They had the advantage not of merely controlling the environment but of being the environment. Subject to the violence of volcanoes and the endless shifting of the planet's crust, aberrations in the plane of rotation, and rapid changes of climate, as ice mounted and retreated and heat waxed and waned, within these limits they could and did make arbitrary decisions. By withdrawing from an area, either of them could create a desert. By doubling their rate of growth in a local tributary of themselves, they could create a forest. Their descendant seeds were as much part of themselves as the original trunks. In fact, they rarely distinguished between that original growth and later developments. It came as quite a surprise to them both to find there was not much left of the first bulb clusters and the first sprawling creeper. * * * * * Once they had induced the more-or-less fishes to leave the water, progress was rapid. There was never a difficulty quite as great as that again. On land, wherever the land happened to be at the time, they could induce generations of different shapes and sizes by modifying the vegetation--themselves, in their many forms. He took his branches higher and higher in a sparse zone, for example, to encourage the necks of the local animals to extend. They were remodeling their program deliberately on their old Earth, cutting off what they knew to be unsuccessful by-paths and nurturing the developments that should lead to man. The original crablike inhabitants had long since passed away, though they had used some features of these. The insects continued to multiply on their own by sheer probability and without their guidance. They were both ruthless in their experiments. Once they abolished whole races of enormous vegetarians by withholding themselves in inaccessible areas. Like the dinosaurs, whom they resembled closely, these great reptiles were too big and too stupid. She blamed him for having allowed them to feed too many generations on too highly radioactive parts of themselves. "I can't be everywhere at once all the time," he said. To annoy her, and because he had been a space captain, he encouraged an entirely abortive series of flying reptiles. His excuse was true. By exerting his consciousness to its maximum, he could be aware of almost all the planet simultaneously, but this awareness lacked intensity and definition. The comfortable maximum for concentration was about a hundred square miles. If he focused his attention within a square mile, his roots and trunks and branches hissed with massive life and rapidly propagated themselves into a thick jungle. This in turn multiplied the surface areas and diffused his attention. There was a lot going on in the undergrowth that they both missed. They almost missed their ultimate triumph. * * * * *