10 Mr. A. Hancock on the Nervous St/stem 



the appearance of a rudimentary spinal cord, as has been before 

 remarked. But certainly they resemble nothing so much as the 

 posterior trunks of the pedial nerves of some of the Gasteropods, 

 — of Vaginulus in particular. In that species the great pedial 

 nerves pass along the median line closely approximated, and 

 associated with the visceral and some of the branchial nerves. 

 This cord, so to speak, gives off filaments on either side as it 

 passes backwards, and might very aptly be compared to a spinal 

 cord were its true nature not fully understood. The anterior 

 pedial nerves of this animal come ofi" from their ganglions in a 

 similar radiating manner to those of the stellate ganglions of 

 the naked Cephalopods. 



Having now gone over the cephalic ganglions of Ommastrephes, 

 we have next to examine the splanchnic system, and this will 

 be found to agree in all essential features with the same portion 

 of the nervous system in the Gasteropods. The great visceral 

 nerves (PI. II. fig. 1 q) are two in number ; these, as before 

 stated, come from the visceral ganglion situated between the 

 branchial. At first these nerves form but one trunk, which is 

 however distinctly composed of two filaments ; they soon divide 

 and resolve themselves into four branches ; but previously give 

 off two minute twigs [q', q'), one on each side, which go to the 

 mantle. Two {t) of the four branches becoming attached to the 

 wall of the anterior vena cava, pass down that vessel as far as 

 the pericardium, where they unite to form a large, depressed, 

 irregularly quadrilateral ganglion (m) which gives off four 

 branches. The two larger {v,v) of these diverging enter the 

 root of the gills, and after giving a branch to the branchial 

 vein swell out to form, on the wall of each branchial artery, 

 an oval ganglion {v', v'), from which a stout nerve passes up the 

 organ, supplying it with a plexus of filaments as it goes. These 

 two branches from the ganghon on the vena cava give off in their 

 course each a nerve or two {w, w) which go to the generative 

 organs. One {x) of the other two branches from this ganglion 

 accompanies the vena cava into the pericardium, and passing 

 along with that vessel sends branches to the two branchial 

 hearts, to the systemic heart, and to the posterior aorta. 



The other pair (r) of visceral nerves from the great trunk 

 come off from one of the branches given to the vena cava as a 

 single stem, which almost immediately forming a small gan- 

 glionic swelling {s), divides into two branches. These are not 

 so large as those applied to the vena cava ; they become at once 

 adherent to the intestine, and tube of the ink-bag, and supply to 

 the walls of these organs a minute nervous plexus most deve- 

 loped towards the orifices of the tubes. These two nerves were 

 traced as far downwards as the ink-bag, where they were lost in 



