sents one of this genus.

[Illustration: Fig. 98.
Pollicipes Mitella.]

Some of these are not only capable of self-impregnation, but likewise
have what are called _complemental males_ attache to some of the
hermaphrodites. In the whole animal kingdom, it may be doubted if there
exists another such class of rudimentary creatures as the parasitic
males, who possess neither mouth, stomach, thorax, nor abdomen. After
exerting a peculiar sexual influence, they soon die and drop off; so
that in this class of animals may be found the sexual distinctions of
male, female, and perfect hermaphrodites.

[Illustration: Fig. 99.
Rotiferia; Brachionus Urceolaris;
largely magnified. ]

There is a class of wheel-animalcules termed _rotifera_, of which the
revolving volvox is one example. They have acquired this name on account
of the apparent rotation of the disc-like organs which surround their
mouths and are covered with _cilia_, or little hairs. They are minute
creatures, and can best be viewed with a microscope, although the larger
forms may be seen without such assistance. They are widely diffused on
the surface of the earth, inhabit lakes as well as the ocean, and are
found in cold, temperate, and tropical climates. The rotifera were once
supposed to be hermaphrodites, but the existence of sexes in one species
has been clearly established. The male, however, is much smaller, and
far less developed than the female. In some of these species,
germ-cells, or eggs, are found, which do not require fecundation for
reproduction or development, so that they belong to the non-sexual
class.

The third variety of hermaphrodites embraces those animals in which the
male organs are so disposed as not to fecundate the ova of the same
body, but require the co-operation of two individuals, notwithstanding
the co-existence in each of the organs of both sexes. Each in turn
impregnates the other. The common leech, earth-worm, and snail,
propagate in this manner.

_Unnatural hermaphrodism_ is characteristic of insects and crustaceans,
in which the whole body indicates a neutral character, tending to
exhibit the peculiarities of male or female, in proportion to the kind
of sexual organs which predominates. Half of the body may be occupied by
male, the other half by female organs, and each half reflects its
peculiar sexual characteristics. Some butterflies are dimidiate
hermaphrodites; _i.e._ one side of the body has the form and color of
the m