This view is now being very generally adopted. Many fine illustrations might be cited. A simple case may be seen in so small a thing as the habit of leaping in play; the difference, for example, between the mountain goat and the common fawn. The former, when playing on level ground makes a very ludicrous exhibition by jumping in little up-and-down leaps by which he makes no progress. In contrast with this the fawn, whose adult life is normally in the plains, takes a long graceful spring. The difference becomes clear from the point of view of this theory, when we remember that the goat is to live among the rocks, where the only useful jump is just the up-and-down sort which the little fellow is now practising; while the deer, in his life upon the plains, will always need the running jump. Finally, on this theory, play becomes a thing for evolution to cultivate for its utility in the progress of animal life, and for that reason we may suppose it has been perfected in the remarkable variety and beauty of form which it shows. On the psychological side, we find a corresponding state of things. The mind in the young animal or child gets the main education of early life through its play situations. Games have an extraordinary pedagogical influence. The more so because they are the natural and instinctive way of getting an education in practical things. This again is of supreme utility to the individuals. Both for body and mind we find that play illustrates the principle of Organic Selection explained above. It makes the young animal flexible, plastic, and adaptable; it supplements all his other instincts and imperfect functions; it gives him a new chance to live, and so determines the course of evolution in the direction which the playful animal represents. The quasi-social and gregarious habits of animals probably owe much of their strength to the play-impulse, both through the training of individual animals and through the fixing of these tendencies as instincts in various animal species in the way just mentioned. In another place below I analyze a child's game and draw some inferences from it. Here it may suffice to say that in their games the young animals acquire the flexibility of mind and muscle upon which much of the social co-operation, as well as the individual effectiveness, of their later life depends. With children, it is not the only agency, of course, though its importance is not less. We have to carry the children further by other means; but the other means should never interfere with this natural schooling. They should aim the rather by supplementing it wisely to direct its operation and to extend its sphere. CHAPTER IV. THE MIND OF THE CHILD--CHILD PSYCHOLOGY.