96 THE GASTROPODA 



in Paludina and Rissoa. But in Otina a dextral form it is the 

 left lobe that is the smaller. The liver discharges its secretion into 

 the stomach, but exceptionally it may discharge into the terminal 

 part of the oesophagus or into the intestine (Phikmycus bilineatus). 

 As a rule there are two hepatic ducts whose openings into the 

 stomach may sometimes be at some distance from one another 

 (Natica), but may sometimes be fused as a result of specialisation, 

 as in the majority of the Docoglossa, certain species of Murex, and 

 some Euthyneura, viz. the Thecosomata (Fig. 60), Ancylm fluviatilis, 

 Latia, etc. On the other hand, one of the orifices may be subdivided, 

 so that three hepatic openings are formed, as in the Fissurellidae. 

 In a few rare cases (Cydostonw,) isolated acini are found on the 

 hepatic ducts, recalling the condition common in the Cephalopoda. 

 Sometimes the liver lobes cover the whole stomach and open into 

 it by multiple orifices ; this arrangement is found in various Opistho- 

 branchs, such as Gastropteron and the Gymnosomata. The extreme 

 form of specialisation consists in the subdivision of the whole 

 organ into tubes, which, like the gastric diverticula of Polyclads, 

 extend through the greater part of the body, and even penetrate 

 into external tegumentary appendages. This peculiarity is found 

 in many Nudibranchs, viz. the Eolidomorpha (Fig. 77) and the 

 Elysiomorpha (excepting Cyerce and Lobiancoia), in which the rami- 

 fications of the liver extend into the dorsal papillae, and in various 

 Eolidomorpha communicate with cnidosacs, structures of ectodermic 

 origin which in turn communicate with the exterior (p. 178). A 

 similar arrangement occurs in the Polyclad Yungia. The digestive 

 glands secrete a diastatic and peptic ferment, but in addition to their 

 digestive properties they exercise, in the Euthyneura at least, an 

 excretory function, and they also arrest the action of poisonous 

 substances. Lastly, the digestive glands take a share in intestinal 

 absorption. 



The intestine proper is a cylindrical tube, generally of uniform 

 calibre throughout its course. It is sometimes separated from the 

 stomach by a sort of valve. In nearly all cases it exhibits a well- 

 marked longitudinal projection, the raphe or typhlosole, along a 

 certain part of its course, and in some forms this projection is 

 divided into two in such a manner as to form a groove bounded by 

 two folds. In herbivorous Gastropods, such as Patella, the intes- 

 tine is very long and thrown into coils ; in carnivorous forms it is 

 short and often straight as in Pteroceras (Fig. 75), Eolis (Fig. 77), 

 Hemifusus (Fig. 99). 



The intestine traverses the ventricle of the heart in most Rhipi- 

 doglossa (Fig. 55), the pericardium in Paludina, and the substance 

 of the kidney in the Doliidae, Cassididae, Triton, and Ranella. In 

 Murex, Purpura, and the Naticidae the rectal portion of the intestine 

 is provided with a somewhat ramified gland, known as the anal 



