It will be interesting to give a slight survey of the fundamental principles of such societies; I intend to draw special attention to one of the essential points in the societies of animals, hoping to elucidate the relations between the individuals and society. In the organisation of human society the most difficult points are the extent to which the society may encroach on the individual and the degree to which the individual may preserve his rights and his independence. Disputes on these have been interminable, and I do not propose to discuss the theories according to which an individual must be sacrificed for the good of the community to which he belongs. I shall limit myself to reviewing the fate of the individuals in societies of beings much inferior to man. There are examples of societies composed of many individuals, even amongst living things on the borderland between the animal and vegetable kingdoms. [Illustration: FIG. 21.—Isolated individuals of a Myxomycete. (After Zopff.) _a_, spore; _b-f_, escape of the zoospores.] [Illustration: FIG. 22.—Myxomycete individuals united to form a plasmodium. (After Zopff.)] There may be found in woods, on dead leaves or on decaying timber, minute plants resembling tiny mushrooms. These are Myxomycetes, and the visible portions are minute sacs filled with microscopical rounded bodies, known as spores. When one of the spores is moistened, there emerges a minute organism with a mobile appendage by which it can be impelled through water. A drop of water on a leaf or on a fragment of timber may be filled with numbers of these tiny swimming bodies (Fig. 21). Their free life as individuals, however, is of brief duration. When they come into contact, their bodies fuse, forming a gelatinous mass which may be quite large (Fig. 22). This mass is called a plasmodium, and is composed of a living substance which can move slowly over leaves and which exhibits streaming movements in the interior, so that the whole resembles in some respects the lava from a volcano. The plasmodia may be regarded as societies in the constitution of which the individuality of the members has been completely sacrificed. The ideal of those philosophers who have urged that man should renounce his individuality and merge himself in the community has been realised in the fullest way at the lower end of the scale of life, at an epoch inconceivably remote from the appearance of the human race.