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 (Philomycus 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), Ancylus 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 (Cyclostoma) 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 cnidosaes, 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 Fanella. In 
Murex, Purpura, and the Naticidae the rectal portion of the intestine 
is provided with a somewhat ramified gland, known as the anal 
