Pila shows a well-developed nervous system. This nervous system will show 5 pairs of ganglia, the connectives and commisures and nerves.
1. Nerve ganglic :
1. Cerebral ganglia
2. Pedal ganglia
3. Visceral ganglia
4. Pleural ganglia
5. Supra and infra intestinal ganglia.
a) On the dorso-lateral sides of the buccal mass cerebral ganglia are present. They are connected by cerebral commisures.
b) On the ventrolateral sides of the buccal mass a pair pleural and a pair pedal ganglia are present. The cerebral ganglia and pleural ganglia are connected by .c :rebro-pleural connectives. The cerebral and pedal ganglia are connected by cerebro-pedal connectives.
c) The two pedal ganglia are connected by pedal commisure.
All these structures will form a nerve ring which looks like a square.
d) At the junction of buccal mass and oesophagus two buccal ganglia are present. They are connected in the cerebral ganglia with connectives
c) In the visceral mass two visceral ganglia are present. The pleural ganglia and visceral ganglia are connected by right and left pleuro-visceral connectives.
From the right pleural ganglion a supra intestinal nerve will arise. It will travel over the oesophagus and is connected to the left pleuro-visceral connective. At this point, it form a supra intestinal ganglion.
f) Left pleural ganglion gives a nerve which connects with right pleuro-visceral connective and a infra intestinal ganglion is formed.
Thus these nerves will give '8' shaped structure.
g) From cerebral nerve ganglia a number of small nerves will arise. They travel to tentacles, eyes, statocysts etc.
h) From pleural tjerve ganglia nerves will arise and will innervate mantle.
i) From visceral ganglia nerves will go to excretory organs, reproductive organs,
and to stomach.
Thus a well-developed nervous system is seen in the pila.