HELIX — ALIMENTARY SYSTEM. 
153 
are approached, becomes veiy symmetrically bifid ; the mesocone also 
gTadually becomes bifid, so that the denticles near the margins 
present four strongly developed sub-equal denticulatious, ivitb a narrow 
basal attachment; additional transverse rows are being constantly 
added within the radular sac at the posterior end, to compensate for 
the wearing away or loss of the functional portion anteriorly. The 
movements of this important organ are controlled by numerous 
extrinsic and intrinsic muscles. 
The buccal cavity opens dorsally by a tbin-walled cesopbagus into 
a large, fusiform and distensible crop, usually conspicuous by the yellow 
colour of its contents and situate partly within the ultimate whorl of 
the shell ; like the cesopbagus and other parts of the alimentary canal. 
F IG. 316. — Alimentar>^ canal of Helix cispcrsa^ with appended glands, dissected out and seen from 
right side. The generative, circulator^*, excretory*, and nervous systems removed and the buccal 
cavity, stomach, bile ducts, intestinal canal, and pedal gland opened up (after Howes). 
b.c. buccal cavity, showing radula, radular sac and jaw ; cr. crop ; f. foot ; h.g. hermaphrodite 
gland or ovotestis ; l.l. anterior lobe of liver ; oesophagus ; p.g. pedal gland ; p.r, phar^'ngeal 
or buccal retractor ; r. rectum ; r.i. posterior lobe of liver ; $.d. salivary duct ; s.g. salivary glands ; 
st. stomach ; ty, typhlosole. 
its lining membrane is tlu’own into a series of longitudinal folds 
visible externally as longitudinal striatiou. ^Vdberent to its sides, 
by fibres of connective tissue, are a pair of whitish lobulated organs, 
the Salivaiy Glands, wbicb discharge their secretion, a soluble ferment 
which converts starch into sugar, into each side of the buccal cavity 
by means of two long and slender ducts. Beyond the crop the canal 
again becomes nari’ow, but at the loop-like extremity of the first tract 
(piickly expands to form the simple sacculated stomach, wbicb is 
slightly constricted by a longitudinal fold, and its mucous membrane 
also thrown into many longitudinal folds or ridges ; the cesopbagus 
enters posteriorly near the external surface and between the right and 
