an oval glass shell. This was
filled with water. A flexible metal tube hung down from the rear.
Evidently it carried a constant stream of fresh water. As we gazed we
saw intermittent trickles emerging from the bottom of the crystalline
case.

Point for point the creature's equipment was the same as diving
equipment used by men, only it was exactly opposite in function. A
helmet that enabled a fish to breathe in air, instead of a helmet to
allow a man to breathe in water!

Stanley was the first of us to recover from the shock of this spectacle.
He faced about and raised his voice in shouts of warning to the resting
Zyobites. For other glass encased monsters had appeared beside the
first, now.

One by one, in single file like a line of enormous marching insects,
they crawled down the wall and humped along on their tentacles--around
the ditch and toward us!

* * * * *

The deadly infallibility of that second attack!

The Quabos advanced on us like armored tanks bearing down on defenceless
savages. Their glass helmets, in addition to containing water for their
breathing, protected them from our knives and axes. We were utterly
helpless against them.

They marched in ranks about twenty yards apart, each rank helping the
one in front to carry the cumbersome water-hoses which trailed back to
the central water supply in the tunnel.

Their movements were slow, weighted down as they were by the great glass
helmets, but they were appallingly sure.

We could not even retard their advance, let alone stop it. Here were no
suffocating, faltering creatures. Here were beings possessed of their
full vigor, each one equal to three of us even as the Professor had
conjectured. Their only weak points were their tentacles which trailed
outside the glass cases. But these they kept coiled close, so that to
reach them and hack at them we had to step within range of their
terrific clutches.

The Zyobites fought with the valor of despair added to their inherent
noble bravery. Man after man closed with the monstrous, armored
Things--only to be seized and crushed by the weaving tentacles.

Occasionally a terrific blow with an ax would crack one of the glass
helmets. Then the denuded Quabo would flounder convulsively in the air
till it drowned. But there were all too few of these individual
victories. The main body of the Quabos, rank on rank, dragging their
water-hose behind them, came on with the steadi