88 THE ESSEX NATURALIST.
and the appearance of gamogenetic females it seems certain that
it is the same or associated environmental influences which
determine that males should be produced and that some
parthenogenetic females should become gamogenetic and produce
ephippia and sexual eggs. These latter are "haploid" and
require fertilization by male sperm, also haploid, before further
development can occur. This is a more complicated case than
that of the production of the male, for the gamogenetic condition
is usually preceded by and sometimes followed by the partheno-
genetic condition. This production of the fully sexed condition
merely as a temporary episode in the life of otherwise partheno-
genetic individuals is very remarkable and shows that the influence
of the environment in the matter is not restricted to the earlier
cell divisions, as it appears to be in the case of the male, but can
make itself felt long after the cell divisions leading to normal
adult development have come to an end. This conclusion is
in fact emphasized by such an androgynous individual as that
described above, which produced an ephippium in spite of the
partially male character which had been impressed upon it,
no doubt at a much earlier stage.
It is difficult enough to understand how, in the case of
an ordinary parthenogenetic female, the genes governing the
production of such a peculiar structure as an ephippium can
be thus stimulated into temporary' dominance by external
conditions after having been recessive during the whole course
of the animal's previous development. But it is still more
difficult to understand this induced activity in the case of an
androgynous individual, though any general theory of sex-
determination must evidently have to cover such cases before
it can be safely accepted.
Another problem raised by androgynous individuals, especially
asymmetrical ones, which in fact are the most frequent, concerns
the degree of importance to be given to the action of the internal
secretions, or hormones, in growth and development. These
are commonly regarded as being the immediate cause of the
formation of various structures, such as, for example, the
secondary sexual characters. Even if it were possible to suppose
that external conditions could so directly affect the production
of these secretions as to give rise to the particular structures in