ngly inherited or tend to reappear after having long been lost.
As this subject will hereafter be seen to be of importance, I will give a
full account of the colouring of horses. All English breeds, however unlike
in size and appearance, and several of those in India and the Malay
archipelago, present a similar range and diversity of colour. The English
race-horse, however, is said[126] never to be dun-coloured; but as dun and
cream-coloured horses are considered by the Arabs as worthless, "and fit
only for Jews to ride,"[127] these tints may have been removed by
long-continued selection. Horses of every colour, and of such widely
different kinds as dray-horses, cobs, and ponies, are all occasionally
dappled,[128] in the same manner as is so conspicuous with grey horses.
This fact does not throw any clear light on the colouring of the aboriginal
horse, but is a case of analogous variation, for even asses are sometimes
dappled, and I have seen, in the British Museum, a hybrid from the ass and
zebra dappled on its hinder quarters. By the expression analogous variation
(and it is one that I shall often have occasion to use) I mean a variation
occurring in a species or variety which resembles a normal character in
another and distinct species or variety. Analogous variations may arise, as
will be explained in a future chapter, {56} from two or more forms with a
similar constitution having been exposed to similar conditions,--or from
one of two forms having reacquired through reversion a character inherited
by the other form from their common progenitor,--or from both forms having
reverted to the same ancestral character. We shall immediately see that
horses occasionally exhibit a tendency to become striped over a large part
of their bodies; and as we know that stripes readily pass into spots and
cloudy marks in the varieties of the domestic cat and in several feline
species--even the cubs of the uniformly-coloured lion being spotted with
dark marks on a lighter ground--we may suspect that the dappling of the
horse, which has been noticed by some authors with surprise, is a
modification or vestige of a tendency to become striped.

[Illustration: Fig. 1.--Dun Devonshire Pony, with shoulder, spinal, and leg
stripes.]

This tendency in the horse to become striped is in several respects an
interesting feet. Horses of all colours, of the most diverse breeds, in
various parts of the world, often have a dark stripe exten