26 



FIRST BOOK OF ZOOLOGY. 



25. In the land snails, it was learned that the eggs 

 were deposited separately, while in the air-breathing, fresh- 

 water snails the eggs were inclosed in a gelatinous substance. 

 Among the sea snails there are many species which inclose 

 their eggs in pods, or capsules, as is also the case in the oper- 

 ciilated fresh-water snails. Sometimes the capsules are 

 clustered together in large masses, as in those of the whelk 

 (Fig. 31): 



Fi&. 31. — A YEEY Small Cluster of Eggs of the Whelk deposited on the Stem op 

 A Laege Sea- Weed. 



In others they are united in a long string (Tig. 32). 



A SB 



Fig. 82.—^, a Portion of a String- of Egg-Capsnles. from a Florida Species of Whellc similar 

 to Fig. 27 ; 5, a single Capsule separated, sliowing Outlet, o, tlirough which the Young 

 escape; 5, Stem. 



The common cockle sticks its separate egg-capsules side 

 by side upon the rock (Fig. 33). 



