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B. *. 25i per C* W NlfrKT ISSUE ON SALE MAY 17, iSlfl AST— IF REACTOR RESEARCH The Atomic Energy Commission has recently put out a brief explanation of some of the research work going on, and the experimental equipment needed to do that research. In par- ticular, research into the nature and usefulness of different types of reac- tors — once called "atomic piles'* — is of considerable i mere si in showing: the state of the art as of now, and the reasons why the nrt is still an art, not a science- Let's go back to the basics of ura- nium fission for a bit. As most people, and practically all science- hctioneers know, the nucleus o£ Uranium isotope of atomic weight 235 is in a state of extreme tension. The introduction of a single extra neutron causes disruption, fission, and the release of several highly important items. 1. An enormous amount of energy. 2. Fission product nuclei — usually two for each fissioned U-235 atom, but esh many as eight have been found occasionally from a single (J-255, 3+ Neutrons- — on the average, the fission of N U-235 nuclei yields new neutrons. That fig- , tire of 23 is a very rough guess ; it's something- over 2, and under 3, A less well real E zed fact is that U- 233 is not stable. U-23R atoms under- go natural, spontart^us fission them- selves, even without being struck by neutrons. It T s extremely rare, but the_ refiction is measurable. And, while a slow-moving neutron is sin] ply ab- sorbed by U-23S, producing in suc- cess ion U-239, then by radioactive decay Neptunium-239 and Plutonium- 239 , that is ttot the only reaction, _ U- 238 fissions exactly the way U-235 does if it is hit by a fast neutron. Let's put down, in tabular fornij a very rough approximation of the re- actions of various isotopes of the super-heavy elements to neutrons of various energies. First, Thorium-232 and Uranium-238 are very similar in their nuclear react ion^, and cadi be classified together. U-238 can be con- verted to plutouiurn, and Tliorium-232 — thorium's only naturally occurring isotope- — can be converted to fission- able U-233. Both U-233 and plutq- nium react as does U-235. The way they react: Paction NEUTHON *i U-3J3, ENERGY U-235cr Reaction of 11-23 ft or in voha Pu-3J3 Th-232 Over Fisltons Fissions l r 000,GGQ 100 to Fissions Low absorption to 1,000,000 yield l : u-239 or U-233 30 to 100 Fissions Moderate absorp- tion 0,5 to SO Fissions High degree of neutron absorp- tion TlelowChS Fissions Low degree of absorption The important general factors are that the so called "fissionable iso- topes"— actual ly, they're all fiss ton- able under the right conditions — are the ones that fission whenever a neu- tron of any energy, including the low- est, enters the nucleus. And they absorb neutrons of extremely low energy, U-238 nuclei will not absorb ASTOUNDING SCIENCE -FICTION . a neutron of less than I /20th of a volt energy; U-235 wiil. If a very ocea- ' sional U-238 nucleus fcs accidentally absorb a l/20th volt neutron, nothing much happens; if U-235 absorbs oue ± the result is catastrophic. One of the most important concepts of modern nuclear physics is the "neu- tron absor]*tion cross-section" of a nu- cleus. It's a bit difficult to get hold of the idea if you insist on a mechani- cal model of an atom. An atom is not subject to the same sort of laws that our macrocosm ic mac] lines are- it works on probability functions, not facts, so to speak. You've seen figures on the "diameter of the nucleus" or the "diameter of an atom." They don't mean a thing, unless it is also specified what measuring technique was used- A mechanical analogy — guaranteed inaccurate, but indicative — may help. Suppose we want to measure the size of a 1>arn, hut we cart 1 ! touch it. So we set up on one side of it a huge metal plate that will go "Bony" every time it's hit, arid a machine gnu on the other side We start firing away, noting the angle of fire of the machine gun, and when we don't get bangs. Pres- ently we have worked out the "sha- dow" of the barn, and then, can de- termine its "diameter/ 7 The diameter turns out to be roughly eight feet, Remarkably small barn, isn't it? Be- coming somewhat suspicious* we change from the SO -caliber machine- gun as a measuring instrument to a sii tall rifle. Now we get an entirely different answer ; there's still a solid structure about eight feet in diameter* but in addition there's a sort of skeletal structure about twenty- five feet in diameter. Kinally, a. third check _ is made using a toy air-rifle as the beam projector. Now the result is a solid RKACTOtt HESEAKCH object twenty -five feet in diameter. For someone who can see, touch t and enter the barn to investigate, the answer is immediately evident- There's a tractor stored in the barn that's solid and massive enough to stop SO-caliber slugs, though the hoard walls and beams of the barn can't. The boards won't stop rifle bullets, either, though they will stop bee -bee's. The beams stopped the rifle bullets t so that a skeletal structure became evident on that test„ But — what is the diameter — the cross- sect ion — of the barn? Well, now, that depends— Tt depends on what you're talking about. There's a fur- ther type of cross section we might determine foT the barn, too. Suppose we start measuring its cross-section with the aid of a 105 mm rifle ; this time we'll determine its "fission cross- section." j The ''fission cross- section" turns out to be aTiout eight feet, too; the tractor's the only" part of the struc- ture that's solid enough to stop the lieavy projectile Uw£ enough to make its delay ed-acti on armor-piercing charge go off, '['his analogy is, as stated, violently distorted — but it is indicative of the genera] proposition that the apparent size of a nucleus depends on the type of particle used in bombardment, and the velocity of that particle, in nuclei, however, much more complicated things #o on, Elnve you ever dropped a small ball -hearing between the poles of a magnet? If it is dropped just right, it will fall through the gap between the poles completely unde- fiected. Slightly off absolute dead-cen- ter, it will fall through, but he twisted in its path to a greater or less degree. In nuclei, forces of that nature are at work, Loo. Finally, there's a resemblance to a rack of pool balls* representing the nuclear particles in the nucleus, being struck by the cue ball. Only our nu- clear pool balls are magnetized, and tend to stick together. The cue ball can't be identified, either, once U ar- rives; the cue bill! wy strike, and the R-ball go flying ont. I£ our identifica- tion instrument can count but not identify balls, it will tell us that the cue ball went right through the whole mass without disturbing it. So we have the concept of "neutron absorption cross-section," which is the most important single item in reactor design. For 7'Cry slow neutrons- — l/20th of a volt, say — the neutron absorption cross section of U-23B and Th-232 is small; thai of U-233 t U-235 or Pu-239 large, and the latter three fission on absorbing the neutron. At about two volts, the absorption cross section of U-238 is large, at ten volt neutron energies it's small again* At twenty- five volts, U-238 absorbs neu- trons heavily a gam — has a large ab- sorption cross-section — and again at about one thousand volts it has a large cross section. At very high voltages — in the millions range— U-23&, Th-232, U-235, TJ-233, and Pu-239 all have relatively small neutron absorption cross-sections, Rut all of these mwlei fission under those conditions. Also, in the multi-mega volt range, elements down to and including lead and bis- 'rnuth will fission. TJ-235 is the only naturally occur- ring isotope which will fission with slow neutrons, thus producing fast neutrons to keep the atomic fire going:, U-233 and Pu-23° can be synthesized and will display the same characteris- tic. But, since U-238 outnumbers U- 235 in natural uranium 140 to l r the first nuclear reactors were designed to trick those odds — stack the cards — in favor of U-235 by slowing the neu- trons escaping to very low speeds. The neutrons emitted by fission are high-speed neutrons; they can, if ab- sorbed immediately, fission either U- 235 or U-238. Since both isotopes have a low absorption cross-section for fast neutrons, however, die neutrons usually escape from the small slugs used in the piles, into the moderator material. The moderator slows them down through the critical speeds— one thousand volts, twenty-five volts, and. two volts — at which U-25S can grab them. Below two volts, the wilt, and U-23S won't absorb them, so de- spite the 140-to-l odds of abundance, TJ-235 gets most of them. So much is past history; the new work has to do with two totally different types of piles. First, when those two-plus neutrons, are released in- a fission, to keep this reaction miming at constant level, one neutron must be used in another U-235 nucleus to cause another fission. Thev other one-plus is available for other uses. U-238 will not fission under or- dinary conditions ; ij; cannot be used to start an atomic reaction., and could fission theoretically only in the type of unmanageably violent reaction used in the atomic bomb, " And there, U-235 would be necessary to get started. But if one neutron is added to U-238 it becomes Pu-239, and that is a useful atomic fuel. The ideal Set-Up then, would be a nuclear reactor using a mixture of U-235 and U-238 such that that fiparc neutron from the U-235 fission wfis absorbed by U-238, gen- erating Pu-239. This way, as the U- 235 was consumed, it would be re- {Confimted on page 160) ASTOUKJOING £ C IE NCE-F ICTlOH NEEDLE BY HAL CLEMENT First of two parte* A detective always- has a tough job; the criminal is a, needle in a hay stack- of people. But this detective of an alien world had a terrible tusk indeed; his - 7teedle could become a wisp of hay in a haystack! illustrate by orJ>an The Hunter suddenly realized that the ship ahead of him had he- come visible without the aid of in- strument^ and the vague alarm that had been nibbling at the outskirts of his hi in (I rocketed into the fore- ground. He had been unable to understand why the fugitive should go below the speed of light at all, except in the hope that the pursuer would overrun him sufficiently to be beyond detection range: ; and when that failed/ the Hunter had fully expected a renewed burst of speed. Instead, the other ship had con- tinned to decelerate. It hid kept dead between the Hunter's machine and one of the planets of the system through which they were passing, so it was dangerous to overhaul it too rapidly; the Hunter had thought that preparation was being- made: for a break hack to Lhe Al- lan e oi" Tordel systems; and he had not realised how close they both were to the looming planet until the appearance of the fugitive's hull as a spark of red against the blackness - of the great world below showed he had actually entered its