Every one
must have heard of cases of albinism, prickly skin, hairy bodies, etc.,
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 for the most part unknown; no one can
say why the same peculiarity in different individuals of the same species,
or in different species, is sometimes inherited and sometimes not so; why
the child often reverts in certain characteristics to its grandfather or
grandmother or 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 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 the 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
reappear 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 the offspring when nearly
mature; peculiarities in the silk-worm are known to appear at the
corresponding caterpillar or cocoon stage.
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