52 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
As regards microscopic structure, the state of preservation leaves so much to 
be desired that it seems hardly worth while to go into very minute details. 
The following is an account of the facts I have been able to elucidate by a 
study of serial sections. 
Each organ. consists of the following parts: — 
1. The Capsule. 
2. The Posterior Cup. 
3. The Inner Cup. 
4. The Central Mass. 
5. The Anterior Jap. 
1. The Capsule (Plate 9, Fig. 2, c) is about 0.04 mm. thick, and consists of 
rather loose connective tissue with small irregularly-shaped nuclei scattered in 
it here and there. "The inner half of the thickness of this layer is deeply 
pigmented, the tissue being permeated by a mass of granular reddish-brown 
particles. The color and density of this layer agree with that to be noticed 
subsequently in other organs of this species, and it is in marked contrast with 
the very opaque black pigment seen in Abraliopsis. It is specially noteworthy 
that no similar layer was observed in the case of Pyroteuthis margaritifera. 
2. The Posterior Cup (Fig. 2, p. c.) is built up of a large number of flattened 
oval or almost circular seales arranged in concentric layers, and leaving a 
hollow in the middle which contains the knob of the central mass. In section 
these scales, being thicker in the middle than at the edges, have an irregularly 
fusiform outline, and their concentric arrangement is very conspicuous. They 
stain very deeply with all the reagents yet tried (haematoxylin, carmine, and 
osmic acid). In some parts of the sections, notably in the more superficial 
layers, they appear to be homogeneous, but in other parts they present a 
frayed-out appearance, and are then seen to be made up of a number of inter- 
lacing fibrils with a less dense substance between them (Fig. 8). They vary 
much in dimensions; the largest, situated in the outer layers, measure 0.08 mm. 
in diameter by 0.03 in thickness, whilst those near the centre measure rather 
less than half these dimensions. The smallest of all are near the rim of the 
cup ; they are sub-eireular rather than fusiform in outline, and the diameter in 
many cases is only about 0.015 min. 
x 
The scales are not in contact with each other, but are separated by inter- 
spaces of about 0.01 mm. in thickness, but varying much in different places. 
A delicate connective tissue, which stains only very feebly with the reagents 
above mentioned, fills up these interspaces. Here and there a radially directed 
passage is seen perforating several of the layers of scales, and in its centre may 
be seen a fibril which can often be traced to the central mass, and is presum- 
ably a nerve (Fig. 2, »). I have not, however, been able to trace these nerves 
to their source in the outer layers of the organ. 
The aetual form of the periphery of these scales is very difficult to determine, 
because the sections cut them at such varying angles. Tangential sections 
