THE RADIATING ORGANS OF THE DEEP SEA FISHES. 187 
9, Figs. 45, 46 p). The cells composing the sheath contain brown pigment. 
They are very closely packed towards the inner well-defined and perfectly 
smooth surface. Towards the outer side they are farther apart and this 
surface is not so well defined, the pigmented tissue passing here somewhat 
gradually into the unpigmented tissue surrounding the pigment sheath. In 
the distal paraboloidal part of the organ a lustrous reflecting layer (Plate 
9, Fig. 45 r) composed of slender fibres, is found within the pigment 
sheath. In the proximal. spherical part no such reflecting layer could be 
made out. A connective-tissue membrane (Figs. 45, 46 c) clothes the whole 
organ. In the proximal spherical part it appears to rest immediately on 
the pigment sheath, in the distal paraboloidal part it rests on the reflecting 
layer. Distally this membrane merges into the transparent connective tissue 
(Fig. 45 d) which occupies the triangular space between the distal limit of 
the radiating cell mass proper and the outer surface of the fish. From the 
whole of the connective-tissue capsule fine radial septa extend inward. 
The radiating cell mass proper is composed of three regions, an inner 
(Fig. 45 i), a middle (m) and an outer (0). The inner region occupies the 
whole of the proximal spherical part of the organ with the exception of a 
distal conic sector. It is composed of large, elongate pyramidal cells (Migs. 
45,46 pe). These are arranged radially in a very regular manner and 
nearly vertical to the connective-tissue capsule, on which their bases rest. 
They do not quite reach the centre to which they converge. ‘This is occu- 
pied by a plug-shaped mass of small cells (Plate 9, Figs. 45, 46 a) which 
appears to be connected with the radial septa extending inward from the 
connective-tissue capsule enclosing the radiating cell mass. These septa 
can often be made out between the pyramidal cells. In sections large blood 
vessels (Plate 9, Fig. 46 b) are frequently seen extending radially inward 
from the surface to the central cell mass. Here they continue their course 
between the latter and the proximal ends of the pyramidal cells, and seem 
to give off exceedingly fine branches which extend radially outward between 
the pyramidal cells (Plate 9, Fig. 46) along the connective-tissue septa, 
separating the latter from one another. The pyramidal cells themselves 
(Plate 9, Figs. 45, 46 pc) are occupied at their distal end by protoplasm 
staining deeply with haematoxylin (Plate 9, Fig. 46 pt) whilst their central 
and proximal parts (ph), about five sixths of the whole, show no great affin- 
The protoplasm occupying this 
ity for haematoxylin and other stains. 
central part of the cell is, however, not hyaline but distinctly granular. In 
