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. 4") r) composed of slender fibres, is found within the pigment 

 sheath. Tn the proximal spherical part no such reflecting layer could be 

 made out. A coiniective-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 (o). The inner region occupies the 

 whole of the proxinuil spherical part of the organ with the exception of a 

 distal conic sector. It is composed of large, elongate pyramidal cells (Figs. 

 45, 46 pc). 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, 40 a) which 

 appears to be connected with the ladial 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 nuiss. Here they continue their course 

 between the latter and the proximal ends of the pyi\amidal 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- 

 ity for haematoxylin and other stains. The protoplasm occupying this 

 central part of the cell is, however, not hyaline but distinctly granular. In 