atmosphere. That was enough for the Hunter. He flun£ every erg his ■converters eould produce into a ([rive straight away from the planet, at the same time pouring the rest of his mass into the control room as a gelatinous cushion to protect his peril f rotn the savage deceleration ; and saw in- stantly that it would not be sufficient. He had just time to wonder that the creature ahead of hem should be willing to risk its sViip and host in what would certainly be a. nasty crash , before 'the outer fringes of the world's gaseous envelope added their resistance to his flight and set his outer hull glowing a brilliant orange, The ships had dived straight down the shadow cone ; they were plunging to the night side. With an effort, the Hunter kept an eye on the instruments that revealed the other vessel's whereabouts; and It was well he did so, for the glowing cylinder abruptly vanished from sight into an enormous mass of e water vapor that veiled the dark sur- face below them. A split second later, the Hunter's ship plunged into the same mass ; and as it did so there was a twisting lurch, and the right- line deceleration changed to a sick- ening spinning motion. The pilot It new that one of the drive plates had gone, probably Cracked off by undis- tributed heat; but there was simply no time to do a thing about it. The other vessel, he noted, had stopped as though running into a brick wall ; now it was settling again slowly* and he himself could be only split seconds from the same obstacle, as- suming it was horizontal. It was? The Hunter's ship, still spinning wildly, though he had shut off the drive platen at the last mo- ment, Struck almost flat on water, and at the impact split from end to end along both sides, as though it has been an eggshell stepped on by a giant. Almost all its kinetic energy was absorbed _ in that blow; but it did not stop altogether. It con- tinued to settle, comparatively gently now, and the half- conscious Hunter felt it bring its shattered hull to a gentle rest on what he realized must be the bottom of a body of water, a few seconds later. At least* he told himself as bis wits began slowly to clear, his quarry must be in the same predica- ment- The abrupt stoppage and subsequent slow descent of the other machine was now explained — even if it struck head on in stead of hori- zontally, 1 lie re would have been no perceptible difference in the result. A5TOUSDIPJG SCIENCE-FICTION It was almost certainly unusable, even though not quite so badly damaged as the Hunter*s + That idea brought the train of thought back to his own predica- ment. He- felt cautiously around hitn, and found lie was no longer entirely in the com ml room — in fact, there was 11 0 longer room for till of him inside it. What had been a cylindrical chamber some twenty inches in diameter and two feet in length was now simply the space between two -badly dented sheets of inch-thick metal, which had been the hulh The scams had parted on either side — or rather, scams had been" made and forced apart : the hull wis originally a single piece of metal worked into tubular shape — and the top and bottom thus formed had been flattened out and were now scarcely more than an inch apart, on the average. The bulkheads at either end of the room had crumpled like tissue. The perit was very dead -^not only crushed by the collapsing walls, hot the hydrostatic shock transmitted through the Hunter's semifluid body, in which it has been Suspended for protection, had rup' tured most of its more delicate or- gans. The Hunter, realizing this slowly, withdrew from around and within the little creature. He did not attempt to eject its mangled re- mains from the ship ; it might he necessary to use it as food later on, though the idea was unpleasant. The Hunter's attitude toward the ■ NEEDLE little animal resembled that of a man toward his dog. He extended his explorations a little, reaching out with slender pseudopod through the rents in the hull. He already knew that the wreck was lying in salt water p but he had no idea of the depth other than that it was not excessive. On his home pkmct, he could have judged it quite- accurately from the pressure ; but lie had not obtained a reading of this world's surface gravity before the crash. It was dark outside the hull. When he constructed an eye from his own tissues — those of the psrit had Ijeert ruptured — it told him ab- solutely nothing of his surroundings. Suddenly, however, he realized that the pressure around him was not constant; it was increasing and decreasing by rather marked incre- ments, with something like regu- larity; and the water was trans- mitting to his sensitive flesh those other pressure waves which he in- terpreted as sound. Listening in- tently, he finally decided he must he fairly close lo the surface of a body of water large enough to develop waves a good many feet in height, and that a storm of considerable violence was in progress. That he had failed to notice any storm d ur- ine; Si is catastrophic descent meant nothing whatever. Poking into the mud around the wreck with other pseudopods, he found to his relief that the planet was not lifeless— he was already pretty sure of that fact, since there was enough oxygen dissolved in the water to satisfy his needs, provided he did not exert himself greatly; Ihere must consequently be free oxygen in the atmosphere above- It was just as well, however,, to have confirmation ; and he was well satis- fied to locate in the mud a number of small, bivalve moll asks which upon trial proved quite edible. Realizing that it was night on this part of the planet, he decided to postpone further outside investiga- tion until thei'« was more light, and turned his "attention to the remains of his ship. He had not expected to find anything encouraging as a result of the examination, but he got a certain glum feeling of accomplish- ment as he realized I he completeness of the destruction. Solid metal parts in the engine room had changed shape under the forces to which they had been subjected. The nearl} r solid conversion chamber of the main drive unit was flattened and twisted. There was no trace re- maining; of certain quartz-shelled gas tubes; they had evidently been pulverized and washed away by the water. No living creature handi- capped by a definite shape and solid parts could have come through ^the crash alive, no matter how well protected. That thought was some com fort to him; he had done his best for the petit even though that had not been sufficient. With these facts deter mined , the Hunter felt that he had done all that was possible for the time being. No really active work could be un- dertaken until he reached open air; and the lack of light was also a severe handicap. He relaxed, there- forCj within the questionable shelter of the ruined hull, and waited for the storm to end and the day to come. With light and calm water, he felt that he could probably reach shore without assistance the wave noise suggested breakers, which im- plied a beach at no great distance. He lay there for several hours* The darkness remained unbroken, and it occurred to him once that he might be on a planet whose rotation matched its revolution; but the pres- ence of liquid water made that most unlikely, as he quickly realized, It was probable that storm clouds were shutting out the daylight. Ever since the ship had first set- tled into the mud, it had remained motionless. The terrific disturb- ance overhead was reflected in cur- rents and backwashes along the bottom which the Hunter could feel, but which were quite unable to shift the half -buried mass of metal. With this conclusion reached long since, the castaway was suddenly startled when his shelter quivered as though to a heavy blow, and changed po- sition slightly. Instantly he sent out an inquiring tentacle. He formed an eye at its tip, but the darkness was still in- tense, and he returned to a strictly tactile exploration. Vibrations sug- gestive of a very rough skin scraping along the hull were coming to him; and abruptly something living ran ASTOUNDING SCIENCE-FICTION into the extended limb. It demon- strated its sentient quality by promptly seizing the appendage in a mouth thftt seemed amazingly well furnished with saw-edged teeth. The Hunter allowed the portion of himself in direct contact with those unpleasant: edges to relax into a semiiiquid condition ; and at the same time he sent more of his body flowing into the arm toward the strange creature. He was a being of quick decisions , and the evident size o£ the intruder had impelled him to a somewhat risky activity. He left his wrecked spaceship entirely, and sent his whole four pounds of jelly- like flesh toward what he hoped was a more useful conveyance. The shark — it was an eight- foot hammerhead — may have been sur- prised, but in common with all its tribe it lacked the brains to be afraid. Its ugly jaws snapped hungrily at what had at first been satis fyingly solid flesh, only to feel it give way before them like so much water. The Hunter made no attempt to avoid the teeth, since he was immune to mechanical damage of that nature, but hi- strenuously resisted the efforts of the fish to swallow that portion of his mass already within its mouth; he had no intention of exposing his flesh to gastric juices. As the shares activities grew more and more frantically vicious, he sent exploratory pscudopods over the ugly, rough- ski nned form, and within a few moments discovered the five gill slits on each side of the need lb creature*s neck. That was enough, His actions were no longer directed by a spirit of inquiry ; he knew, with a precision born of long experience, what to do. He was a metazoan — a many- celled creature^- in spite of his ap- parent lack of structure, but the individual cells of his body were far smaller than those of most life forms : they compared in size with the larger protein molecules. Conse- quently, he could put forth and control a pseudopod fine enough to enter the very capillaries of a more orthodox organism without inter- fering seriously with its blood circu- lation. He had, therefore, no difficulty in insinuating himself into the shares relatively huge body. .He avoided nerves and blood vessels as much as possible, and poured himself into such muscular and visceral interstices as he could locate. The shark calmed down at once, after the thing in its mouth and on its body ceased causing; tactile messages to reach its minute brain; its memory was to all intents and purposes nonexistent. For the Hunter, however, successful inter- stition was only the beginning of a period of in tense activity, First and most important, oxygen. There was enough of the precious element absorbed on the surfaces of his body cells for only a few minutes of life at most. But it could always be obtained ; in the body of a creature that also con- sumed oxygen; and the Hunter 11 rapidly sent submicroscopk appen- dages between the cells that formed the walls of blood vessels, and