As we climbed, I could hear the haunting melody of Mildred's wordless song coming faint across the distance. Once I glanced back for a moment, and glimpsed her tiny white figure above the black water, with the thousands of green antennae rising in a luminous forest about her. We reached the top of the cliff, where the opalescent river plunged down in the flaming fall. Ray chose convenient boulders for shelter and quickly we flung ourselves flat. Ray replaced the fired cartridges in the rifle and leveled it across the rock before him. I unslung the binoculars and focussed them. "Watch 'em close," Ray muttered. "And tell me when to shoot." * * * * * The black lake lay below us, with the weird city of sapphire cylinders on its floor. I got the glasses upon Mildred's white form. Soon she dived from the turquoise pedestal, swam swiftly ashore and vanished in the vivid fungous jungle. The wavering green antennae vanished below the water; I watched the crabs swimming away. Some of them climbed out of the water and lumbered off in various directions. In fifteen minutes the slender white form of Mildred appeared at the foot of the ladder. She sprang over the dead crabs and scrambled nimbly up. Soon she was halfway up the face of the cliff, and there had been no sign of discovery. My hopes ran high. I was sweeping the whole plain with the binoculars, while Ray peered through the telescopic sights of the rifle. Suddenly I saw a giant crab pause as he lumbered along the edge of the black lake. He rose upright; his shining green antennae wavered. Then I saw him reaching with a knobbed claw for a slender silver tube slung to his harness. "Quick! The one by the lake! To the right of that canal!" I pointed quickly. Ray swung his gun about, aimed. A broad red beam flashed from the tube the thing carried, and fell upon the cliff. The report of Ray's rifle rang thunderously in my ears. The red ray was snapped off abruptly, and the giant crab rolled over into the black water of the lake. Half a dozen of the huge crabs were in sight. They all took alarm, probably having seen the flash of the red ray. They raised grotesque heads, twisted stalked eyes and waved green antennae. Some of them began to raise the metal tubes of the heat-ray. "Let's get all there are in sight!" Ray muttered. He began firing regularly, with deliberate precision. A few times he had to take two shots, but ordinarily one was enough to bring down a giant crab in a writhing red mass. Three times a red ray flashed out, once at the girl clambering up the ladder, twice at our position above the precipice. But the intense color of the ray announced its source, and Ray stopped each before it could be focussed to do damage. I looked over at Mildred and saw that she was still climbing bravely, a little over a hundred feet below. * * * * *