The lowest animal and vegetal forms--_Protozoa_ and _Protophyta_--are chiefly inhabitants of the water. They are minute bodies, most of which are made individually visible only by the microscope. All of them are extremely simple in structure, and some of them, as the _Rhizopods_, almost structureless. Multiplying, as they ordinarily do, by the spontaneous division of their bodies, they produce halves which may either become quite separate and move away in different directions, or may continue attached. By the repetition of this process of fission, aggregations of various sizes and kinds are formed. Among the _Protophyta_ we have some classes, as the _Diatomaceæ_ 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 _Vorticellæ_, 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.