began lobbing the oxygen -bearing cells, of their precious load. He needed but little, and on his home world he bad livied for years within the body of an intelligent oxygen-breathe r, as did most of bis kind, with the other's full knowledge and consent. He had more than paid for tvis keep. The second need was vision. His host presumably possessed eyes ; and with his oxygen supply assured the Hunter began to search for them. He could, of course, have sent enough oE his own material through the shark's skin to const rue I an organ of vision, but he might not be able to avoid disturbing the creature by such an act. Ready-made lenses - were to be preferred; so he began seeking them. He was interrupted very quickly. The crash had taken place., as he bad deduced* rather close to land ; the encounter with the shark had occurred in relatively shallow water, and had taken only a" short time. Sharks are not fond of disturbance; it is hard to understand why this one had been so close to the surf. Dur- ing the monster's struggle with the Hunter, it had drifted or been carried still closer to the beach ; and with its attention no longer taken up by the intruder, it turned all its energies toward getting into deep water. This the Hunter did not know, having no sensory contact with the outer world. But once the shark began to exert itself, after the 12 Hunter's establishment of. an. oxy- gen-theft system, things, began to happen. The breathing system of a fish operates under a disadvantage, since the oxygen in the water is never at a very high concentration ; and a water-breathing creature never has much oxygen to spare. Little as the Hunter was taking, in was enough to eut down the shark's physical powers markedly ; at the same time, its blood-oxygen content decreased, and the Hunter almost unconsciously increased his drain on the system. It was a vicious circle that could have but one ending. The Hunter realized what was happening before the shark actually died, but he could not cut down his own use of the precious gas any further. He could have left the shark, of course, hut that would have left him almost completely help- less and adrift in the sea. Also, he had long since realized perfectly the sh ark's position on the evolutionary scale, and felt no particular com- punction in sacrificing a savage carnivore to his own needs. The fact that the creature's efforts were probably being made against the waves, and that these were almost certainly carrying him where he wanted most to go, influenced his decision. The shark took a long time ac- tually to die, though it became help- less very quickly. Once it had ceased to struggle, the Hunter con- tinued the search for its eyes, and eventually found them. He de- posited a film of himself around and ASTOUNDING SCIENCE -SECTION between their retinal cells, in antici- pation of the time: when there would be enough light for him to see by* and then let nature take its course. The breakers were sounding much more loudly by this time, and he realized that the assumption that he was drifting shoreward had been justified. The shark was drifting toward the surface as well* and a sickening up-and-down motion he- came perceptible as it entered the sphere of influence of the waves. Once or twice it actually broke the surface, and I lie Hunter, who had oxygen-seeking appendants already extended from the great fish's gill Openings h profited thereby. The rolling, tossing and pounding suffered by the shark when its body finally entered the breakers was of such a nature that the Hunter was a little surprised at the small amount of resultant damage. Even he did not fully appreciate the enormous toughness of that semi- vertebrate structure. At l£st, after many min- utes of forward-and-back motion in the shallows, they grounded ; and though the backwash of the waves strove to drag the great body back to the sea, it was never quite suc- cessful. A ftcr a long time, the num- ber of waves breaking over them began gradually to decrease, and the Hunter suspected that the storm was diminishing in intensity. In actuality;, the tide bad turned; but the result was the same. By the time the combination of approaching dawn and thinning needle storm clouds provided enough light for the Hunter to see a little of his surroundings T his late host was thoroughly stranded , several yards above the reach of the heaviest waves, and well entangled in a mass of seaweed. The shark's eyes re- fused to focus on their own retinas out of the water, but the Hunter found a focal surface within the eyeball and built a retina of his own on it. He was also forced to modify certain imperfections in the lenses with more of his own body sub- stance; but at last he was able to see about him with satisfactory clarity, yet without exposing him- self. * There were rifts in the storm clouds now + through which a few of the brighter stars were visible against the fray background of ap- proaching dawu. Slowly these breaks grew larger, and by the time the sun appeared above the horizon the sky wiis almost clear, though the wind still blew fiercely. His vantage point was not ideal, but he was able to make out a good deal of his surroundings. In one direction the beach extended a short distance to a line of tall, slender trees t crowned by feathery tufts of leaves. He could not sec beyond these, his vantage point being too low, though they were not them- selves thickly enough set to obstruct the view* In the opposite direction was more debris- strewn beach, with the roar of the surf sounding be- yond it. The Hunter could not actually sec the ocean, but its di ree- ls lion was obvious. To the rig lit as one looked at the trees was a hotly of water; and for a moment the Hunter was a trifle surprised, for it showed 110 sign of the huge waves that were still pounding behind him. Then he realized it must be a small pool, filled by the storm, but now emptying back into the sea so that the large waves con Id not enter. This, he realized, was probably the reason he had stranded so easily ; his shark had been washed into this pool, and left behind by its diminish- ing 1 waters. Several times he heard raucous screeching sounds and saw birds overhead. This pleased him greatly ; evidently there were higher forms of life than fishes on the planet, and there *vas some hope of obtaining a more suitable host. An intelligent one w on Id be best, since it would ordinarily be best able to protect it- self and him and was also likely to travel more widely, thus facilitating the now necessary search for the pilot of the other ship ; but he rea- lized that there might be some diffi- culty in obtaining access to the body of an intelligent being who was not accustomed to the idea of symbiosis. \l\ that, however, would have to wait on chance. Kven if there were intelligent beings on the planet, they mighty never come to this spot. It .would be best to wait, several days if need be, to find out just what forms of life frequented the lo- cality ; and then make plans to m- vade the one tliat seemed best suited to his purposes. Time was probably not vital ; it was as certain as any- thing could be that his quarry was no more able to leave the planet than was the Hunter himself* and while he remained on it the search would be long and arduous. Time spent in careful preparation would undoubt- edly pay dividends. He waited, therefore, while the sun rose higher in the sky and the wind gradually died down to a mild . breeze. It became quite warm ; and a growing -awareness of chemical change going on around him caused him to realize that, if a sense of smell were common equipment among the life forms of this world, he was certain to have visitors be- fore long. He could have halted the process of decay by the simple ex- pedient of consuming the bacteria causing it : but he had no objection to company. 1 His first visitors were gulls. One by one they descended, attracted by sight or smell or both, and began tearing at the sheltering carcass. The Hunter withdrew himself to the lower portions of the body., and made no attempt to drive them away — even when they pounced on the eyes of the great fish and speedily deprived him of visual eon- tact with the outside world. Tf other life forms came, he would know it anyway ; and if tbey didn't, it was just as well to have the gulls there. The greedy birds remained undis- turbed until midafteruoori. They did not make too much progress in disposing nf the shark ; the tough ASTOUKDIKfl SOI KNOE -FICTION skin defied their beaks in most places. They were persistent,, how- ever, and when they Suddenly took wing and departed altogether it was evident to the Hunter that there must be something of interest in the neighborhood. He hastily extruded enough tissue from one of the gill slits to make an eye, and looked cautiously about him. He saw why the gulls had left. From the tlireetion of the trees a number nf much larger creatures were approaching;. They were bi- peds, and the Hunter estimated, with easy skill, that the largest must weigh fully a hundred aud twenty pounds — which meant that the ad- dition of his own" mass was unlikely to prove a set' ions burden. Much closer to him was a quadruped, run- ning rapidly toward the dead shark arsd uttering a;t apparently endless string of sharp yelping sounds. The Hunter placed it at about fifty pqunds, and reserved the informa- tion for future use* if it became necessary . The four bipeds were running as welt, but not nearly sd rapidly. As they approached, the bidden watcher , examined them carefully, and was greatly pleased at what he saw. They could travel with respectable ' speed; then- skulls gave promise of considerable intelligence, if one coukl safely assume that they were the receptacles of brains; their skins were almost entirely unprotected giv- ing promise of relatively easy access through the pores. As they slowed up and stopped beside the hamtner- XEEDLE head's body, another indication of intelligence appeared— they gave utterance to articulate sounds that could only represent speech. The Hunter was delighted; he had not flared hope lor such an ideal host so quickly. Of course, there were si ill prob- lems to be solved. They were prob- ably not used to symbiosis, Tor the Hunter was quite sure he had never encountered a member of this race before, and be was familiar with alf those with whom his people nor- mally associated. Therefore, as was id most certain that the idea would be repulsive to them, unless full ex-" 1 planations could be made before any other contact were attempted. They would almost certainly take it for granted that a mass of unfamiliar jelly trying to cling to one of. them was an inimical creature. Subtlety would have to be employed. The four bipeds reclined looking down at the shark and conversing fur only a few minutes; then they walked off up the beach a little dis- tance. Somehow, the Hunter got a vague impression from their atti- tudes that they considered the neigh- borhood