"You know Nerado mentioned several times the 'semi-civilized fishes of the greater deeps'?" he reminded her. "I gather that there are at least three intelligent races here. We know two--the Nevians, who are amphibians, and the fishes of the greater deeps. The fishes of the lesser deeps are also intelligent. As I get it, the Nevian cities were originally built in very shallow water, or perhaps were upon islands. The development of machinery and tools gave them a big edge on the fish; and those living in the shallow seas, nearest the islands, gradually became tributary nations, if not actually slaves. Those fish not only serve as food, but work in the mines, hatcheries, and plantations, and do all kinds of work for the Nevians. Those so-called 'lesser deeps' were conquered first, of course, and all their races of fish are docile enough now. But the deep-sea breeds, who live in water so deep that the Nevians can hardly stand the pressure down there, were more intelligent to start with, and more stubborn besides. But the most valuable metals here are deep down--this planet is very light for its size, you know--so the Nevians kept at it until they conquered some of the deep-sea fish, too, and put 'em to work. But those high-pressure boys were nobody's fools. They realized that as time went on the amphibians would get further and further ahead of them in development, so they let themselves be conquered, learned how to use the Nevians' tools and everything else they could get hold of, developed a lot of new stuff of their own, and now they're out to wipe the amphibians off the slate completely, before they get too far ahead of them to handle." "And the Nevians are afraid of them, and want to kill them all, as fast as they possibly can," guessed Clio. "That would be the logical thing, of course," commented Bradley. "Got pretty nearly enough distance now, Costigan?" "There isn't enough distance on the planet to suit me," Costigan replied. "We'll need all we can get. A full diameter away from that crew of amphibians is too close for comfort--their detectors are keen." "Then they can detect us?" Clio asked. "Oh, I wish they hadn't hit us--we'd have been away from here long ago." "So do I," Costigan assented, feelingly. "But they did--no use squawking. We can rivet and weld those seams and pump out the shell, and we'd have to fill our air-tanks to capacity for the trip, anyway. And things could be a lot worse--we are still breathing air!" In silence the lifeboat flashed onward, and half of Nevia's mighty globe was traversed before it was brought to a halt, in the emptiest reaches of the planet's desolate and watery waste. Then in furious haste the two officers set to work, again to make their small craft sound and spaceworthy. CHAPTER VI Worm, Submarine, and Freedom