t me,
and brought me here. No escape now, until I die."

"The Ralas--you mean these frog-men?" Norman asked.

Sarja nodded. "Of course. They are the tyrants and oppressors of this
world. Our little world is but a tenth or less the size of your great
Earth which it circles, but it has its lands and rivers, and this one
great fresh-water sea into which the latter empty. In this sea long
ago developed the Ralas, the great frog-men who acquired such
intelligence and arts that they became lords of this world.

"Through the centuries, while on the land our races of green men have
been struggling upward, the Ralas have oppressed them. Long ago the
Ralas left all their other cities to build this one great amphibian
city at the sea's center. Entrance to it is only by the water-tunnel
from without, and being frog-people entrance thus is easy for them
since they can move for many minutes under water, though they drown
like any other breathing animal if kept under too long. Humans dare
not try to enter it thus by the water-tunnel, since, before they could
find it and make their way up through it, they would have drowned.

* * * * *

"So the Ralas have ruled from this impregnable amphibian city. Its
colossal metal dome is invulnerable to ordinary attack, and though
solid and without openings it is always as light beneath the dome here
as outside, since the Ralas' scientists contrived light-condensers and
conductors that catch light outside and bring it in to release inside.
So when it is day outside the sunlight is as bright here, and when
night comes the Earth-light shines here the same as without.

"From this city their raiding parties have gone out endlessly to swoop
down on the cities of us green men. Since we learned to make
flying-boats like theirs, with molecular-motors, and to make the guns
like theirs that fire shells filled with annihilating force, we have
resisted them stoutly but their raids have not ceased. And always they
have brought their prisoners back in to this, their city.

"Tens of thousands of green men they have prisoned here like us, for
the sole purpose of supplying them with blood. For the Ralas live on
this blood alone, changing it chemically to fit their own bodies and
then taking it into their bodies. It eliminates all necessity for food
here for them. Every few days they drain blood from us, and since we
are well fed and cared for to keep us good blood-producers, we