_ and the
Yeast-plant, in which the individuals may be either separate or attached
in groups of two, three, four, or more; other classes in which a
considerable number of cells are united into a thread (_Conferva_,
_Monilia_); others in which they form a network (_Hydrodictyon_); others
in which they form plates (_Ulva_); and others in which they form masses
(_Laminaria_, _Agaricus_): all which vegetal forms, having no
distinction of root, stem, or leaf, are called _Thallogens_. Among the
_Protozoa_ we find parallel facts. Immense numbers of _Amoeba_-like
creatures, massed together in a framework of horny fibres, constitute
Sponge. In the _Foraminifera_ we see smaller groups of such creatures
arranged into more definite shapes. Not only do these almost
structureless _Protozoa_ unite into regular or irregular aggregations of
various sizes, but among some of the more organized ones, as the
_Vorticellae_, there are also produced clusters of individuals united to
a common stem. But these little societies of monads, or cells, or
whatever else we may call them, are societies only in the lowest sense:
there is no subordination of parts among them--no organization. Each of
the component units lives by and for itself; neither giving nor
receiving aid. The only mutual dependence is that consequent on
mechanical union.

Do we not here discern analogies to the first stages of human societies?
Among the lowest races, as the Bushmen, we find but incipient
aggregation: sometimes single families, sometimes two or three families
wandering about together. The number of associated units is small and
variable, and their union inconstant. No division of labour exists
except between the sexes, and the only kind of mutual aid is that of
joint attack or defence. We see an undifferentiated group of
individuals, forming the germ of a society; just as in the homogeneous
groups of cells above described, we see the initial stage of animal and
vegetal organization.

The comparison may now be carried a step higher. In the vegetal kingdom
we pass from the _Thallogens_, consisting of mere masses of similar
cells, to the _Acrogens_, in which the cells are not similar throughout
the whole mass; but are here aggregated into a structure serving as leaf
and there into a structure serving as root; thus forming a whole in
which there is a certain subdivision of functions among the units, and
therefore a certain mutual dependence. In the animal kingdom we fi