Hafner looked pained. "Are they likely to bother the crops we plant?"

"Offhand, I would say they aren't. But then I would have said the same

about our clothing."

Hafner made up his mind. "All right. You worry about the crops. Find

some way to keep them out of the fields. Meanwhile, everyone sleeps in

the ship until we can build dormitories."

Individual dwelling units would have been more appropriate in the

colony at this stage, thought Marin. But it wasn't for him to decide.

The executive was a man who regarded a schedule as something to be

exceeded.

"The omnivore--" began Marin.

Hafner nodded impatiently. "Work on it," he said, and walked away.

The biologist sighed. The omnivore really was a queer little

creature, but it was by no means the most important thing on Glade.

For instance, why were there so few species of land animals on the

planet? No reptiles, numerous birds, and only four kinds of mammals.

Every comparable planet teemed with a wild variety of life. Glade, in

spite of seemingly ideal conditions, hadn't developed. Why?

He had asked Biological Controls for this assignment because it had

seemed an interesting problem. Now, apparently, he was being pressed

into service as an exterminator.

He reached in the cage and picked up the omnivore. Mammals on Glade

were not unexpected. Parallel development took care of that. Given

roughly the same kind of environment, similar animals would usually

evolve.

In the Late Carboniferous forest on Earth, there had been creatures

like the omnivore, the primitive mammal from which all others had

evolved. On Glade, that kind of evolution just hadn't taken place.

What had kept nature from exploiting its evolutionary potentialities?

There was the real problem, not how to wipe them out.

Marin stuck a needle in the omnivore. It squealed and then relaxed. He

drew out the blood and set it back in the cage. He could learn a lot

about the animal from trying to kill it.

* * * * *

The quartermaster was shouting, though his normal voice carried quite

well.

"How do you know it's mice?" the biologist asked him.

"Look," said the quartermaster angrily.

Marin looked. The evidence did indicate mice.

Before he could speak, the quartermaster snapped, "Don't tell me

they're only mice-like creatures. I know that. The question is: how

can I get rid of them?"

"Have you tried poison?"

"Tell me what poison to use and I'll use it."

It wasn't the easiest question to answer. What was poisonous to an

animal he had never seen and knew nothing about? According to

Biological Survey, the animal didn't exist.

It was unexpectedly serious. The colony could live off the land, and

was expected to. But another group of colonists was due in three

years. The colony was supposed to accumulate a surplus of food to feed

the increased numbers. If they couldn't store the food they grew any

better than the concentrates, that surplus was going to be scanty.

Marin went over the warehouse thoroughly. It was the usual early

construction on a colonial world. Not esthetic, it was sturdy enough.

Fused dirt floor, reinforced foot-thick walls, a ceiling slab of the

same. The whole was bound together with a molecular cement that made

it practically airtight. It had no windows; there were two doors.

Certainly it should keep out rodents.

A closer examination revealed an unexpected flaw. The floor was as

hard as glass; no animal could gnaw through it, but, like glass, it

was also brittle. The crew that had built the warehouse had evidently

been in such a hurry to get back to Earth that they hadn't been as

careful as they should have been, for here and there the floor was

thin. Somewhere under the heavy equipment piled on it, the floor had

cracked. There a burrowing animal had means of entry.

Short of building another warehouse, it was too late to do anything

about that. Mice-like animals were inside and had to be controlled

where they were.

The biologist straightened up. "Catch me a few of them alive and I'll

see what I can do."

* * * * *

In the morning, a dozen live specimens were delivered to the lab. They

actually did resemble mice.

Their reactions were puzzling. No two of them were affected by the

same poison. A compound that stiffened one in a matter of minutes left

the others hale and hearty, and the poison he had developed to control

the omnivores was completely ineffective.

The depredations in the warehouse went on. Black mice, white ones,

gray and brown, short-tailed and long-eared, or the reverse, they

continued to eat the concentrates and spoil what they didn't eat.

Marin conferred with the executive, outlined the problem as he saw it

and his ideas on what could be done to combat the nuisance.

"But we can't build another warehouse," argued Hafner. "Not until the

atomic generator is set up, at any rate. And then we'll have other

uses for the power." The executive rested his head in his hands. "I

like the other solution better. Build one and see how it works."

"I was thinking of three," said the biologist.

"One," Hafner insisted. "We can't spare the equipment until we know

how it works."

At that he was probably right. They had equipment, as much as three

ships could bring. But the more they brought, the more was expected of

the colony. The net effect was that equipment was always in short

supply.

Marin took the authorization to the engineer. On the way, he privately

revised his specifications upward. If he couldn't get as many as he

wanted, he might as well get a better one.

In two days, the machine was ready.

It was delivered in a small crate to the warehouse. The crate was

opened and the machine leaped out and stood there, poised.

"A cat!" exclaimed the quartermaster, pleased. He stretched out his

hand toward the black fuzzy robot.

"If you've touched anything a mouse may have, get your hand away,"

warned the biologist. "It reacts to smell as well as sight and sound."

Hastily, the quartermaster withdrew his hand. The robot disappeared

silently into the maze of stored material.

In one week, though there were still some mice in the warehouse, they

were no longer a danger.

* * * * *

The executive called Marin into his office, a small sturdy building

located in the center of the settlement. The colony was growing,

assuming an aspect of permanency. Hafner sat in his chair and looked

out over that growth with satisfaction.

"A good job on the mouse plague," he said.

The biologist nodded. "Not bad, except there shouldn't be any mice

here. Biological Survey--"

"Forget it," said the exec. "Everybody makes mistakes, even B. S." He

leaned back and looked seriously at the biologist. "I have a job I

need done. Just now I'm short of men. If you have no objections...."

[Illustration]

The exec was always short of men, would be until the planet was

overcrowded, and he would try to find someone to do the work his own

men should have done. Dano Marin was not directly responsible to

Hafner; he was on loan to the expedition from Biological Controls.

Still, it was a good idea to cooperate with the executive. He sighed.

"It's not as bad as you think," said Hafner, interpreting the sound

correctly. He smiled. "We've got the digger together. I want you to

run it."

Since it tied right in with his investigations, Dano Marin looked

relieved and showed it.

"Except for food, we have to import most of our supplies," Hafner

explained. "It's a long haul, and we've got to make use of everything

on the planet we can. We need oil. There are going to be a lot of

wheels turning, and every one of them will have to have oil. In time

we'll set up a synthetic plant, but if we can locate a productive

field now, it's to our advantage."

"You're assuming the geology of Glade is similar to Earth?"

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