There had to be some way of being sure. Then as his shoulder touched the closet door, he remembered the padded mailer.

He turned toward the closet, opened the door, and reached up to feel along the shelf. The mailer was still there. He took it down and read the address on the front: Sandra Parnell, 2754 Cunningham Court, Bayswater, London W.2, U.K. His hands started trembling when he saw that it had been stamped and mailed in the U.S.A. He turned the mailer over and read on the back:

Sender: Mrs. Lisa Stone Box 3683 Las Vegas Nevada 89109

A strangled moan escaped his lips as the mailer dropped to the floor. But his anguish was not due to remorse over Lisa or the realization that Sandra didn"t exist. It was due to pure terror.

For all of a sudden he knew why Sandra was always away, but always managed to be free when he himself was away from home, and he knew why she had needed to leave early on Friday, what Max"s flymobile had been doing outside the house, and where the infusers had come from. But what was worse, he knew now why Lisa had stopped off in the bathroom on her way back from getting his cigarettes from the den, and why there were only two left when he knew there had been some full packs around the night before.

"You b.i.t.c.h!" he breathed as it all became clear in its gruesomeness. And then a senseless rage welled up at his own predicament and helplessness, and he hurled himself across the room and began pounding furiously at the unfeeling face and body. "b.i.t.c.h! b.i.t.c.h! Bi-!" he screamed. But the words died in a gurgle in his throat as a wave of tiredness and heaviness swept suddenly over him. His body collapsed in a limp heap on top of the other. After a few seconds, another voice began speaking to fill the room with a macabre canon of out-of-phase intonations.

". . . We regret any inconvenience. A recovery team is already on its way. . . . Please do not be alarmed. this is a malfunction of a remotely . . ."

Two lamps were flashing to accompany the emergency tone sounding from a monitor panel in the control room of the Las Vegas branch of Remote-Activated Biovehicles, Inc. "Hey, Al," the operator called over his shoulder to the day manager, who was coming out of his office to investigate. "I"ve never even seen one crash all the time I"ve been here. We"ve got two at the same time, and in adjacent cubicles.

What odds do you think the guys in town would give against the chances of something like that?

Afterword, 1996 "Till Death Us Do Part" first appeared in the sixth of Judy-Lynn Del Rey"s Stellar anthologies (1981). A second story based on the same premise, ent.i.tled "Ident.i.ty Crisis," was included in Stellar 7. Our thought was to produce a series of "Rentabody" stories over the ensuing years, and then bring them all together into a single volume. Some readers sensed this and asked if they could expect to see more. As things turned out, it ended up as one of those projects that was just filed away. But who knows? It could be revived again one day.

FORTUNE COOKIE.

Preface.

Sometimes ideas come from talking to people. The following is more a thought than a story, but it ill.u.s.trates what sometimes happens. It resulted from a conversation over breakfast one morning with a computer wizard called Charles Curley, during a convention in Sacramento at which I was guest of honor.

It also cost me twenty dollars. I didn"t know how thick a postcard was for the example that I use in the opening sentence, and n.o.body I called on the phone could tell me. So I went into the hardware store next door to my office and bought a micrometer to measure one (it"s 0.013 inch to save anyone who"s insatiably curious twenty dollars). Perhaps this also says something about how science-fiction writers think. Ideas come from asking questions, and to ask questions you have to be curious.

One year is to 4.5 billion years as a cent is to 45 million dollars, or as the thickness of a postcard is to the distance between New York and the Mississippi.

That long ago, the earth formed as one of several acc.u.mulations of matter falling together in a spinning pancake of dust and gas that had condensed from the exploding debris of an earlier generation of stars.

As the final meteorite bombardment died away and the planetary smelter processed and separated its rocky slags into mantle and crust, rain fell from the hot outga.s.sings to become the first oceans.

There, in shallows and pools invigorated by young radionuclides and a raw, unshielded sun, a new chemistry began of molecules too elaborate to have come together in the rarified depths of s.p.a.ce, and impossible in the plasma maelstroms of stars. Colliding, fragmenting, and recombining at quantum-mechanical speeds, billions of different combinations came and went during every second of hundreds of millions of years. Some of them proved stable and remained intact, and were able to grow into progressively more elaborate structures by further additions from the molecular constructor-kit soup.

Eventually a few, or possibly only one, hit upon a configuration that would act as a template for parts to come together in the right way to form a copy of itself. Self-replication had appeared.

