Garth Wilson, Age 12, Of Peterborough, Ont . , Canada, for his question:

What is a paramecium?

We share our world with countless trillions of these little animals. As a rule, we do not know the paramecia are there, because they are too small for our eyes to see. They are one cel1ed protozoa, teeming in lakes and riyers and fresh water streams .

The slipper shaped paramecium is slightly more advanced than its shapeless, je114fied cousin, the amoeba. Its single cell is coated with a stiff material which gives it a permanent shape. It has a front end and a back end, and it is covered with hairy cilia, which it uses to wave its small body through the water.