3. The tadpole can swim with its tail, like a fish. On each side of the head is a small tuft of soft pink threads. These are gills, through which it can breathe the air which is in the water.
4. Then the body grows, and in a short time two little legs come out right where the tail joins the body. In a few days more two other legs come out just back of the eyes, and then we have a tadpole with four legs.
5. But now another change takes place. Lungs for breathing air begin to grow inside, and the gills become smaller. For a time the tadpole breathes partly in the water, with his gills, and partly in the air, with his lungs.
6. Next the gills dry up, and then it comes to the top of the water to breathe; and it looks very much like a frog, except that it has a tail.
7. At last the tail shrinks away, and the tadpole has become a perfect frog. In hot weather all these changes take place in a few weeks; but when it is cold, they take a longer time.
8. The frog, when full grown, can live on the land or in the water. It can stay under water some time, but must come to the top to breathe.