In their resource-rich primeval surroundings, the replicating molecules proliferated at an exponential rate and soon extinguished the feeble compet.i.tion put up by their crude predecessors. The copies were not always accurate-mutations occurred, each yielding its own line of offspring, and the compet.i.tion came to be between different designs of replicators, all experimenting with different survival strategies. A potent strategy came with the invention of chemical warfare, which some varieties used to physically dismantle their rivals-it reduced the compet.i.tion and increased available resources at the same time. In reply to this, the replicators that survived learned to build themselves protective molecular coatings. Defense stimulated new methods of attack, which resulted in improved defenses. . . .

In the billions of years that followed, the primitive molecular coats evolved into huge, elaborate survival machines which the replicators continue to control by remote programming from secure command bunkers deep inside. When a particular survival-machine begins wearing out and slowing down, the replicators-virtually immortal experts at survival-copy themselves through into a new one. On their way down through the ages, acting through their progressively improving sequence of robot proxies, they have continued to invent new technologies that have opened up new realms of survival-enhancing resources. Early on, the blue-green algae freed themselves from dependency on food produced through slow, abiotic processes, by patenting the chlorophyll molecule and photosynthesis, which opened up the entire ocean surface as a resource. Even greater ingenuity turned the ensuing planetwide catastrophe-its inundation with the toxic, corrosive waste, oxygen-into an opportunity by evolving metabolisms which not only tolerated it, but thrived on it and harnessed it as fuel for better engines. Double-stranded instruction tapes enabled error-correction for accurate copying of the vast amounts of information necessary to build multicellular organisms; the s.e.xual mixing of instructions from the growing information pool produced new combinations much faster than coincidences of mutations ever could; and the invention of the s.p.a.cesuit in the form of the amphibian egg led to the colonization and exploitation by animals of a completely new, initially hostile, alien environment.

The progression led on through warm-blooded metabolisms, mammalian reproduction, and upright posture to binocular vision, opposable thumbs, and bigger brains. Eventually the species that represented the culmination of the process became self-aware, and learned to make tools and build artificial, inorganic survival-facilitating environments around the organic survival machines. That same self-awareness caused him to wonder where he had come from and why. He used his intelligence to construct enormous instruments, with which he scanned the remote reaches of the cosmos in search of a sign from his creator.

Eventually he found his creator in the opposite direction-at the other end of a proton microscope. And at last he decoded the sign he had been seeking, which had been written into the creation: HELP! I"M A PRISONER IN A DNA FACTORY!.

Afterword, 1996 The thing that strikes me most on rereading the above years later is its tone of blithe certainty about things that happened billions of years ago, shrouded in mists of time so deep as to defy comprehension. I wasn"t around to know what went on, neither was anyone else, and the evidence to reconstruct it could fairly be called nonexistent. Speculation and conjecture abounds, of course (where else was what I wrote drawn from?), and there"s nothing wrong with that-as long as we remain mindful of what it is, and don"t begin confusing plausibility and pleasing self-consistency with proof of reality. Much of what I read in science these days comes across with the same oversure ring to it of expecting Nature to be somehow obliged to imitate the model, instead of the other way around. Maybe it reflects a necessity today of developing phony sales pitches to impress bureaucrats who allocate funding. This trend didn"t trouble me very much ten years ago, but it"s starting to now.

MORE ON REPLICATION.

I mentioned earlier in Minds, Machines and Evolution that contemporary science is satisfied that such phenomena as the emergence of life and conscious mind can be adequately explained by the laws of physics and the principle of evolution, without needing any additional guiding powers. Given variability and selection, the rest follows mechanically. Thinking about this got me intrigued by the thought of a story involving a world inhabited by a naturally evolving biosphere made up of machines. The problem was, I couldn"t think of a way to get it started. We can see how abiotic molecules could a.s.semble themselves into structures that eventually came to exhibit self-replication and life, but with machines it"s not so simple.

As Taya insisted in Silver Shoes for a Princess, something had to make the first machine.

Then in 1982, Rodger Cliff, an AI scientist with NASA, invited me to take part in a one-week seminar at the G.o.ddard s.p.a.ce Center which NASA was arranging to examine the role of computers in future s.p.a.ce missions. The group included people from NASA, from the academic world, and from industry.

