n in
hermaphrodite animals is very peculiar. In some cases, as in the snail,
the union of two individuals is usually necessary, though each
possesses both kinds of organs. In other cases, as in the tape-worm,
the oyster, and numerous other mollusks, a single individual has the
power to fertilize its own ova, thus being wholly independent. Human
hermaphrodites are usually so deformed that fecundation is not effected,
which is a fortunate safeguard against the multiplication of such
monstrosities.

Development.--After the union of the two elements, known as fecundation
or _conception_, if the conditions are favorable, development occurs,
and the little germ is in due process of time developed into an
individual which is an exact counterpart of its parents. During this
developmental process, the embryonic being is variously treated by
different classes of animals.

Unprotected Development.--Most fishes and reptiles discharge their ova
before fecundation, or soon after, and pay no further attention to them.
The fish deposits its eggs in a little hollow scooped out in the gravelly
bed of a stream, or sows them broadcast upon the waters. The turtle
buries its eggs in the sand, and leaves them to be hatched by the sun.
The ostrich disposes of her eggs in the same way. Many other species
of animals pay no regard to the protection of the germs which are
destined, if placed under favorable conditions, to become individuals
like themselves.

Partial Protection of the Ovum.--There are some exceptions, however,
to this general rule among fishes and reptiles. Even fishes manifest
a degree of parental solicitude in certain cases. The male of a species
of South American fish gathers up the eggs after fecundation has taken
place, and carries them in his mouth until they are hatched. Another
male fish carries the eggs of his mate in a little pouch upon the lower
and posterior part of his body.

Certain species of frogs carry their eggs wound about their legs; others
suspend them from the abdomen. Another variety carries its young upon
its back. Prof. Wyman describes a "swamp toad" which patiently takes
the eggs of his mate, one by one, and fastens them upon her back,
observing great regularity in arrangement. These several devices are
evidently for the purpose of protecting, in some degree, the young
individual during the helpless stage of its existence.

Development in the Higher Animals and Man.--Higher animals are less
prolific