"Sun, dry up the marshes, and see what happens." So the Sun blazed down on the marshes and began to dry them up. It took him thousands of years to do it, for they were very large, but he did not mind that, for he had nothing to do but shine. The fish that had been carried into the marshes had a great time, at first, swimming about in the shallow water quite as much at home as they had been in the Ocean. But after a while, as the marshes began to dry up, some of the fish got caught in the mud on the edges, and they couldn't breathe, with their heads out of water, so they flopped their fins in the mud, and tried to breathe the air, and at last, by pushing with their fins, they managed to get back into the deeper water again. Every time this happened, their fins got a little tougher and stronger, from pushing themselves along in the mud, and their lungs got a little more used to breathing air, instead of water, and by the time thousands of years had gone by, and the water in the marshes was nearly all dried up, the great-great-great-grandchildren of the first fish had got so used to breathing air that they did not mind it a bit, and their fins had got so used to rubbing along on the mud that they weren't fins any longer, but had changed to short, strong little webbed feet. Mother Nature came and looked at them, and laughed. "You see, Ocean," she said, "I knew what I was about. Your fish have turned into reptiles. They can live on land as well as in the water, and they have legs and feet." "How did you do it?" the Ocean asked. "I did not do it. There is a wonderful law, made by God, which takes care of all such things. No matter what sort of a life any creature is in the habit of living, if you make him live another kind of life, he will change himself to suit it. Your fish couldn't breathe air, when they first tried it, but as soon as they _had_ to breathe it, this law I speak of helped them, so that their lungs began to change, and before long, they had grown a new pair of lungs, fitted to breathe air. It was the same way with their feet; the tender fins they used to swim about in the water with weren't hard and tough enough to scrape against the mud and rocks, so they have grown tougher and stronger fins, like little legs, to get about with. You may be sure that God knew what He was about when He planned the Universe, and made its laws. You just watch these reptiles we have made, and see what happens to them. I'll be back in a million years or so, and see how things are getting along. We'll be ready for Man pretty soon." Then Mother Nature went away to look after some comets that had gotten lost and were dashing madly through space, trying to find out where they belonged.