The great relation of pursuer and pursued is constantly mimicked among animals with interchanging of parts. So also among children the commonest plays are those of fleeing and chasing, as tag, hare and hound, hide and seek, etc., the fundamental elements of life being re-enacted under the superfluous energy which tends to flow most easily into the oldest and most habitual channels. Thus play has a high historic psychic importance. To attack and to run away are the most necessary and essential of life activities, and play has a certain pedagogic and preparative value, and has thereby been sanctioned by natural selection, for we see that in the evolution of life the tendency has constantly been to lengthen the play period. Among the lowest animals the individual at birth is immediately thrown into the struggle for existence and must battle for itself; there is no play time for it, but at once it enters upon direct life struggle; but in higher life there is a period of spontaneous free dramatic activity. But not only is anger and fear shammed as a prominent and primitive play, but it is most common to stimulate to real anger or fear, and then in glee to show the inadequacy of the occasion to the victim. Every one has observed how frequently young animals play by teasing and scaring each other. The tricks of boys and practical jokes of men both point to the deep inbred power of anger and fear in life, and are at the same time symptomatic of their decline in power as dominant life factors. All children delight in scaring one another on pretence, in seeing the real expression and feeling themselves the moving powers in bringing it about. This satisfaction, which is aboriginal, which is the reflex of the original pleasure sanction when power to scare others for one’s own benefit was being evolved in life, makes a large part of the enjoyment of such action. A large part of play-pleasure must, indeed, be set down to reflex of the earliest hard-earned pleasure experience; but a large part is also due to the thrill of excitement and the delight in activity _per se_. Later forms of plays are largely due to pure imitative propensity, though often helped by reversal tendencies.