowish-white; but between tho 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 tho distribution of the tints· thus with the body-feathers of a mongrel from tb~ same black Spanish cock and a silver-spangled Polish hen, tho 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 brownishwhit~. In these case.s we see feathers becoming symmetncally shaded, hke those which give so much elegance to the plumage of many natural species. I h~ve also ~oticcd a variety of the common pigeon w1th the wmg-bars symmetrically zoned with three bright shades, instead of being simply black on a slatyblue ground, as in the parent-species. In many large groups of birds it may be observed that the plum~go is differently coloured in each species, y~t th~t certam spots, marks, or stripes, though likewise differently coloured, are retained by all the species. An~logous cases occur with the breeds of the pigeon, whwh usually retain tho two wing-bars, though they may be coloured red, yellow, white, black, or blue, the I·est of the plumage being of some wholly different tint. Here is a more cmious case, in which certain marks .are retained, though coloured in almost an exactly r~verscd manner to what is natural; the aboriginal pJgeon has a blue tail, with the terminal halves of the K 2 |