or breed absorbs and obliterates another by repeated crosses,
depends in chief part on prepotency in transmission.

In conclusion, some of the cases above given,--for instance, that of the
trumpeter pigeon,--prove that there is a wide difference between mere
inheritance and prepotency. This latter power seems to us, in our
ignorance, to act in most cases quite capriciously. The very same
character, even though it be an abnormal or monstrous one, such as silky
feathers, may be transmitted by different species, when crossed, either
with prepotent force or singular feebleness. It is obvious, that a
purely-bred form of either sex, in all cases in which prepotency does not
run more strongly in one sex than the other, will transmit its character
with prepotent force over a mongrelized and already variable form.[156]
From several of the above-given cases we may conclude that mere antiquity
of character does not by any means necessarily make it prepotent. In some
cases prepotency apparently depends on the same character being present and
visible in one of the two breeds which are crossed, and latent or invisible
in the other breed; and in this case it is natural that the character which
is potentially present in both should be prepotent. Thus, we have reason to
believe that there is a latent tendency in all horses to be dun-coloured
and striped; and when a horse of this kind is crossed with one of any other
colour, it is said that the offspring are almost sure to be striped. Sheep
have a similar latent tendency to become dark-coloured, and we have seen
with what prepotent force a ram with a few black spots, when crossed with
sheep of various breeds, coloured its offspring. All pigeons have a latent
tendency to become slaty-blue, with certain characteristic marks, and it is
known that, when a bird thus coloured is crossed with one of any other
colour, it is most difficult afterwards to eradicate the blue tint. A
nearly parallel case is offered by those black bantams which, as they grow
{70} old, develop a latent tendency to acquire red feathers. But there are
exceptions to the rule: hornless breeds of cattle possess a latent capacity
to reproduce horns, yet when crossed with horned breeds they do not
invariably produce offspring bearing horns.

We meet with analogous cases with plants. Striped flowers, though they can
be propagated truly by seed, have a latent tendency to become uniformly
coloured, but when once crossed by a