One of the possibilities we talked about was an idea for a self-replicating lunar factory-an initial package of robots and machines to be landed on the Moon, which would grow exponentially and transform the entire lunar surface into an automated ma.s.s-production facility dedicated to supplying Earth"s needs for products and materials. The implications were staggering. From an initial one-hundred-ton "seed" system, the annual output after ten years of unrestricted, self-reproducing growth would be a million tons, and by twenty years it would exceed the entire yearly output of today"s human civilization!

I"m a rather slow thinker, which is perhaps why I chose to be a writer and not a talker. The connection didn"t occur to me until I was on the plane back to California. Of course! Here, possibly, was the means I"d been looking for to get a machine biosphere started. Suppose, for example, that long ago an alien civilization sent out seeds like that on an interstellar scale, and one of them had mutated and gone out of control for some reason.

This must have been genuine inspiration, because I began typing Code of the Lifemaker the very next day. Since then, a number of readers have written or told me that the prologue alone was worth the price of the book.

So, hoping among other things that it might sell a few more copies, I thought I"d include it here.

CODE OF THE.

LIFEMAKER: PROLOGUE.

THE SEARCHER.

1.1 Million Years B.C.; 1,000 Light-Years from the Solar System Had English-speaking humans existed, they would probably have translated the s.p.a.cecraft"s designation as "searcher." Unmanned, it was almost a mile long, streamlined for descent through planetary atmospheres, and it operated fully under the control of computers. The alien civilization was an advanced one, and the computers were very sophisticated.

The planet at which the searcher arrived after a voyage of many years was the fourth in the system of a star named after the king of a mythical race of alien G.o.ds, and could appropriately be called Zeus IV. It wasn"t much to look at-an airless, lifeless ball of eroded rock formations, a lot of boulders and debris from ancient meteorite impacts, and vast areas of volcanic ash and dust-but the searcher"s...o...b..tal probes and surface landers found a crust rich in t.i.tanium, chromium, cobalt, copper, manganese, uranium, and many other valuable elements concentrated by thermal-fluidic processes operating early in the planet"s history. Such a natural abundance of metals could support large-scale production without extensive dependence on bulk nuclear trans.m.u.tation processes-in other words, very economically-and that was precisely the kind of thing that the searcher had been designed to search for.

After completing their a.n.a.lysis of the preliminary data, the control computers selected a landing site, composed and transmitted a message home to report their findings and announce their intentions, and then activated the vessel"s descent routine.

Shortly after the landing, a menagerie of surveyor robots, equipped with imagers, spectrometers, a.n.a.lyzers, chemical sensors, rock samplers, radiation monitors, and various manipulator appendages, emerged from the ship and dispersed across the surrounding terrain to investigate surface features selected from orbit. Their findings were transmitted back to the ship and processed, and shortly afterward follow-up teams of tracked, legged, and wheeled mining, drilling and transportation robots went out to begin feeding ores and other materials back to where more machines had begun to build a fusion-powered pilot extraction plant. A parts-making facility was constructed next, followed by a parts-a.s.sembly facility, and step by step the pilot plant grew itself into a fully equipped, general-purpose factory, complete with its own control. The master program from the ship"s computers were copied into the factory"s computers, which thereupon became self sufficient and a.s.sumed control of surface operations. The factory then began making more robots.

Sometimes, of course, things failed to work exactly as intended, but the alien engineers had created their own counterpart of Murphy and allowed for his law in their plans. Maintenance robots took care of breakdowns and routine wear and tear in the factory; troubleshooting programs tracked down causes of production rejects and adjusted the machines for drifting tolerances; breakdown teams brought in malfunctioning machines for repair; and specialized scavenging robots roamed the surface in search of wrecks, write-offs, discarded components, and any other likely sources of parts suitable for recycling.

Time pa.s.sed, the factory hummed, and the robot population grew in number and variety. When the population had attained a critical size, a mixed workforce detached itself from the main center of activity and migrated a few miles away to build a second factory, a replica of the first, using materials supplied initially from Factory One. When Factory Two became self-sustaining, Factory One, its primary task accomplished, switched to ma.s.s-production mode, producing goods and materials for eventual shipment to the alien home planet.

While Factory Two was repeating the process by commencing work on Factory Three, the labor detail from Factory One picked up its tools and moved on to begin Factory Four. By the time Factory Four was up and running, Factories Five through Eight were already taking shape, Factory Two was in ma.s.s production mode, and Factory Three was building the first of a fleet of cargo vessels to carry home the products being stockpiled. This self-replicating pattern would spread rapidly to transform the entire surface of Zeus IV into a totally automated manufacturing complex dedicated to supplying the distant alien civilization from local resources.

