300 Mr. A. Hancock on the Anatomy of Oithona. 



pair of nerves issue apparently from the outer border of the 

 branchial ganglia, and go to the skin by the side of the head. 

 The sixth pair are small, and come from the upper surface of the 

 branchial ganglions ; these nerves go to the skin of the sides of 

 the back. The seventh, much larger than the sixth, emerge 

 from the posterior margin of the same ganglions, and supply the 

 dorsal skin, and apparently likewise the papillae. These are the 

 branchial nerves. The eighth and ninth pairs are large nerves ; 

 they issue from the outer border of the pedial ganglions and go 

 to the foot. The posterior margins of these ganglions are united 

 by a stout, shortish commissure, composed of two or three cords, 

 which, passing below the gullet, form the great oesophageal 

 collar {i.) . The tenth pair of nerves are given off from the pos- 

 terior margin of the buccal ganglions ; these pass into the buccal 

 mass and go to supply the tongue. The eleventh pair, issuing 

 from the outer extremities of the buccal ganglions, are distri- 

 buted to the muscles of the buccal mass. The twelfth pair 

 come from the apex of the gastro-cesophageal ganglions, and 

 being applied to the gullet, each divides into two branches, one 

 of which supplies the upper portion of that tube, the other, pass- 

 ing down it, undoubtedly goes to the stomach as in the other 

 Nudibranchs. The thirteenth pair are large; these are the 

 hepatic nerves ; they issue from the buccal mass in the same 

 manner as similar nerves do in Eolis, and probably, as in that 

 genus, are connected at their origin with ganglions, which must 

 be looked upon as belonging to the sympathetic system. Imme- 

 diately on emerging from the buccal mass, they are connected 

 to the buccal ganglions at their point of union with the gastro- 

 oesophageal, and then, arching outwards and upwards, pass from 

 within the anterior oesophageal collar, and go to supply the 

 glands of the papillae. 



These are all the pairs. of nerves that we have traced : there 

 is, however, a single nerve given oflF from a delicate collar (/^), 

 the ends of which are united to the under-surface of the central 

 masses, just where they are connected to the pedial ganglions. 

 This is the genital nerve (1.4), and similar to that which we 

 have described in Eolis. We saw another nerve (15), which 

 was apparently also distributed to the genitalia ; this seemed to 

 come from the right branchial ganglion, at its union with the 

 pedial. These two nerves, which however require further exa- 

 mination, probably repi-esent those that come from the visceral 

 ganglion in Doris, and which in that genus are distributed to 

 the sympathetic ganglions of the digestive, reproductive, respira- 

 tory, and circulatory organs. 



