The Descent of Man

sharp only when he is adult: whilst young they
are broad and flat like those of the female. As
so frequently occurs with secondary sexual
characters, both sexes of some species of rays
(for instance R. batis), when adult, possess
sharp pointed teeth; and here a character, proper
to and primarily gained by the male, appears
to have been transmitted to the offspring
of both sexes. The teeth are likewise pointed in
both sexes of R. maculata, but only when quite
adult; the males acquiring them at an earlier
age than the females. We shall hereafter meet
with analogous cases in certain birds, in which
the male acquires the plumage common to both
sexes when adult, at a somewhat earlier age
than does the female. With other species of rays
the males even when old never possess sharp
teeth, and consequently the adults of both sexes
are provided with broad, flat teeth like those of
the young, and like those of the mature females
of the above-mentioned species. (10. See Yarrell's
account of the rays in his 'History of Bri-