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TEXTBOOK OF ZOOLOGY 



which terminates in a thick-walled muscular vagina. During this 

 journey the ova are fertilized by sperm from the seminal receptacle 

 and coated with albumin from the albumin glands. Both the penis 

 and vagina have a common genital opening to the exterior. 



Album in qland ;^ 



Liver 



^Hermaphroditic qland 



i 



Crop 



WJf^ Oviduct 



-— Oort sac 



- - Mucous qiands 



Fig. 137. — Genitalia of Helix aspersa; act of union. (Modified, after Cooke, Cam- 

 bridge Natural History. By permission of The Macmillan Company.) 



Most of the fresh-water snails deposit eggs in clear gelatinous 

 masses on submerged objects, such as twigs and rocks. The land 

 snails usually deposit their eggs singly or in clusters in well-pro- 

 tected places, such as in rotten wood or beds of humus. The eggs 



