man of the Ertak. And these things are his particular pets. Right, Hendricks?"

"Right, sir!" said my third officer grimly.

Correy muttered under his breath, something which sounded very much like profanity, but I let it pass.

I knew just how he felt.

I have never liked to wear a breathing mask. I feel shut in, frustrated, more or less helpless. The hiss of the air and the everlasting flap-flap of the exhaust-valve disturb me. But they are very handy things when you walk abroad on a world which has no breathable atmosphere.

You've probably seen, in the museums, the breathing masks of that period. They were very new and modern then, although they certainly appear cumbersome by comparison with the devices of to-day.

Our masks consisted of a huge shirt of air-tight, light material which was belted in tightly around the waist, and bloused out like an ancient balloon when inflated. The arm-holes were sealed by two heavy bands of elastic, close to the shoulders, and the head-piece was of thin copper, set with a broad, curved band of crystal which extended from one side to the other, across the front, giving the wearer a clear view of everything except that which was directly behind him. The balloon-like blouse, of course, was designed to hold a small reserve supply of air, for an emergency, should anything happen to the tank upon the shoulders, or the valve which released the air from it.

They were cumbersome, uncomfortable things, but I donned mine and adjusted the menore, built into the helmet, to full strength. I wanted to be sure I kept in communication with both Hendricks and the sentries at the air-lock exit, and of course, inside the helmets, verbal communication was impossible.

I glanced at Hendricks, and saw that he was ready and waiting. We were standing inside the air-lock, and the mighty door of the port had just finished turning in its threads, and was swinging back slowly on its massive gimbals.

"Let's go, Hendricks," I emanated. "Remember, take no chances, and keep your eyes open."

"I'll remember, sir," replied Hendricks, and together we stepped out onto the coarse gravel of the beach.

Before us, waves of an unhealthy, cloudy green rolled slowly, heavily shoreward, but we had no eyes for this, nor for the amazing vegetation of the place, plainly visible on the curving shores. We took a few hurried steps away from the ship, and then turned to survey the monsters which had attacked it.

They literally covered the ship; in several places their transparent, glowing bodies overlapped. And the sides of the Ertak, ordinarily polished and smooth as the surface of a mirror, were dull and deeply eroded.

"Notice, sir," emanated Hendricks excitedly, "how much brighter the things are! They are feeding, and they are growing stronger and more brilliant. They —look out, sir! They're attacking! Our copper helmets—"

But I had seen it as quickly as he. Half a dozen of the glowing things, sensing in some way the presence of a metal which they apparently preferred to that of the Ertak's hull, suddenly detached themselves and came swarming directly down upon us.

I was standing closer to the ship than Hendricks, and they attacked me first. Several of them dropped upon me, their glowing bodies covering the vision-piece, and blinding me with their light. I waved my arms and started to run blindly, incoherent warnings coming to me through the menore from Hendricks and the sentries.

The things had no weight, but they emitted a strange, electric warmth which seemed to penetrate my entire body instantly as I ran unseeingly, trying to find the ship, tearing at the fastenings of my mask as I ran. I could not, of course, enter the ship with these things clinging to my garments.

Suddenly I felt water splash under my feet; felt its grateful coolness upon my legs, and with a gasp I realized I had in my confusion been running away from the ship, instead of toward it. I stopped, trying to get a grip on myself.

The belt of the breathing mask came loose, and I tore the thing from me, holding my breath and staring around wildly. The ship was only a few yards away, and Hendricks, his mask already off, was running toward me.

"Back!" I shouted. "I'm all right now. Back!" He hesitated for an instant until I caught up with him, and then, together, we gained the safety of the air-lock. Without orders, the men swung shut the ponderous door, and Hendricks and I stood there panting, and drawing in breaths of the Ertak's clean, reviving air.

"That possibility was one we overlooked, sir," said Hendricks. "Let's see what's happening."

We opened the shutter of a port nearby and gazed out onto the beach we had so hurriedly deserted. There were three or four of the glowing things huddled shapelessly around our abandoned suits, and ragged holes showed in several places in the thin copper helmets. Even as we looked, they dissolved into nothingness, and after a few seconds of hesitation, the things swarmed swiftly back to the ship.

"Well," I commented, trying to keep my voice reasonably free from the feelings which gripped me, "I believe we're beaten, Hendricks. At least, we're helpless against them. Our only chance is that they'll leave us before they have eaten through the second skin; so long as we still have that, we can live ... and perhaps be found."

"I doubt they'll leave us while there's a scrap of metal left, sir," said Hendricks slowly. "Something's brought them from their usual haunts. There's no reason why they should leave a certainty for an uncertainty. But we're not quite through trying. I saw something—have I your permission to make another try at them? Alone, sir?"

"Any chance of success, lad?" I asked, searching his eyes.

"A chance, sir," he replied, his glance never wavering. "I can be ready in a few minutes."

"Then, go ahead—on one condition: that you let me come with you."

"Very good, sir; as you wish. Have two other breathing masks ready. I'll be back very soon."

And he left me hastily, taking the steps of the companionway two at a time.

It was nearly an hour before Hendricks returned, bringing with him two of the most amazing pieces of apparatus I have ever seen.

To make each of them, he had taken a flask of compressed air from our emergency stores, and run a flexible tube from it into a cylindrical drinking water container. Another tube, which I recognized as being a part of our fire-extinguishers, and terminating in a metal nozzle, sprouted from the water container. Both tubes were securely sealed into the mouth of the metal cylinder, and lengths of hastily-knotted rope had been bound around each contrivance so that the two heavy containers, the air flask and the small water tank could be slung from the shoulders.

"Here, sir," he said hastily, "get into a breathing mask, and put on these things as you see me do. No time to explain anything now, except this: as soon as you're outside the ship, turn the valve that opens the compressed air flask. Hold this hose, coming from the water container, in your right hand. Don't touch the metal nozzle. Use the hose just as you'd use a portable disintegrator-ray projector."

I nodded, and followed his instructions as swiftly as possible. The two containers were heavy, but I adjusted their ropes across my shoulders so that my left hand had easy access to the valve of the air flask, and the water container was under my right arm where I could have the full use of the hose.

"Let me go first, sir," breathed Hendricks as we stood again in the air-lock, and the door turned out of its threaded seat and swung open. "Keep your eyes on me, and do as I do!"

He ran heavily out of the ship, his burdens lurching. I saw him turn the pet-cock of the