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FIRST BOOK OF ZOOLOGY. 



bubble of air, which may be seen escaping from the breathing- 

 orifice, as in Fig. 14, B. 



t e e t 



A view from the back, 

 or dorsal view. 



tide-view. 



ventral view 

 1 1. Tentacles. 

 e e, Eyes. 



b, Breathing-orifice, 

 m, Mouth. 



Fig. 13. — A Fresh- Water Snatl seen from above, from the Side, and from below 



