lines. Overhead, the wide blades of the
helicopter flapped around and around, accompanied by little hissing
puffs of rocket smoke. They could see Boulton looking down at them from
the tiny cabin.

Russ was scooping up bits of soil to bring back for analysis when he saw
what seemed to be a wet patch on top of the wall. As he watched, it
spread until it reached the bottom. In a remarkably short time a whole
section of wall was gleaming wet. A patch of damp oiliness spread over
the floor.

"This I've got to get a sample of," said the rusty-haired astronomer. He
reached for a sampling bottle in his pocket, and at the same time the
patch of wetness spread to his shoes.

As Russ stepped forward, there was a sucking sound, and he lifted a
thick gummy mass that was stuck to his sole. He shook his foot, set it
down, and lifted the other, but it, too, was imbedded in thick slime.
The stuff now was running up his ankle.

"Hey!" he called out, and swung one foot vigorously to free it. More
swiftly than he could move, the whole patch slid down the wall and swept
around him. It was moving up his legs, as if trying to envelop him.

"It's alive!" he shouted, and grabbed for the knife in his belt. In vain
he tried to slash out. "It's like a giant amoeba that engulfs its food!
Get it off me!"

But the knife was ineffective. He fired his pistol, but the thing was
just a vast wide puddle of slime, without brain, heart or organ that
could be harmed. The soles of Russ's boots were already half eaten away
and his socks were going fast. Some of it was touching the skin of his
knees.

He screamed as the stuff burned him.

Burl had joined the attack with his knife, but leaped back when that
proved useless. His mind raced for a way to help. Above them, Boulton
was swinging the helicopter down so Russ could hoist himself out of
harm's way, but time would not permit it. In another instant the mass
would have Russ.

Burl grabbed at the straps crossing his shoulder and swung the two
oxygen tanks from his back. He snatched one from its leather holster,
and pointed its nozzle at the mass of slime. He turned the stream of
oxygen on, and then, taking his pistol, held its muzzle in the jet of
oxygen and fired it.

The roar of the gun was matched by the roar of a stream of fire that
shot from the tank. Wherever the burning jet of oxygen touched, the mass
shriveled and blackened. Yards and yards of amoeba seemed to writhe,
hump upward in agony