In ages past, when ants were tiny creatures of lengths to be measured in fractions of an inch, learned scientists debated gravely if their tribe possessed a cry. They believed that certain grooves upon the body of the insects, after the fashion of those upon the great legs of the cricket, might offer the means of uttering an infinitely high-pitched sound too shrill for man's ears to catch. Burl knew that the stridulation was caused by the doubtful insect before him, though he had never wondered how it was produced. The cry was used to summon others of its city, to help it in its difficulty or good fortune. Clickings sounded fifty or sixty feet away. Comrades were coming to aid the pioneer. Harmless save when interfered with--all save the army ant, that is--the whole ant tribe was formidable when aroused. Utterly fearless, they could pull down a man and slay him as so many infuriated fox terriers might have done thirty thousand years before. * * * * * Burl fled, without debate, and nearly collided with one of the anchoring cables of the web from which he had barely escaped a moment before. He heard the shrill sound behind him suddenly subside. The ant, short-sighted as all ants were, no longer felt itself threatened and went peacefully about the business Burl had interrupted, that of finding among the gruesome relics beneath the spider's web some edible carrion which might feed the inhabitants of its city. Burl sped on for a few hundred yards, and stopped. It behooved him to move carefully. He was in strange territory, and as even the most familiar territory was full of sudden and implacable dangers, unknown lands were doubly or trebly perilous. Burl, too found difficulty in moving. The glutinous stuff from the spider's shroud of silk still stuck to his feet and picked up small objects as he went along. Old ant-gnawed fragments of insect armour pricked him even through his toughened soles. He looked about cautiously and removed them, took a dozen steps and had to stop again. Burl's brain had been uncommonly stimulated of late. It had gotten him into at least one predicament--due to his invention of a spear--but had no less readily led to his escape from another. But for the reasoning that had led him to use the grease from the fish upon his shoulder in oiling his body when he struggled out of the spider's snare, he would now be furnishing a meal for that monster. Cautiously, Burl looked all about him. He seemed to be safe. Then, quite deliberately, he sat down to think. It was the first time in his life that he had done such a thing. The people of his tribe were not given to meditation. But an idea had struck Burl with all the force of inspiration--an abstract idea.