PHYSIOLOGY Of THE IXVERTEBRATA. 



339 



TAiKjala has alsD the pal Hal and bracliial systems of nerves as 

 well developed as in Tcrcbratular* 



The Mollusca. 



In the MoUusca there are usually at least three ganglia with 

 I'adiating nerves — one in the head, one in the foot, and one 

 posterior and above the alimentary canal. 



A B C 



Fig. 68. — Nkrvous Systkms ok the Molllsca. 



A = diagram of nervous system oi A/iodonta. a — cerebral ganglia. 

 b — pedal ganglia, c = parieto-splanchnic ganglia. 



B — nervous system of Liinax. a = cerebral ganglia. he = pedal 

 parieto-splanchnic ganglia. d = nerves to foot. 



C = nervous system of Sepia. a = posterior buccal ganglion. 



b = anterior buccal ganglion. <■ = pedal ganglion. d = parieto- 

 splanchnic ganglion, e = cerebral ganglion. / — optic nerve and 

 ganglion, g — splanchnic ganglion. h = ganglion stellatum. 



As an example of the LamcUihrancJiiata, we describe the 

 neiTous system of Anodonta. There are three pairs of 

 ganglia. («) The cerebral ganglia, which are united by a com- 

 missure, are situated at the sides of the mouth. They send 



* Owen's Comparative Anatomy and Phi/siolotjy of the Invertebrate Animals, 

 p. 492 (2nd ed.). 



