Polly Hays, age 10, of Pittsburgh, Pa., for her question:

What is a protozoa?

If he were big enough to have a brain, this fellow might want you to call him a protozoan. But he is too small to care that scientists use the word protozoa when they mean more than one of these single celled creatures. Protozoan is the singular form and protozoa is the plural form of his name. WE share our world with countless trillions of these little animals and most of them are too small for our eyes to see.

The word protozoa means first 1ife and it was given to a vast tribe of animals that have bodies made from just a single living cell. Countless varieties of these midgets swarm on land, in the water and the air. Your body has millions of cells, some built to do one job and some built to do other jobs. The single cell of a protozoan can find and digest its food and uses air and moisture to keep itself in good condition. Most important, the tiny animal can multiply and hand on life to a new generation of protozoa just like itself.