154 MOLLUSKS. 



of food. A complete retreat within its shell is its only 

 means of defense. But the hard, closed shell is protec- 

 tion, strong in proportion as the instincts are weak. 



The river mussel is a representative of the group Mol- 

 lusca (or soft-bodied animals). 



Other Mollusks. There are three forms of snails, 

 very common throughout the interior : (1) land snails, 

 found under the fallen leaves and decaying logs in hard- 

 wood groves, and easily collectible in warm weather ; 

 (2) pond snails, found on the submerged vegetation of 

 ponds throughout the year; (3) river snails (opercu- 

 lates), found in the same situations with river mussels. 

 The most available of these for study in the winter is the 

 pond snail. 



THE POND SNAIL. 



(Limnea.) 



Haunts. This animal may be found in almost every 

 natural small pond, adhering closely to the stems and 

 leaves of aquatic plants, to the dead stems of " cat-tail 

 flags," to sticks, boards, old boots, etc. ; in fact, to almost 

 anything that may have chanced to get into the water. 

 These things may be slowly drawn out of the water, and 

 the snails picked off them by hand. . The only apparatus 

 necessary for collecting pond snails is a small vessel of 

 water to carry them home in. 



Aquarium Study. They may be kept in an aquarium, 

 or, better for study, in a bowl, or dish, or fruit jar, in 

 water. The vessel should be kept clean, and they should 

 be fed daily with leaves of cabbage or lettuce. They 

 are very easy to keep ; there is much that is novel 

 and interesting in their habits that is quite easy of 



