Chap. XIY. 
VAETABILITY. 
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 Avith a narrow space on each 
side, was greenish-black, and this w^as surrounded by 
a regular zone of dark-brown, edged with brownish- 
white. In these cases Ave see feathers becoming sym- 
metrically shaded, like those Avhich 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 parent-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 stripes, 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 wing-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 what is natural ; the aborimnal 
pigeon has a blue tail, with the terminal halves of the 
