The Snail. 



55 



shell that covered the bahy snail. Then we follow the 

 whorls from the apex to the aperture, and watch them 

 grow larger at every turn. We remember the lines of 

 growth on the clam and oyster shells, and decide that the 

 delicate lines running parallel with the edge of the aper- 

 ture must be the snail's lines of growth. 



Fig. 2. 



Fig. a. 



Fig. 3 shows how a shell giowa. .^ is a jonog shell ; B, the 

 same, full; grown ; and C la the same as B, bnt with the lines of 

 growth represented on it. The dotted lines on G show the way in 

 which it grows, a representing the first added layer, b the seccnd, 

 and c the appearance of the shell when another half-whorl has 

 been formed. Some of onr sheila have a layer of thin and very 

 brittle shell around the aperture, evidently just (ormed and not yet 

 hardened. 



Some snails' eggs, or very young snails, will add interest to this 

 part of the lesson. In spring and summer the eggs of the pond 

 anail may be found on the nnder surface of the leaves of water- 

 planta in masses of jelly, in which the eggs look like little dots. 

 These will soon hatch out, if kept in a jar of water. The shells of 

 young snails are transparent, and the growth of the body and the 

 gradual coiling of the shell can be easily watched. 



Holding the shell in the hand with the opening toward 

 us and the apex uppermost, the aperture is toward the 

 right hand. It is usually on the right, so when we find 

 one on the left, we will be careful to keep the shell. 



Our snails have closed up the aperture of their shells 



