Andrea Gannon, ape 8, of Oak Hill, W. Virginia, for her question:

Why do fish have fins?

When you go for a swim, you use your arms and legs to push yourself. through the water. But a fish has no arms or legs. Yet, as you know, he can swim around this way and that way and even rise higher or lower in the water. However, he could not do this without his fins and his tail, just as you could not swim without arms or legs. True, his fins do not look big enough or strong enough to help him along. Besides, he does not seem to move them, at least not very much.

If you watch a pretty goldfish in his glass bowl, you can see how he does it. His fins are like gauzy little fans and he keeps waving them to and fro, very slightly. They move the water aside so that his streamlined body can glide through. He has strong muscles to wag his tail. His tail pushes him along and helps guide him around the curves. His fins help direct the fishy swimmer as he slides and glides through the water.