For fifty years he had tried to colonize Mars and all his efforts had failed. Besides this dome which had been built for us there was only one other outpost, another glassite dome much smaller and less than a mile away. It had looked as though mankind could never spread to the other planets of the solar system besides Earth for of all of them Mars was the least inhospitable; if he couldn't live here there was no use even trying to colonize the others. And then, in 2034, thirty years ago, a brilliant biochemist named Waymoth had discovered daptine. A miracle drug that worked not on the animal or person to whom it was given, but on the progeny he conceived during a limited period of time after inoculation. It gave his progeny almost limitless adaptability to changing conditions, provided the changes were made gradually. Dr. Waymoth had inoculated and then mated a pair of guinea pigs; they had borne a litter of five and by placing each member of the litter under different and gradually changing conditions, he had obtained amazing results. When they attained maturity one of those guinea pigs was living comfortably at a temperature of forty below zero Fahrenheit, another was quite happy at a hundred and fifty above. A third was thriving on a diet that would have been deadly poison for an ordinary animal and a fourth was contented under a constant X-ray bombardment that would have killed one of its parents within minutes. Subsequent experiments with many litters showed that animals who had been adapted to similar conditions bred true and their progeny was conditioned from birth to live under those conditions. "Ten years later, ten years ago," the Head Teacher told us, "you children were born. Born of parents carefully selected from those who volunteered for the experiment. And from birth you have been brought up under carefully controlled and gradually changing conditions. "From the time you were born the air you have breathed has been very gradually thinned and its oxygen content reduced. Your lungs have compensated by becoming much greater in capacity, which is why your chests are so much larger than those of your teachers and attendants; when you are fully mature and are breathing air like that of Mars, the difference will be even greater. "Your bodies are growing fur to enable you to stand the increasing cold. You are comfortable now under conditions which would kill ordinary people quickly. Since you were four years old your nurses and teachers have had to wear special protection to survive conditions that seem normal to you. "In another ten years, at maturity, you will be completely acclimated to Mars. Its air will be your air; its food plants your food. Its extremes of temperature will be easy for you to endure and its median temperatures pleasant to you. Already, because of the five years we spent in space under gradually decreased gravitational pull, the gravity of Mars seems normal to you.