THE RADIATING ORGANS OF THE DEEP SEA FISHES. 177 



dense, and of uniform thickness in the inner spherical part and the proxi- 

 mal portion of the outer parabolic part. Towards the surface it thins out. 

 The reflecting layer (Figs. 35, 37 r) is about as thick as the pigment layer 

 and composed of longitudinally arranged fibrous cells. It does not extend 

 to the surface and terminates some distance within the margin of the 

 pigment layer. On the inner side of the reflecting layer a conspicuous 

 connective-tissue membrane (Figs. 35, 37 c) about as thick as the two other 

 layers, is met with. Distally this membrane passes into the gelatinous 

 portion of the outer region of the organ. 



Three regions (Plate 7, Fig. 37 g, 1, s), can be distinguished in the tissue 

 forming tlie internal part of this organ in Lychnopoles as in Argyropelecus 

 and Sternoptyx ; in Lychnopoles, however, these are built on a somewhat 

 different plan. 



From the connective-tissue membrane (Plate 7, Figs. 35, 37 c) mentioned 

 above membranous diverticula extend inward which join to form facets 

 arranged radially. In the proximal spherical part of the organ these mem- 

 branes are straight and each facet encloses a regular pyramidal space. 

 Its apex lies near the centre of the sphere, and its base abuts on the 

 connective-tissue membrane overlying the reflecting layer (Plate 7, Fig. 37). 

 The radial membranes (facets) do not extend quite to the axis. A some- 

 what irregular tubular cavity (Plate 7, Fig. 37 cc) occupies that portion 

 of the axial part of the organ which lies between the centre of the proxi- 

 mal sphere and the focus of the distal paraboloid. The margin of this 

 tube is so well defined that it looks as if a special limiting membrane were 

 present. Its cavity appears empty, neither blood corpuscles nor other 

 bodies were found in it. In the pyramidal spaces enclosed by the facets, 

 nuclei and residual protoplasmatic masses highly stainable with acid-fuchsin 

 are met with. These adhere chiefly to the connective-tissue membrane 

 at the base of the pyramid and to the adjoining parts of the radial membranes: 

 the central parts of the facets (Plate 7, Fig. 37 ci) are pretty free from 

 them. 



The facets in the distal paraboloid are not so regular as those in the 

 proximal sphere. The inner (proximal) part of the paraboloid is occupied 

 by pretty narrow, more or less curved facets (Plate 7, Fig. 37, cm) extend- 

 ing from the sides towards the distal end of the tubular cavity above 

 described. These facets are pyramidal, distally broad and proximally con- 

 tracted. The outer (distal) part of the paraboloid is occupied by regular 



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