With a struggle Westover roused himself, first sitting up, then swaying to his feet, frowning with the effort to look sanely at the terrible inspiration that had come to him. The cloud blanket was breaking up, the sun already high, beating down on the naked moving plateau on which the man stood. The idea born in him seemed to stand that light, even to expand into hope. Fingers shaking, he unhitched the light ax from his belt and began to hack with feverish industry at the monster's crusted hide. The scaly, weathered epidermis seemed immeasurably thick. But at last he had chopped through it, reached the softer protoplasm beneath. Clawing and hewing in the hole he had made, he tore out heavy slabs of the monster's flesh. A ripple that did not belong to the crawling motion ran over the thing's surface round about. Westover laughed wildly with a sudden sense of power. He, the insignificant human mite, had made the miles-long beast twitch like a flea-bitten dog. The analogy was pat; like a flea, he had lodged on a larger animal and was about to nourish himself from it. The slabs of flesh he had cut off were gray and unappetizing, but he knew from the studies he had helped Sutton make that the monsters, extraterrestrial though they were, were in the basic chemistry of proteins, fats and carbohydrates one with man or the amoeba, and therefore might be--food. His matches were dry in their water-proof case; he made a smoldering fire from the loose fibrous scale of the monster's back, and half an hour later was replete. Either the long fast, or involuntary revulsion, or perhaps merely the motion of the creature brought on nausea, but he fought it sternly back and succeeded in keeping his strange meal down. Then he was tormented by thirst. It was some time, though, before he could bring himself to drink the colorless fluid that had collected in the wound he had inflicted on the monster. Thus began for him a weird existence--the life of a parasite, of a flea on a dog. The monster crawled by day and rested by night; strengthened, the man could have left it then, but somehow night after night he did not. It wasn't, he argued with himself sometimes in the days when he lay torpidly drowsing, lulled by the long sway, arms over his head to protect him from the sun's baking, merely that he was chained to the only source of food he knew in all the world--not just that he was developing a flea's psychology. He was a man and a scientist, and he was conducting an experiment.... His life on the monster's back was proving something, something of vast importance for man, the extinct animal--but for increasingly longer periods of time he could not remember what it was.... There came a morning, though, when he remembered. [Illustration: _Thus began for him a weird existence--the life of a parasite, of a flea on a dog._] * * * * *