Paul watched the professor's bright eyes and took the lecture quietly.
"And so, before I illuminate you, I want to make an impossible request."
"Yes, sir."
"I ask you to be completely objective," Seevers continued, rubbing the bridge of his nose and covering his eyes with his hand. "I want you to forget you ever heard of neuroderm while you listen to me. Rid yourself of all preconceptions, especially those connected with fear. Pretend these are purely hypothetical events that I'm going to discuss." He took his hands down from his eyes and grinned sheepishly. "It always embarrasses me to ask for that kind of cooperation when I know damn well I'll never get it."
"I'll try to be objective, sir."
"Bah!" Seevers slid down to sit on his spine, and hooked the base of his skull over the back of the chair. He blinked thoughtfully at the ceiling for a moment, then folded his hands across his small paunch and closed his eyes.
When he spoke again, he was speaking to himself: "Assume a planet, somewhat earthlike, but not quite. It has carboniferous life forms, but not human. Warm-blooded, probably, and semi-intelligent. And the planet has something else-it has an overabundance of parasite forms. Actually, the various types of parasites are the dominant species. The warm-blooded animals are the parasites' vegetables, so to speak. Now, during two billion years, say, of survival contests between parasite species, some parasites are quite likely to develop some curious methods of adaptation. Methods of insuring the food supply-animals, who must have been taking a beating."
Seevers glanced down from the ceiling. "Tell me, youngster, what major activity did Man invent to secure his vegetable food supply?"
"Agriculture?"
"Certainly. Man is a parasite, as far as vegetables are concerned. But he learned to eat his cake and have it, too. He learned to perpetuate the species he was devouring. A very remarkable idea, if you stop to think about it. Very!"
"I don't see-"
"Hush! Now, let's suppose that one species of micropar-asites on our hypothetical planet learned, through long evolutionary processes, to stimulate regrowth in the animal tissue they devoured. Through exuding controlled amounts of growth hormone, I think. Quite an advancement, eh?"
Paul had begun leaning forward tensely.
"But it's only the first step. It let the host live longer, although not pleasantly, I imagine. The growth control would be clumsy at first. But soon, all parasite-species either learned to do it, or died out. Then came the contest for the best kind of control. The parasites who kept their hosts in the best physical condition naturally did a better job of survival-since the parasite-ascendancy had cut down on the food supply, just as Man wastes his own resources. And since animals were contending among themselves for a place in the sun, it was to the parasite's advantage to help insure the survival of his host-species-through growth control."
Seevers winked solemnly. "Now begins the downfall of the parasites-their decadence. They concentrated all their efforts along the lines of… uh… scientific farming, you might say. They began growing various sorts of defense and attack weapons for their hosts-weird bio-devices, perhaps. Horns, swords, fangs, stingers, poison-throwers-we can only guess. But eventually, one group of parasites hit upon- what?"
Paul, who was beginning to stir uneasily, could only stammer. Where was Seevers getting all this?
"Say it!" the scientist demanded.
"The… nervous system?"
"That's- right. You don't need to whisper it. The nervous system. It was probably an unsuccessful parasite at first, because nerve tissue grows slowly. And it's a long stretch of evolution between a microspecies which could stimulate nerve growth and one which could direct utilize growth for the host's advantage-and for its own. But at last, after a long struggle, our little species gets there. It begins sharpening the hosfs senses, building up complex senses from aggregates of old-style receptors, and increasing the host's intelligence within limits."
Seevers grinned mischievously. "Conies a planetary shake-up of the first magnitude. Such parasites would naturally pick the host species with the highest intelligence to begin with. With the extra boost, this brainy animal quickly down its own enemies, and consequently the enemies of its microbenefactor. It puts itself in much the same position that Man's in on Earth-lord it over the beasts, divine right to run the place, and all that. Now understand-it's the animal who's become intelligent, not the parasites. The parasites are operating on complex instinct patterns,, like a hive of bees. They're wonderful neurological engineers-like bees are good structural engineers; blind instinct, accumulated through evolution."
He paused to light a cigarette. "If you feel ill, young man, there's drinking water in that bottle. You look ill."
"I'm all right!"
"Well, to continue: The intelligent animal became master of his planet. Threats to his existence were overcome-unless he was a threat to himself, like we are. But now, the parasites had found a safe home. No new threats to force readaptation. They sat back and sighed and became stagnant-as unchanging as horseshoe crabs or amoeba or other Earth ancients. They kept right on working in their neurological beehives, and now they became cultivated by the animal, who recognized their benefactors. They didn't know it, but they were no longer the dominant species. They had insured their survival by leaning on their animal prop, who now took care of them with godlike charity-and selfishness. The parasites had achieved biological heaven. They kept on working, but they stopped fighting. The host was their welfare state, you might say. End of a sequence."
He blew a long breath of smoke and leaned forward to watch Paul, with casual amusement. Paul suddenly realized that he was sitting on the edge of his chair and gaping. He forced a relaxation.
"Wild guesswork," he breathed uncertainly.
"Some of it's guesswork," Seevers admitted. "But none of it's wild. There is supporting evidence. It's in the form of a message."
"Message?"
"Sure. Come, I'll show you." Seevers arose and moved toward the wall. He stopped before the two hemispheres. "On second thought, you better show yourself. Take down that sliced meteorite, will you? It's sterile."
Paul crossed the room, climbed unsteadily upon a bench, and brought down the globular meteorite. It was the first time he had examined one of the things, and he inspected it curiously. It was a near-perfect sphere, about eight inches in diameter, with a four-inch hollow in the center. The globe was made up of several concentric shells, tightly fitted, each apparently of a different metal. It was not seemingly heavier than aluminum, although the outer shell was obviously of tough steel.
"Set it face down," Seevers told him. "Both halves. Give it a quick little twist. The shells will come apart. Take out the center shell-the hard, thin one between the soft protecting shells."
"How do you know their purposes?" Paul growled as he followed instructions. The shells came apart easily.
"Envelopes are to protect messages," snorted Seevers,
Paul sorted out the hemispheres, and found two mirror-polished cells of paper-thin tough metal. They bore no inscription, either inside or out. He gave Seevers a puzzled frown,
"Handle them carefully while they're out of the protectors. They're already a little blurred…"
"I don't see any message."
"There's a small bottle of iron filings in that drawer by your knee. Sift them carefully over the outside of the shells. That powder isn't fine enough, really, but it's the best I could do. Felger had some better stuff up at Princeton, before we all got out. This'business wasn't my discovery, incidentally."
Baffled, Paul found the iron filings and dusted the mirror-shells with the powder. Delicate patterns appeared-latitudinal circles, etched in iron dust and laced here and there with diagonal lines. He gasped. It looked like the map of a planet.