o/ Ommasti'ephes todarus. 11 



the investing membrane. These four branches of the visceral 

 nerves^ the ganglion on the vena cava, and the gastric ganglion 

 to be shortly described, have usually been considered as all that 

 represent in the Cephalopods the par vagum and sympathetic 

 system of the higher animals. This, howevei*, is not correct. It 

 has been already stated that the buccal ganglions give off a pair 

 of oesophageal nerves, which passing down that tube give to it a 

 plexus of nervous filaments. These two nerves (PI. II. fig. 1 F, F) 

 leave the ganglions as one trunk passing fi'om the median line, 

 and are at first applied to the under wall of the tube ; they soon, 

 however, divide and approach the sides, and in their course ap- 

 pear to turn completely round the oesophagus. On attaining its 

 lower extremity they go to be united to a considerable elliptical 

 ganglion {z), situated on the first stomach or gizzard close to the 

 cardia. From this gastric centre various nerves ramify. Two 

 or three small twigs (E) are given off close to the oesophageal 

 nerves, and are applied to the cardiac portion of the gizzard. 

 From the opposite side of the ganglion a stout nerve (A) goes to 

 the spiral stomach, and two or three large nerves issue from the 

 ends of this centre ; those (B, B, B) from one of the extremities, 

 three in number, go to the gizzard ; those from the other ori- 

 ginate as one trunk, but soon separate into three branches ; two 

 of these (C, C) supply the pancreatic organ, and one (y) is con- 

 tinued on to be joined to the ganglion on the vena cava, forming 

 the fourth cord issuing from that centre. A small twig (D) also 

 springs from this end and supplies the pylorus. 



We see then that the nerves applied to the anterior aorta, and 

 those from the visceral ganglion, and their dependencies, repre- 

 sent only the splanchnic or sympathetic system of the higher 

 animals ; while in the oesophageal nerves are found the analogues 

 of the gastric portion of the par vagum. And it is interesting 

 to observe that these two parts of the nervous system — one 

 originating in the visceral, the other in the buccal ganglions, 

 exactly as in Doris, — are interconnected by a nervous filament 

 in the same way as they are in that mollusk. The single 

 gastric ganglion in Ommastrephes represents the principal centre 

 of the collar of ganglions about the cardiac extremity of the 

 stomach in Doris, and the ganglion situated on the vena cava, and 

 those attached to the gills, are the equivalents of the branchio- 

 cardiac and genital centres of that animal. It is therefore evident 

 that this division of the nervous system of the Cephalopod is 

 formed on the type of that of the Gasteropod; the only dif- 

 ference being that the ganglions are much less numerous than 

 in Doris. In other Gasteropods, however, these centres are 

 frequently very limited in number. 



The cephalic portion, though exhibiting several deviations, is 



