ce with their conquerors.

"Why, they look just like us!" Joe Buckner said indignantly. He sounded
outraged at the resemblance.

"There are many differences," the instructor said quickly. "Note their
clothing, how poorly made it is. They make it themselves out of the wool
of some kind of animal--deer, I believe, or bear."

"Sheep," Billy Kasker corrected.

"Oh, yes, sheep is the name of the animal. Thank you, Billy."

"You're welcome, sir."

"But they oughtn't to look like _us_!" Joe Buckner continued.

"There are chemical differences," Susan Sidwell said. "Once, in the
laboratory, we analyzed their blood. The color was different for one
thing. They also have a much different metabolism."

"But suppose one of them escaped from the museum and got into our part
of the world. How would we know he wasn't one of us, if he put on our
clothes?" Joe Buckner sounded outraged.

"That is one purpose our bracelets serve," the instructor answered. "A
very good question, Joe. As you know, each of us receives a bracelet at
birth, which is slipped over the hand and onto the wrist. Made of
_plasticum_, which cannot be cut by any method, the bracelet has the
unique property of expanding in size as the wearer grows. It cannot be
removed except by cutting off the arm of the wearer." He laughed as if
he had made a good joke. "But I am sure no one would ever think of doing
that. The bracelet carries the serial number assigned to each of us."

He held up his arm, exhibiting the gleaming circle of _plasticum_ on his
wrist. To him--to all of them--it was a badge of honor, a mark that
proved one belonged to a superior race. "If one of the natives escaped,
the absence of a bracelet would disclose his identity at once. We would
take measures to have him eliminated."

"I see," Joe Buckner said. He sounded mollified. "How would we eliminate
him?"

"I believe it is customary to use a _Thor_ gun in such cases--a large
caliber which will disintegrate him instantly. The model I have will
only blast a hole a few inches in diameter."

"I'm going to be a _Thorgunman_," Joe Buckner said with sudden
enthusiasm.

"Good!" the instructor said. "That is a very fine calling. If I had my
life to live over again--" He sighed for lost opportunities.

At the announcement of his ambition, Joe Buckner rose higher in the
opinion of the class.

"Observe how they make their living," the instructor continued.

The class saw the natives at work tilling