10 



FIRST BOOK OF ZOOLOGY. 



bubble of air, which maybe seen escaping from the breathing- 

 orifice, as in Fig. M, B. 



A view from the back, 

 or dorsal meio. 



t e 



side-view. 



m 



ventral view. 

 1 1. Tentacles. 

 e e, Eyes. 



b, Breathing-orifice. 

 i, Mouth. 



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



