‘and lateral parts of the upper chamber. 
THE RADIATING ORGANS OF THE DEEP SEA FISHES. 193 
connective-tissue sheath enclosing the whole organ. The upper portion of 
this pigment sheath forming the roof of the upper part is dome-shaped, the 
lower portion, forming its floor and separating it from the lower spherical 
part, is flat or even a little concave. At the circular line where the upper part 
joins the lower a conspicuous ring-shaped thickening of the pigment layer 
(pt) is observed. From this a small annular ridge extends outwards and 
downwards, forming the rudiment of a cup enclosing the basal, upper portion 
of the lower, spherical part of the organ. 
The interior of the upper part of the organ is traversed by a horizontal, 
strongly pigmented membrane (pm), which divides it into a larger upper 
and a smaller lower chamber. In both these chambers large cavities (cv) 
are seen. In the upper one there seems to be only one such cavity. This 
is situated ventrally and surrounded by a special endothelial cell layer, 
separating it from the transparent connective tissue occupying the dorsal 
In the lower chamber more 
cavities than one are seen. ‘These lie dorsally. Below them in the ventral 
part of this chamber large sinuous blood vessels (b) extend. 
The lower part of the organ (B) is covered dorsally by the pigmented 
floor of the upper part of the organ and the annular rudiment of a pigment 
cup referred to above. Laterally and ventrally it is surrounded by the 
transparent connective-tissue sheath only. From the middle of the roof 
of this lower spherical part of the organ a cylindrical thread composed of 
connective tissue (z) arises which extends vertically downward to its centre. 
This thread is composed of longitudinally arranged, spindle-shaped connec- 
tive-tissue cells with oval nuclei. Along this thread blood vessels (b) and 
probably also a nerve extend from above down to the centre of the sphere. 
The lower end of the thread is thickened to form a terminal knob in which 
a sinuous cavity, filled with blood corpuscles, is observed. Apart from this 
thread with its terminal knob the whole of the sphere is occupied by large 
radially arranged conic cells (pe) equal in length to its radius. In arrange- 
ment and structure these cells are similar to the conic elements in the inner 
region of the compound organs of Chauliodus barbatus described above. 
They are, however, more slender. The inner seven eighths are occupied by 
finely granular, transparent protoplasm not re 
eighth of the length coarser grained protoplasm showing grea 
hematoxylin and other stains is observed. In the peripheral part of each 
adily stainable ; in the outer 
t affinity to 
cell one small, spherical nucleus is situated. 
13 