unpleasant. The quadruped remained a little longer, examining the carcass closely; but it apparently failed to notice the rather oddly placed eye that was f olio wing its movements with so much interest* A call from the direction in which the others had gone finally attracted its attention, and as he watched it bound off, the Hunter saw with 16 some surprise that the others had entered the water find were swim- ming around with considerable facility. He marked dewn the fact as another point in their favor — he had seen no trace of gills, and as air breathers they must have had a cou- s\ durable margin of o^y^m-intake capacity above their minimal needs , to remain under water as long as he saw one of them do. Then He rea- lized that there was another good -point ; he could probably approach them much more easily in the water. It was evident from their behavior that they could not see too clearly below the surface — they invariably raised their heads out of the water to orient themselves, and did this ivith considerable frequency. The quadruped was evidently no cause for worry ; it kept its head and eyes above the surface at all times. The thought led tu instant action. A threadlike pseudopod groped rapidly toward the pool, an inch or two under the sand. The eye was kept in operation until most of the jelly like body had crossed the four- yard gap ; then another was formed at the water's edge, and the Hunter drew the rest of his body into a compact mass just below iL The operation had taken several minutes; winding among sand-grains had been an' annoyingly devious method of approach, The water was quite clear, so it was not necessary to keep an eye above the surface to direct the stalk. The mass of jelly was quickly molded into an elongated, nshlike shape with an eye in front, and the Hunter swatu toward the boys with considerable speed, In one way, lie reflected;, it was really easier to see tinder water ; he could use an air lens, held in place by a very thin film of flesh, and this was much more transparent. His own sub- stance did not make a very satisfac- tory lens — it was too opaque. He had planned to swim right up to one of the boys, hoping his ap- proach won Id not be noticed and that the swirl of water or possibly con- tact with one of the - other boys* would mask his own efforts. Half- way there, however, he found w r hat seemed a be tier way to approach unnoticed. It was a large jellyfish, bobbing along after the manner of its kind ; and with his attention drawn to the creature^ the Hunter suddenly realized that there were quite a number of them in the vicinity. Evidently the bipeds did not consider them dangerous, Or they would not be swimming at this place. Accordingly, he changed his form and method of locomotion to agree with those characteristics of the Medusae, and con tinned' his ap- proach. His color was slightly off, but he felt that this fact was less likely to attract notice than was a radically wrong sliape. He may have been right, for he got almost up to one of the boys without ex- citing alarm. They were fairly close together at the moment, splash- ing anil ducking each other, and he had high hopes of making contact needle ■ — rhe did, in fact, with 'a cautiously extended tentacle, discover that the varicolored integument covering a portion of their bodies was an arti- ficial fabric; but before he could do any more, the subject of his investi- gations slid to one side and moved several feet away. He gave no sign of alarm, however, and the Hunter at once resumed his approach. It ended in precisely the same fashion, except that this time he did not get quite so close. He tried each of the other boys in turn, with the same annoying near-success. Then, puzzled by a phenomenon which seemed to be ex- ceeding the generous limits of the laws of chance, he drifted a short distance away and watched, trying to learn the reason for it. Within five minutes he realized that, while the creatures apparently had no serious fear of jellyfish, they most sedulously avoided actual contact with them. He had chosen an un- fortunate camouflage. Robert Kinnaird avoided jellyfish almost without conscious thought. He had learned to swim at the age of five, and in that and each of the nine subsequent years of his life had had enough, painful experience with the things to assure his avoid- ing their ■ company. He had been fully occupied in ducking one of his companions when the Hunter had First touched him, and had dodged hastily when lie saw the blob of jelly in the water beside him ; but the only red emotion he felt on the IT subject was relief at escaping con- tact with the stinging tentacle*. He had forgotten the encounter imme- diately, but his attention had been sufficiently diffused by it to prevent the thing's again approaching so closely. About the time the Hunter real- ized what was wrong, the boys grew tired of swimming, and retired r to the beadta He watched them go in mounting annoyance, and con- tinued to watch as they ran hack and forth along the sand playing some obscure game. Were the mad creatures never still? How in the Calaxy could he ever come into contact with such externally active beings? He watched, and pondered. Ashore, once the salt had dried on their sun-browned hides, the boys began to quiet down, and cast ex- pectant glances toward the grove of coconut palms that hid the center of the island from their direct view. One of them seated himself, facing the ocean, and suddenly spoke. **Bob ( when are your folks coming with the grub?" Robert Kinnaird flung himself face downward in the sunlight before replying. " 'Bout four or half past, Mother said. Don't you ever think of any- thing but eating ? IJ The other mum- bled an inarticulate reply t and subsided flat on his back, gazing up into the cloudless blue sky. An- other of the boys took up the con- versational ball. "It's tough, you having to go tomorrow," he said, "I kind of -wish I was going with you, though, is t I haven't been in the States since my folks came out here. I was only a kid then," he added serenely, "It's not so bad/' returned J3ob slowly. "There are a lot of good fellows at the school, and there's skating and skiing in the winter, that you don't get here. Anyway, I'll be back next summer, 1 ' The talk died down, and the boys basked in the hot sunshine, as they waited for Mrs, Kinnaird and the eatables for the farewell picnic. Bob was closest to the water, lying stretched in the full sunshine — the others had sought the rather . thin shade of the nearest palms. He was already well tanned, but wanted to get the last possible bit of benefit from tire tropical sun, which he. would miss for the next ten months. It was hot, and he had just spent an active half hour, and there was nothing to keep him awake— ■ The Hunter was still "watching, eagerly now. Were the peripatetic things really settling down at last? It looked like it^ The four bipeds were sprawled on the sand in va- rious positions, which they presum- ably found comfortable ; the other animal came as he watched and set- tled down beside one of them, letting its head rest on its forelegs. The conversation, which had been almost incessant up to this point, ceased; and the amorphous watcher decided- to take a chance. He moved rapidly to the edge of the pool. The nearest of the boys was nearly ten yards from the water, AKTOl-^rnS'O SCIEWCB-PICTION It would not be possible to maintain a natch from the Hunter's present position, and at the same time send himsel f under the sand to a point below the motionless body ; and he must keep his goal in sight. Onqe more camouflage seemed called for; and once more, the ever-present jellyfish seemed to fill the .want. There were a number of them lying stranded on the sand, motionless; pei' haps, if he moved slowly and emulated their shape, the Hunter could escape notice until lie was close enough for an underground attack. He may have been excessively cautious/ since none of the creatures was facing his way and all were nearly if not entirely asleep; but caution is never wasted, and the Hunter never regretted the twenty minutes he took getting from the. water's edge to a point three yards from Robert Kinnaird. That, judg- ing by the previous experience* was close to enough. Had anyone been watching the large jellyfish lying apparently help- less a few feet from the boy at that instant, he might have noticed a peculiar dimunition in its size. The shrinking itself was not remarkable; it is the inevitable fate of a jelly- fish on a hot beach; but the more orthodox Medusae merely grow thinner until only a 'cobwebby skele- ton remains, while this specimen dwindled not only in thickness but in diameter, and there were no remains whatever. Until it had almost com- pletely gone, of course, there was an NEEDLE odd little lump or knot right in the center which preserved its size and shape while the body around it dwindled; but this a^ last went too, and no trace except a slight de- pression remained on the sand — a depression which, that careful ob- server might have noticed, extended all the way from the water's edge. The Hunter kept the eye in use during most of the underground search. His {juestiug appendage at last reached sand that was more closely compacted than usual and, advancing now very caution sly t fi- nally, encountered what could only be living flesh. Robert's toes had betome rather deeply buried in the sand T as he was lying on his stomach ; and the Hunter found that he could operate without emerging at all to the surface. With that fact estab- lished, he dissolved the eye, and drew the last of bis mass out of sight beloiv the sand— with consider- able relief, as the unobstructed sun- light affected his unprotected tissues pain fully. He did not attempt to penetrate until his whole body was .wrapped about the half -buried foot. He sur- rounded the limb with extreme care, and finally was in direct contact with the skin over an area of several square inches. Then he commenced interstition, letting the submicro- scopic cells of his flesh slide through pores, between cells, under arid around the toenails — into all the thousands of openings that lay un- guarded . in this, to his way of thinking, singularly coarse organism. The boy was sound asleep, and remained so. The alien organism ilowed smoothly along the bones and tendons in his foot and ankle ; up within the muscle sheaths of calf and thigh; switched to the outer wall of the femora] artery and the tubelets within the structure of the thigh bones; around points, and along still other blood vessels. It filtered through the peritoneum without causing the least damage; and slowly the whole four pounds of matter accumulated in the ab- dominal cavity, not only without liarming the boy in the least but without even disturbing his slumber. And there, for a few minutes, the Hunter rested. Bob was aroused, like the other hoys, by his mother 1 s voice. She had come silently, laid a blanket in the shade, and