arred
door slid slowly up, to reveal the receding darknesses of some great
cave, or room, that adjoined the laboratory. Dex rolled his eyes so
that he could watch the doorway; and, in a cold perspiration, waited
for whatever might appear.

It was not long in coming!

The reptilian smell suddenly grew stronger. There was a booming hiss,
a savage bellowing. A clattering of vast scales rattled out as some
body weighing many tons was dragged over rock flooring. Then, before
Dex's staring eyes appeared a huge, wedge-shaped head, at sight of
which he bit his lips to keep from crying aloud.

Often enough he had seen one of those terrific heads looming in the
fog of the northern hemisphere of Jupiter. He did not know the genus
of the vast monster that bore it, but he did know it for the fiercest
of the lizard giants that roamed the Jovian jungles. A creature larger
than a terrestrial whale, with great long neck and heavy long tail
dragging yards behind it, it would find the puny bulk of a man nothing
but a morsel in its jaws!

Again the gigantic thing hissed and bellowed. And then its huge head
came through the six-foot door and its neck uncoiled to send the
gaping jaws within a foot of Dex. There it struggled to reach him,
prevented by the small doorway that restrained the bulk of its
enormous body, its head only inches away from the cleverly measured
spot to which the metal rack had been wheeled.

* * * * *

Dex stared, hypnotized, into the dull, stony eyes of the beast,
gasping for breath in the stench of its exhalations. The jaws snapped
shut, fanning his cheek. He fought for self-control. Steady! Steady!
The slimy Rogans had no intention of feeding him to the thing yet. Not
till they had made more determined efforts to wring from him the
secret of the motor. They were just prefacing actual physical torture
with hellish mental torture, that was all.

That he was right in his guess was proved in a few moments. He heard a
louder hiss from the great lizard so near him. Opening his eyes, he
saw the Rogan leader in the process of forcing the serpentine neck to
withdraw foot by foot back into the doorway, using his shock-tube as a
sort of distant prod.

The monster swayed its ugly flat head back and forth, hissing
deafeningly at the sting of the tube, now and again lunging with its
vast unseen body at the too narrow entrance that kept it from entering
the laboratory. Dex could hear the fo