From within the searcher"s control computers, the Supervisor program gazed out at the scene through its data input channels and saw that its work was good. After a thorough overhaul and systems checkout, the searcher ship reembarked its primary workforce and launched itself into s.p.a.ce to seek more worlds on which to repeat the cycle.

FIFTY YEARS LATER.

Not far-as galactic distances go-from Zeus was another star, a bluish white star with a ma.s.s over fifteen times that of the Sun. It had formed rapidly, and its life span-the temporary halt of its collapse under self-gravitation by thermonuclear radiation pressure-had demanded such a prodigious output of energy as to be a brief one. In only ten million years the star, which had converted all the hydrogen in its outer sh.e.l.l to helium, resumed its collapse until the core temperature was high enough to burn the helium into carbon, and then, when the helium was exhausted, repeated the process to begin burning carbon.

The ignition of carbon raised the core temperature higher still, which induced a higher rate of carbon burning, which in turn heated the core even more, and a thermonuclear runaway set in, which in terms of stellar timescales was instantaneous. In mere days the star erupted into a supernova-radiating with a billion times the brightness of the Sun, exploding outward until its photosphere enclosed a radius greater than that of Ura.n.u.s"s...o...b..t, and devouring its tiny flock of planets in the process.

Those planets had been next on the searcher"s list to investigate, and it happened that the ship was heading into its final approach when the star exploded. The radiation blast hit it head-on at three billion miles out.

The searcher"s hull survived more-or-less intact, but secondary x-rays and high-energy subnuclear particles-things distinctly unhealthy for computers-flooded its interior. With most of its primary sensors burned out, its navigation system disrupted, and many of its programs obliterated or altered, the searcher veered away and disappeared back into the depths of interstellar s.p.a.ce.

One of the faint specks lying in the direction now ahead of the ship was a yellow-white dwarf star, a thousand light-years away. It too possessed a family of planets, and on the third of those planets the descendants of a species of semi-intelligent ape had tamed fire and were beginning to experiment with tools chipped laboriously from thin flakes of stone.

Supernovas are comparatively rare events, occurring with a frequency of perhaps two or three per year in the average galaxy. But as with most generalizations, this has occasional exceptions. The supernova that almost enveloped the searcher turned out to be the first of a small chain that rippled through a localized cl.u.s.ter of ma.s.sive stars formed at roughly the same time. Located in the middle of the cl.u.s.ter of was a normal, longer-lived star which happened to be the home star of the aliens. The aliens had never gotten round to extending their civilization much beyond the limits of their own planetary system, which was unfortunate because that was the end of them.

Everybody has a bad day sometimes.

ONE MILLION YEARS B.C.

One hundred thousand years after being scorched by the supernova, the searcher drifted into the outer regions of a planetary system. With its high-alt.i.tude surveillance instruments only partly functioning and its probes unable to deploy at all, the ship went directly into its descent routine over the first sizable body that it encountered, a frozen ball of ice-encrusted rock about three thousand miles in diameter, with seas of liquid methane and an atmosphere of nitrogen, hydrogen and methane vapor. The world came nowhere near meeting the criteria for worthwhile exploitation, but that was of no consequence since the computer programs responsible for surface a.n.a.lysis and evaluation weren"t working.

The programs to initiate surface activity did work, however, more or less, and Factory One, with all of its essential functions up and running to at least some degree, was duly built on a rocky shelf above an ice beach flanking an inlet of a shallow methane sea. The ship"s master programs were copied across into the newly installed factory computers, which identified the commencement of work on Factory Two as their first a.s.signment. Accordingly, Factory One"s Supervisor program signaled the ship"s databank for a copy of the "How to Make a Factory" file, which included a set of subfiles on "How to Make the Machines Needed to Make a Factory," i.e., robots. And that was where everything really started to go wrong.

The robots contained small internal processors that could be reprogrammed via radiolink from the factory computers for each new task to be accomplished. This allowed the robots to proceed with their various jobs under autonomous local control and freed up the central computers for other work while they were waiting for the next "Done that-what do I do now?" signal. Hence many software mechanisms existed for initiating data transfers between the factory computers and the remote processors inside the robots.

When the copying of the "How to Make a Factory" file from the ship to Factory One was attempted, the wrong software linkages were activated; instead of finding their way into the factory"s central system, the subfiles containing the manufacturing information for the various robots were merely relayed through the factory and beamed out into the local memories of the respective robot types to which they pertained.

