Veo NeiteaeN ry RVOUS SY STEM {Or 
Aver Osi AeA GL OB 0 SvAt 
By EKENDRANATH GHOSH, Assistant Professor of 
Biology, Medical College, Calcutta. 
The present animal is a common pond-snail of Bengal, and 
can be procured in any number from the ponds in the suburbs 
of Calcutta. Having access to an ample supply of specimens, 
I availed myself of the opportunity of studying the nervous 
system by dissecting a large number of them. 
The comparative anatomy of the genus Ampullaria was 
studied by Prof. E. I. Bouvier, who published an excellent mono- 
graph [1] on the subject in connection with other Prosobranchiate 
Molluscs in 1887. He described the nervous system and general 
morphology of Ampullaria carinata, which differs from the present 
species in several interesting points. In 1g1o0, Capt. R. E. Lloyd 
described the anatomical features of the present species in his 
Introduction to biology for students in India [2j. The book, .being 
meant for the junior students of biology, dealt with the matter 
in a concise form, and did not enter into any detail. The present 
article is meant to describe the subject in some detail. 
General.—The cerebral ganglia are widely separated by a 
tibbon-shaped inter-cerebral commissure. The cerebro-pleural and 
cerebro-pedal commissures are long, while the pleuro-pedal com- 
missure is practically absent, the ganglia being closely apposed to, 
although distinct from, each other ; this constitutes a “‘ hypo- 
athroid condition.” The supra-intestinal nerve passes from the 
right pleural over the oesophagus to the supra-intestinal ganglion 
also connected to the pleural ganglion of the left side by a secondary 
commissure forming a zygoneurous type [2]. The infra-intestinal 
nerve passes from the left pleural ganglion to the infra-intestinal, 
being connected to the pleural ganglion of the other side on its 
way to the latter. The pedal ganglia are connected to each other 
by an inter-pedal commissure. 
Each cerebral ganglion gives off a fine nerve connected to the 
buccal ganglion of the same side through the intervention of a 
small nerve from the latter. 
Cerebral ganglion.—Each ganglion is triangular in shape and 
is situated on the sides of the buccal bulb on its dorsal aspect. 
From the antero-superior angle of the ganglion is given off the 
flattened ribbon-like inter-cerebral commissure to the ganglion of 
the opposite side. The connective lies at the anterior end of the 
buccal bulb and on its dorsal surface. From the postero-inferior 
