at gemmules derived
from an enfeebled and useless rudiment would be more liable to perish than
those derived from other parts which are still in full functional activity.

With respect to mutilations, it is certain that a part may be removed or
injured during many generations, and no inherited result follow; and this
is an apparent objection to the hypothesis which will occur to every one.
But, in the first place, a being can hardly be intentionally mutilated
during its early stages of growth whilst in the womb or egg; and such
mutilations, when naturally caused, would appear like congenital
deficiencies, which are occasionally inherited. In the second place,
according to our hypothesis, gemmules multiply by self-division and are
transmitted from generation to generation; so that during a long period
they would be present and ready to reproduce a part which was repeatedly
amputated. Nevertheless it appears, from the facts given in the twelfth
chapter, that in some rare cases mutilations have been inherited, but in
most of these the mutilated surface became diseased. In this case it may be
conjectured that the gemmules of the lost part were gradually all attracted
by the partially diseased surface, and thus perished. Although this would
occur in the injured individual alone, and therefore in only one parent,
yet this might suffice for the inheritance of a mutilation, on the same
principle that a hornless animal of either sex, when crossed with a perfect
animal of the opposite sex, often transmits its deficiency.

The last subject that need here be discussed, namely Reversion, rests on
the principle that transmission and development, though generally acting in
conjunction, are distinct powers; and the transmission of gemmules and
their subsequent development show us how the existence of these two
distinct powers is possible. We plainly see this distinction in the many
cases in which a grandfather transmits to his grandson, through his
daughter, characters which she does not, or cannot, possess. Why the
development of certain characters, not necessarily in any way connected
with the reproductive organs, should be confined to one sex alone--that is,
why certain cells in one sex {399} should unite with and cause the
development of certain gemmules--we do not in the least know; but it is the
common attribute of most organic beings in which the sexes are separate.

The distinction between transmission and development is likewi