No copies at all were retained in the factory databank. And even worse, the originals inside the ship managed to self-destruct in the process and were irretrievably erased. The only copies of the "How to Make a Fred-type Robot" subfile were the ones contained inside the Fred-types out on the surface. And the same was true for all the other types as well.

So when the factory"s Supervisor program ordered the Scheduler program to schedule more robots for manufacture, and the Scheduler lodged a request with the Databank Manager for the relevant subfiles, the Databank Manager found that it couldn"t deliver. Neither could it obtain a copy from the ship. The Databank Manager reported the problem to the Scheduler; the Scheduler complained to the Supervisor; the Supervisor blamed the Communications Manager; the Communications Manager demanded an explanation from the Message handler; and after a lot of mutual electronic recriminations and accusations, the system logging and diagnostic programs determined that the missing subfiles had last been tracked streaming out through the transmission buffers on their way to the robots outside. Under a stern directive from the Supervisor, the Communications Manager selected a Fred from the first category of robots called for on the Scheduler"s list, and beamed it a message telling it to send its subfile back again.

But the Fred didn"t have a complete copy of the subfile; its local memory simply hadn"t been big enough to hold all of it. And for the same reason, none of the other Freds could return a full copy either. They had been sprayed in succession with the datastream like buckets being filled from a fire-hose, and all had ended up with different portions of the subfile; but they appeared to have preserved the whole subfile among them. So the Supervisor had to retrieve different pieces from different Freds and try to fit them together again in a way that made sense. And that was how it arrived at the version it eventually handed to the Scheduler for manufacture.

Unfortunately, the instruction to store the information for future reference got lost somewhere, and for each batch of Freds the relevant "How to Make" subfile was promptly erased as soon as the Manufacturing Manager had finished with it. Hence when Factory One had spent some time producing parts for Factory Two and needed to expand its robot workforce to begin surveying sites for Factory Three, the Supervisor had to go through the whole rigmarole again. And the same process was necessary whenever a new run was scheduled to provide replacements for robots that had broken down or were wearing out.

All of this took up excessive amounts of processor time, loaded up the communications channels, and was generally inefficient in the ways that cost accountants worry about. The alien programmers had been suitably indoctrinated by the alien cost accountants who ran the business-as always-and had written the Supervisor as a flexible, self-modifying learning program that would detect such inefficiencies, grow unhappy about them, and seek ways to improve things. After a few trials, the Supervisor found that some of the Freds contained about half their respective subfiles, which meant that a complete copy could be obtained by interrogating just two individuals instead of many. Accordingly it made a note of such "matching pairs" and began selecting them as its source for repeat requests from the Scheduler, ignoring the others.

Lost along with the original "How to Make a Fred" subfiles were the subsubfiles on "Programs to Write into a Fred to Start it Up After You"ve Made It." To make up for the deficiency, the Supervisor copied through to the Scheduler the full set of programs that it found already existing in the Freds selected to provide reproduction information, and these programs, of course, included the ones on how to make Freds. Thus the robots began coming off the line with one half of their "genetic" information automatically built in, and a cycle a.s.serted itself whereby they in turn became the source of information to be recombined later for producing more Freds. The method worked, and the Supervisor never figured out that it could have saved itself a lot of trouble by storing the blueprints away once and for all in the factory databank.

The program segments being recombined in this way frequently failed to copy faithfully, and the "genomes" formed from them were seldom identical, some having portions of code omitted while others had portions duplicated. Consequently, the Freds started taking on strange shapes and behaving in strange ways.

Some didn"t exhibit any behavior at all but simply fell over or failed during test, to be broken down into parts again and recycled. A lot were like that.

Some, from the earlier phase, were genetically incomplete-"sterile"-and never called upon by the Supervisor to furnish reproductive data. They lasted until they broke down or wore out, and then became extinct.

Some reproduced pa.s.sively, i.e., by transmitting their half-subfiles to the factory when the Scheduler asked for them.

A few, however, had inherited from the ship"s software the program modules whose function was to lodge requests with the Scheduler to schedule more models of their own kind-program modules, moreover, which embodied a self-modifying priority structure capable of raising the urgency of their requests within the system until they were serviced. The robots in this category sought to reproduce actively: they behaved as if they experienced a compulsion to ensure that their half-subfiles were always included in the Scheduler"s schedule of "Things to Make Next."

