On along the tunnel they went. And as they progressed, Dennis got the answer to something that had troubled him a great deal before their entrance here—a problem which had been solved, rather amazingly, of itself.

Termitaries, as far as the entomologist knew, were pitch-black places which no ray of light ever entered. He had been afraid he would be forced to stumble blindly in unlit depths, able to see nothing at all, on a par with the blind creatures among whom he moved. Yet he and Jim could see in this subterranean labyrinth.

He observed now the reason for that. The walls on all sides, made of half-digested cellulose, had rotted just enough through long years to be faintly phosphorescent. And that simple natural fact was probably going to mean all the difference between life and death: it gave the two men at least the advantage of sight over the eyeless savage creatures among whom, helped by the termite-smell given by the paste, they hoped to glide unnoticed.

However, even the termite-paste, and the fact that the termitary citizens were blind, didn't seem enough to account for the immunity granted the two men as they began to come presently to more crowded passages and tunnels near the center of the mound.

On every side of them now, requiring the utmost in agility to keep from actually brushing against them, were hordes of the worker termites, and dozens of the frightful soldiers. Yet on the two men moved, ever more slowly, without one of the monsters attempting to touch them. It was odd—almost uncanny.

"Surely the noise of our walking, tiptoe as we may, must be heard by them—and noted as different from theirs," whispered Dennis. "Yet they pay no attention to us. If it is due to the paste, I must say it's wonderful stuff!"

Jim nodded in a puzzled way. "It's almost as if they wanted to make our inward path easy. I wonder—if it's going to be different when we try to get out again!"

Dennis was wondering that, too. It seemed absurd to suspect the things of being intelligent enough to lay traps. But it did look almost as though they were encouraging their two unheard-of visitors from another world to go on deeper and deeper into the heart of the eerie city (all the tunnels sloped down now), there perhaps to meet with some ghastly imprisonment.

He gave it up. Sufficient for the moment that they were unmolested, and that he had a chance at first hand to make observations more complete than the world of entomology had ever dreamed of.

They stumbled onto what seemed a death struggle between one of the giant soldiers and an inoffensive-looking worker. The drab, comparatively feeble body of the worker was wriggling right in the center of the great claws which, with a twitch, could have sliced it in two endwise. Yet the jaws did not twitch; and in a few moments the worker drew unconcernedly out and moved away.

"The soldier was getting his meal," whispered Denny, enthralled. "Their mandibles are enlarged so enormously that they can't feed themselves. The workers, who digest food for the whole tribe, feed them regularly. Then if a soldier gets in the least rebellious, he can simply be starved to death at any time."

"Ugh!" Jim whispered back. "Fancy being official stomach to three or four other people! More of your wonderful 'organization,' I suppose."

They went on, down and down, till Denny calculated they had at last reached nearly to the center of the vast city. And now they stumbled into something weird and wonderful indeed. Rather, they half fell into it, for it lay down a few feet and came as a complete surprise in the dimness; and not till they had recovered from their near fall and looked around for a few seconds did they realize where their last few steps—the last few steps of freedom they were to have in the grim underground kingdom—had taken them.

They were in a chamber so huge that it made the largest of man-made domes shrink to insignificance by comparison.

Ahundred yards or more in every direction, it extended. And far overhead, lost in distance, reared the arched roof. A twenty-story building could have been placed under that roof without trouble.

Lost in awe, Dennis gazed about him; and he saw on the floor, laid in orderly rows in countless thousands, that which gave further cause for wonderment: new-hatched larvae about the size of pumpkins but a sickly white in color—feeble, helpless blobs of life that one day develop into soldiers and workers, winged rulers or police. The termite nursery.

"Whew!" gasped Jim, wiping his face. "From the heat in here you'd think we were getting close to the real, old-fashioned hell instead of an artificial, insect-made one. What are all these nauseating-looking blobs of lard lying about here, anyway?"

Denny told him. "Which is the reason for the heat," he concluded. "Jim, it's twenty degrees warmer in here than it is outdoors. How—how—can these insects regulate the temperature like that? The work of the ruling brain again? But where, and what, can that brain be?"

