"I don't smoke. You know that." 

A stupid answer. "Anything?" I said in exasperation.

"Look, Joe. Over there. Over there.'' 

He lunged for it. I could have told him it would do no good.

By now, though, our poking around in the computer seemed to have stirred things up. We were seeing them wherever we looked. They were floating in the air-currents. 

I stopped one at last. Or, rather, it stopped itself for it was on the elbow of Joe's suit. I snatched it off and shouted. Joe jumped in terror and nearly knocked it out of my hand. 

I said, "Look!"

There was a shiny circle on Joe's suit, where I had taken the thing off. It had begun to eat its way through. 

"Give it to me," said Joe. He took it gingerly and put it against the wall to hold it steady. Then he shelled it, gently lifting the paper-thin metal. 

There was something inside that looked like a line of cigarette ash. It caught the light and glinted, though, like lightly woven metal. 

There was a moistness about it, too. It wriggled slowly, one end seeming to seek blindly. 

The end made contact with the wall and stuck. Joe's finger pushed it away. It seemed to require a small effort to do so. Joe rubbed his finger and thumb and said, "Feels oily." 

The metal worm-I don't know what else to call itseemed limp now after Joe had touched it. It didn't move again. 

I was twisting and turning, trying to look at myself. 

"Joe," I said, "for Heaven's sake, have I got one of them on me anywhere?"

"I don't see one," he said. 

"Well, look at me. You've got to watch me, Joe, and I'll watch you. If our suits are wrecked we might not be able to get back to the ship." 

Joe said, "Keep moving, then." 

It was a grisly feeling, being surrounded by things hungry to dissolve your suit wherever they could touch it. When any showed up, we tried to catch them and stay out of their way at the same time, which made things almost impossible. A rather long one drifted close to my leg and I kicked at it, which was stupid, for if I had hit it, it might have stuck. As it was, the air-current I set up brought it against the wall, where it stayed. 

Joe reached hastily for it-too hastily. The rest of his body rebounded as he somersaulted, one booted foot struck the wall near the cylinder lightly. When he finally righted himself, it was still there. "I didn't smash it, did 1?"

"No, you didn't," I said. "You missed it by a decimeter. It won't get away."

I had a hand on either side of it. It was twice as long as the other cylinder had been. In fact, it was like two cylinders stuck together longways, with a construction at the point of joining.

"Act of reproducing," said Joe as he peeled away the metal. This time what was inside was a line of dust. Two lines. One on either side of the constriction.

"It doesn't take much to kill them," said Joe. He relaxed visiby. "I think we're safe."

"They do seem alive," I said reluctantly.

"I think they seem more than that. They're viruses-or the equivalent."

"What are you talking about?"

Joe said, "Granted I'm a computertechnologist and not a virologist-but it's my understanding that viruses on Earth, or `downstairs' as you would say, consist of a nucleic acid molecule coated in a protein shell.

"When a virus invades a cell, it manages to dissolve a hole in the cell wall or membrane by the use of some appropriate enzyme and the nucleic acid slips inside, leaving the protein coat outside. Inside the cell it finds the material to make a new protein coat for itself. In fact, it manages to form replicas of itself and produces a new protein coat for each replica. Once it has stripped the cell of all it has, the cell dissolves and in place of the one invading virus there are several hundred daughter-viruses. Sound familiar?"

"Yes. Very familiar. It's what's happening here. But where did it come from, Joe?"

"Not from Earth, obviously, or any Earth settlement. From somewhere else, I suppose. They drift through space till they find something appropriate in which they can multiply. They look for sizable objects ready-made of metal. I don't imagine they can smelt ores."

"But large metal objects with pure silicon components and a few other succulent matters like that are the products of intelligent life only," I said.

"Right," said Joe, "which means we have the best evidence yet that intelligent life is common in the universe, since objects like the one we're on must be quite common or it couldn't support these viruses. And it means that intelligent life is old, too, perhaps ten billion years old-long enough for a kind of metal evolution, forming a metal/silicon/oil life as we have formed a nucleic/protein/water life. Time to evolve a parasite on space-age artifacts."

I said, "You make it sound that every time some intelligent life-form develops a space-culture, it is subjected before long to parasitic infestation."

"Right. And it must be controlled. Fortunately, these things are easy to kill, especially now when they're forming. Later on, when ready to burrow out of Computer-Two, I suppose they will grow, thicken their shells, stabilize their interior and prepare, as the equivalent of spores, to drift a million years before they find another home. They might not be so easy to kill then."