So when Factory One switched over to ma.s.s-production mode, the robots competing for slots in its product list soon grabbed all of the available memory s.p.a.ce and caused the factory to become dedicated to churning out nothing else. When Factory Two went into operation under control of the programs copied from Factory One, the same thing happened there. And the same cycle would be propagated to Factory Three, construction of which had by that time begun.

More factories appeared in a pattern spreading inland from the rocky coastal shelf. The instability inherent in the original parent software continued to manifest itself in the copies of copies of copies pa.s.sed on to later generations, and the new factories, along with their mixed populations of robot progeny, diverged further in form and function.

Material resources were scarce almost everywhere, which resulted in the emergence of compet.i.tive pressures that the alien system designers had never intended. The factory-robot communities that happened to include a balanced mix of surveyor, procurement, and scavenger robots with "appet.i.tes"

appropriate to their factories" needs, and which enjoyed favorable sites on the surface, usually managed to survive if not flourish. Factory Ten, for example, occupied the center of an ancient meteorite crater twelve miles across, where the heat and shock of the impact had exposed metal-bearing bedrock from below the ice; Factory Thirteen established itself inside a deep fissure where the ice beneath was relatively thin, and was able to melt a shaft down to the denser core material; and Factory Fifteen resorted to nuclear trans.m.u.tation processes to build heavier nuclei from lighter ones frozen in solution in the ice crust. But many were like Factory Nineteen, which began to take shape on an ill-chosen spot far out on a bleak ice-field, and ground to a halt when its deep-drilling robots and trans.m.u.tation reactors failed to function, and its supply of vital materials ran out.

The scavenger and parts-salvaging robots a.s.sumed a crucial role in shaping the strange metabolism that was coming into being. Regardless of what the Schedulers in the various factories would have liked to see made, the only things that could be a.s.sembled readily were the ones for which parts were available, and that depended to a large degree on the ability of the scavengers to locate them, or alternatively to locate a.s.semblies suitable for breaking down-"digesting"-and rebuilding into something useful. Factory Twenty-four was an extreme case. Unable to "metabolize" parts directly from any source of raw materials because of the complete failure of its materials-procurement workforce, it relied totally on its scavengers. Factory Thirty-two, on the other hand, could acquire raw materials but couldn"t use them since it had been built without a processing facility at all. Its robots delivered instead to Forty-seven, which happened to produce parts for some of the scavengers being manufactured by Thirty-two, and the two factory-robot organisms managed to coexist happily in their bizarre form of symbiosis.

The piles of a.s.sorted junk, which shouldn"t have acc.u.mulated from the earlier phases of the process but had, were eaten up; the machines that broke down were eaten up; and the carca.s.ses of defunct factories were eaten up. When those sources of materials had been exhausted, some of the machines began to eat each other.

The scavengers had been designed, as they had to be, to discriminate between properly functioning machines and desirable products on the one hand, and rejects in need of recycling on the other.

However, as with everything else in the whole, messed-up project, this function worked well in some cases, not so well in others, and often not at all. Some of the models turned out to be as likely to attempt the dismantling of a live, walking-around Fred as of a dead, flat-on-its-back one. Many of the victims were indifferent to this kind of treatment and soon died out, but others succeeded in developing effective fight-or-flee responses to preserve themselves, thus marking the beginnings of specialized prey and predators in the form of "lithovores" and "artifactovores."

This development was not always an advantage, especially when the loss of discrimination was total.

Factory Fifty was consumed by its own offspring, who began dismantling it at its output end as soon as they came off the a.s.sembly line, and then proceeded proudly to deliver the pieces back to its input end.

Its internal repair robots were unable to undo the undoings fast enough, and it ground to a halt to become plunder for marauders from Thirty-six and Fifty-three. The most successful factory-robot organisms protected themselves by evolving aggressive armies of "antibody" defenders, which would recognize their own factory and its "kind" and leave them alone, but attack and attempt to destroy any "foreign" models that ventured too close. This gradually became the dominant form of organism, usually a.s.sociated with a distinct territory which its members cooperated in protecting collectively.

By this time only a few holes in the ground remained at opposite ends of the rocky shelf to mark where Factories One and Two had once stood. They had failed to keep up with the times, and the area had become the domain of Factory Sixty-five. The only trace left of the searcher s.p.a.cecraft was a long, rounded depression in the ice beach below, on the sh.o.r.e of the liquid methane sea.