EVERYONE has seen snails on trees or on the ground. Some snails are just as much at home in a pond as others are on land. There are so many water snails that you are almost sure to find a few in any pond, or wherever you find caddis fly larvae or water beetles and their neighbors.

A snail slides along on his broad, flat foot. If you put him inside a glass jar, you can see exactly how he moves. Little waves of movement begin at the front of the foot and pass along the bottom of it as he creeps along the side of the jar.

A snail cannot move quickly to escape his enemies, as the crayfish does. His shell protects his soft body from some of the smaller animals, but not from his larger carnivorous neighbors, who will often eat shell and all.

Snails are harmless animals. They never seem to bother any of their neighbors. They help keep an aquarium clean by eating small water plants that cling to the glass, as well as the leaves of larger plants.

Inside the snail's mouth are one or more jaws and an odd tongue, called a radula. The snail uses his radula, with its rows of tiny teeth, like a file to rasp and tear his food into shreds before he swallows it. The radula, teeth, and jaw are hard, and are made of chitin. The hard jaws and exoskel-eton of an insect larva or a crayfish are made of similar material. You can watch a snail eat while he moves over the glass sides of your aquarium. His mouth will then be toward you. If you watch closely, you can see it move.

When a watersnail is moving, you can see that he has a distinct head, to which is attached one pair of tentacles. Snails that live on land have two pairs of tentacles, with eyes at the tip of one pair, but water snails do not. Their eyes are at the base of their one pair of tentacles. If you watch closely, you will be astonished to see how far a snail can stretch these tentacles, and how easily he bends them in every direction.