spread the eatables on it before speaking: and her first words were the ancient, "Come and get it," which have stimulated boys and men to sometimes startling ac- tivity for a good many decades. She would not slay to help them eat it,, though cordially and sincerely pressed to do so by the boys, with whom she was popular, but went back through the palm grove to the road that led to their home. M Try to be back by sundown/* she called to Bob over her shoulder as she reached the trees, "you still have to pack, and you'll have to be up early in the morning/' Bob nodded, with his mouth full, and turned back to the food-laden blanket. After disposing of that which lay before them'j the boys sat and talked for the standard hour-after-eating; then they returned to the water, where they indulged further ill games of violence; and at last, realizing that the abrupt tropical night would soon be upon them, they gathered up the blanket and started for the road and their re- spective dwellings. They were rather silent* with the awkwardness natural to their age when faced by a situation which adults would treat either emotionally or with studied easualness, The farewells, as they passed their • respective dwellings, were brief, and accompanied by reiterated and reciprocated promises to "write as soon as you can," Bob, proceeding at last alone to his own house, felt the customary mixture of regret and pleasurable anticipation which he had come to associate with these occasion s< By the time he reached home, the latter feeling had gained the ascendance, and he was looking forward with considerable eagerness to meeting again the school friends be had not seen for over two months. He was whistling cheerfully as he entered the house. The packing, done with the tactful assistance of his mother, was quickly completed, and by nine o'clock he was in bed and asleep. He himself considered the hour rather early, but he had learned the value of obedience at certain times very early in life. ASTOUNDING &CT E*f OH -F I CTlOM All this tune the Hunter had re- mained quiescent. Having entered from air rather than water, he had been able to bring quite a supply of oxygen with him ; and it was some hours before he found it needful to draw on his host for more. He would have liiced to remain inactive for an entire day, til order to learn more about the cycle of physiological processes which this organism un- doubtedly performed differently fro hi any other lie had ever used; but that was not possible. Like any other life fornix he used some energy in living, no matter how quietly; and at last he found it necessary to commence exploration. For some time he had been aware that his ho^t was asleep: but this in no way decreased his caution. He rein ained for the time being below the diaphragm, not wishing to disturb the heart which he could feel beating just above it, and quickly located a very large artery which offered no more resistance to his penetration than had any other part of the human organism thus far. He found to his intense satisfaction that he could draw sufficient oxygen for his needs from this vessel without seriously diminishing the total quantity that passed through it. He checked this very carefully; his whole attitude in the present ex- ploration was utterly different from that which had characterized his actions within the shark ; for he had already tome to look upon Robert in the light of a permanent com- panion during his stay on the earth, NEEDLE and his actions .were ruled by a law of his kinrl so ancient and so rigid as to assume almost the proportions of an instinct. Do nothing that can harm your host. It was a law as binding as the Hippocratic oath or a marriage vow. To the majority of the Hun- ter's kind, even the desire to break it never existed, since they lived on terms of the warmest friendship with the intelligent metazoans who harbored their formless bodies ; and the few individuals who proved to be exceptions to this rule were looked on by their fellows with the liveliest horror and detestation. It was such a being whom the Hunter had been pursuing at the time of his crash on Karth ; and that being must still be found, to preserve a defense- less race from the inroads of the irresponsible creature. Do nothing that host. From the instant of the Hunter's arrival, the swarming leu- cocytes in the boy's healthy blood' had been up in arms. He had avoided the most serious contact with them up to now by avoiding the interiors of blood vessels, though there were enough of them wander- ing free in the lymphatics and con- nective tissue to be a nuisance. His hotly cells were not immune to their powers of absorption, and only by keeping any part exposed to their attack iti constant evasive motion had he been able to avoid; serious damage to himself. He knew that this could not go on indefinitely ; for one thing, he must occasionally si direct hia attention to other matters, and for another, the continuation of such a misunderstanding, whether he continued evasive action or began to fight back, would mean an in- crease in white Mood cell concen^ tration and most probably illness of some sort to 'the host. Therefore, the leucocytes must be paciEicd. His race had f of course, acquired a gen- eral technique for solving this prob- lem long; since; but care had to be taken in individual cases— particu- larly unfamiliar ones, lly a trial- and- error process, carried out with as much speed as was practical, the Hunter determined the nature of the chemical clues by which the white cells differentiated invading organ- isms from legitimate members of the human body ; and after pro- longed and still extremely careful effort, he exposed every one of his own cells to sources of the appro- priate chemicals in the blood stream, A few molecules of the desired sub- stance were adsorbed on the surface of each of the cells, and this proved, to Ins relief, to be sufficient, The leucocytes ceased to bother him, and he could use the larger blood vessels safely as avenues of exploration for his questing pseudopodia. Do nothing that can harm ycxtr host. He needed food as well as oxygen. There was not a single form of tissue around him which lie could not have consumed with relish ; but selection must obviously he practiced* There were certainly intruding organisms in this body — ■ besides himself — and they were the £2 natural food source ; for by consum- ing them he would be eliminating their menace to his host h and thereby helping earn his keep. Identifying them would be easy ; anything a leucocyte attacked Was legitimate prey for him, Ii was improbable, of course, that this source of food would prove adequate for, long, small as his needs were ; it would soon he necessary to tap Lbe alimen- tary canal as well. That, however* would be simple and would in no way harm the boy. His appetite might be increased very slightly over a long period, but a little additional chewing was no cause for alarm. For many hours the cautious. ex- ploration and adjustment continued. The 1 tunter felt hi.s host awaken and resume activity, but he made as yet no etfort to look outside. Me had one problem which must be carefully and accurately solved ; and, although his avoiding thousands of leucocytes at once, as he had dotie for a time, may seeni evidence to the contrary, his powers of attention were limited. Filaments of his mass, far finer than human neurons, gradually formed an all-inclusive network throughout Bob's body from head to toe ; and through those threads the Hunter gradually came to know the purpose and customary uses of every muscle, gland, and sense organ in that body. Throughout this period most of his mass remained in the abdominal cavity; and it was fully seventy-two hours after his first intrusion that the alien felt secure enough in his ASTOUNDING SCIENCE-FICTION. position to pay attention ortce more to outside affairs. As he had done with the sharks he began to Ji.ll the spaces between the hoy's retina] cells with his own body substance. He was actually able to make better use of the eyes than could hob himself, for the human eye sees in ma^hi-ium detail only the objects whose images fall within an area of retina scarcely a millimeter across; the Hunter could use the whole area on which the lens focused with reasonable sharp- ness* which was considerably greater. fn consequence, he could examine objects with Bob's eyes at whielv the boy was not looking di- rectly. This was a help, since many of the things in which the hidden searcher was most interested were too commonplace to the hitman being to attract more than momentary at- tention. The Hunter could hear dimly even within the human body ; but he found it helpf ul to establish physical contact with the bones of the middle ear. Thus, hearing as well and see- ing better than bis host, he felt ready to investigate the planet on which chance had marooned him and his quarry. He began to look and listen. There was no further reason for delay in prosecuting his mission to track down and destroy the other member of his race now free on the planet. He had not, up to this moment, really appreciated the magnitude of the task. He had not considered particularly the fact that the other N E IS IlLE might be as well" hidden as was he himself, that the planet represented an enormous search area however small it might be as planets went, and that even a very small popula- tion of possible hosts meant a most appalling amount of search work even if he could recognise the presence of the alien at sight — which he most certainly could not. All these facts were brought to his attention with shocking sudden- ness as he took his first clear look around since meelin^ Robert Kin- naird. The picture that fell on their common retinas was that of the in- terior of a cylindrical object that vaguely suggested his own space- ship, filled with several rows of seats, most of them occupied by other human beings. Beside him was a window, through which Uob was looking; at the moment; and the suspicion that had entered the Hunter's mind at sight of the ^ ^ e- bicle was instantly confirmed by the view through that window. They were on board an aircraft, traveling at a considerable altitude with a. sjseed and in a direction which the Hunter was in no position to guess. He bad hoped at least to begin his search in a region of the crash of the two spaceships ; now he realised he would be extremely fortunate even to find that region. The flight lasted for several hours, and the Hunter quickly gave up the attempt to memorize landmarks -over which they passed. One or two of them did stick in his mind, and might give a rough clue to direction 2* if he could ever identify them later ; but lie put little trust in this cha.nct:. He must keep track oi time rather than position* and when he was, more familiar with human way$ t find out where his host had been at the time of his own intrusion. The view was interest ifigt how- ever. It was a beautiful planet, even from his alien viewpoint ; mountains, and plains, rivers antl lakes, forests and prairies were all visible at va- rioxis times, now clearly through a crystal atmosphere and now in glimpses between billowing clouds of .water vapor/ The machine he rode occupied some of his attention, as well ; from Robert's window he could see a portion of a metal wing, hearing at least one attachment which evidently contained art engine, as a rapidly rotating airfoil xvas via- i bl e ahead o fit . 