Tracy Sincicome, age 3, of Owasso, Oklahoma, for her question:

Do fish sleep with their eyes closed?

You have eyelids that flap down when you close your eyes and go to sleep. A fish also has eyelids, but they are not at all like yours. For one thing, they are made of glassy clear skin. For another thing, they are permanently closed. This is fine, because his fishy eyelids are like window panes. They are closed all the time, but he can see through them. As a matter of fact, he needs eyelids of this sort to protect his eyes from scratchy objects floating in the water. They also protect his eyes from the salty sea water.

Fishes don't curl up and go to sleep like cats and dogs. But most of them take rest periods when they get tired. A goldfish may be dozing when he rests quietly near the bottom of his bowl. Fishes that live in streams often go to rest among the water weeds. Some of the ocean fishes hide among the stones or in underwater caves when they want to take a nap. But none of them close their staring eyes.