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 tunnel. 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, 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 underthe 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). 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 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 seenis 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 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 subhyaline 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 
