1889.] ANATOMY OF GONATUS FABRICII. 123 



unite so that each forms a cone, the inferior layer being internal to 

 the superior (Plate XIV. figs. 2, 3). They are not in contact, but a 

 narrow space is left between them, which of necessity has the form 

 of a funnel. Furthermore the internal epithelial cone is truncated, 

 so that a conical space is left between it and the outer cone. In the 

 preparations the epithelial surfaces had shrunk away at many points 

 from the chitinoid material below. 



The epithelium lining the pen-sac (e, e") is, in this region, thin 

 and composed of cubical cells, except at a point near the tip of the 

 pen on the dorsal aspect, wliere the cells are almost columnar. The 

 appearance of the shell itself does not differ from that seen in the 

 more anterior regions except that it is paler in colour and seemingly 

 sotter in consistency, for it does not crack under the razor. A very 

 curious tissue, however, fills up the small conical space, which was 

 described as existing at the extreme tip of the pen-sac (c.p.). Im- 

 mediately lining the epithelium is a layer of normal pen-substance, 

 that is to say, not differing from that seen in the adjacent parts. 

 Within it is the mass of tissue just mentioned (c.p.). It consists of 

 a matrix which takes up borax carmine very faintly, but still just 

 sufficiently to mark it off clearly from the chitinoid pen-substance. 

 It presents a series of striations, which pass over it irregularly in 

 very various directions, sometimes straight, sometimes curved. Quite 

 at the posterior extremity an appearance is presented as though the 

 dorsal limb of the pen had been bent sharply backwards upon itself 

 (fig. 3). 'J'he matrix contains a large number ot vacuoles, of spherical 

 or ovoid form, their long axes, in the latter case, lying parallel with 

 the striations above mentioned. They vary considerably in size. 

 AVithin the matrix, moreover, numerous nuclei are embedded ; but 

 in only one or two instances was 1 able to make out any cell-substance 

 connected with them, and in these it had a loose granular appearance. 

 Two or three examples showed the cell-substance passing off from 

 the nucleus in the form of radiating threads, such as have been fre- 

 quently figured in representations of the cartilage of the Cephalopoda; 

 I was, however, unable in the preparations examined to trace the 

 processes of the cells into the matrix. Many of the nuclei could be 

 easily seen to be lying in the vacuoles in the matrix, but many looked 

 precisely as though they were closely surrounded by the matrix 

 itself. This was probably erroneous, for with the highest powers 

 which the preparations would bear the number of cells which could 

 be distinctly seen to be surrounded by vacuities was greatly increased. 

 The conclusion seems to be that we have here to deal with a form 

 of cartilage, but of a degenerate type. It will be interesting to 

 assertain whether any material of similar nature occurs in corre- 

 sponding situations in Ommustrephes and Onychotev.this, 



In the other specimen of which longitudinal sections were made 

 (fig. 2) the appearance presented was somewhat different. The 

 matrix had entirely lost its subhyaliue as well as its striated look 

 and was evenly granular throughout. Only a vacuole could be seen 

 here and there, and the nuclei also had almost disappeared ; so that 

 one might suppose that here the degeneration of the cartilage had 