1 \ y sy m n letry , there must be at least two and possibly four of these engines, the Hunter realized ; and the machine, as a whole, suggested a very considerable degree of mechanical advancement ,on the part of this race. If this were the case* it might be worth while to attempt direct communi cation with the individual serving as his host. That, however, must await further developments. Eventually the machine began to descend gradually. The Hunter could not see directly ahead, and it happened that they entered a solid cloud layer almost immediately, so he was unable to get any idea of their destination until just before 24: the lauding ; but at that moment, as they broke out of the lower fringe iof clouds* they made a broad turn over a large seaport city. The Hunter saw a great harbor, with docks and shipping galore^ and build- ings that reached as far as he could see ; then the faint drone of the engines that penetrated the air- plane's cabin increased in pitch, a huge wheel appeared below the visi- ble nacelle, and the big machine glided downwards to contact with a faint jar a broad, hard -surfaced runway located on a point of land across the harbor from the city's largest buildings. As Robert disembarked, he glanced back at the airplane: so the Hunter was able to form a better estimate of its size and construction details. He had no idea of the power developed by the four huge engines, and consequently could form no estimate of the machine's speed ; but he could see the quivering above the nacelles that told of hot metal within, and realized that at Teas I they were not the phoenix con- verters most familiar to his own civilization. Whatever they were T it had already become evident that the craft could put a very respect- able traction of the planet's circum- ference behind it without descending for fuel, A f ler alighting from the airplane, the; boy entered a large building nearby, which was crowded with other human beings, and waited for a time. Presently he made his way through the throng to a broad court- ASTOCNDma SCIENCE- FICTION ter, and received his baggage, which be bore off to the other end of the building where a number oi ground vehicles were standing. He boarded one of these, which remained where it was until nearly full of passen- gers, and then moved ofT toward tlie denser portion of the city. During the next several hours, the hoy's actions were largely mean- ingless to his hidden guest^ He changed buses several times, wan- dered about the city on foot far a while with no apparent purpose, and attended a movie. Fortunately the Hunter's vision persistence Involved a time lapse of approximately the same duration as the human retina, so he also saw moving pictures NEEDLE! rather than discrete projections. It was still daylight when they left the theater, and the Hunter decided that it must have been fairly early in the morning when he had first estal> lished visual connection with the outside world. Now his host was walking with what seemed lo he a purpose. They returned to a building where they had been earlier, where Robert once more collected his bags ; thcn T after the ticket- window preliminaries which the Hunter was beginning to recognize „as customary before a ride, they lx>arded still another bus. This was decidedly the tangest single ride they had taken since leaving the airplane; they were well outside 25 the city, having passed through several smaller collections of build- ings> and I he sun was almost flown when the bus left them at the road- side. A smaller road led off up a gentle slope* ant! at the top of this slope was a large, sprawling building— or group of buildings; the Hunter was not Sure which, Robert Kin- naird picked up his bags and walked up the hill toward the structure, and the alien began to hope that the journey had ended for the time being at least. He was right, as it turned out, To Robert, the return to school, assignment to a room, and meeting with old acquaintances was by now a familiar story ; but to the Hunter every activity and everything seen and heard was of absorbing interest lie realized that most of it could have no direct application to his mission, but that was no reason to ignore possible sources of knowl- edge. He was a being of omniv- orous interests, and was beginning to realize that direct communication witb the human race was going to be necessary. That meant under- standing them and their customs, preparatory to learning their spoken and written languages. So he looked and listened almost feverishly, as Bob went to his room, unpacked, and then wandered about the school meeting friends from former terms. Most particularly he sought to connect spoken words with their meanings; and at first he had a good deal of trouble s for the * conversations were mostly about events of the past two mouths va- cation f so that the words usually lacked visible referents. He did learn a few personal names this first evening, among them that of his host , and decided that he could ac- quire an understanding of the spoken language with little loss of time. He spent Robert's sleeping hours in organizing the few words he had learned,, and developing a definitely planned campaign for learning more as rapidly as possible. It may seem odd that one who was so completely unable to control his own goings and comings should dream of planning anything; but the extra effective width of his vision angle must be rememhered. He was to some ex- tent able to determine what be saw, and therefore felt that he should decide what to look for. It would have been so much sim- pler if he could control his liost's movements in some way, or interpret or influence the multitudinous re- actions that went on in his nervous system. He had controlled the perit, of course , but not directly ; the little creature had been trained to respond to twinges given mechanically to the appropriate muscles, a$ a horse learns to respond to the re ins r The Hunter's kind used the per its to per- form actions which their 1 own scmi- liquid bodies lacked the physical strength to do^ and which were too delicate for their intelligent ho-sts to perform — or which must be per- ASTouNr>i*ra jscie> t cb-fict(on not reach, such as the interior of the tiny racer that had brought the Hunter to Earth, But Robert Kinnatrd was not a per it, and could not be treated as one. It was necessary to appeal to his mind, not Ins body. The Hunter had come to about the best possible place for that purpose, though he did not yet ktLQjw it. Classes began the next day. Their purpose was at once obvious to the unlisted pupil, though the subjects were frequently obscure- Ktnnaird's courses included, among other sub- jects, English, physics, I*atm, and French ; and of these font, physics proved most helpful to the Hunter in learning the English language. After witnessing a demonstrated experiment in elementary mechanics and comparing it with the explana- tory diagrams -produced on the board by the instructor, he was able to interpret most of the diagrams in Bob's textbook — he had learned the relatively few and simple drawing conventions. Slowly, helped by other experiments performed either by the instructor or Bob himself, many of the printed words became intelligible. Un fortunately for the Hunter's needs. Bob was a suffi- ciently advanced reader to have long outgrown subvocaKzation, so at was some time before the Hunter could determine the relationship between written and spoken words; but one day a heavily- lettered diagram was explained vocally by the teacher, and '.FEE OLE! a few days the Hunter was able to picture the written form of any new word he heard — allowing, of course, for the spelling: irregularities which are a curse of the English tongue. By the beginning of November, two months after the opening of the school, the alien's vocabulary had about the size though not the content of an intelligent ten -year-old 1 5. He had a rather excessive store oi scientific terms, and many blanks where less specialized words should have been," Also, the meaning he attached to such words as "work" was the purely physical one — jiofc the more inclusive meaning con- veyed to the mind oE the average layman. He thought it meant "force times distance" and only that Ry this time, however, he had reached a point where tenth-grade English had some meaning to him ; and Robert's literature assignments began to be of some help — new words were frequently intelligible from context, ignorant as the Hunter was of human customs. About the beginning of Decem- ber, a slight interruption occurred to the unregistered pupil s education, Robert Kinnaird had been a member of the school's footbalt team during tlit: fall. The Hunter, with his in- tense interest in the health of his host, somewhat disapproved of this* though he understood the need o£ any muscled animal for exercise, The final game of the school season was played on Thanksgiving Day, and when the Hunter realized ft mas- ■ •• the final game, no one gave more thanks than he. But he. rejoiced too soon. Bob, reconstructing one of the more ex- citing moments of the game .to prove his point in an argument, slipped hi some very greasy mud and twisted an ankle severely enough to put him in hed for several days. The Hunter was not' annoyed so much at the enforced absence From classes, since the boy did a certain amount of reading even tn the infirmary, but at his own failure to prevent the accident. Had ho realized the danger even two or three seconds in adrance > he could have supplied con- siderable reinforcement to the ten- dons throughout the body.; but once the sprain had occurred, he could do practically nothing to speed up its healing — the danger of .infection was already nil without his help. The incident at least recalled him to some of the duties of a syntbiote. From then on, the web of alien cells surrounding Uob*s bones and muscle sheaths was ready at an instant's notice to tighten to the limits of the Hunter's physical power. This was not very great, but it helped salve the intruder's conscience- Back in class, host and symbiote both worked harder than usual to make up for lost time. By now, the Hunter felt quite at home in the English language* understanding both what he heard and read with very satisfactory proficiency. Though vastly interested in this task for its own sake, lie had never forgotten his primary mission. He had learned quite early that he was in a school, and deduced from this that his host was not an adult; he knew the names