M 



0/ Ommastrephes todarus. 9 



however, in detecting near the region of the eye of Ommastrephes, 

 any organ likely to be the seat of this sense. 



The great visceral nerves (PI. I. figs. 1, 2, 3 z), combined 

 as one trunk, come off from the posterior margin of the visceral 

 ganglion, forming the central lobe in the posterior mass. But 

 it is better to defer the description of these visceral nerves until 

 we come to speak of them under the head of Splanchnic system. 

 We will therefore without further interruption examine the only 

 remaining pair of cephalic ganglions. These are the stellate 

 ganglions (PI. I. fig. \ g,g) of authors; they are large, depressed 

 and irregularly ovate, and rest upon the great muscular enve- 

 lope — the sleeve, one a little on each side of the median line, not 

 far from the anterior border, and having the cyst containing the 

 pen between them. These ganglions are connected to the branchial 

 by a stout commissure {h, h) which comes off from these latter, as 

 before stated, in connexion with two or three nerves, which we 

 have seen distribute most of their filaments to the mantle. This 

 commissure is united to the anterior margin of the stellate gan- 

 glions, and they communicate with each other across the median 

 line by a stout nervous cord {i), which passing from their inner 

 margins goes through the wall of the cyst inclosing the pen ; at 

 this part the wall of the cyst is thick and fleshy. This latter 

 cord or commissure, which appears hitherto to have escaped de- 

 tection, is of course above the oesophagus. Were therefore the 

 stellate ganglions only accessory branchial, they would have no 

 connecting commissure above that tube. These ganglions dis- 

 tribute to the sleeve numerous nerves (y, y, y, y) which pass off 

 from their outer margin in a radiating manner. The fins are 

 supplied from a different source. Just before the great branchial 

 cord reaches the stellate ganglion it gives off a stout nerve (a?' a^) 

 which passes freely under that centre, and becomes united to the 

 great posterior sleeve nerves {x, x) ; as they pass backwards 

 together these latter distribute their filaments to the sleeve, and 

 on arriving at the commencement of the fin, the large nerve from 

 the branchial cord dips through the muscles and reaches the 

 substance of that organ ; it then divides at once into numerous 

 branches, which diverging go to all parts of this powerful pro- 

 pelling instrument. 



The fin is then supplied with nerves, not from the stellate gan- 

 glions, but apparently from the branchial. From this fact, it 

 would seem that the fin is not a mere development of the sleeve, 

 but must represent some other organ. What this is it is diffi- 

 jCult to say. 



As the fin nerves pass backwards in connexion with those of 

 he posterior portion of the sleeve, they have, on account of their 

 central position, their parallelism and approximation, somewhat 



