others,—that is to say, a division of the nervous system comparable with the division of the nervous system of the worm by the stroke of the knife which seems to split the psychical individual into two. The facts of both these orders would appear, then, to indicate that the physical organisation of the cells of a complex organism is accompanied by an organisation of their psychical lives to form a ‘collective consciousness,’ which in the human being becomes a personal self-consciousness; and they would seem to show that the unity of personal consciousness has for its main condition the functional continuity of the protoplasm of the cells of the nervous system. Even before the facts of disintegration of personalities were known, several authors, notably von Hartmann[21] and G. T. Fechner[22], did not hesitate to make this last assumption; and to assert that, if the brain of a man could be divided by a knife into two parts each of which continued to function, his consciousness would thus be divided into two consciousnesses; and conversely, that, if a functional bridge of nervous matter could be established between the brains of two men, their consciousnesses would fuse to a single consciousness. The discovery of these facts has greatly strengthened the case for this view; and it has been accepted by so sound a psychologist and sober a philosopher as Fouillée[23]. It may be claimed that the consideration of the nature and behaviour of animal societies points to a similar conclusion, and supplements in an important manner the argument founded on the divisibility of individual organisms. Such a line of reasoning has been most thoroughly pursued by Espinas in his very interesting book on animal societies[24]. He begins by considering the lower polycellular forms of animal life. Among them, especially among the hydrozoa or polypes, we find compound or colonial animals; such an animal is a single living mass of which all the parts are in substantial and vital connexion with one another, but is yet made up of a number of parts each of which is morphologically a complete or almost complete creature; and these parts, though specialised for the performance of certain functions subserving the economy of the whole animal or coherent group of animals, are yet capable, if separated from the mass (as they sometimes are by a natural process), of continuing to live, of growing, and of multiplying. There are found among such creatures very various degrees of specialisation of parts and of interdependence of parts; and in those cases in which the specialisation and interdependence of parts is great, the whole compound animal exhibits in its reactions so high a degree of integration that we seem justified in supposing that a common or ‘collective consciousness’ is the psychical correlate of these integrated actions of the separable parts. Why then, it is asked, should this ‘collective consciousness’ cease to be, when the substantial continuity of the parts is