tended rather to less than the required amount, than more. The phenomena of diffusive expression, in the strict sense, are thus rather late in appearance. The very lowest forms of life have no infancy or play period, and from the first are directly active in the struggle for existence. Yet the play period was certainly evolved through natural selection as a fully educative and preparatory stage, wherein the actions most demanded in actual life are unconsciously practised and a general basis of reserve force is accumulated. Play activity is a living on inherited energy and in the inherited modes: the kitten pouncing, the horse prancing, etc. Play is then rather a mode of activity than a mode of expression; it is expressive only in the way that all action is expressive. Expression proper is only in those modes of action which are carried on, whether consciously or unconsciously, by virtue of their significance value. If everything which is expressive is called an expression, we must include all the bodily actions and phenomena which can in any wise be connected with consciousness. I use the term diffusion in the narrow sense of spontaneous overflow of energy in excess of that absolutely required for the advantageous action. I do not refer to the general diffusion of emotional effect throughout the whole organism, which always occurs by the very nature of organism. Thus the pain from a pin-prick certainly modifies to some extent every cell in the body; there is a direct wave of influence from the psychic experience, and this is propagated throughout the whole organism by reason of its essential interdependency of parts; it echoes and re-echoes throughout the whole. The physiological result is then in simplest cases extremely complicated. However, this mere general fact of diffusion is a biological truism, and does not explain any expression, but simply asserts that every feeling, by virtue of its physical basis, affects the organism as a whole. Emotion issues specially in motor activities because its origin was as stimulant to necessary action, but this action involved internal organs, especially the circulatory and respiratory, and indirectly the whole body in every part. The explanation of an expression must always be in tracing back to the original serviceable actions with their demands on special subsidiary organs, and their depression of certain related organs, and not in reference to the general law of diffusion, which is but another term for the essential continuity of the organism. A useful principle of expression must not merely say that there is by the nature of organism a general bodily result from every emotion, but it must explain the particular expressions.