Introduction to Animal Morphology. 291 



and vegetable feeders like limpets it is long and 

 coiled. A crystal style, like that of bivalves, exists 

 in Bithynia, Strombus, Trochus, &c., in a pyloric 

 csecal pouch. The primary flexure of the intestine is 

 haemal in branchiate, neural in pulmonate forms. The 

 anus has a sphincter, and in Purpura and Murex 

 grape-like excretory glands open into it. Entoconcha, 

 Rhodope, and some other Apneusta, are aproctous. 

 The mouth and anus are never on the same medial 

 plane, but in some Opisthobranchs the latter is medio- 

 dorsal. A transverse mesentery is only found in the 

 last-named group. The few- or many-lobed liver 

 surrounds the intestine in Prosobranchs and Pulmo- 

 nates, slung by funnel-like threads in Tethys. In 

 Heteropods it is deep brown, and mixed with the sex- 

 gland, with one or more ducts, and often with con- 

 cretions, as among Opisthobranchs. 



In some of this latter division the liver has one duct 

 opening to the right behind the kidney ; in others it consists 

 of a number of gastric caeca (Doris), or two lateral rows of 

 brown intestinal diverticula, the ends of which may be within 

 the body (in Pleurophyllidise and Rhodope scattered over the 

 Avhole intestine), or in a side expansion of the body (Elysia), 

 or in long papillae on the dorsal surface (^olidas). These 

 caeca are widened ducts, and resemble somewhat the branched 

 canals of Dendrocoela. The ducts of these caeca may unite 

 into a common pouch opening into the intestine, and this 

 may be single, under (Dotonidae) or over the ovary (^olidae), 

 or double (Fionidae), or three (Proctonotidae). Detached 

 elliptical (pancreatic ?) follicles exist singly in Aplysia and 

 Doris, a pair in Doridium. 



The heart* is dorsal, rarely median (Doris), usually 



* Absent in Entoconcha and Rliodope. 

 U 2 



