Instantly sharp-ribbed wings battered at him, an open hand struck him a terrific blow behind the ear, and a second later something long and steel-hard thudded into his ribs. He was flung forcibly against the side of the nearby building. Only the mechanical obedience of the levitator saved him--it had been set for "up," and it dragged him on up, willy-nilly. A hot liquid oozed down his side from the blow of the vacuum-rod. In a fog of pain he saw Atel banking purposefully for another assault, and clutched at the "Up" control again. [Illustration: _Wings battered him, and Atel's club thudded against his ribs._] The levitator could climb faster than the Varan could, and Andreson had a moment's respite. Grimly he kept on going, until a growing sense of pressure and heat warned him that the rock dome was near. Should he try to lose himself among the city towers, or yell to Johnny Kimball for help? His whole heart turned from the thought. His earthly life had not kept him in very good physical shape, but he'd always fought his own battles. It made no difference that his life was the stake of this one. _I'll get him yet_, he thought intensely. _Get him without help--if it kills me._ "Well, Earthman," Atel's voice rang out below. The rock dome sent back a huge echo. "Running already? If Jina could see her hero now!" For a moment Andreson was about to dive furiously after the Varan again, but he thought better of it. He remembered Johnny's words: "You're no match for him in his own environment." But-- Atel was not fighting another winged man. He was fighting an Earthman with a levitator. That scrap between the buildings--had Atel given such a buffeting to a Varan he would have knocked him and that would have been the end of it. But the levitator couldn't be knocked out, no matter what happened to the man operating it. It wouldn't fall unless it was set to fall. There was something else, too. Birds fly because they're built for it--among other things they have a huge keel-like breastbone to which their flying muscles are anchored. But bats don't, and Andreson bet that the Varans didn't either. Rodents are ancestrally ground-animals, just like Earthmen, and have to adapt for flying in some other way.... Andreson smiled crookedly. There was only one way to test the idea. He touched the belt again, and the city began to swell beneath him-- Atel glided cautiously out of the way of his fall, then closed in. The Earthman shot off laterally, turned, began a tail-chase. For a few seconds the absurd circling continued, each combatant trying to gain on the other. Then Atel realized that the levitator could drive Andreson faster than he could fly, and spun to face him with a single sweep of his wings.