way, dearest, you can't possibly rescue me," Clio's voice broke.
"Why, there are thousands of them, all around here. If you can get away,
go, dear, but don't...."

"I said I was coming after you, and if I can get away I'll be there. A
good whiff of this stuff will lay out a thousand of them just as easily
as it will one. Here's the idea. I've made a gas mask for myself, since
I'll be in it where it's thick, but you two won't need any. The gas is
soluble enough in water so that three or four thicknesses of wet cloth
over your noses will be enough. I'll tell you when to wet down. We're
going to break away or go out trying--there aren't enough amphibians
between here and Andromeda to keep us humans cooped up like menagerie
animals forever! But here comes my specialist with the keys to the city;
time for the overture to start. See you later!"

The Nevian physician directed his key-tube upon the transparent wall of
the chamber and an opening appeared, an opening which vanished as soon
as he had stepped through it; Costigan kicked a valve open; and from
various innocent tubes there belched forth into the water of the central
lagoon and into the air over it a flood of deadly vapor. As the Nevian
turned toward the prisoner there was an almost inaudible hiss and a tiny
jet of the frightful, outlawed stuff struck his open gills, just below
his huge, conical head. He tensed momentarily, twitched convulsively
just once, and fell motionless to the floor. And outside, the streams of
avidly soluble liquefied gas rushed out into air and into water. It
spread, dissolved, and diffused with the extreme mobility which is one
of its characteristics; and as it diffused and was borne outward the
Nevians, in their massed hundreds, died. Died not knowing what killed
them; not knowing even that they died. Costigan, bitterly resentful of
the inhuman treatment accorded the three and fiercely anxious for the
success of his plan of escape, held his breath and, grimly alert,
watched the amphibians die. When he could see no more motion anywhere he
donned his gas-mask, strapped upon his back a large canister of the
poison--his capacious pockets were already full of smaller
containers--and two savagely exultant sentences escaped him.

"I am a poor, ignorant specimen of ape, that can be let play with
apparatus, am I?" he rasped, as he picked up the key-tube of the
specialist and opened the door of his prison. "Maybe they'll learn
sometime that it ain't