10 



FIRST BOOK OF ZOOLOGY. 



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

 orifice, as in Fig. 14, B. 



t e 



A view from the back, 

 or dorsal view. 



tide-meio. 



ventral view. 

 1 1. Tentacles. 

 e e, Eyes. 



6, Breathing-orifice. 

 ?tt, Mouth. 



FIG. 13. A FRESH-WATER SNAIL SEEN FKOM ABOVE, FBOM THE SIDE, AND FROM BELOW, 



