178 THE RADIATING ORGANS OF THE DEEP SEA FISHES. 
straight, prismatic facets (Plate 7, Fig. 37 co) which are parallel to the axis 
of the organ; they are rounded off distally and drawn out proximally to 
points converging towards the distal end of the tubular cavity. ‘The distal 
ends of these facets lie in a surface convex outwardly and in folo vertical 
to the axis of the whole organ. The triangular space outside these facets, 
between them and the surface, is occupied by gelatinous tissue (gl). 
The small curved facets and the proximal portions of the large straight 
ones which together occupy the inner part of the paraboloid and form the 
middle region of the organ (Plate 7, Fig. 37) are clothed with a single layer 
of cylindrical cells which form a kind of simple epithelium (Plate 7, Fig. 36). 
These cells take up the greater part of the space within the facet and only 
leave an exceedingly narrow central canal (Plate 7, Fig. 36 en) free. This 
canal extends longitudinally in the axis of the facet towards the tubular 
space in the interior of the organ. Probably it opens into it, as I have seen 
many indications of such a connection, but Iam not certain about it. The 
cylindvical cells forming the epithelial clothing of these facets and surround- 
ing the central canal are composed of two kinds of protoplasm. The proxi- 
mal three quarters of each cell (lying next the canal) (Plate 7, Fig. 36 ph) 
are transparent and only slightly stainable; the distal quarter (lying next 
the facet wall) (Plate 7, Fig. 86 pt) is granular and takes stains very readily, 
so that it appears dark and not transparent in the stained sections. In this 
highly stainable, basal portion of the cell the nucleus (nu) is situated. 
It is probable that the facets of the proximal spherical part of the organ 
described above contain the same kind of tissue, but the condition of the 
material does not allow of this being definitely determined. 
The tissue occupying the distal parts of the large straight cylindrical 
facets and forming the outer region of the organ (Plate 7, Fig. 37 s) is of 
an entirely different character. Here we find elongated, slender cells, 
which are rather indifferent to most stains, but become intensely yellow 
after treatment with picric acid. Inthe distal basal part of each of these 
facets these cells are very slender, spindle-shaped, and arranged longitudi- 
nally, parallel to the axis of the facet (Plate 7, Fig. 34 sp). Towards the 
proximal part they become stouter and shorter and here they often appear 
club-shaped. The cells appear to rise from the walls of the facet. Those 
joined to the terminal face of the facet arise more or less vertically ; those 
joined to the sides arise very obliquely and extend nearly parallel to the 
facet. wall to which they are attached. The cells in the distal part of the 
