Page:Popular Science Monthly Volume 7.djvu/582

564 objects will be left behind. The dipper may be made as seen in Fig. 1.

Shells collected with the snails inside, and cleaned for the cabinet, are called live shells. They are always more fresh and perfect than dead shells. Having made the collection, the snails should be kept alive in a wide-mouthed jar, or bottle, care being taken not to have more than fifteen or twenty in a jar holding a quart of water.

Some of the following forms will have been secured:



The broad, creeping disk upon which the snail rests, and by which it retains its hold to the glass, is called the foot. The snail moves about, and crawls or glides slowly along, by means of the foot.

The two little horns or feelers, in front, are called tentacles and, as the snail moves, the tentacles are seen stretched out in front, and occasionally bending, as if the creature were feeling its way along. The eyes are seen at the base of the tentacles, as two minute black dots. The mouth is between the tentacles, and below. The part from which the tentacles spring is called the head and the opposite end of the body is called the tail. The surface upon which the snail rests is called the ventral or lower surface, and consequently that portion of the body which is above is called the dorsal surface, or back.

In watching the habits of the snails he has collected, the reader will notice some of them crawling to the surface of the water to breathe air. The snail accomplishes this by raising the outer edge of the aperture to the water's edge, and then opening a little orifice in the side, through which the air enters to the simple lung within. This orifice is on the right side in those snails having dextral or right-handed shells, and on the left side in those snails having sinistral or left-handed shells.

Many kinds of snails which live in fresh water are called air-breathers, because they are forced to come to the surface of the water to breathe air. In doing so they first expel a bubble of air, which may be seen escaping from the breathing-orifice, as in Fig. 4, B.

These fresh-water air-breathing snails may be kept under water for many hours before life is extinct.