IIG CLxVMS, (lY.STEliS, AxM) MUSSELS 



foot (Fi^. 02). The head bears two feelers, or tentacles, 

 and a pair of eyes. 



Physa la>-s its eggs in February or March, in bean-shapetl, 

 transparent, gelatinous masses, tm leaves oi' sticks in the 

 water. Liimuea lays fewer eggs ui a mass, and lays them 

 later in the s[)i'ing. 



Besides Limna'a and PIn-sa, the snails that belong to the 

 genera Planorjjis and Paludina arc^ commonly known as 

 "pond snails." The members (A the former genus have 

 sliells coiled in a flat spiral, like a. roll of tape, and breathe 

 air directly, like Linnuva. The members of the latter genus 

 have, generally', a longer and more pointetl shell and breathe 

 by means of gills, nuich like an oyster. 



Helix. — The conmion gai'i'en snail will serve well as an 

 example of the genus lieiix Fig. (io). It has a horn-colored 



shell within which it 

 can con tract the whole 

 body. It has two 

 eyes, one at the end 

 of eacli of tlie lai'ge 

 tentacles. It breathes 

 Ijy means of a lung 

 which communicates 

 with the outside by an opening in the side of the snail's 

 neck that c;in be closed oi- opened at will. This snail lives 

 on ]")lants. In Fi'ance, some membei's of the genus, Hidix, 

 somcnvhat l.'U'ger than oiii' own garden snail, are extensively 

 eaten as food. 



Slugs. — These are .snails that have no visible shell, — 

 in fact, some of them ha\'e none at all. Tliey usually feed 

 only in the night time, lien( c iivc not often seen. k)ue, which 

 is sometimes found crawling along roads or \\'alks, is laiown 



