How did the thing feed itself? There was no discernible mouth on the forepart, and the segments were not in a position to feed effectively. Yet more and more of them appeared, each neatly taking up the full width of the ledge. It was apparent now for whose use the convenient path had been cut.

People scrambled over each other and fell into the water in their mad effort to escape. Those still standing were crowded into less than half the circle—and still the thing advanced. The segments most distant from the ugly head were oddly shriveled, sucked dry of juices; if the thing went hungry, Aton thought, it did so from the rear forward.

At last the end appeared. There was a concerted sigh of relief. The thing would not force them all into the water.

The final segment finished in a needle-like stinger projecting some four feet.

There was a scream above the prevailing bedlam. All heads turned involuntarily. Almost every person’s whole attention had been absorbed by the caterpillar, so that another development in the pool had gone unnoticed.

A shape had risen from below, coming up slowly under the water. Whale-like, it filled the pool from side to side, an immense mass of turgid black blubber a hundred feet across. The last covering of water dribbled from its convex and waxy surface to expose a large circular orifice: a mouth.

Aton recognized it now. It was one of the jellyfish, grown to a shocking magnitude. It was, he strongly suspected, carnivorous. The animal bodies had disappeared down the river drain, so the evidence was not immediate.

Proof was not long in coming. The mouth gaped wider, disclosing a whitish internal tunnel that frothed and gurgled and belched a noxious yellow stomach vapor. A tubular tongue snaked out. It cast about blindly, then slapped over the body of a woman in the water and hauled her shrieking into the maw.

Meanwhile the caterpillar was busy, too. The head commanded the water-exit, and the tail had projected itself across the entrance and was moving backwards along the opposite ledge, preventing any escape that way. Its mighty prong was, if anything, more frightening than the head itself.

The tail suddenly shot out, extending its length a good four feet. It neatly impaled the nearest man, who had been foolishly threatening it with a fragment of stone, stabbing through his middle and emerging behind his back. He brayed horribly and collapsed; but his body was held upright by the spike. This contracted, pulling him up against the concluding segment of the caterpillar.

What awful power! Aton thought. To ram through gut and muscle and backbone and come out cleanly.

Then, hideously, part of the corpse returned to life. The man’s head and arms hung slackly—but his legs picked up the same measured tempo of the segments. The other segments.