124 MR. w. E. HOYLE ON THE [Mar. 5, 



reached a more advanced stage. Another observation, too, indicates 

 beyond a doubt that the process of pen-formation has proceeded 

 further in this specimen than in the other. At the base of this cone 

 the epitlielium has been retracted away from it, and on the surface 

 thus liberated could be seen a film of highly refractive material (sep.). 

 A similar film is also discernible on the ventral aspect of the base of 

 this cone, and they both become thinner and disappear as they pass 

 towards the centre of the base. I think it is safe to conclude that 

 we have here the incipient formation of the phragmocone which is 

 known to be present at the posterior extremity of the pen of Gonatus. 

 The conical mass of degenerate cartilage then serves the purpose of 

 a mould upon which the septa of the phragmocone are deposited. 



Hear the middle of the granular mass was a curved band of 

 apparently denser material than the rest, in the centre of which a 

 faint line could be traced. Whether this is merely accidental or 

 "whether it indicates the position of an earlier incomplete septum [ 

 have no means of ascertaining. 



V. The Muscles. 



Regarding the disposition of the muscles not verymuch is to be said ; 

 on the whole it resembles the arrangement found in Onychoteuthis 

 and Enoploteuthis, but differs from both these in certain respects. 



The capsule of the liver, formed by the retractor muscles of the 

 head, is much less strongly developed than in Onychoteuthis, the lateral 

 portions being, to all appearance, merely membranous without any 

 muscular fibres. The retractores capitis mediani arise separately in 

 their usual situation near the middle line ; as they pass forward they 

 approach each other and fuse together a short distance behind the 

 point at which the cephalic aorta enters them ; in front of this they 

 are again easily separable. In a specimen of Onychoteuthis hanksii 

 which was examined for the sake of comparison there is a union in 

 the same place, but less complete. 



The retractores capitis laterales are slightly developed and they 

 seem to be distinctly separated from the median retractors by a 

 membranous interval in the capsule of the liver. 



No muscle is present running from the head to the ventral surface 

 of the pen-sac, and passing over the commissure between the two 

 ganglia stellata, such as is described by Brock ^ in the case of Eno- 

 ploteuthis. 



The coUaris muscle has the usual disposition and relations. 



The adductor infundibuli inferior has pretty much the same 

 arrangement as in Onybhoteuthis. It arises far forwards and some 

 distance from the ventral line, and is inserted nearly in the middle 

 line a little distance behind the posterior infundibular nerve. 



VI. The Nervous System and Sense-Organs. 

 The central nervous system (Plate XIII. figs. 1, 2) resembles most 



^ Brock, " Versuch einer Phylogenie der dibrancbiaten Cephalopoden/' Morph. 

 Jahrb. vi. p. 198 (18S0). 



