prove that hormones from the gonads play no part at all in the development
of somatic sexual characters. Kellog, an American zoologist, in 1905
[Footnote: _Journ. Exper. Zool._ (Baltimore), vol. i., 1905.] described
experiments in which he destroyed by means of a hot needle the gonads in
silkworm caterpillars (_Bombyx mori_), and found no difference in the
sexual characters of the moths reared from such caterpillars. Oudemans had
previously obtained the same result in the Gipsy Moth, _Limantria dispar_.
Meisenheimer [Footnote: _Experimentelle Studien zur Soma- und
Geschlechtedifferenzierung_. Jena, 1909.] made more extensive
experiments on castration of caterpillars in the last-mentioned species,
in which the male is dark in colour and has much-feathered antennae, while
the female is very pale and has antennae only slightly feathered. In the
moths developed from the castrated larvae there was no alteration in the
male characters, and in the females the only difference was that some of
them were slightly darker than the normal. Meisenheimer and Kopee after
him claim to have grafted ovaries into males and testes into females, with
the result that the transplanted organs remained alive and grew, and in
some cases at least became connected with the genital ducts. Even in these
cases the moth when developed showed the original characters of the sex to
which belonged the caterpillar from which it came, although it was
carrying a gonad of the opposite sex. It will be seen that these results
are the direct opposite of those obtained by Steinach on Mammals. We have
no evidence that the darker colour of the normal male in this case is
adaptive, or due to external stimuli, but the feathering of the antennae
is generally believed to constitute a greater development of the olfactory
sense organs, and is therefore adaptive, enabling the male to find the
female. This is therefore the kind of organ which would be expected to be
affected by hormones from the generative organs. It is stated that the
sexual instincts were also unaltered, a male containing ovaries instead of
testes readily copulating with a normal female.