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.