The Descent of Man

the laws of inheritance, as far as they are
known. Two distinct elements are included
under the term "inheritance"— the transmission,
and the development of characters; but as
these generally go together, the distinction is
often overlooked. We see this distinction in
those characters which are transmitted through
the early years of life, but are developed only at
maturity or during old age. We see the same
distinction more clearly with secondary sexual
characters, for these are transmitted through
both sexes, though developed in one alone.
That they are present in both sexes, is manifest
when two species, having strongly- marked
sexual characters, are crossed, for each transmits
the characters proper to its own male and
female sex to the hybrid offspring of either sex.
The same fact is likewise manifest, when characters
proper to the male are occasionally developed
in the female when she grows old or
becomes diseased, as, for instance, when the
common hen assumes the flowing tail- feathers,