212 NERVOUS SYSTEM. 



the muscles of the mouth. The two lateral ganglia are con- 

 nected together by a broad nervous band, which passes be- 

 low the oesophagus and completes the posterior ring around 

 that passage. The muscles of the head, the superior tenta- 

 cula, and the small eyes, receive their nerves from the cere- 

 bral ganglion (a.) The optic is a branch from the large ten- 

 tacular nerve on each side. The nerves from the lateral 

 ganglia are spread chiefly on the muscular parietes of the 

 trunk, and those from the aortic ganglion (e 9 ) are observed 

 ramifying on the liver, the intestines, the branchiae, and the 

 generative organs. The aorta receives a minute branch 

 from the two anastomosing filaments of the lateral ganglia, 

 which embrace it, and a second ganglion almost impercepti- 

 ble, is found on one of the branches proceeding from the 

 great abdominal sympathetic ganglion. The sympathetic 

 ganglia are also distinct in the scylltea, the glaucus, and many 

 other small naked gasteropods. The nervous oesophageal 

 ring of the haliotis has two lateral ganglia which supply 

 nerves to the tentacula, the pedunculated eyes, and other 

 parts of the head, and presents below the oesophagus a large 

 median ganglion from which a series of long nerves extend 

 backwards along the inferior surface of the abdomen, as in 

 the carinaria, and the same plan of distribution is seen in 

 the nervous system of the patella and many similar forms. 

 In the bulla lignaria (Fig. 91,) there is a small lobed gan- 

 glion anterior to the usual cephalic ring (e,) and which is si- 

 tuate below the bulb (d 9 ) of the oesophagus (a,) behind the 

 salivary glands (b, b 9 ) and anterior to the insertions of the 

 diverging muscular bands (c 9 c,) of the bulb of the oesopha- 

 gus. This ganglion is situate like the small anterior infra- 

 cesophageal ganglion of the aplysia. The cephalic ring (e, e,) 

 enveloping the oesophagus, behind this single ganglion, has 

 two large trilobate ganglia (/, /,) at its sides, which send 

 numerous branches to the surrounding muscular parts, and 

 two long branches (A, A,) extend backwards from them along 

 the sides of the abdomen to two symmetrical sub-ventral 

 ganglia (i 9 i,) placed above the muscular foot. Behind these 

 are two sympathetic ganglia (k, &,) which send filaments to 

 the digestive organs, the ovary (o,) the oviduct (/?,) the uter- 

 ine sac (q,) the vulva (m,) and the urinary organs (n.) Two 

 anterior small sympathetic ganglia, which receive nerves 



