NERVOUS SYSTEM 



FIG. in. 



from the lateral ganglia (f,f,) of the brain (e, e } ) are perceiv- 

 ed in this animal near the cardiac orifice of the strong, dense 

 muscular gizzard. So that, although the bulla is almost 

 acephalous, it has attained a considerable development both of 

 its symmetrical and sympathetic systems of nerves. Instead of 

 a simple nervous band passing over the oesophagus to connect 

 the lateral ganglia, as in the bulla, there are two pairs of gan- 

 glia around that passage in the jantkina, and in the limnea ; 

 the ganglia are approximated to form a collar around the 

 oesophagus. In the doris, the testacella, and many others, 

 these ganglia are confined to a supra-oesophageal position, 

 extending as a broad lobed nervous mass across the upper 

 part of that canal. In the chitons there is a broad supra- 

 cesophageal band and two closely approximated lateral gan- 

 glia below the oesophagus which send back large nerves to 

 the foot and sympathetic filaments to the abdominal viscera. 



