188 THE RADIATING ORGANS OF THE DEEP SEA FISHES. 
the distal highly stainable terminal part of each cell one rather small nucleus 
(nu) is situated. 
The middle region (Plate 9, Fig. 45 m) occupies the distal sector of the 
proximal spherical part of the organ and the proximal portion of the distal 
paraboloidal part. The proximal limit is conic, the distal limit very regularly 
convex. The cells occupying the space between these limits (1) are well 
defined and polyedric in shape. The distal ones are small. From here they 
increase in size inwardly, the innermost ones being four to five times as large 
as the outermost ones. The protoplasm of these cells is homogeneous, not 
granular, and hardly stainable with haematoxylin. It shows a great affinity 
to picric acid and the whole cell mass of this region appears bright yellow 
in sections stained with picric acid-haemotoxylin. The nucleus is nearly 
spherical and larger in the large cells than in the small. 
The distal limit of the outer region is nearly a plane vertical to the axis 
of the organ, and so, its inner limit being concave and some distance away, 
the outer region (Plate 9, Fig. 45 0) has the shape of a thick plane concave 
lens. From the mass of connective tissue which abuts distally on the outer 
region, septa, nearly vertical to the limiting surface and parallel to the axis 
of the organ, extend inward, dividing the outer region into prismatic facets 
rounded off distally. These facets are occupied by small elongated cells, 
the protoplasm of which behaves towards stains in a similar manner as the 
protoplasm of the cells of the middle region. 
The compound radiating organs of Chauliodus were first studied in 0. 
sloani by Leuckart (64, pp. 153-155). According to his description these 
organs of C. sloawi are similar to those of C. barbatus. Leuckart chiefly 
studied the branchiostegal radiating organs (1. ¢., p. 154). These are 
cylinders, 1 mm. long and 500 p broad. Their distal portion is occupied by 
a structure Leuckart considers as a lens. From the proximal face of this a 
conic protuberance arises, penetrating some distance into the inner cell 
mass; as mentioned above such a cone is also observed in C. barbatus. The 
reflecting layer consists of hexagonal pavement cells occupied by numerous 
crystals. In the outer part of the distal mass, that is, in the “lens,” Leuckart 
claims to have seen fibres, whilst the inner part, and the proximal cone are 
composed of closely packed rods 5 p thick radiating from the apex of the 
cone. The substance composing these rods is highly refractive. No fibres 
or rods of this description occur in the middle and outer regions, which cor- 
respond to Leuckart’s “lens,” in the compound organs of C. barbatus. The 
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