564 THE POPULAR SCIENCE MONTHLY. 



objects will be left behind. The clipper 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 : 



Fig. 2. Fresh- Water Snails. 



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 creatui'e 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 jaart 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- 

 lianded 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-breath- 

 ers, 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. 



