“But why do you want to keep the embryo below par?” asked an ingenuous student. “Ass!” said the Director, breaking a long silence. “Hasn’t it occurred to you that an Epsilon embryo must have an Epsilon environment as well as an Epsilon heredity?” It evidently hadn’t occurred to him. He was covered with confusion. “The lower the caste,” said Mr. Foster, “the shorter the oxygen.” The first organ affected was the brain. After that the skeleton. At seventy per cent of normal oxygen you got dwarfs. At less than seventy eyeless monsters.
