390 



ESSENTIALS OF ZOOLOGY 



B 





D E F 



Fig. 156. — Egg masses of common snails. A, Lymnaea (fresh-water; gelatinous 

 mass); B, Heliosoma (fresh-water; gelatinous mass); C, Physa (fresh-water; 

 gelatinous mass) ; D, Pleurocera (fresh-water branchiate; tough gelatinous mass) ; 

 E, Polygyra texasiona (terrestrial; eggs in cluster) ; F. egg capsules of Busycon. 



Qoniobasis comQlenjiS 

 (Pleuroceridae) 



Cowpeloma decisurr) 

 (Viviporidac) 



(§ (^ ^ 





Amnicoia comalensls 





Cochliopo teKona 

 (AmnicolidQe) 



Fig. 157. — Some common fresh-water branchiate snails. 



