On the Origin of Species By Means of Natural Selection: Or, the Preservation of Favoured Races in the Struggle for LifeDarwin, Charles
Science
On the Origin of Species By Means of Natural Selection: Or, the Preservation of Favoured Races in the Struggle for Life
Darwin, Charles
Evolution (Biology); Natural selection
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 a
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
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.
Public-domain text, read in full here on John Shaqi.
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