greatly changed creature, a mutant.
"Because of this, many biologists now believe that the radiation from the radioactive deposits inside earth, acting upon all the genes of every living thing on earth, are what cause the constant change of species, the procession of mutations, that has brought life up the evolutionary road to its present height.
"That is why I say that on any other world but earth, evolutionary progress might never have happened. For it may be that no other world has similar radioactive deposits within it to cause by gene-effect the mutations. On any other world, the first protoplasmic things that began life might have remained forever the same, down through endless generations.
"How thankful we ought to be that it was not so on earth! That mutation after mutation has followed, life ever changing and progressing into new and higher species, until the first crude protoplasm things have advanced through countless changing forms into the supreme achievement of man!"
WOODIN'S enthusiasm had carried him away as he talked but now he stopped, laughing a little as he relit his pipe.
"Sorry that I lectured you like a college freshman, Ross. But that's my chief subject of thought, my idée fixé, that wonderful upward climb of life through the ages."
Ross was staring thoughtfully into the fire. "It does seem wonderful the way you tell it. One species changing into another, going higher all the time—"
Gray stood up by the fire and stretched. "Well, you two can wonder over it but this crass materialist is going to emulate his remote invertebrate ancestors and return to a prostrate position. In other words, I'm going to bed."
He looked at Ross, a doubtful grin on his blond young face, and said, "No hard feelings now, feller?"
"Forget it," the aviator grinned back. "The paddling was hard today and you fellows did look mighty skeptical.
"But you'll see! To-morrow we'll be at the forks of the Little Whale and then I'll bet we won't scout an hour before we run across those jelly-creatures."
"I hope so," said Woodin yawningly. "Then we'll see just how good your eyesight is from a mile up, and whether you've yanked two respectable scientists up here for nothing."
Later as he lay in his blankets in the little tent, listening to Gray and Ross snore and looking sleepily out at the glowing fire embers, Woodin wondered again about that.
What had Ross actually seen in that fleeting glimpse from his speeding plane? Something queer, Woodin was sure of that, so sure that he'd come on this hard trip to find it. But what exactly?
Not protoplasmic things such as he described. That couldn't be, of course. Or could it? If things like that had existed once, why couldn't they—couldn't they—
Woodin didn't know he'd been sleeping until he was wakened by Gray's cry. It wasn't a nice cry, it was the hoarse yell of someone suddenly assaulted by bone-freezing terror.
He opened his eyes at that cry to see the Incredible looming against the stars in the open door of the tent. A dark, amorphous mass humped there in the opening, glistening all over in
