springs from another source—the instinct to develop the particular powers that their life-careers will most require. Puppies and kittens fight mock battles and pursue and capture mock game, kids leap and bound, colts run and leap, birds swoop and dive as if to escape a hawk: in each case training the powers that are likely to be the most useful to them in after-life. Our play-instinct is no doubt of animal origin, but not in the same sense is our sense of the humorous of animal origin. It originated in man, as did so many of the higher emotions.
II
One of the best illustrations I ever had of the difference between animal and human behavior under like conditions, was afforded me one May day in the woods, when I unwittingly pulled down the stub of a small tree in which a pair of bluebirds had a nest and young. Now, if a man were to come home and find his house gone, and only empty space where it had stood, he would not go up to the place where the door had been and try repeatedly to find the entrance. But this is exactly what the bluebirds did. As I have elsewhere described, I had pulled down the stub that held their nest and young, not knowing there was a nest there; and then on discovering my mistake had set the stub up again twelve or fifteen feet from where I had found it. Presently the mother-bird came with food in her bill, and alighted on a limb a few feet above the spot where the trunk of the tree holding her nest had been, and where, doubtless, she was in the habit of alighting. She must have seen at once that her house was gone, but if she did, the fact made no impression upon her.
Quite undisturbed, she dropped down to the exact spot in the vacant space where the entrance to her nest used to be. She hovered there a moment and then, apparently greatly bewildered, flew back to the perch above. She waited there a moment, peering downward, and then tried it again. Could she not see that her house was gone? But the force of habit was stronger with her than any free intelligence she might possess. She had always found the nest there and it must be there still. An animal's reflexes are not influenced by the logic of the situation. Down she came again and hovered a moment at the point of the vanished nest, vainly seeking the entrance. This movement she repeated over and over. I have no doubt that she came each time to the precise spot in the air where her treasures had been. It seemed as if she could not convince herself that the nest was not there. She had brought a beetle in her bill, and this she hammered upon the limb each time she perched, as if it in some way might be at fault. How her blue wings flickered in the empty air above the dark water, not more than ten or twelve feet from the actual visible entrance to the nest she had lost!
Presently she dropped her bug and flew off through the woods, calling for her mate. Her action seemed very human. Surely he would clear up the mystery. In a moment or two, both birds with food in their bills were perched upon the branch a few feet above the spot where the nest had been. I can recall yet the confident air with which the male dropped down to that vacant spot. Could he not see that there was nothing there? No, seeing was not convincing. He must do just as he had done so many times before. He tried it again and again; then the two birds took turns in trying it. They assaulted the empty air vigorously, persistently, as if determined that it must give up their lost ones. Finally they perchedVOL. 106 - NO. 5
