iples of reversion and prepotency.

_Conclusion._

It has, I think, been shown in the early part of this chapter how strongly
new characters of the most diversified nature, whether normal or abnormal,
injurious or beneficial, whether affecting organs of the highest or most
trifling importance, are inherited. Contrary to the common opinion, it is
often sufficient for the inheritance of some peculiar character, that one
parent alone should possess it, as in most cases in which the rarer {27}
anomalies have been transmitted. But the power of transmission is extremely
variable: in a number of individuals descended from the same parents, and
treated in the same manner, some display this power in a perfect manner,
and in some it is quite deficient; and for this difference no reason can be
assigned. In some cases the effects of injuries or mutilations apparently
are inherited; and we shall see in a future chapter that the effects of the
long-continued use and disuse of parts are certainly inherited. Even those
characters which are considered the most fluctuating, such as colour, are
with rare exceptions transmitted much more forcibly than is generally
supposed. The wonder, indeed, in all cases is not that any character should
be transmitted, but that the power of inheritance should ever fail. The
checks to inheritance, as far as we know them, are, firstly, circumstances
hostile to the particular character in question; secondly, conditions of
life incessantly inducing fresh variability; and lastly, the crossing of
distinct varieties during some previous generation, together with reversion
or atavism--that is, the tendency in the child to resemble its
grand-parents or more remote ancestors instead of its immediate parents.
This latter subject will be fully discussed in the following chapter.

* * * * *

{28}

CHAPTER XIII.

INHERITANCE _continued_--REVERSION OR ATAVISM.

DIFFERENT FORMS OF REVERSION--IN PURE OR UNCROSSED BREEDS, AS IN
PIGEONS, FOWLS, HORNLESS CATTLE AND SHEEP, IN CULTIVATED
PLANTS--REVERSION IN FERAL ANIMALS AND PLANTS--REVERSION IN CROSSED
VARIETIES AND SPECIES--REVERSION THROUGH BUD-PROPAGATION, AND BY
SEGMENTS IN THE SAME FLOWER OR FRUIT--IN DIFFERENT PARTS OF THE BODY IN
THE SAME ANIMAL--THE ACT OF CROSSING A DIRECT CAUSE OF REVERSION,
VARIOUS CASES OF, WITH INSTINCTS--OTHER PROXIMATE CAUSES OF
REVERSION--LATENT CHARACTERS--SECONDARY SEX