the other, so as
to produce the intermediate form. But the best evidence is afforded by
parts or organs of an important and uniform nature occasionally varying so
as to acquire, in some degree, the character of the same part or organ in
an allied species. I have collected a long list of such cases; but {163}
here, as before, I lie under a great disadvantage in not being able to give
them. I can only repeat that such cases certainly do occur, and seem to me
very remarkable.

I will, however, give one curious and complex case, not indeed as affecting
any important character, but from occurring in several species of the same
genus, partly under domestication and partly under nature. It is a case
apparently of reversion. The ass not rarely has very distinct transverse
bars on its legs, like those on the legs of the zebra: it has been asserted
that these are plainest in the foal, and from inquiries which I have made,
I believe this to be true. It has also been asserted that the stripe on
each shoulder is sometimes double. The shoulder-stripe is certainly very
variable in length and outline. A white ass, but _not_ an albino, has been
described without either spinal or shoulder stripe; and these stripes are
sometimes very obscure, or actually quite lost, in dark-coloured asses. The
koulan of Pallas is said to have been seen with a double shoulder-stripe.
The hemionus has no shoulder-stripe; but traces of it, as stated by Mr.
Blyth and others, occasionally appear: and I have been informed by Colonel
Poole that the foals of this species are generally striped on the legs, and
faintly on the shoulder. The quagga, though so plainly barred like a zebra
over the body, is without bars on the legs; but Dr. Gray has figured one
specimen with very distinct zebra-like bars on the hocks.

With respect to the horse, I have collected cases in England of the spinal
stripe in horses of the most distinct breeds, and of _all_ colours;
transverse bars on the legs are not rare in duns, mouse-duns, and in one
instance in a chestnut: a faint shoulder-stripe may sometimes be seen in
duns, and I have seen a trace in a {164} bay horse. My son made a careful
examination and sketch for me of a dun Belgian cart-horse with a double
stripe on each shoulder and with leg-stripes; and a man, whom I can
implicitly trust, has examined for me a small dun Welch pony with _three_
short parallel stripes on each shoulder.

In the north-west part of India the Kattywa