Humans do have ancestral behavior-patterns built into their nervous systems. A frightened small child does not flee; it swarms up the nearest adult to be carried away from danger. At ten a child does not climb but runs. And there is an age when it is normal for a man to stand at bay. This last instinct can be conditioned away. In Burl's fellows and his immediate forbears it had been. But things had happened to Burl to break that conditioning. He flung the pointed boulder down. For the fraction of a second he heard only the bubbling, gnashing sounds the spider made as it climbed toward him. Then there was a quite indescribable cushioned impact. After that, there were seconds in which Burl heard nothing whatever--and then a noise which could not be described either, but was the impact of the spider's body on the ground a hundred feet below, together with the pointed boulder it had fought insanely during all its fall. And the boulder was on top. The noise was sickening. Burl found himself shaking all over. His every muscle was tense and strained. But the spider did not crawl over the edge of the precipice and something had hit far below. A long minute later he managed to look. The nest still dangled at the end of the single cable, festooned with its gruesome trophies. But Burl saw the spider. It was, of course, characteristically tenacious of life. Its legs writhed and kicked, but the body was crushed and mangled. As Burl stared down, trying to breathe again, an ant drew near the shattered creature. It stridulated. Other ants came. They hovered restlessly at the edge of the death-scene. One loathesome leg did not quiver. An ant moved in on it. The ants began to tear the dead spider apart, carrying its fragments to their city a mile away. Up on the cliff-top Burl got unsteadily to his feet and found that he could breathe. He was drenched in sweat, but the shock of triumph was as overwhelming as any of the terrors felt by ancestors on this planet. On no other planet in the Galaxy could any human experience such triumph as Burl felt now because never before had human beings been so completely subjugated by their environment. On no other planet had such an environment existed, with humans flung so helplessly upon its mercy. Burl had been normal among his fellows when he was as frightened and furtive as they. Now he had been given shock treatment by fate. He was very close to normal for a human being newly come to the forgotten planet, save that he had the detailed information which would enable a normal man to cope with the nightmare environment. What he lacked now was the habit. But it would be intolerable for him to return to his former state of mind.