THE GASTROPODA 95 
_ glossa, viz. in Plewrotomaria (Fig. 127, sp.c), Haliotis, the Turbinidae, 
etc., and in Nassopsis and Chytra (which, according to Moore, possess 
both the spiral caecum and the style-sac), but is simple and straight 
in Ampullaria, a large number of Opisthobranchia, the Limacinidae, 
the majority of the Cavoliniidae, Aplysia, several Doridomorpha (in 
which it is rugose internally, and has incorrectly been described as 
a “pancreas”), and finally in a number of Basommatophora, the 
Limnaeidae, and various Planorbidae. 
The liver or digestive gland constitutes the essential organ of 
digestion. It more or less completely surrounds the stomach, and is 
divided into lobes, the number 
and form of which vary in 
Fic. 76. 
Philine aperta, dorsal aspect; the body-wall is 
supposed to be transparent. a, anus; @.g, ab- 
dominal ganglion; c.g, cerebral ganglion; c.h, 
cephalie hood ; g, gill; g.o, genital (hermaphroditic) 
orifice; gz, gizzard; h, heart; in, intestine; k, Fic. 77 
kidney; m, mouth; m.p, masticatory plate; os, 
osphradium; po, mantle; par, parapodia (lateral Alimentary canal of Zolis papil- 
lobe of foot); p.g, pedal ganglion; p./, inferior losa, dorsal view. an, anus; e, hind- 
pallial lobe; pl.g, pleural ganglion ; 7.m, retractor gut; h, hepatic appendages of the 
muscle of buccal mass; 7.0, renal opening; 7.p, mid-gut (all of which are not 
reno-pericardial opening ; s.g, seminal groove; sh, figured) ; m, mid-gut ; ph, pharynx. 
shell; s.i, supra-intestinal ganglion; st, stomach. (From Lankester, after Alder and 
(After Guiart.) Hancock.) 
different groups. Primitively there were two lobes, as in other 
Molluscs, and this number is, as a rule, retained in the Gastropods, 
but there are very few forms in which the lobes are equal and 
symmetrical, as in Neritina and Valrata. More frequently the topo- 
graphically left lobe is more deeply involved in the spire, and is 
larger from larval life onwards than the right lobe in dextral Gas- 
tropods (Figs. 61 and 116, B); the reverse is the case in sinistral 
forms. The right lobe may disappear, and the left lobe only persist 
