They walked down to the hold for another look at their uninvited guest, and almost wished they hadn't.

It had reached the size of a small hippopotamus, although the resemblance ended there. Twenty hours had elapsed since the survey had begun. The _hlorg_ had used every minute of it, draining the tanks, engulfing dry stores, devouring walls and floors as it spread out in search of food, leaving trails of eroded metal wherever it went.

It was ugly--ugly in its pink shapelessness, ugly in its slimy half-sentient movements, in its very _purposefulness_. But its ugliness went even deeper, stirring primordial feelings of revulsion and loathing in their minds as they watched it oozing implacably across the hold to another dry-storage bin.

Wally Stone shuddered. "It's _grown_."

"Too fast. Bowman charts it as geometric progression."

Stone scratched his jaw as a lone pink pseudopod pushed out on the floor toward him. Then he leaped forward and stamped on it, severing the strand from the body.

The severed member quivered and lay still for a moment. Then it flowed back to rejoin the body with a wet gurgle.

Stone looked at his half-dissolved shoe.

"Egotropism," Jenkins said. "Bowman played around with that, too. A severed piece will rejoin if it can. If it can't it just takes up independent residence and we have two _hlorgs_."

"What happens to it outside the s.h.i.+p?" Stone wanted to know.

"It falls dormant for several hours, and then splits up into a thousand independent chunks. One of the boys spent half of yesterday out there gathering them up. I tell you, this thing is equipped to _survive_."

"So are we," said Green Doctor Stone grimly. "If we can't outwit this free-flowing gob of obscenity, we deserve anything we get. Let's have a conference."

They met in the pilot room. The Black Doctor was there; so were Bowman and Hrunta. Chambers, the physiologist, was glumly clasping and unclasping his hands in a corner. The geneticist, Piccione, drew symbols on a scratch pad and stared blankly at the wall.

Jenkins was saying: "Of course, these are only preliminary reports, but they serve to outline the problem. This is not just an annoyance any longer, it's a crisis. We'd all better understand that."

The Black Doctor cut him off with a wave of his hand, and glowered at the papers as he read them through minutely. As he sat hunched at the desk with the black cowl of his office hanging down from his shoulders he looked like a squat black judge, Jenkins thought, a shadow from the Inquisition, a Pa.s.ser of Spells. But there was no medievalism in Black Doctor Neelsen. In fact, it was for that reason, and only that reason, that the Black Service had come to be the leaders and the whips, the executors and directors of all the manifold operations of Hospital Earth.

The physicians of the General Practice Patrol were fledglings, newly trained in their specialties, inexperienced in the rigorous discipline of medicine that was required of the directors of permanent Planetary Dispensaries in the heavily populated systems of the Galaxy. On outlying worlds where little was known of the ways of medicine, the temptation was great to subst.i.tute faith for knowledge, cant for investigation, nonsense rituals for hard work. But the physicians of the Black Service were always waiting to jerk wandering neophytes back to the scientific disciplines that made the service of Hospital Earth so effective. The Black Doctors would not tolerate sloppiness. "Show me the tissue, Doctor," they would say. "Prove to me that what you say is so. Prove that what you did was valid medicine...." Their laboratories were the morgues and autopsy rooms of a thousand planets, the Temples of Truth from which no physician since the days of Pasteur and Lister could escape for long and retain his position.

The Black Doctors were the pragmatists, the gadflies of Hospital Earth.

For this reason it was surprising to hear Black Doctor Neelsen saying, "Perhaps we are being too scientific, just now. When the creature has exhausted our food stores, it will look elsewhere for food. Perhaps we must cut at the tree and not at the root."

"A frontal attack?" said Jenkins.

"Just so. Its enzyme system is its vulnerability. Enzyme systems operate under specific optimum conditions, right? And every known enzyme system can be inactivated by adverse conditions of one sort or another. A physical approach may tell us how in this case. Meanwhile we will be on emergency rations, and hope that we don't starve to death finding out."

The Black Doctor paused, looking at the men around him. "And in case you are thinking of enlisting help from outside, forget it. I've sent plague-warnings out for Galactic relay. We have this thing isolated, and we're going to keep it that way as long as I command this s.h.i.+p."

They went gloomily back to their laboratories to plan their frontal attack.

That was the night that Hrunta disappeared.

He was gone when they came to wake him from his sleep period. His bunk had been slept in, but he wasn't in it. In fact, he wasn't anywhere on the s.h.i.+p.

"But he couldn't just vanis.h.!.+" the Black Doctor burst out when they told him the news. "Maybe he's hiding somewhere. Maybe this business was working on his mind."

Green Doctor Stone took a crew of men to search the s.h.i.+p again, even though he considered it a waste of precious time. He had his private convictions about where Hrunta had gone.

So did every other man on the s.h.i.+p, including Jenkins.

The _hlorg_ had stopped eating. Huge and round and wet and ugly, it squatted in the after-hold, quivering gently, without any other sign of life.

Surfeited. Like a fat man after a turkey dinner.

Jenkins reviewed progress with the others. No stone had been left unturned. They had sliced the _hlorg_, and squeezed it. They had boiled it and frozen it. They had dropped chunks of it in acid vats and covered other chunks with desiccants and alkalis. Nothing seemed to bother it.

A cold environment slowed down its activity, true, but it also stimulated the process of fission. Warmed up again, the portions sucked back together again and resumed eating.

Heat was a little more effective, but not much. It stunned the creature for a brief period, but it would not burn. It hissed frightfully and gave off an overpowering stench, and curled up at the edges, but as soon as the heat was turned off it began to recover.

In Hrunta's lab chunks of the _hlorg_ sat in a dozen vats on tables and in sinks. Some contained antibiotics, some concentrated acids, some desiccants. In each vat a blob of pink protoplasm wiggled happily, showing no sign of discomfiture. On another table were the remains of Hrunta's (unsuccessful) attempt to prepare an anti-_hlorg_ serum.

But no Hrunta.

"He was down there with the thing all day," Bowman said sadly. "He felt it was his responsibility, really. Hrunta thought biochemistry was the answer to all things, of course. Very conscientious man."

"But he was in _bed_."

"He claimed he did his best thinking in bed. Maybe he had a brainstorm and went down to try it out, and--"

"Yes." Jenkins nodded sourly. "And." He walked down the row of vats.

"You'd think that at least concentrated sulphuric would dessicate it a little. But it's just formed a crust of coagulated protein around itself, and sits there--"

Bowman peered over his shoulder, his mustache twitching. "But it does dessicate."

"If you use enough long enough."

"How about concentrated hydrochloric?"

"Same thing. Maybe a little more effective, but not enough to count."

"Okay. Next we try combinations. There's got to be _something_ the wretched beast can't tolerate--"

There was, of course.

Green Doctor Stone brought it to Jenkins as he was getting ready to turn in for a sleep period. Jenkins had checked to make sure double guards were posted in the _hlorg's_ vicinity, and jolted them with Sleep-Not to keep them on their toes. All the same, he tied a length of stout cord around his ankle just to make sure he didn't do any sleepwalking. He was tying it to the bunk when Stone came in with a pan in his hand and a peculiar look on his face.

"Take a look at this," he said.

Jenkins looked at the sickly brown ma.s.s in the tray, and then up at Stone. "Where did you find it?"