result of a long series of such advances would be the gradual obliteration
of characters proper to the embryo and larva, which would thus come to
resemble more and more closely the mature parent-form. But any structure
which was of service to the embryo or larva would be preserved by the
destruction at this stage of growth of each individual which manifested any
tendency to lose at too early an age its own proper character.

Finally, from the numerous races of cultivated plants and domestic animals,
in which the seed or eggs, the young or old, differ from each other and
from their parent-species;--from the cases in which new characters have
appeared at a particular period, and afterwards have been inherited at the
same period;--and from what we know with respect to disease, we must
believe in the truth of the great principle of inheritance at corresponding
periods of life.

* * * * *

_Summary of the three preceding Chapters._--Strong as is the force of
inheritance, it allows the incessant appearance of new characters. These,
whether beneficial or injurious, of the most trifling importance, such as a
shade of colour in a flower, a coloured lock of hair, or a mere gesture; or
of the highest importance, as when affecting the brain or an organ so
perfect {81} and complex as the eye; or of so grave a nature as to deserve
to be called a monstrosity, or so peculiar as not to occur normally in any
member of the same natural class, are all sometimes strongly inherited by
man, the lower animals, and plants. In numberless cases it suffices for the
inheritance of a peculiarity that one parent alone should be thus
characterised. Inequalities in the two sides of the body, though opposed to
the law of symmetry, may be transmitted. There is a considerable body of
evidence showing that even mutilations, and the effects of accidents,
especially or perhaps exclusively when followed by disease, are
occasionally inherited. There can be no doubt that the evil effects of
long-continued exposure in the parent to injurious conditions are sometimes
transmitted to the offspring. So it is, as we shall see in a future
chapter, with the effects of the use and disuse of parts, and of mental
habits. Periodical habits are likewise transmitted, but generally, as it
would appear, with little force.

Hence we are led to look at inheritance as the rule, and non-inheritance as
the anomaly. But this power often appears to