PHYSIOLOGY OF THE INVERTEBRATA. 



339 



Li'ngula, has also the pallial and brachial systems of nerves as 

 well developed as in Terehratula." * 



The Mollusca. 



In the Molhisca there are usually at least three ganglia with 

 radiating nerves — one in the head, one in the foot, and one 

 posterior and above the alimentary canal. 



B 



C 



A 



Fig. 68. — Nervous Systems of the Mollusca. 



A = diagram of nervous system oi Anodonta. a = cerebral ganglia. 

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



B = nervous system of Limax. a = cerebral ganglia. be = pedal 

 parieto-splanchnic ganglia. d = nerves to foot. 



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



b = anterior buccal ganglion, c = pedal ganglion. d = parieto- 

 splanchnic ganglion, e = cerebral ganglion, f = optic nerve and 

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



As an example of the Zamellibranchiata, we describe the 

 nervous system of Anodonta. There are three pairs of 

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

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



* Owen's Cmnparatiue Anatomy and Physiology of tlie Invertebrate Animals, 

 p. 492 (2nd ed.). 



