Catherine Pitts, age 10, of Tucson, Arizona, for her question:

Why don’t fish blink?

Our eyelids blink by themselves, somewhat like built in windshield wipers. Their duty is to wash the shiny surface of the eyes, removing fine particles of dust. Blinking also is necessary for us because the shiny surface of the eyes must be kept moist. In addition to eyelids, the blinking operation also requires a steady supply of cleaning fluid. This material is manufactured in the tear glands inside the corners of the eyes.

A fish does not need any of the built in equipment because it is not necessary for him to blink. The water in which he lives washes his eyes for him. He never sheds tears of sorrow and he needs no special cleaning fluid to wash his eyes. So he has no tear glands    and he has no eyelids. Day and night, waking or sleeping, his eyes stay open in a fishy stare.