of the city T state, and even the country in which the school was located ; and he had never ceased from striving to learn the name and location relative to his present position of the place where the boy had spent his last vacation. He wasted no time in vituperating the luck which had led him to select as host probably the only individual iti a large group who was going to leave the neighborhood □£ the crash so soon and travel so far; it was a misfortune, be would readily have admitted* but there was no point in worrying about what was past. He did learn, from a chance re- mark passed between Bob and one of his friends, that the place was an island. That wonld he some help, anyway ; even though the fugitive was most probably no longer there, he or rather the being he took as host must have used a vehicle of some sort for his departure; the Hunter remembered his attempt to use the shark too vividly to suppose that the other could escape in a fish, and he had never heard of a warm- blooded air breather that lived in the water. Seals and whales had never come up in Bob's conversation, at least not since the Hunter had been able to understand it. If a vehicle had been used, it could probably be traced— more easily than a free organism, at any A5T0ttKI>IXG SCIENCE-FICTION ' rate. The Hunter was thankful for small blessings. It remained to learn the location of the island. Bob received fre- quent letters from his parents ; but for some time these did not strike the Hunter as chics, partly because he had a good deal of trouble read- ing script and partly because he did not know the relationship to the boy of the senders of the letters. He had no scruples about reading Bob*s mail, of course ; he simply found it difficult, Robert did write to his parents, at somewhat irregular inter- vals; but he had other correspon- dents as well, and it was not until nearly the end of January that the Hunter found that by far the greater number of his letters were going to and coming from one par- ticular address. This discovery was eased by the boy's receipt of a typewriter as a Christmas present ; this greatly fa- cilitated the Hunter's reading of the outgoing mail, and be quickly learned that the letters went to Mr. and Mrs, Arthur Kinnaird, He knew from his reading of the custom of family names descending from fa- ther to son; and the deduction seemed defensible that the boy would spend his vacation with his parent s. If this were true, be had the name of the island. It was now simply a question of locating it — and getting there as soon as possible. He realized that Robert would probably be going hack for bis next vacation, but that would give the fugitive five more months to cover NEEDLE his tracks ; and he had had five al- ready* To anyone but the Hunter, the search would already have seemed utterly hopeless. There was a large globular map of the planet in the school library, and almost a plethora of flat maps and charts on walls and in the vari- otis books in the school. Robert's persistent failure to bestow more than a passing glance al any of them quickly grew maddening ; and the Hunter began to be tempted to try forcing his eyes. It was a bad idea* and no one knew it better than he; but he possessed emotions as power- ful as those of any human being, and experienced fully as much difficulty at times in keeping them in check* \ He controlled himself, however — partially. He successfully re- sisted the temptation to tamper with Robert's sclerotic muscles ; but grad- ually there welled up within his being: a growing conviction that direct communication with his host must be attempted if any further progress were to be made on his mission. The idea had, of course, been in the back of his mind from the time he had first entered the boy's body. At that time he had hoped the necessity would not present itself N for a number of grave problems were in- volved ; but now he felt convinced that there was no alternative He might ride Robert Kinnaird's body for the rest of the human being's life — which, with the hidden visitor* would probably be long — without ever approaching a place where clues 29 to the whereabouts - o f his quarry could be obtained. With the active and intelligent assistance of the host, however; with his knowledge of Earth and its people confined with the Hunter's familiarity with the ways of his own kind ; with an able and healthy body willing to assist the alien instead of bearing hhn willy-nilly o%'cr the face of the globe — there could be no comparison of the relative chances. Communica- tion was essentia] ; and now, the means was at hand. With the beings who normally served as hosts to the Hunter's kind, conversation eventually reached a high level of speed and comprehensiveness^ It must be re- membered that the union took place with the host's full knowledge and consent ^ and therefore almost any- thing; the symhiote did to affect the former's sense organs could be, and .was interpreted as a means of com- munication. It was immeasurably more complex than vocal speech ; twinges at any and all muscles^ shadow-images built directly^ on the retina of an eye t motions of the fur with whi^h the Allanese were thickly covered- — for the most part, the meaning of any of the "signs" was self-evident ; and after a few years' companionship, conversation was al-' most telepathic in lucidity and speed between host and indweller. Even with this background lack- ing for the second party, however, the Hunter felt that he could make himself known to and understood by hie human host. Though the latter had no inkling of his exist- ence, and would probably have suf- fered a severe emotional shock had the fact been proven to' him, the Hunter suddenly realized the cir- cumstance had played into his hands. There was the protective net he had constructed over Bob's muscles ; and there was the typewriter. The net cou]d be contracted, Uke the muscles it covered — rthough with far less pow r er. If a time were chosen when Bob was sitting at the typewriter without particular plans of his own, it might be possible for the Hunter to strike a few keys in his own intere&t. The chances were really not too good ; they depended upon l-iob h s reaction when he found his fingers acting without orders. Two nights after the Hunter had made his decision to act P the oppor- tunity occurred. It was a Saturday evening, and tlie school had won a hockey game that afternoon. This proved a sufficient stimulus to cause Kob to write to his parents. He went to his room — the other occu- pant was not in at the time — got out the typewriter, and pounded off a description of the day's events with very fair speed and accuracy. At no time did he relax sufficiently to make an opportunity for control, in the Hunter's opinion; but with the letter finished and sealed, Robert suddenly remembered a composition which his English teacher had de- creed should be turned" in the follow- ing Monday. It was as foreign to his nature as to that of most other ASTOUNDlJie S C I HNCE -FICTION schoolboys to work so far in ad" vancc; but the typewriter was out, and the hockey game offered itself as a subject which fie could treat ■with sumc enthusiasm. He inserted a fresh piece of paper in the ma- chine, rapidly typed the standard heading of title, pupil's name, and date ; then he paused to think. He had just written about this subject, but the readers of the first composi- tion would be somewhat less critical of form, spelling and grammar til an would his English teacher. A little care must be exercised. The Hunter neither knew nor cared what Robert was planning to write. The fact that blazed itself on the amorphous tissue that in some obscure fashion acted as his brain was that they were sitting in front of a typewriter containing a blank piece of paper, with fingers resting on the keyboard and every muscle controlling those ten digits com- pletely relaxed. The alien wasted no time whatever. He had long since decided on the wording of the first message- Its first letter lay directly under the boy's left middle finger ; and the net of alien flesh about the appropriate muscle promptly tugged as hard as it could on the tendon controlling that fin- ger. The finger bent downward obed- iently, and contacted the desired key T which with equal complaisance de- scended — halfway. The tug was not powerful enough to lift the type bar from its felt rest. The Hunter had not realised that he was so weak, compared with human mus- cle-; Bob's manipulation of the type- writer had seemed so completely effortless. He sent more of his flesh flowing into the net which was trying to do the work of a small muscle, and tried again — and again and again. The result was the same. The key descended far enough to take up the slack in its linkage and stopped. AH thiSj of course, had attracted T-Sob^s attention. 1-1 e had, of course ¥ experienced before the quivering of muscles abruptly released from a heavy load \ but there had been no- load here. Me pulled the offending hand away from the keyboard, and the suddenly frantic Hunter promptly transferred his attention to the other. As with a human being, his control, poor enough in the be- ginning, grew worse with haste and strain ; and the fingers of Robert's right hand twitched in a most un- nerving fashion, The boy stared at them, terrified. He was more or less hardened to the prospect of physical injury, as anyone who plays, football and hockey must be, but there was something about nervous disorder that undermined His morale. It is a horrible jott for a person still young enough never to have doubted seriously his own physical and mental powers suddenly to bt given cause to question his own saniTy; and even if Bob did not go quite that far, the inability to stop- his fingers from quivering was. nearly as unpleasant. It gave him 8L a completely unaccustomed helpless feeling. He clenched his ftsts tightly. The quivering stopped, to his 'relief— the Hunter knew he could never overcome muscles opposed to' his awn attempts. When the fists were cautiously relaxed* after a few mo- ments, the alien made another try— this time on arm and chest muscles j in an effort to bring the hands back to the typewriter, Hob, with a gasp of dismay* leaped to his feet, knock- ing his chair back against his room- mate's bed. The Hunter was ahle to deposit a. much heavier net of his flesh about these larger muscles, and the unwilled tug had been quite per- ceptible to the boy. He stood mo- tionless, now badly frightened, and tried to decide between two courses of action. There was, of course, a stringent rule that all injuries and illnesses must he reported promptly to the schoo] infirmary. Had Dob suf- fered damage such as a cut or bruise, or even had a headache or stomach disorder, he would have had no hesi- tation in complying with this order ; but somehow the idea of owning to a nervous complaint seemed rather shameful, and the thought of re- porting his trouble grew more re- pugnant every moment. As