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Show 1889.] ANATOMY OF GONATUS FABRICII. 123 unite so that each forms a cone, the inferior layer being internal 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 chitiuoid 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, where 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 softer 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.). Immediately 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). The matrix contains a large number of 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. Within the matrix, moreover, numerous nuclei are embedded ; but in only one or two instances was I 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 frequently 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 corresponding situations in Ommastrephes and Onychoteuthis. In the other specimen of which longitudinal sections were made (fig. 2) the appearance presented was somewhat different. The matrix had entirely lost its suhhyaline as well as its striated look aud 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 |
