Weber was almost beside himself.

"They'll come back," said Kemper. "With that appetite of theirs, they won't stay away for long."

And he was right about that part of it. The punkins were the hungriest creatures in the Galaxy. You could never feed them enough to satisfy them. And they'd eat anything. It made no difference to them, just so there was a lot of it. And it was that very factor in their metabolism that made them invaluable as research animals.

The other animals thrived on the critter diet. The carnivorous ones ate the critter-meat and the vegetarians chomped on critter-fruit and critter-vegetables. They all grew sleek and sassy. They seemed in better health than the control animals, which continued their regular diet. Even the pigs and rats that had been sick got well again and as fat and happy as any of the others.

Kemper told us, "This critter stuff is more than just a food. It's a medicine. I can see the signs: "Eat Critter and Keep Well!""

Weber grunted at him. He was never one for joking and I think he was a worried man. A thorough man, he'd found too many things that violated all the tenets he'd accepted as the truth. No brain or nervous system. The ability to die at will. The lingering hint of wholesale symbiosis. And the bacteria.

The bacteria, I think, must have seemed to him the worst of all.

There was, it now appeared, only one type involved.

Kemper had hunted frantically and had discovered no others, Oliver found it in the grass. Parsons found it in the soil and water. The air, strangely enough, seemed to be free of it.

But Weber wasn't the only one who worried. Kemper worried, too. He unloaded most of it just before our bedtime, sitting on the edge of his cot and trying to talk the worry out of himself while I worked on my reports.

And he'd picked the craziest point imaginable to pin his worry on.

"You can explain it all," he said, "if you are only willing to concede on certain points. You can explain the critters if you're willing to believe in a symbiotic arrangement carried out on a planetary basis. You can believe in the utter simplicity of the ecology if you're willing to assume that, given space and time enough, anything can happen within the bounds of logic."

"You can visualize how the bacteria might take the place of brains and nervous systems if you're ready to say this is a bacterial world and not a critter world. And you can even envision the bacteria — all of them, every single one of them — as forming one gigantic linked intelligence. And if you accept that theory, then the voluntary deaths become understandable, because there's no actual death involved — it's just like you or me trimming off a hangnail. And if this is true, then Fullerton has found immortality, although it's not the kind he was looking for and it won't do him or us a single bit of good.

"But the thing that worries me," he went on, his face all knotted up with worry, "is the seeming lack of anything resembling a defense mechanism. Even assuming that the critters are no more than fronting for a bacterial world, the mechanism should be there as a simple matter of precaution. Every living thing we know of has some sort of way to defend itself or to escape potential enemies. It either fights or runs and hides to preserve its life."

He was right, of course. Not only did the critters have no defense, they even saved one the trouble of going out to kill them.

"Maybe we are wrong," Kemper concluded. "Maybe life, after all, is not as valuable as we think it is, Maybe it's not a thing to cling to. Maybe it's not worth fighting for. Maybe the critters, in their dying, are closer to the truth than we."

It would go on like that, night after night, with Kemper talking around in circles and never getting anywhere. I think most of the time he wasn't talking to me, but talking to himself, trying by the very process of putting it in words to work out some final answer.

And long after we had turned out the lights and gone to bed, I'd lie on my cot and think about all that Kemper said and I thought in circles, too. I wondered why all the critters that came in and died were in the prime of life. Was the dying a privilege that was accorded only to the fit? Or were all the critters in the prime of life? Was there really some cause to believe they might be immortal?

I asked a lot of questions, but there weren't any answers.

We continued with our work. Weber killed some of his animals and examined them and there were no signs of ill effect from the critter diet. There were traces of critter bacteria in their blood, but no sickness, reaction or antibody formation. Kemper kept on with his bacterial work. Oliver started a whole series of experiments with the grass. Parsons just gave up.

The punkins didn't come back and Parsons and Fullerton went out and hunted for them, but without success.

I worked on my report and the pieces fell together better than I had hoped they would. It began to look as though we had the situation well nailed down. We were all feeling pretty good. We could almost taste that bonus.

But I think that, in the back of our minds, all of us were wondering if we could get away scot free. I know I had mental fingers crossed. It just didn't seem quite possible that something wouldn't happen.

And, of course, it did.

We were sitting around after supper, with the lantern lighted, when we heard the sound. I realized afterward that we had been hearing it for some time before we paid attention to it. It started so soft and so far away that it crept upon us without alarming us. At first, it sounded like a sighing, as if a gentle wind were blowing through a little tree, and then it changed into a rumble, but a far-off rumble that had no menace in it. I was just getting ready to say something about thunder and wondering if our stretch of weather was about to break when Kemper jumped up and yelled.

I don't know what he yelled. Maybe it wasn't a word at all. But the way he yelled brought us to our feet and sent us at a dead run for the safety of the ship. Even before we got there, in the few seconds it took to reach the ladder, the character of the sound had changed and there was no mistaking what it was — the drumming of hoofs heading straight for camp.

They were almost on top of us when we reached the ladder and there wasn't time or room for all of us to use it. I was the last in line and I saw I'd never make it and a dozen possible escape plans flickered through my mind. But I knew they wouldn't work fast enough. Then I saw the rope, hanging where I'd left it after the unloading job, and I made a jump for it. I'm no rope-climbing expert, but I shinnied up it with plenty of speed. And right behind me came Weber, who was no rope-climber; either, but who was doing rather well.

I thought of how lucky it had been that I hadn't found the time to take down the rig and how Weber had ridden me unmercifully about not doing it. I wanted to shout down and point it out to him, but I didn't have the breath.

We reached the port and tumbled into it. Below us, the stampeding critters went grinding through the camp. There seemed to be millions of them. One of the terrifying things about it was how silently they ran. They made no outcry of any kind; all you could hear was the sound of their hoofs pounding on the ground. It seemed almost as if they ran in some blind fury that was too deep for outcry.

They spread for miles, as far as one could see on the star-lit plains, but the spaceship divided them and they flowed to either side of it and then flowed back again, and beyond the spaceship there was a little sector that they never touched.

I thought how we could have been safe staying on the ground and huddling in that sector, but that's one of the things a man never can foresee.

The stampede lasted for almost an hour. When it was all over, we came down and surveyed the damage. The animals in their cages, lined up between the ship and the camp, were safe. All but one of the sleeping tents were standing. The lantern still burned brightly on the table. But everything else was gone. Our food supply was trampled in the ground. Much of the equipment was lost and wrecked. On either side of the camp, the ground was churned up like a half-plowed field. The whole thing was a mess.