hat the
alterations observe a specific variableness, which is finally completed
by its assuming again the original form. (See page 16, Figs. 2 and 3).

_Reproduction_ may be _sexual_ or _non-sexual._ In some plants and
animals it is non-sexual. The propagation of species is accomplished by
buds. Thus the gardener grafts a new variety of fruit upon an old stock.
The florist understands how to produce new varieties of flowers, and
make them radiantly beautiful in their bright and glowing colors. The
bud personates the species and produces after its kind. Some of the
_annelides_, a division of articulate animals, characterized by an
elongated body, formed of numerous rings or annular segments, multiply
by spontaneous division. A new head is formed at intervals in certain
segments of the body. (See Fig. 97).

Something similar to this process of budding, we find taking place in a
low order of animal organization. Divide the fresh water polyp into
several pieces, and each one will grow into an entire animal. Each piece
represents a polyp, and so each parent polyp is really a compound
animal, an organized community of beings. Just as the buds of a tree,
when separated and engrafted upon another tree, grow again, each
preserving its original identity, so do the several parts of this
animal, when divided, become individual polyps, capable of similar
reproduction.

[Illustration: Fig. 97.
An annelid dividing spontaneously, a new head having been formed toward the
hinder part of the body of the parent.]

The revolving volvox likewise increases by growth until it becomes a
society of animals, a multiple system of individuals. There are
apertures from the parent, by which water gains a free access to the
interior of the whole miniature series. This monad was once supposed to
be a single animal, but the microscope shows it to be a group of animals
connected by means of six processes, and each little growing volvox
exhibits his red-eye speck and two long spines, or horns. These animals
also multiply by dividing, and thus liberate another series, which, in
their turn, reproduce other groups.

Generation requires the concurrence of _stimuli_ and _susceptibility_,
and, to perfect the process, two conditions are also necessary. The
first is the sperm, which communicates the principle of action; the
other is the germ, which receives the latent life and provides the
conditions necessary to organic evolution. The vivifying function
b