toward the huts. They obeyed, with one
or two backward glances. Left alone with Parr, Sadau looked up with a
wise, friendly expression.

"I won't waste time trying to be scientific or convincing. I'll give you
facts--we older exiles know them only too well. This asteroid seems a
sort of Eden to you, I daresay."

"I told the Martians that I knew there was a catch somewhere."

"Your instinct's sound. The catch is this: Living
creatures--Terrestrials anyway--degenerate here. They go backward in
evolution, become--" Sadau broke off a moment, for his lips had begun to
quiver. "They become beasts," he finished.

"What?" growled Parr. "You mean that men turn into apes?"

"Yes. And the apes turn into lower creatures. Those become lower
creatures still." Sadau's eyes were earnest and doleful. "The process
may run back and down to the worm, for all we can judge. We try not to
think too much about it."

"This is a joke of some kind," protested Parr, but Sadau was not
smiling.

"Martian joke, perhaps. The treaty keeps them from killing us--and this
is their alternative punishment. It makes death trivial by
comparison.... You don't believe. It's hard. But you see that some of
us, oldest in point of exile, are sliding back into bestiality. And you
saw us drive away, as our custom is, a man who had definitely become a
beast."

"That thing was a man?" prompted Parr, his spine chilling.

"It had been a man. As you wander here and there, you'll come upon queer
sights--sickening ones."

Parr squinted at the huts, around the doors of which lounged the other
men. "That looks like a permanent community, Sadau."

"It is, but the population's floating. I came here three months
ago--Earth months--and the place was operating under the rules I
outlined. Latest comer, necessarily the highest-grade human being, to be
chief; those who degenerate beyond a certain point to be driven out; the
rest to live peaceably together, helping each other."

Parr only half heard him. "Evolution turned backward--it can't be true.
It's against nature."

"Martians war against nature," replied Sadau pithily. "Mars is a dead
world, and its people are devils. They'd be the logical explorers to
find a place where such things can be, and to make use of it. Don't
believe me if you don't want to. Time and life here will convince you."

* * * * *

In the days that followed--the asteroid turned once in approximately
twenty-t