The Descent of Man

sider such cases as the minute teeth, which
never cut through the jaw in the ox, or the
mammae of male quadrupeds, or the wings of
certain beetles, existing under the soldered
wing-covers, or the vestiges of the pistil and
stamens in various flowers, and many other
such cases. Although I greatly admire Prof.
Bianconi's work, yet the belief now held by
most naturalists seems to me left unshaken,
that homological structures are inexplicable on
the principle of mere adaptation.) It is no scientific
explanation to assert that they have all
been formed on the same ideal plan. With respect
to development, we can clearly understand,
on the principle of variations supervening
at a rather late embryonic period, and being
inherited at a corresponding period, how it is
that the embryos of wonderfully different
forms should still retain, more or less perfectly,
the structure of their common progenitor. No
other explanation has ever been given of the
marvellous fact that the embryos of a man, dog,