"They dropped seeds from space," said Siegel. "That's what Dr. Zymph says."
"Yes and no-the problem with that theory is that it doesn't work. We tried simulating a drop from space. If the package is too small, it burns up on reentry. If it's well padded, it still burns up, only it takes longer. If it's big enough to reach the ground intact, it's big enough to leave a crater. Out of hundreds of simulations, both real and virtual, only the simplest of seeds survived, none of the eggs; the exposures were too extreme, the impacts too severe. The Denver labs worked on it for three years before they gave up and turned to more immediate concerns.
"See, here's the problem. Assume that you're Chtorra-forming a planet. You can't worry about landing individual plants and animals; that's too slow. You have to think about your larger purpose. What you really want to do is get the genetic heritage of the ecology established, right?"
"Right. I guess."
"Okay. We're humans, so we think in terms of seeds and eggs. But Chtorrans don't necessarily have to think the same way. Let's just think about the genetic code alone. That's all you're really interested in. You can strip the naked code out of a cell and store it as a meta-viral chain. So now you've got the information for your critter; but how do you get the code down to the surface of the planet? You can drop an insulated package that can survive the heat of the drop and even the impact. But you still need something to grow it in-some environment in which the code can generate critters-so you're back to seeds and eggs again, aren't you?
"See, the problem with seeds and eggs, especially eggs, is that the more complex the adult creature, the more fragile the egg, and the more nurturing it needs to hatch. And that doesn't even get into the problem of nurturing the young. Anything you can come up with, organic or technological, that can hatch an egg and nurture the infants, is going to be even more complex and more fragile than the creature it's designed to support.
"Think about it. How do you send a millipede egg across ten or twenty light-years and guarantee its survival? How do you get it safely down to the surface of the planet? How do you guarantee that the egg will be nurtured and protected in the right kind,of nest long enough for it to hatch? How do you make certain that the right kind of food will be available for the millipede to eat so that it can live long enough to reach adulthood and reproduce and make more millipedes? And that's just one species. We've identified hundreds of Chtorran creatures. How do you provide for all of their separate and individual concerns? Bunnydogs and snufflers and gorps and Enterprise fish-what kind of machinery do you provide to nurture all those?"
Siegel shrugged. "I dunno. I never thought about it before."
"This is the answer," I said. "A big part of it, anyway. Dr. Zymph was right; the Chtorrans are seeding the planet from space. But not with ordinary seeds and eggs. They've been dropping mama-shambler seeds. Have you ever seen a shambler seed? They're big, they look like pineapples. You cut one open, and you see that the outer shell is layer upon layer upon layer of gauzy stuff; you can spend a lifetime unraveling it.
"The inner shell of the shambler seed is filled with even more layers of the same fibrous matting, only this stuff is thicker and more gritty. You look at it under the microscope and you see that it's really thousands and thousands of tiny little structures, not quite cells, but not quite anything else either; they don't grow, they don't do anything that we can recognize. We couldn't figure out whether the inner layers were intended as food or padding or insulation or what, but I bet I know now. Those little structures are the freeze-dried nuclei of all the other critters in the ecology.
"See, a shambler seed is one of the few things you can drop from space with a reasonable expectation of it surviving the impact. It sheds its outer skin, layer after layer, like a series of drogues. It slows the descent, it's like concentric parachutes. In fact, I'll bet that the seeds that fell from space had even thicker shells than Earth-grown shambler seeds. Anyway, the mama-seed impacts, right? If conditions are right, it grows into a shambler bush, later a tree. It spreads its seeds and grows more shambler trees; pretty soon, you have a herd of shamblers prowling around the countryside. What are they looking for? A place with the right combination of sunlight and water and soil and probably even prey animals for the tenants. The grove of shamblers takes up a position, the individual trees sink their roots, they link up and begin carving out or growing a large central underground chamber. There's got to be some mechanism, some creature or process or something." I realized that my enthusiasm for the subject must have been startling to my listeners, but I couldn't contain myself, I was so excited. Even as I spoke, the idea was becoming clearer in my mind.
"Okay, so pretty soon you have this womb nest here. That's when some of the organs within the shambler start maturing; or maybe they aren't shambler organs, but more like symbionts. I don't know. But whatever they are, they grow into this stuff, all these tunnels and pipes and tubes, all these big rubbery blobs and squids and slugs and things. Everything."
"I love it when you talk scientific," said Willig, but despite her interruption, she was as rapt as all the others. The entire crew-not just Willig, but Reilly, Siegel, Locke, Lopez, and Valada-were caught up in this extrapolation.
"Go on," said Siegel, impatiently.
"The big red blubbers are egg-factories. All the other things are the support systems. The little flecks are the freeze-dried nuclei, duplicated by some kind of organic copying mechanism-and not just the simple nuclei alone; there also has to be the instructions included on what kind of egg to grow around each nucleus and what kind of nurturing that egg is going to need to hatch. I'll bet that some of these other organs are here to act as incubators to hatch the eggs and nurture whatever creatures pop out of them. That tunnel we came down-it isn't an entrance, it's an exit. That's the birth canal."
"Worms come out of it?"
"Everything comes out of it," I said, shuddering at the thought.
I sank back in my chair, stunned at the size of the realization. "This hole hasn't been here for six months; it's been here for six years at least. Probably longer. These groves-all over the world-this is how the infestation started. If we had known, if we had realized-" I felt suddenly helpless.
"We've gotta burn these things wherever we find them." Siegel spoke with determination. "Maybe we still have a chance-"
"It's too late," I said. "These womb-nests are only landing vehicles, the last part of the transportation process. You can grow Chtorran babies in it, but once they leave the nest, they'll grow their own babies." I realized how defeatist that sounded, and added perfunctorily, "You're right, though, we should burn these wombs, at least to slow down the infestation every way we can. But we should study them too. There might still be things growing in the raspberry Jell-O that we haven't met yet."
"What about these little slugs?" Willig asked. "Are they baby worms or not?"
"I dunno. They're a little small, but that might not mean anything under these circumstances; we're at almost double atmosphere down here. And they don't have any fur either. Without its fur, a worm is both blind and catatonic; and these guys seem kind of lively. But-"I shrugged"—maybe there are things that need to be taken up to the surface, and these little fellas are the taxis. If that's all they are, then it doesn't matter if they live or die, does it?"
"Guess not."
"But… if they are worms, then this is our opportunity to study their breeding patterns. Dr. Zymph thinks that our best chance of defeating them is to find some agent, biological or chemical, that will interrupt their reproductive cycle. The problem is, nobody really knows how they breed. We know they hatch from some kind of large leathery eggs; but we've never actually seen a worm laying eggs. In fact, we still haven't been able to identify the worm sexes. That's assuming that they have different sexes. We can't tell."