pearance of so many unusual characters by reversion
to a single ancient form; but we must believe that all the members of
the family have inherited a nearly similar constitution from an early
progenitor. Our cereal and many other plants offer similar cases.

With animals we have fewer cases of analogous variation, independently
of direct reversion. We see something of the kind in the resemblance
between the short-muzzled races of the dog, such as the pug and
bulldog; in feather-footed races of the fowl, pigeon, and canary-bird;
in horses of the most different races presenting the same range of
colour; in all black-and-tan dogs having tan-coloured eye-spots and
feet, but in this latter case reversion may possibly have played a
part. Low has remarked[871] that several breeds of cattle are
"sheeted,"--that is, have a broad band of white passing round their
bodies like a sheet; this character is strongly inherited and sometimes
originates from a cross; it may be the first step in reversion to an
original or early type, for, as was shown in the third chapter, white
cattle with dark ears, feet, and tip of tail formerly existed, and now
exist in a feral or semi-feral condition in several quarters of the
world.

Under our second main division, namely, of analogous variations due to
reversion, the best cases are afforded by animals, and by none better
than by pigeons. In all the most distinct breeds sub-varieties
occasionally appear coloured exactly like the parent rock-pigeon, with
black wing-bars, white loins, banded tail, &c.; and no one can doubt
that these characters are simply due to reversion. So with minor
details; turbits properly have white tails, but occasionally a bird is
born with a dark-coloured and banded tail; pouters properly have white
primary wing-feathers, but not rarely a "sword-flighted" bird, that is,
one with the few first primaries dark-coloured, appears; and in these
cases we have characters proper to the rock-pigeon, but new to the
breed, evidently appearing from reversion. In some domestic varieties
the wing-bars, instead of being simply black, as in the rock-pigeon,
are beautifully edged with different zones of colour, and they then
present a striking analogy with the wing-bars in certain natural
species of the same family, such as _Phaps chalcoptera_; and this may