take these dozen spat we found. Year after next, they'd be
breeding size, and would produce about three hundred million larvae. If
everything went right, some three years later those three hundred
million would produce _nine thousand trillion_ baby oysters! Can you
image how much territory nine thousand trillion oysters would cover?"

I stopped listening right then, and started looking at the map of Niobe
pinned on the wall. "Good Lord! They'd cover the whole eastern seaboard
of Alpha from pole to pole."

Bergdorf said smugly, "Actually, you're a bit over on your guess.
Considering the short free swimming stage of the larvae, the slow
eastern seaboard currents, poor bottom conditions and overcrowding, I
doubt if they would cover more than a thousand miles of coastline by the
fourth year. Most of them would die from environmental pressures.

"But that isn't the real trouble. Niobe's oceans aren't like Earth's.
They're shallow. It's a rare spot that's over forty fathoms deep. As a
result, oysters can grow almost anywhere. And that's what'll happen if
they aren't stopped. Inside of two decades they'll destroy this world!"

"You're being an alarmist," I said.

"Not so much as you might think. I don't suppose that the oysters will
invade dry land and chase the natives from one rain puddle to another,
but they'll grow without check, build oyster reefs that'll menace
navigation, change the chemical composition of Niobe's oceans, pollute
the water with organic debris of their rotting bodies, and so change the
ecological environment of this world that only the hardiest and most
adaptable life forms will be able to survive this!"

"But they'll be self-limiting," I protested.

"Sure. But by the time they limit themselves, they will eliminate about
everything else."

"If you're right, then, there's only one thing to do. We'll have to let
the natives know what the score is and start taking steps to get rid of
them."

"Oh, I'm right. I don't think you'll find anyone who'll disagree with
me. We kicked this around at the Lab for quite a spell before I came up
here with it."

"Then you've undoubtedly thought of some way to get rid of them."

"Of course. That was one of the first things we did. The answer's
obvious."

"Not to me."

"Sure. Starfish. They'll swamp up the extra oysters in jig time."

"But won't the starfish get too numerous?"

"No. They die off pretty fast without a source of food supply. From what
we ca