It looked much like his old one, but it was definitely smaller. The rounded ceiling could be made out quite clearly and he estimated its diameter as not more than a half mile. The far side of the bubble could be seen clearly and this one, he noticed, even from where he stood, had many such clefts and cracks in the wall. It was, he supposed, either an older bubble, more cracked in the course of eons of moonquakes and heat changes, or else it was more tightly knitted in a close mass of such bubbles. A thick jungle of giant Moontrees was growing here, stalklike plants resembling those he knew, but seemingly larger and more profuse. Robin started to walk through it toward the farther wall of the bubble. Cheeky had leaped into the stalks and was swinging through them ahead of him, when suddenly the monkey uttered a terrified shriek and there arose a strange high-pitched barking sound. Robin pushed through and saw the monkey, high in the top of a Moontree and a strange sort of Moonhound leaping for him. This kind of Moonhound was considerably bigger than the ones he had seen in his original bubble. It was uttering the eager bark of a hungry beast sighting its prey. Robin unlimbered his bow and fitting an arrow into it, let fly. The sharp missile skewered the Moonbeast and the animal twisted in mid-air and fell thrashing to the ground. Robin dashed in and finished it off with a blow from the stone club he carried. Cheeky came down from the tree cautiously, advanced to the dead animal, and prodded it. Then the monkey uttered a shriek, bared its teeth, and began to pommel the dead body as if he had been the one to bring it down. Robin examined the animal. It was similar in many ways to the Moonhounds, yet different, and Robin's private theory that the Moonhound represented the equivalent of a mammal type seemed verified. Whereas the Moonhound was a wolf or dog, this creature corresponded more closely to a leopard or tiger. The flesh of this creature seemed as if it might possibly make a substitute for leather--although it, too, was eerily transparent and it, too, possessed but one central eye and a large light organ. Robin trekked on through this jungle until at last he reached the opposite wall. He was aware as he walked that there was a good deal of native life here, much more than had been evident in his own cavern. Evidently the first bubble was pretty much cut off from the general labyrinth of sublunar caverns. For as Robin walked, he caught glimpses of other Moonbeasts, slipping in and out, sometimes surprised and scurrying away. Moonworms, the equivalent of Earth's insect life, were here in plenty too, and there were many giant growths which were different from those in his own cave, and some fruits of considerable promise were growing on them. "We could do some farming now," said Robin to Cheeky. "I'll bring back some of the seeds from these bigger trees and plant them back home. It'll give us some variety."