whether it may not be due to the same cause having acted on both; but when
amongst individuals, apparently exposed to the same conditions, any very
rare deviation, due to some extraordinary combination of circumstances,
appears in the parent--say, once amongst several million individuals--and
it reappears in the child, the mere doctrine of chances almost compels us
to attribute its reappearance to inheritance. Every one must have heard of
cases of albinism, prickly skin, hairy bodies, &c., appearing in several
members of the same family. If strange and rare deviations of structure are
truly inherited, less strange and commoner deviations may be freely
admitted to be inheritable. Perhaps the correct way of viewing the whole
subject, would be, to look at the inheritance of every character whatever
as the rule, and non-inheritance as the anomaly.

The laws governing inheritance are quite unknown; no one can say why a
peculiarity in different individuals of the same species, or in individuals
of different species, is sometimes inherited and sometimes not so; why the
child often reverts in certain characters to its grandfather or grandmother
or other more remote ancestor; why a peculiarity is often transmitted from
one sex to both sexes, or to one sex alone, more commonly but not
exclusively to the like sex. It is a fact of some little importance to us,
that peculiarities appearing in the males of our domestic breeds are often
transmitted either exclusively, or in a much greater degree, to males
alone. A much more important rule, which I think may be trusted, is that,
at whatever period of life a peculiarity first appears, it tends to appear
in the offspring at a corresponding age, though sometimes earlier. In many
cases this could not be otherwise: thus the inherited peculiarities in the
horns of cattle could appear only in {14} the offspring when nearly mature;
peculiarities in the silkworm are known to appear at the corresponding
caterpillar or cocoon stage. But hereditary diseases and some other facts
make me believe that the rule has a wider extension, and that when there is
no apparent reason why a peculiarity should appear at any particular age,
yet that it does tend to appear in the offspring at the same period at
which it first appeared in the parent. I believe this rule to be of the
highest importance in explaining the laws of embryology. These remarks are
of course confined to the first _appearance_ of the peculiar