I. S o c ie t ie s of invertebrate animals frequently exhibit structures, or patterns, upon which the life of the individual is essentially dependent. But on this level the social structure is individualistic in its transmission; it is deter­ mined by the specific organismic structure of the com­ ponent individuals. Among higher vertebrates which are characterized by a greater plasticity of individual be­ haviour, social ways are gradually built up, accumulated, interrelated, and transmitted in social tradition inde­ pendently of changes in physiological inheritance. Thus birds or apes, to a slight degree, and human beings, to a very high degree, are “ social animals ” in a sense which is not true of ants or parasites. Personality and behaviour are largely constituted on this level by social processes.