HELIX — NERVOUS SYSTEM. 
147 
proximity and actual connection with the pericardium by the ciliated 
reno-pericardial funnel. The alimentary canal, with its enlarged food 
receptacles, is convoluted chiefly amongst the lobes of the voluminous 
liver, which occupies most of the upper whorls of the shell, and in 
aa pg. 
Fig. 307. — Slightly oblique transverse section in front of the columella of Helix aspct-sn, to 
how the arrangement of the internal organs X 2 (after Howes). 
a. a. anterior aorta ; alb.g. albumen gland ; cr. crop ; c.r. columellar retractor ; h.d. hermaphrodite 
duct; h.g. hermaphrodite gland ; i. intestine; l.l. anterior lobe of liver; is, lateral pedal blood 
sinus: ovispermatoducL ; pedal gland ; /.r. penis retractor ; p.v. pulmonary vessels; 
r. rectum ; r,c. respiratory cavity; r.L posterior lobe of liver ; s.g. salivary glands ; sp.d. sperma- 
theca duct ; st. stomach ; u. ureter ; v.s. visceral hlood sinus. 
which are also imbedded the gonads or germinal glands ; the other 
or accessory organs of the reproductive system are usually of a very 
noticeable size and have the external aperture for their functional 
exercise at the right side of the neck. 
The Nervous system of Helix asperm is of a highly specialized 
character, consisting of several more or less distinctly paired supra- 
and sub-cesophageal ganglionic masses, which are concentrated around 
the anterior end of the oesophagus and more or less completely fused 
together to form the nerve collar, the component ganglia of which 
are better studied in immature animals, as in adults they become more 
welded together and less clearly distinguishable. The supra-oeso- 
phageal mass is formed solely by the cerebral ganglia and the sul)- 
msophageal by the buccal, the pedal, and the aggregated visceral 
ganglia ; from these conjoined centres, which are all enclosed or 
buried amidst a layer or sheath of connective tissue, nerves are 
distributed to all pai'ts of the body. 
The supra-fTeso])hageal or cerebral ganglia, the chief seat of the 
sensory functions, are dorsally placed, a broad transverse commissural 