"Maybe we'll find out before we leave this place," said Jim, more prophetically than he knew. "Hello—we can't get out through the door we entered. We'll have to find another exit. Look."

Dennis looked. In the doorway they had just come through was a soldier—a giant even among giants. Its ten-foot jaws, like a questing, gigantic vise, were opening and closing regularly and rapidly across the opening of the portal. It made no attempt to enter the great nursery, just stood where it was and sliced the air rhythmically with its jaws.

"We haven't a chance of walking through that exit!" Dennis agreed. "Let's try the other side."

But before they could half cross the great room—walking between rows of life that weakly stirred like protoplasmic mud on either side of them—a soldier appeared at that door, too. Like the first, it stationed itself there, and began the same regular, swift slicing movements of jaws that compassed the doorway from side to side and halfway from top to bottom.

"We might possibly be able to run through that giant's nut-cracker before it smashed shut on us," said Jim dubiously. "But I'd hate to try it. There's a door at the end, too."

They made for this, running now. But a third soldier appeared to block the way out with those deadly, clashing mandibles.

"You're sure they can't see?" demanded Jim, clutching his spear while he hesitated whether to try an attack on the fearful guard or to turn tail again. "Because they certainly act as if they did!"

"Direct commands from the ruling brain," Denny surmised soberly. "Somewhere, perhaps half a mile down in the earth, Something is able to see us through solid walls, read in our minds our intentions of what we're to do next, and send out wordless commands to these soldiers to execute countermoves."

"Rot!" said Jim testily. "These things are bugs, not supermen. And the fact that they're now bigger than we are, and much better armed, doesn't keep them from being just bugs. There's no real brain-power in evidence here."

But an instant later he changed his mind. They approached the fourth and last exit from the giant chamber. And here there was no guard. They were able to race out of it without interference. The oddity of that was glaring.

"Denny," gasped Jim, "we're being herded! Driven in a certain direction, and for a certain reason, by these damned things! Do you realize that?"

Dennis did realize it. And a moment later, when he glanced behind, he realized it more.

Behind them, marching in orderly twos that filled the tunnel from side to side, moved a body of the soldiers. As the men moved, they moved; never coming nearer and never dropping behind.

Experimentally, Dennis stopped. The grim soldiers stopped, too. Dennis walked back toward them a step or two, spear held ready.

The monsters did not try to attack. On the other hand they did not give ground, either; and as Denny got to within a few yards of them, one in the front line suddenly opened and shut his ponderous jaws.

They clashed together a matter of inches from Denny's torso—a clear warning to get on back in the direction he had come.

Jim came and stood beside him, heavy shoulder muscles bunched into knots, standing on the balls of his feet as a boxer stands before flashing in at an opponent.

"Shall we have it out with them here and now?" said Jim, his jaws set. "We wouldn't have a chance—but I'm beginning to get awfully doubtful about the fate these things have in store for us. I can't even guess at what it may be—but I've an idea it may be a lot worse than a quick, easy death!"

Denny shook his head. "Let's see it through," he muttered, looking at the nightmare jaws of their guard. Two sweeps of those jaws and he and Jim would lie in halves.

They started back down the corridor, the monstrous shepherds moving as they did. The way descended so steeply now that it was difficult for them to keep their footing. Then, yards below the level of the horrible nursery, the tunnel narrowed—and widened again into a chamber which had no other opening save the one they were being herded into. A blind end to the passageway.

"The bug Bastille," said Jim with a mirthless grin. "Here, I guess, we're going to wait for the powers-that-be to judge us and give us our sentence."

The giant soldiers halted. Two of them stood in the narrowed part of the tunnel, one behind the other, blocking it with a double, living barrier. Their jaws commenced moving regularly, savagely back and forth, open and closed. Blind these guards might be; but no living thing, even though it bristled with eyes, could creep out unscathed through the animated threshing machine those jaws made of that doorway. The two men were more securely held in their prison cell than they would have been by two-inch doors of nickel-steel. They could only wait there, helpless prisoners, to learn the intentions of the unknown Something that ruled the great city, and that held them so easily in its grasp.