might be expected, he finally decided to put it off, in the hope that matters would be improved by morning. He put the typewriter away, L took out a bookj and settled down to read. At first he felt decidedly uneasy ; but 52 as the minutes parsed without fur- ther misbehavior on the part of his muscular system, he gradually cahned down and became more ab- sorbed in the reading matter. The increasing peace of mind was not, however, shared by his unsuspected companion. The Hunter had relaxed in dis- gust as soon as the writing machine had been put away ; but he had no intention of giving up. The fact that lie con id impress himself on the boy's awareness without doing him physical damage had been something gained; even though interference with his muscles produced such a [narked disturbance/ there were other methods which suggested themselves to the alien. Perhaps they would prove less di sconce rting, and he kne™ they could be equally effective as means of communica- tion. The 1-1 u titer was no psycholo- gist, and had never actually faced the problem now before him — though he had read a few purely theoretical books dealing with it. The symbiosis now so com en on be- tween his race and r the Allanese had started in a small way before the written history of the latter people ; tli ere had always been, as far back as the records went, someone of the prospective host's own species to explain and persuade solitary beings to take up the relationship ; and with the beginning of interwnrld travel^ there had always been the means for similar preparation of new races. Tf was. tint too surprising, there- fore } that the Hunter did not blame AS TOUtfO I NO SCIENCE-FICTION the disturbance he had created $t> : much on the mere fact that there had been interference as on the par- ticular method lie had used* and felt no misgivings as to the effect on his host's mind of further attempts. He did just the worst thing he could possibly have done ; lie waited until his host appeared to be over the shgck of the first attempt, and promptly tried again. This time he worked on EoVs voca] cords. They were similar in structure, to those of the Allanese,. and the Hunter could alter their ten- sion mechanically just as he had pulled at the muscles of the limbs. He did not, of course* expect to form words; that requires control of diaphragm, tongue* jaw* and lips as well as vocal chords* and the sytubiote was perfectly aware of the fact; hut if he exerted his influence when the host was exhaling, he could at least produce sound- He was trusting to a frequency method —repeating, numbers and their squares by means of interrupted sounds; precisely the method which many human Icings have advocated should occasion ever arise for dem- onstrating the existence of intelli- gence on this planet. He got farther than any human being, knowing the facts, would have expected* principally because Kinnaird was just finishing; a yawn as the interruption started and was not able to control his own breath- ing right away. The Hunter was busily engaged In producing a series NEEDLE of four rather sickly croaks, having completed two and paused, when the boy caught his breath and art expression of undiluted terror spread over his face. He tried to let out his breath slowly and care- fully; but the Hunter, completely absorbed in his work, continued the unnerving operation regardless of the fact that he had been inter- rupted. It took him some seconds to realize that the emotional dis- turbance of his host had reappeared in full force. His own emotional control must have related to some extent at this realization. No other means of explaining the thing he did next makes any sense whatever. Recog- nizing clearly that he bad failed again, knowing perfectly that his host was almost frantic with an emotion that robbed him of most of his cuntrol, the alien nevertheless not only failed to desist from his attempts but started still another form of "communication." Perhaps he felt that he had gone too far to retreat; perhaps he had recognized the damage done by the pause be- tween the first two attempts and wag determined not to repeat the error; whatever his excuse may be, he was certainly not using the common sense he normally displayed. His third attempt involved cutting off light from his host's retina in patterns according to letters of the English alphabet — regardless of the fact that by this time Robert Kinnaird was rushing down the hallway outside his room, bound for the dispensary, as and the Hunter knew perfectly well that there lay ahead a rather poorly lighted stairway. The inevitable results of interfer- ence with, his host's eyesight under such circumstances did not impress themselves upon the Hunter's mind until Bob actually missed a step and lunged Forward, grasping futilely for the rail. It must be said for the alien that lie recovered his sense of Suty rapidly enough. Before the hur- tling body touched a single obstacle he had tightened around every joint and tendon with his utmost strength ; and it is quite possible that Robert was saved a severe sprain thereby. £4 One thing certainly was done most efficiently; as the shaip f upturned corner of one of the metal cleats which held the rubber treads on the stairs opened the Boy's arm from wrist to elbow, the alien was on the job so fast that the blood which escaped was not sufficient to flow away from the immediate neighbor- hood of the wound Bob felt the pain, looked at the injury which was being held closed under an almost invisible film of unhuman flesh, and actually thought it was a scratch that had barely penetrated the skin. He turned the corner of the cleat down with his heel , and proceeded to the dispensary at a more moderate pace. ASTOUNDING SC 1 E N CE -FICEl ON He was calmer when he got: there, for the Hunter had been sobered into di scout i nuing his attempts to make himself known. The school did tiot have a resident doctor, but did keep a nurse on constant duly at the dispensary. She could make little of Robert's descrip- tion of his nervous troubles — the fact is by no means to her discredit — and advised him to return the next day at th» hour one of the local doctors normally visited the school. She did examine the cm on his arm, however. "It's clotted over P now/ 1 she told the boy. "You should have come here with it sooner — though I prob- ably would n T t have done much to it," "It happened less than five min- utes ago/' was the answer, "I fell on the stairs coming down to see you ah out the other business — I couldn't have brought it to you any faster- If it's already closed, though, I guess it doesn't matter'/* Miss Rand raised her eyebrows a trifle. She had been a school nurse for fifteen years, and was pretty sure she. had encountered all the more common tales of malin- gerers. What pulled her now was that there seemed no reason for the boy to prevaricate ; she decided, rather against her will, that he was probably telling the truth. Of course* some people's blood does clot with unusual speed , she remembered. She examined Rob- ert's forearm again, more closely. YeSj the clot was extremely fresh ; the shiny, dark red of newly con- gealed blood. She or u shed it lightly with a fingertip — and felt, not the dry, smooth surface she had ex- pect ed, or even the faint stickiness of nearly-dry blood, but a definite and unpleasant jlimtuess. The Hunter was not a mind reader and had not foreseen such a move, Even if he had, he could not have withdrawn his flesh from the surface of Robert's skin; it would be hours, more probably a day or two, before the edges of that gash could be trusted to hold them- selves together ujider normal usage of the arm. He had to stay, whether he betTayed himself or not. He watched through his host's eyes with some Uneasiness as Mlss Rand drew her hand away sharply, and leaned over to look still more closely at the injured arm. This time she saw the transparent, almost invisible film that covered the cut, and leaped to a perfectly natural but completely erroneous conclusion. She decided that the injury was not as fresh as Robert had claimed, that he had "treated" it himself with the first substance that he had found handy — possibly airplane dope or something of that order — and had not wanted the fact to come out. She was doing the boy's common 'sense a serious injustice, but she had no means of knowing that. She was wise enough to make no accusa- tions, however, and without saying anything more took a small bottle AST— IF 35 of alcohol, moistened a swab with it, and started to clean away the for- eign, material. Had the Hunter been in control of a set of vocal chords, he would probably have been unable to sup- press a howl of anguish. He pos- sessed no true skin, and the body cells overlaying the cut. on his host's arm were completely unprotected from the dehydrating net ion of the fluid on the swab. Direct sunlight had been bad enough. Alcohol felt to him about the same as concen- trated sulphuric acid feels to a hu- man being — and for the same reason. Those outer cells were killed almost instantly, desiccated to a brownish powder that could have been blown away, and would undoubtedly have interested the nurse greatly had she had a chance to examine it. There was no time for that, how- ever. In the shock of the sudden |>ain> the Hunter relaxed all of the "muscular" control he was exerting in that region to keep the wound closed, and the nurse found herself confronted with a long, clean slash some eight inches from end to end and half an inch deep tn the middle, which suddenly started to bleed very enthusiastically. She was almost as startled as Robert, but her training showed its value ; she bad coin- presses applied and bandaged in place in very creditable time, though she was rather surprised at the ease with which she managed to stop the bleeding. Then she reached for the telephone. 30 ^Robert Kinnaird was rather late in getting to bed that night. He was tired, but had trouble getting to sleep ; the local anaesthetic the doc- tor had used while he was sewing up the arm was starting to wear off, and he was becoming progressively more aware of the member as time went on. He had almost forgotten the original purpose of his visit to the dispensary hi the subset] uent excitement ; and now, separated by a reasonable time from the initial fright, he was able to view the mat- ter more clearly. He thought about it now, staring into the darkness of his room. The Hunter had also had time to alter his viewpoint. He had left the arm completely when the anaes- thetic was injected, and busied him- self entirfly with his problem. He now realized that the disturbance of any natural function or sense organ was likely to upset his host's emotional control seriously, and he was beginning to have a rather ac- curate suspicion of the effect that realization of his own presence where he was would probably have. Nothing originating in his own body would be interpreted by a human host as an attempt