Rural School Leaflet 



1171 



reaching their gieatest growth by midsummer. Normally they live 

 but one or two years. In winter they bury themselves in the ground 



and close their shells 

 cretion of mucus, 

 cover themselves with 

 Two types of shells 

 the land snails, con- 

 (Fig. 1) and orb 

 latter are nearly flat 

 though spirally form- 

 inactive, snails with- 

 bodies into their shells. 



Fig. 2 



with a leathery se- 

 The naked slugs also 

 this secretion, 

 will be found among 

 ical, or turreted, shells 

 shells (Fig. 2). The 

 and are circular, al- 

 ed. When startled or 

 draw their whole 

 The clear, jelly-like 

 are found under 



masses of their eggs 



leaves or other vegetation in moist places. 



The common slug, often found under boards in our gardens, looks 



like a snail that has lost its shell; but close observation shows that there 

 is a small, shell-like scale on its back. This scale covers 

 and protects the lungs of the slug. The garden slugs are 

 a great nuisance, as they destroy so many plants, 

 eating out the heart of celery or the center of 

 a head of lettuce. They may be kept from a 

 small area by surrounding it with ashes, which 

 form a barrier that snails cannot cross. 



Three types of pond snails are easily found — 

 those with orb shells, those with conical shells 

 spirally wound to the left (Fig. 3), and those 



spirally wound to the right (Fig. 1). Watching these snails as they 



Fig. 3 



Fig. 4 



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~~f-- 



>» 



Fig. 5 



travel over the glass sides of an aquarium, one can see them eat the 

 minute green algae growing there. The horny lingual ribbon, with its 



