The fact was that I had something more in the lab than I had bargained for. I had aimed only at a gliding mammal a little more efficient than the Dusky Glider of Australia, a marsupial. Even in the basically mutating colony, there had been a decidedly simian appearance in recent years, a long shift from the garbage-dump rats I had started with. But my first volplas were shockingly humanoid. They were also much faster than had been their predecessors in organizing their nervous activity after the slumbrous explosion of growth in the metabolic accelerator. When I returned to the lab, they were already moving about on the mattress and the male was trying to stand. He was a little the larger and stood twenty-eight inches high. Except for the face, chest and belly, they were covered with a soft, almost golden down. Where it was bare of this golden fur, the skin was pink. On their heads and across the shoulders of the male stood a shock of fur as soft as chinchilla. The faces were appealingly humanoid, except that the eyes were large and nocturnal. The cranium was in the same proportion to the body as it is in the human. * * * * * When the male spread his arms, the span was forty-eight inches. I held his arms out and tried to tease the spars open. They were not new. The spars had been common to the basic colony for years and were the result of serial mutations effecting those greatly elongated fifth fingers that had first appeared in Nijinsky. No longer jointed like a finger, the spar turned backward sharply and ran alongside the wrist almost to the elbow. Powerful wrist muscles could snap it outward and forward. Suddenly, as I teased the male volpla, this happened. The spars added nine inches on each side to his span. As they swept out and forward, the lateral skin that had, till now, hung in resting folds was tightened in a golden plane that stretched from the tip of the spar to his waist and continued four inches wide down his legs to where it anchored at the little toe. This was by far the most impressive plane that had appeared till now. It was a true gliding plane, perhaps even a soaring one. I felt a thrill run along my back. By four o'clock that afternoon, I was feeding them solid food and, with the spars closed, they were holding little cups and drinking water from them in a most humanlike way. They were active, curious, playful and decidedly amorous. Their humanoid qualities were increasingly apparent. There was a lumbar curvature and buttocks. The shoulder girdle and pectoral muscles were heavy and out of proportion, of course, yet the females had only one pair of breasts. The chin and jaw were humanlike instead of simian and the dental equipment was appropriate to this structure. What this portended was brought home to me with a shock.