SPECIAL ANATOMY. 75 



The " integument of the eye-peduncles is very freely supplied with 

 nerves from the supra-cesophageal ganglia. 



Taste. If existent, it is probably dependent upon nerves distributed 

 within the buccal body, and derived from the stomato-gastric ganglia. 

 The structure of the lingual membrane precludes any idea of its exist- 

 ence there. 



Smell. The presence of this sense is undoubted, though there is 

 much discrepancy of opinion as to its situation. I have suspected that 

 it probably may be placed in the blind sac, or depression, which opens 

 just below the mouth. This sac varies in its degree of development in 

 the different genera : in Limax it is a superficial depression ; in Vagi- 

 mdus it extends backwards beneath the buccal body for half an inch, is 

 conical in shape and yellowish-white in color ; in Liguus fasciatus it 

 extends back, in the excavation of the foot, to the tail, and is folded 

 several times upon itself. 



Hearing. The acoustic apparatus consists of a pair of transparent 

 vesicular bodies, placed upon the postero-inferior part of the sub-cesopha- 

 geal ganglia, one on each side. They are placed in a depression of the 

 ganglia formed by a separation of the nerve-tubuli as they pass from 

 and into the latter, immediately upon the ganglionic globules. Their 

 interior is filled with a transparent fluid, containing numerous otoco- 

 nites, which vary in size, are oval in form, transparent, composed of con- 

 centric layers of carbonate of lime, and frequently have a small cavity 

 in their centre. During life, and for a short time after the death of 

 the animal, the otoconites are endowed with a peculiar vibratory move- 

 ment, by which they are disposed to accumulate into a mass in the 

 centre of the auditory vesicle. After the cessation of the movement 

 they become diffused through the fluid of the vesicle. 



Sight. The eyeball is placed beneath the integument, on the outer 

 side of the constriction which exists between the gangliform swellings 

 at the free extremity of the eye-peduncles. The optic nerve is derived 

 from the inferior part of the first gangliform enlargement, is tortuous 

 or undulating, and reaches the eyeball at its posterior part. Its course 

 is frequently indicated by a deposit of pigmentum nigrum. 



The eyeball is globular, and is invested exteriorly by a transparent 

 tunic, corresponding to the sclerotica and cornea. 



The choroidea forms two thirds of a sphere, and is inflected anteriorly 

 into a sort of depressed disk, perforated in the centre. It consists of a 

 delicate, translucent membrane, with a deposit of a single layer of irreg- 



