nest indigenous
snake. The ringed snake lays eggs which require three weeks time to
develop; but when it is kept in captivity, and no sand is strewn in the
cage, it does not lay eggs, but retains them until the young ones are
developed. This only shows how powerfully influences affect the habit of
animals.

DOUBLE-SEXED INDIVIDUALS.

Another difficulty might be supposed to arise between animals which
produce themselves other than by sexual reproduction. This has already
been slightly touched upon; and it has been shown that numerous plants
and animals propagate themselves through their double-sexed organs. It
occurs in a great majority of plants, but only in a minority of animals;
for example, the garden-snail, leeches, earth-worms, and many other
worms. Every garden-snail produces in one part of its sexual gland eggs,
and in another part sperm.

Parthenogenesis offers an interesting form of transition from sexual
reproduction to the non-sexual formation of germ-cells (which most
resembles it). It has been demonstrated to occur in many cases among
insects, especially by Seebold's excellent investigations. Among the
common bees, a male individual (a drone) arises out of the eggs of the
queen, if the eggs have not been fructified; a female (a queen or
working bee), if the egg has been fructified.

Gonochorismus or sexual separation, which characterizes the more
complicated of the two kinds of sexual reproduction, has evidently been
developed from the condition of hermaphroditism at a late period of the
organic history of the world. In this case the female individual in both
animal and plant produces eggs or egg-cells. In animals, the male
individual secretes the fructifying sperm (sperma); in plants, the
corpuscles, which correspond to the sperm.

INHERITANCE.

The remarkable facts of inheritance, extending to the reproduction of
unimportant peculiarities of parts or organs (rudimentary parts)
mentioned above, and the occasional outbreak of ancestral characters
that have been dormant through several generations (some of which I will
mention further on), might be thought perfectly unexplainable; but they
are readily accounted for by the supposition that each part of an
organism contributes its constituent and effective molecules to the germ
and sperm particles. Mr. Sorby made numerous investigations with
relation to the number of molecules in the germinal matter of eggs, and
the spermatic matter supplied by the