DECEMBER 



125 



vals, forces out a bubble of air, and takes in a fresh 

 supply. Both sexes are united in the one animal, and 

 the semi-transparent eggs, laid in gelatinous masses, are 



BrEatming HOLt. 



fENTACU. 



BoDy Whorl. 



Apex 



LUMG 



jEMTACLt 



MOUTH- 



Limnea, a lung-breather. 



to be found on the plants in the aquarium or along the 

 sides. In dry or cold weather it protects itself by secret- 

 ing a membrane which covers the opening. 



