said. "A human being has to have a soul, doesn't it?"

The Old Man looked at him sharply. "That is not the same definition you offered a few years back."

Healey blushed. "No, sir. I was wrong, and I'm sorry. They have souls, all right. Any kind of creature that loves the ether as the Martians do—he simply has to have a soul."

The Old Man nodded. "I think you're right. No matter what else a man may be, if he hasn't got that spark inside of him, space travel will give him the wiggles."

The Zytztzes had that spark, Healey knew. From the way they had taken to it from the first, Healey could not escape the impression that they must have had indelible memories of days in the dim past, when perhaps their forefathers had traveled in space.

"It's funny," Lieutenant Browne said one day. "You'd think they'd been so long on Mars they'd have taken root, but they don't even get space-sick the first time they fly."

"There are a lot of things about them that I don't understand," Healey said.

In 2125 the IWC ordered a census of the Martians. There were exactly seven hundred and seventy-seven. There were, oddly enough, no young ones. All were adults.

In another five years every single Zytztz held a rating of seaman, first class. Only one had advanced beyond that, because space travel very quickly had developed the most rigid caste system of all history. It was an anomaly, being, as it was, developed within the ranks of men who themselves were discriminated against by the Air Marines. Or perhaps it was because of that. At any rate, space-sailors and space-officers were exclusive far past anything the Air Marines could offer. Perhaps it was because of the glamour lent by the proximity of sudden death, but no Earth-man would take orders from a non-human.

The one who had gone beyond seaman was Mr. Zytztz, who had been made a chief bos'n's mate—and that promotion had precipitated a riot and near-mutiny on the crack passenger run to Luna. By intercession of Admiral Pickens, Mr. Zytztz was not demoted, but his authority was rigidly limited to Martians.

No one had any complaint whatever against Mr. Zytztz except that he was "a century-plant," and presently there was an IWC rule passed that no Earth-man could be put under the supervision of anybody but an Earth-man. That made it official.

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