MOLLUSCA. 



205 



hibit a great diversity of form and a variety of beautiful 

 colors. The Sea-lemon, (Doris,} the beautiful Tritonia, 

 (Fig. 103,) the painted Eolis, the Sea-hare, (Aplysia,) 

 which emits a violet or reddish fluid from the man- 

 tle when alarmed, and 

 the Bubble-shell (Bui- 

 la) are examples. 



The embryo of the 



naked-gilled Mollusks /V^l / I t\ 

 is very minute, and 

 resembles a Rotifer 



rather than a Mollusk. FlG " '^-Embryos of Nudibranchiate Gasteropods. 



It is inclosed in a transparent nautilus-like shell, pro- 

 vided with an operculum. (Fig. 104.) 



FIG. 105. Snails and Slugs. 



3. Pulmonates (having lungs) are air-breathing Gaster- 

 opods, represented by the common Snail. They have 

 18 



