242 
SONANT AND GUSTATORY ORGANS. 
Sound is said to be produced or eiuitted by certain foreign niollnsks, 
and Ileli.r apertd, a reputed Briti.s]i species, is stated to emit a distinctly 
audible cry wbeii disturbed, but our native species are not known 
to emit any sound whatever, except perhaps the audible snap or click 
which may be beard when an aipiatic i)ulmonate, as Limnaa, opens 
its pnlmonary aperture fjr respiration upon reaching the surface of 
the water ; pnlmonate mollusks generally when suddenly alarmed 
may however b)" the spasmodic contraction of their bodies and the 
conseipient forcible expulsion of the air from the mantle cavity, 
ju-oduce a perceptible noise, varying somewhat in character according 
to the force of the contraction and the (piantity of mncus accumulated 
arouud the respiratory oritice. 
What has been called the “IMusicof Snails” is created by the 
crawling of the animal on a pane of glass or other suitable substance, 
bnt the sound thus produced is a purely mechanical effect and in no 
sense the voice of the animal — it may be easily imitated by drawing a 
moist huger along the edge of a wine glass, 'rids sound, which 
resemliles that of an .3i](dian hai'i), is usually only lieard at du.sk or 
during the night; and the source of the mysterious sound being 
fre([uently nnsu.sj)ected it has often caused a feeling of su})erstitions 
dread and forms the basis of an interesting story l)y ^Irs. Bowdich. 
'I'be (tUSTATOry sense is doubtless i)osse.ssed l)y the (hustropoda, as 
is evidenced by the predilection of different species for special foods, 
'rids faculty i)robably has its locaticm within or al)out the Imccal 
cavity, as the tongue being closely beset with bard chitinous denticles, 
neces.sary for the rasping and comminution of fooil does not ap])ear 
to be a suitable organ for the development of this special sense. 
'I'lie multilobular dor.sal and lateral li})S, wbich constitute the 
organ of >Senii)er, are probably the seat of the gustatory sense, each 
lobe l)eing furnished with a small ganglion ])laced beneath a deep 
ej)itbelium with a thick cuticle and connected with a branch from the 
anterior tentacular nerve. 
In the Streptonenra the organs of Semper are not developed, but 
Garnault has detected within the buccal 
cavity of Cyddutomd elepans a number 
of nerve cells beneath a thick cuticle, 
some terminated by a delicate blament. 
Fig. 488. — Gustatory cellule from 
the wall of the buccal cavity of 
Cyclostoma clegans ('Miill.), highly 
magnified (after Garnault). 
which, although somewhat similar in general character to tactile cells, 
he considers may have a gustatory function. 
