with white loins;
but the Indian sub-species, C. intermedia of Strickland, has this
part bluish. The tail has a terminal dark bar, with the outer feathers
externally edged at the base with white. The wings have two black bars.
Some semi-domestic breeds, and some truly wild breeds, have, besides the
two black bars, the wings chequered with black. These several marks do
not occur together in any other species of the whole family. Now, in
every one of the domestic breeds, taking thoroughly well-bred birds, all
the above marks, even to the white edging of the outer tail-feathers,
sometimes concur perfectly developed. Moreover, when birds belonging to
two or more distinct breeds are crossed, none of which are blue or have
any of the above-specified marks, the mongrel offspring are very apt
suddenly to acquire these characters. To give one instance out of
several which I have observed: I crossed some white fantails, which
breed very true, with some black barbs--and it so happens that blue
varieties of barbs are so rare that I never heard of an instance in
England; and the mongrels were black, brown and mottled. I also crossed
a barb with a spot, which is a white bird with a red tail and red spot
on the forehead, and which notoriously breeds very true; the mongrels
were dusky and mottled. I then crossed one of the mongrel barb-fantails
with a mongrel barb-spot, and they produced a bird of as beautiful a
blue colour, with the white loins, double black wing-bar, and barred and
white-edged tail-feathers, as any wild rock-pigeon! We can understand
these facts, on the well-known principle of reversion to ancestral
characters, if all the domestic breeds are descended from the
rock-pigeon. But if we deny this, we must make one of the two following
highly improbable suppositions. Either, first, that all the several
imagined aboriginal stocks were coloured and marked like the
rock-pigeon, although no other existing species is thus coloured and
marked, so that in each separate breed there might be a tendency to
revert to the very same colours and markings. Or, secondly, that each
breed, even the purest, has within a dozen, or at most within a score,
of generations, been crossed by the rock-pigeon: I say within a dozen
or twenty generations, for no instance is known of crossed descendants
reverting to an ancestor of foreign blood, removed by a greater number
of generations. In a breed which has been crossed only once the tendency
to rever