yonic life; but this may partly result from some one part, which
has been injured during an early period, affecting by its abnormal
growth other parts subsequently developed; and this would be less
likely to occur with parts injured at a later period.[653] When any
part or organ becomes monstrous through abortion, a rudiment is
generally left, and this likewise indicates that its development had
already commenced.

Insects sometimes have their antennae or legs in a monstrous condition,
and yet the larvae from which they are metamorphosed do not possess
either antennae or legs; and in those cases, as Quatrefages[654]
believes, we are enabled to see the precise period at which the normal
progress of development has been troubled. But the nature of the food
given to a caterpillar sometimes affects the colours of the moth,
without the caterpillar itself being affected; therefore it seems
possible that other characters in the mature insect might be indirectly
modified through the larvae. There is no reason to suppose that organs
which have been rendered monstrous have always been acted on during
their development; the cause may have acted on the organisation at a
much earlier stage. It is even probable that either the male or female
sexual elements, or both, before their union, may be affected in such a
manner as to lead to modifications in organs developed at a late period
of life; in nearly the same manner as a child may inherit from his
father a disease which does not appear until old age.

In accordance with the facts above given, which prove that in many
cases a close relation exists between variability and the sterility
following from changed conditions, we may conclude that the exciting
cause often acts at the earliest possible period, namely, on the sexual
elements, before impregnation has taken place. That an affection of the
female sexual element may induce variability we may likewise infer as
probable from the occurrence of bud-variations; for a bud seems to be
the analogue of an ovule. But the male element is apparently much
oftener affected by changed {270} conditions, at least in a visible
manner, than the female element or ovule; and we know from Gaertner's
and Wichura's statements that a hybrid used as the father and crossed
with a pure species gives a greater degree of variab