Ab, who could climb like a young monkey, laid most casually the foundation for this companionship which was to affect his future life. He had scrambled, one day, up a tree standing near the cave, and, climbing out along a limb near its top, had found a comfortable resting-place, and there upon the swaying bough was "teetering" comfortably, when something in another tree, further up the river, caught his sharp eye. It was a dark mass,--it might have been anything caught in a treetop,--but the odd part of it was that it was "teetering" just as he was. Ab watched the object for a long time curiously, and finally decided that it must be another boy, or perhaps a girl, who was swaying in the distant tree. There came to him a vigorous thought. He resolved to become better acquainted; he resolved dimly, for this was the first time that any idea of further affiliation with anyone had come into his youthful mind. Of course, it must not be understood that he had been in absolute retirement throughout his young but not uneventful life. Other cave men and women, sometimes accompanied by their children, had visited the cave of One-Ear and Red-Spot and Ab had become somewhat acquainted with other human beings and with what were then the usages of the best hungry society. He had never, though, become really familiar with anyone save his father and mother and the children which his mother had borne after him, a boy and a girl. This particular afternoon a sudden boyish yearning came upon him. He wanted to know who the youth might be who was swinging in the distant tree. He was a resolute young cub, and to determine was to act.