HOYLE: REPORTS ON THE CEPHALOPODA. 61 
In general, too, the deeper half is a little more bointed than the more super- 
: » boo, ] ] : 
ficial, so that the form of the organ approaches that of a peg-top (Fig. 4). 
a : ; i 
Each organ consists of the following parts : — 
o o 
l. The Lens. 
2. The Pigment Cup. 
3. The Inner Cup. 
4. The Posterior Hemisphere. 
5. The Internal Cone. 
l. The Lens (Plate 10, Figs. 4, 5, Z) consists of a pale struetureless material 
Which is not acted upon by staining fluids. It is divided up by faint irregular 
lines of demarcation and occasional cleavage gaps into more or less rounded 
Masses, in the interstices between which nuclei are found here and there, 
Viewed in a section taken along the axis (Fig. 4) the lens is seen to be sep- 
arated by an equatorial groove into an inner and outer portion. These differ 
Somewhat in their structure. In the deeper portion, the pieces of which the 
lens is built up are rounder and more irregular, their depth being not infre- 
quently equal to their transverse diameter. In the more superficial portion, 
these pieces are more flattened and taper to their edges on either side, and are 
fitted into each other something like flattened epithelial cells near the surface 
of the epidermis. The nuclei are modified in accordance with the tissue in 
which they are found, being rounded or sub-polygonal in the deeper portion 
and flattened in the superficial. The groove above mentioned receives the 
inturned edge of the pigment cup. 
2. The Pigment Oup (Figs. 4, 6, 7,8, p. c.) is in the shape of a goblet without 
a stem and with the edge somewhat inverted. It is built up of a number of 
Separate pigment masses which are seen in section to be hollow sacs with a 
thick lining of black pigment, a structure which suggests the view that they 
are possibly modified chromatophores. Their boundaries are not always 
Visible, and hence it is impossible to determine their exact number, the more 
80 as the sections of the posterior part of the organ are never entire, In a 
horizontal section taken just below the lens (Fig. 6) there are usually six of 
these which make up a more or less complete ring, and in such cases the 
boundaries of the individual sacs are pretty easy to determine. This ring 
Appears to correspond to the inturned edge of the pigment cup. In the 
déeper portions the hollow cavities of the pigment masses are not so easily 
seen, nor are the boundaries so distinct. The aperture of the cup, as above 
Stated, is occupied by the lens. In its bottom is situated the posterior hemi- 
Sphere, whilst the remainder is lined by connective tissue with numerous 
large nuclei (Figs. 4, 7, 8, c. t) 
3. The Inner Cup (Figs. 4, 7, ù c.) lies inside the pigment cup just described. 
It might perhaps be more correctly described as a funnel, for a conical perfora- 
tion runs right through its middle, diminishing in diameter as it descends, 
The substance of which it is composed stains only very faintly. In an axial 
