"Besides," said Parsons, "we don't cook all of it. We don't cook the fruit and most of you guys raise hell if a steak is more than singed."

"What I can't figure out is why it should be Fullerton," Weber said. "Why should his count be higher? He started on the critter the same time as the rest of us."

I remembered that day down by the creek.

"He got a head start on the rest of you," I explained. "He ran out of toothpicks and took to chewing grass stems. I caught him at it."

I know it wasn't very comforting. It meant that in another week or two, all of them would have as high a count as Fullerton. But there was no sense not telling them. It would have been criminal not to. There was no place for wishful thinking in a situation like that.

"We can't stop eating critter," said Weber. "It's all the food we have. There's nothing we can do."

"I have a hunch," Kemper replied, "it's too late anyhow."

"If we started home right now," I said, "there's my diet kit…"

They didn't let me finish making my offer. They slapped me on the back and pounded one another and laughed like mad.

It wasn't funny. They just needed something they could laugh at.

"It wouldn't do any good," said Kemper. "We've already had it. Anyhow, your diet kit wouldn't last us all the way back home."

"We could have a try at it," I argued.

"It may be just a transitory thing," Parsons said. "Just a bit of fever. A little upset from a change of diet."

We all hoped that, of course.

But Fullerton got no better.

Weber took blood samples of the animals and they bad a bacterial count almost as high as Fullerton's — much higher than when he'd taken it before.

Weber blamed himself. "I should have kept closer check. I should have taken tests every day or so."

"What difference would it have made?" demanded Parsons. "Even if you had, even if you'd found a lot of bacteria in the blood, we'd still have eaten critter. There was no other choice."

"Maybe it's not the bacteria," said Oliver. "We may be jumping at conclusions. It may be something else that Fullerton picked up."

Weber brightened up a bit. "That's right. The animals still seem to be okay."

They were bright and chipper, in the best of health.

We waited. Fullerton got neither worse nor better.

Then, one night, he disappeared.

Oliver, who had been sitting with him, had dozed off for a moment. Parsons, on guard, had heard nothing.

We hunted for him for three full days. He couldn't have gone far, we figured. He had wandered off in a delirium and he didn't have the strength to cover any distance.

But we didn't find him.

We did find one queer thing, however. It was a ball of some strange substance, white and fresh-appearing. It was about four feet in diameter. It lay at the bottom of a little gully, hidden out of sight, as if someone or something might have brought it there and hidden it away.

We did some cautious poking at it and we rolled it back and forth a little and wondered what it was, but we were hunting Fullerton and we didn't have the time to do much investigating. Later on, we agreed, we would come back and get it and find out what it was.

Then the animals came down with the fever, one after another — all except the controls, which had been eating regular food until the stampede had destroyed the supply.

After that, of course, all of them ate critter.

By the end of two days, most of the animals were down.

Weber worked with them, scarcely taking time to rest. We all helped as best we could.

Blood samples showed a greater concentration of bacteria. Weber started a dissection, but never finished it. Once he got the animal open, he took a quick look at it and scraped the whole thing off the table into a pail. I saw him, but I don't think any of the others did. We were pretty busy.

I asked him about it later in the day, when we were alone for a moment. He briskly brushed me off.

I went to bed early that night because I had the second guard. It seemed I had no more than shut my eyes when I was brought upright by a racket that raised goose pimples on every inch of me.

I tumbled out of bed and scrabbled around to find my shoes and get them on. By that time, Kemper had dashed out of the tent.

There was trouble with the animals. They were fighting to break out, chewing the bars of their cages and throwing themselves against them in a blind and terrible frenzy. And all the time they were squealing and screaming. To listen to them set your teeth on edge.

Weber dashed around with a hypodermic. After what seemed hours, we had them full of sedative. A few of them broke loose and got away, but the rest were sleeping peacefully.

I got a gun and took over guard duty while the other men went back to bed.

I stayed down near the cages, walking back and forth because I was too tense to do much sitting down. It seemed to me that between the animals" frenzy to escape and Fullerton's disappearance, there was a parallel that was too similar for comfort.

I tried to review all that had happened on the planet and I got bogged down time after time as I tried to make the picture dovetail. The trail of thought I followed kept turning back to Kemper's worry about the critters" lack of a defense mechanism.

Maybe, I told myself, they had a defense mechanism, after all — the slickest, smoothest, trickiest one Man ever had encountered.

As soon as the camp awoke, I went to our tent to stretch out for a moment, perhaps to catch a catnap. Worn out, I slept for hours.

Kemper woke me.

"Get up, Bob!" he said. "For the love of God, get up!"

It was late afternoon and the last rays of the sun were streaming through the tent flap. Kemper's face was haggard. It was as if he'd suddenly grown old since I'd seen him less than twelve hours before.

"They're encysting," he gasped. "They're turning into cocoons or chrysalises or…"

I sat up quickly. "That one we found out there in the field!"

He nodded.

"Fullerton?" I askecl

"We'll go out and see, all five of us, leaving the camp and animals alone."

We had some trouble finding it because the land was so flat and featureless that there were no landmarks.

But finally we located it, just as dusk was setting in. The ball had split in two — not in a clean break, in a jagged one. It looked like an egg after a chicken has been hatched. And the halves lay there in the gathering darkness, in the silence underneath the sudden glitter of the stars — a last farewell and a new beginning and a terrible alien fact.

I tried to say something, but my brain was so numb that I was not entirely sure just what I should say. Anyhow, the words died in the dryness of my mouth and the thickness of my tongue before I could get them out.

For it was not only the two halves of the cocoon — it was the marks within that hollow, the impression of what had been there, blurred and distorted by the marks of what it had become.

We fled back to camp.

Someone, I think it was Oliver, got the lantern lighted. We stood uneasily, unable to look at one another, knowing that the time was past for all dissembling, that there was no use of glossing over or denying what we'd seen in the dim light in the gully.

"Bob is the only one who has a chance," Kemper finally said, speaking more concisely than seemed possible. "I think be should leave right now. Someone must get back to Caph. Someone has to tell them."

He looked across the circle of lantern light at me.

"Well," he said sharply, "get going! What's the matter with you?"

"You were right," I said, not much more than whispering. "Remember how you wondered about a defense mechanism?"

"They have it," Weber agreed. "The best you can find. There's no beating them. They don't fight you. They absorb you. They make you into them. No wonder there are just the critters here. No wonder the planet's ecology is simple. They have you pegged and measured from the instant you set foot on the planet. Take one drink of water. Chew a single grass stem. Take one bite of critter. Do any one of these things and they have you cold."