Jake's gasp came through the earphones and then his giggle, "He--he--he, Mr. Adam, there's two more forms of life and we make another one, if we stay alive till we get back." Another three steps, and they halted again at the sight of a shapeless, almost white mass looming through the fog of green ahead. It was alive; it moved, but flowing, rather than swimming, and as nearly as they could make out in the dimness was without eyes, mouth or visible organs of any kind, a huge, shapeless jelly. Adam reached for the rocket pistol at his belt, but Jake's eye had caught the motion and his voice came through the earphones, "Don't use that thing, Mr. Adam. It ain't--Holy catfish!" The huge colorless jelly had sidled toward them through the water, then sheered off, revealing as it did so, a core of some darker color through its translucent sides and three shapeless legs whose motion propelled it. As it made the turn away from the explorers it bumped one of the curious segmented weeds and Jake had cried out. * * * * * For where the animal had bumped the weed a huge dent appeared in its rounded forward end, growing rapidly till it was a cavern, a cavern which engulfed the chain-weed. Instantly the lips of the cavern closed; Adam could see that the surface had become as smooth as before, while inside the translucent structure of the animal the outline of the weed was faintly visible. "I've seen things like that before," said Adam softly, as though fearful of attracting the monster's attention. "Where? I ain't never seen nothing like that. And I'm telling you, Mr. Adam, I been around a lot. Even in those dinosaur swamps on Venus." "Ever look through a microscope, Jake?" "Can't say as I have very often, Mr. Adam." "That's just what you see in a microscope, Jake. That brown thing was just like a rotifer. Those big white lumps, that can turn themselves into mouths anywhere they want to and then close up and turn themselves into stomachs, they're amoebas. Amoebas as big as whales! They're the most savage animals in the whole created kingdom--and just about the most dangerous for their size." The engineer's voice was doubtful. "You mean we're sort of in a microscope?" Adam grunted. "Microscope my left foot! Those things are real! They're dangerous! They're the lowest form of life, but what happened is probably that they couldn't develop into any higher forms on this cold planet, so they simply grew to gigantic size. Let's get out of here." He took off in a long soaring step that carried him jerkily six feet through the water, Jake following. They had progressed perhaps three leaps, when the engineer's voice was suddenly loud inside Adam's helmet--"Look! On the left there!" Adam checked himself in mid-leap and saw a dark figure in the green gloom of the undersea world, with one of the giant amoebas swooping toward it. "A man!" came Jake's voice. "It's attacking one of the crew. Stand still you, we're coming!"