horse is particularly apt to have bars on its legs. I once saw a mule
with its legs so much striped that any one at first would have thought
that it must have been the product of a zebra; and Mr. W. C. Martin, in
his excellent treatise on the horse, has given a figure of a similar
mule. In four coloured drawings, which I have seen, of hybrids between
the ass and zebra, the legs were much more plainly barred than the rest
of the body; and in one of them there was a double shoulder-stripe. In
Lord Moreton s famous hybrid from a chestnut mare and male quagga, the
hybrid, and even the pure offspring subsequently produced from the mare
by a black Arabian sire, were much more plainly barred across the legs
than is even the pure quagga. Lastly, and this is another most
remarkable case, a hybrid has been figured by Dr. Gray (and he informs
me that he knows of a second case) from the ass and the hemionus; and
this hybrid, though the ass seldom has stripes on its legs and the
hemionus has none and has not even a shoulder-stripe, nevertheless had
all four legs barred, and had three short shoulder-stripes, like those
on the dun Welch pony, and even had some zebra-like stripes on the
sides of its face. With respect to this last fact, I was so convinced
that not even a stripe of colour appears from what would commonly be
called an accident, that I was led solely from the occurrence of the
face-stripes on this hybrid from the ass and hemionus,
to ask Colonel Poole whether such face-stripes ever occur in the
eminently striped Kattywar breed of horses, and was, as we have seen,
answered in the affirmative.
What now are we to say to these several facts? We see several very
distinct species of the horse-genus becoming, by simple variation,
striped on the legs like a zebra, or striped on the shoulders like an
ass. In the horse we see this tendency strong whenever a dun tint
appears a tint which approaches to that of the general colouring of the
other species of the genus. The appearance of the stripes is not
accompanied by any change of form or by any other new character. We see
this tendency to become striped most strongly displayed in hybrids from
between several of the most distinct species. Now observe the case of
the several breeds of pigeons: they are descended from a pigeon
(including two or three sub-species or geographical races) of a bluish
colour, with certain bars and other marks; and when any breed assumes
by simple variation a bluish tint, these bars and other marks
invariably reappear; but without any other change of form or character.
When the oldest and truest breeds of various colours are crossed, we
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