IV. GASTEROPODA: PULMONATA 



335 



The head and usually eyes and tentacles are lacking, while the fins 

 (greatly developed parapodia) are highly characteristic, giving the name 

 'wing-footed' to these forms. They have rarely a single ctcnidium. 

 The THECASOMATA have shells, LIMACINID^E, HYALEID.*: The shells of 



br 



FIG. 343. FIG. 344. 



FIG. 343.- Hvaltfa complanata from above (after Gegenbaur). a, anus; br, gill; 

 c, heart; g, gonad; h, liver; m, mantle; oe, oesophagus; re, nephridium; v, stomach; 

 II, pedal ganglion and otocyst. 



FIG. 344. A, Clione papilionacea.* 



CAVOLINID^ make the 'pterpod ooze' of the deep seas. GYMNOSOMATA; 

 shell lacking. Pneumodermon, Clime* Sub Order III. NUDIBRANCHIA. 

 Shell, ctenidia, and osphradia lacking; most possessing accessory gills (ccrata) of 

 varying form and distribution. DORIDIID^; (Fig. 345;. TRITONIID^;, 



FIG. 345. Doris bilamellata* 



FIG. 346. .Eolidia papillosa (from 

 Lud \vig-Leunis). 



(Dendronolus*}; ELYSHD^E, cerata lacking. In ^olidae branches of the diges- 

 tive tract enter the cerata, expand distally to small sacs filled with nettle cells 

 (p. 207) used for defense,; they are derived from hydroids on which these 

 animals feed 



Order III. Pulmonata. 



In several respects the Pulmonata are intermediate between the Proso- 

 branchs and Opisthobranchs. Like the latter they are orthoneurous and her- 

 maphroditic (fig. 339). On the other hand, the respiratory organ is far forwards 



