The natives, like all Martian fauna, were multi-legged. Also like all Martian fauna, they moved so fast that you couldn't see how many legs they did have. Actually, however, the natives had six legs apiece--or, more properly, four legs and two arms. Their lungs were not as large as they appeared, being collapsed at the moment. What caused the bulge that made their torsos look like sausages was a huge air bladder, with a valve arrangement from the stomach and feeding directly into the bloodstream. Their faces were vaguely canine, but the foreheads were high, and the lips were not split. They did resemble dogs, in that their thick black fur was splotched with irregulate patches of white. These patches of white were subject to muscular control and could be spread out fanwise; or, conversely, the black could be expanded to cover the white, which helped to take care of the extremes of Martian temperature. Right now they were mostly black. The natives slowed down and spread out to surround the wrecked sand car, and it could be seen that most of them were armed with spears, although some had the slim Benson energy guns--strictly forbidden to Martians. Syme stopped cursing and watched tensely. Tate said nothing, but he swallowed audibly. One Martian, who looked exactly like all the rest, stepped forward and motioned unmistakably for the two to come out. He waited a moment and then gestured with his energy gun. That gun, Syme knew from experience, could burn through a small thickness of steelite if held on the same spot long enough. * * * * * "Come on," Syme said grimly. He rose and reached for a pressure suit, and Tate followed him. "What do you think they'll--" he began, and then stopped himself. "I know. They're unpredictable." "Yeah," said Syme, and opened the door. The air in the car _whooshed_ into the near-vacuum outside, and he and Tate stepped out. The Martian leader looked at them enigmatically, then turned and started off. The other natives closed in on them, and they all bounded along under the weak gravity. They bounded along for what Syme figured as a good kilometer and a half, and they then reached a branch in the gully and turned down it, going lower all the time. Under the light of their helmet lamps, they could see the walls of the gully--a tunnel, now--getting darker and more solid. Finally, when Syme estimated they were about nine kilometers down, there was even a suggestion of moisture. The tunnel debouched at last into a large cavern. There was a phosphorescent gleam from fungus along the walls, but Syme couldn't decide how far away the far wall was. He noticed something else, though. "There's air here," he said to Tate. "I can see dust motes in it." He switched his helmet microphone from radio over to the audio membrane on the outside of the helmet. "_Kalis methra_," he began haltingly, "_seltin guna getal._"