the stimulation will affect the papilla at the base of the feather
follicle, so as to cause increased growth of the succeeding feather. But
we have no reason to believe that erection in display occurs only when the
growth of the feathers is completed, still less that it did so always at
the beginning of the evolution.

The antlers of stags are the best case in favour of the Lamarckian view of
the evolution of somatic sexual characters. The shedding of the skin
('velvet') followed by the death of the bone, and its ultimate separation
from the skull, are so closely similar to the pathological processes
occurring in the injury of superficial bones, that it is impossible to
believe that the resemblance is only apparent and deceptive. In an
individual man or mammal, if the periosteum of a bone is destroyed or
removed the bone dies, and is then either absorbed, or separated from the
living bone adjoining, by absorption of the connecting part. In the stag
both skin and periosteum are removed from the antler: probably they would
die and shrivel of their own accord by hereditary development, but as a
matter of fact the stag voluntarily removes them by rubbing the antler
against tree trunks, etc. When the bone is dead the living cells at its
base dissolve and absorb it, and when the base is dissolved the antler
must fall off.

The adaptive relation is not the only common characteristic of these
somatic sexual characters. Another most important fact is not only that
they are fully developed in one sex, absent or rudimentary in the other,
but that their development is connected with the functional maturity and
activity of the gonads. There is usually an early immature period of life
in which the male and female are similar, and then at the time of puberty
the somatic sexual characters of either sex, generally most marked in the
male, develop. In some cases, where the activity of the gonads is limited