HELIX — INTERNAL ORGANIZATION. 
UG 
hinder pallia! maro'in develops the cohuuellar lobule, a special jirocess 
which forms the retlection coverini’' the umbilicus of the shell. 
The Visceral or body region is developed dorsally to the foot and 
abruptly protruded from its upper surface as a spirally twisted and 
tapering sac, enclosed bj" the mantle and covered by a shell of similar 
shape : it contains the hulk of the viscera of the animal and the repro- 
ductive glands : the length or number of whorls of the sac in the 
different species, corresponding to the obesity or slenderness of the 
visceral mass. 
Internally, although the primitively .symmetrical organization 
has been more or less destroyed by the twisting or torsion the body 
has undergone, j'et the organs may still be grouped under the 
six heads proi)nsed for the classitication of the organs in mollusca 
generally, viz. : Tlie Ner\'ons, the Alimentary, the Vascular, the 
(Tlaudular, the [Muscular, aud the Reproductive systems. The 
Fig. 30G . — Helix asf>ersa dissected from right side with liody wall and a portion of the genitalia 
removed to show the relative po.sitions of some of the chief organs of the body. The kidney, the 
ureter, and the pulmonary chamber opened and turned back (after Howes). 
rt. auricle and v. ventricle of the heart; n.n. anterior aorta; alh.^l. albumen gland; a.7>. 
afferent pulmonary veins; r..^. cerebral ganglia; cr. crop; c.r. columcllar retractor; f. foot; 
h.ii. hermaphrodite duct; hermaphrodite gland; /•. kidney; cn'. ovispermatoduct ; 
posterior aorta ; p.h. pharyngeal or buccal bulb ; pharyngeal retractor ; r. rectum ; s.g. salivary 
glands ; sp. spermatheca ; u. ureter. 
general and relative arrangement of the chief organs in our type does 
not materially differ from that of onr other momecions monotremate 
gastropods. The res])iratory organs are anteriorly ])laced, with the 
external oritice at the right side of the body, the heart, within its 
])ericaT’dial chamlier, being always in close connection with them and 
normally situate towards the left side, the renal organ being in close 
