HELIX — AUHITOliY AND GUSTATURY ORGANS. I o I 
nieiit or ganglion before piercing the enclosing outer coat or sclera 
and spreading out beneath the retina, not penetrating through and 
overlaying the I’etinal rods, as in the vertebrates and in the pallial eyes 
(jf the opisthobranchs. 
The Auditory or E({uilibrating organs, known as the otocysts, 
consist of a pair of convex and prominent vesicles, ivith a thin, colour- 
less and transparent investment, 
lined internally with sensorial and 
ciliated epithelium, and containing, 
suspended in the fluid contents, 
numerous calcareous concretions or 
otoconia of variable sizes, of which 
1 20 have been counted in the upper 
layers, within a single capsule, 
though many were overlaid and 
concealed and therefore uncounted. 
The otoconia are oval and trans- 
parent, with elongate nuclei, and 
vary in number according to age, 
being proportionately fewer in im- 
mature animals ; they are always 
in a state of inces.sant oscillation, 
owing to the activity of the ciliated investment of the interior of the 
sac, although they remain persistently aggregated towards its centre, 
leaving a distinct space between the mass of otoconia and the walls 
of the capsule. The otocysts are placed 
upon the nnder-side of the pedal ganglia, 
at or near the posterior outer corners, though 
receiving their innervation from the cerebral 
centre, the auditory nerve running from 
the cerebral ganglia between the cerebro- 
pedal and cerebro-visceral connectives to 
the otocyst of their respective sides. The 
otocysts, in addition to the auditory func- 
tion they are assumed to possess, are 
probably important aids in determining the 
orientation of the body during locomotion. 
The sense of Taste is considered by Simroth to be diffused over 
the surface of the body, but to be specially localized in the terrestrial 
Fig. 313. — Underside of sub- 
oesophageal ganglia of Helix 
aspersa, showing otocysts zfi 
highly magnified. 
a, abdominal ganglion : c-p.c. 
cerebrO-pedal connective; c-pl.c. 
cerebro-pleural connective ; <?/. 
otocysts ; r.p. and l.p. right and 
left pedal ganglia ; r.pl. and 
l.pL right and left pleural gang- 
lia ; r.zK and l.v. right and left 
visceral ganglia. 
nc, 
F IG. 312. -Otocyst of Helix poniatia^ slightly 
compressed, showing the internal ciliated 
tract, etc., highly magnified (after Leydig). 
azid. 71. auditory nerve ; c. cuticle ; cp. epi- 
thelial layer ; muscular layer ; nc. epithelial 
cells with large fusiform nuclei ; ot. otoconia. 
