THE ANIMALS AND MAN 



water (fig. 3). They should be fed pieces of lettuce or 

 cabbage leaves. Observe the habits of the snails; how 

 they come to the surface to breathe; how they crawl about; 

 how they eat by rasping off bits of the leaves with the rough, 

 horny tongue; how they protrude from and withdraw into 

 the shell; how the feelers move in and out. 



Examine a specimen with body extended from the shell, 

 and note that it is not made up of segments or rings, as the 



locust, but is a soft, un- 

 segmented mass with 

 a firm, muscular, flat- 

 tish disk on its lower 

 side called the foot. 

 How does the snail 

 "walk" by means of 

 this "foot" ? The body 

 is covered by the man- 

 tle, an edge of which 

 may be seen just at 

 the margin of the 

 shell. The soft, flex- 

 ible body and firmer 

 muscular foot can 

 both be withdrawn 

 into the protecting 

 shell. 



Fig. 3. Pond snails in a battery jar aquarium. ^^^°- '^^ *^"^ ^^^°- 

 (One-third natural size; from life.) a pair of extensible 



tentacles, the feelers, 

 with the eyes (dark spots) at their bases. Most other snails 

 and slugs have two pairs of tentacles or horns, the eyes being 

 on the tip of the second pair. Find also the mouth, and 

 examine with a lens the peculiar ribbon-like radula or 

 tongue, which is covered with fine curved teeth. The 

 radula is drawn back and forth across the food, and by it 



