316 THE VOYAGE OF H.M.S. CHALLENGER. 



b. Structure. 



The patch is about 3 mm. long, and 2 mm. broad, with a slightly irregular lobate 

 outline. Structurally it resembles very closely the irregular organs on the sides of the 

 body of Astronesthes. It consists (in the only specimen which I was able to examine) 

 of a granular mass containing very many small nuclei which stain deeply (PI. LXXIII. 

 fig. 46, o). Outside, the organ is covered by a thin epithelium (PI. LXXIII 

 fig. 46, e). In the granular mass of the organ a few comparatively large, irregular cells, 

 with two or more processes, are found, and these contain larger nuclei than those 

 scattered in such abundance throughout the whole of the mass (PI. LXXIII. figs. 47, 

 48). The organ is traversed by threads placed perpendicularly to the surface (PI. LXXIII. 

 figs. 45, b, 46, b). These threads are attached to the fiat base by broad trumpet-shaped 

 extensions, and taper towards the upper end, which lies just below the surface. They 

 consist chiefly of a tough cartilaginous supporting rod and a large bloodvessel ; nerve 

 fibres are also found in them. The floor of the organ consists of a thick structureless 

 cuticle (PL LXXIII. fig. 46, c) overlying the ordinary superficial pigment layer of the 

 skin (PI. LXXIII. fig. 46, d). This structureless cuticle is continued, rapidly becoming 

 thinner, some distance up the vertical threads which penetrate into the organ. 



c. Function. 



The state of preservation of the specimens at my disposal does not permit me to draw 

 any very definite conclusion from the structure in regard to the function of the organ. In 

 colour and general appearance it resembles very closely other undoubtedly phosphorescent 

 organs of fishes. 



"■b" 



11. Suborbital glandular organs, without reflector. 

 a. Distribution. 



These organs are found in Astronesthes niger and Opostomias micripnus, in both 

 of which they occupy the same position, being situated on the upper jaw just Ijelow 

 the eye. As, however, they structurally diff"er very much in these two species, it will 

 be best to describe them separately. 



b. Structure. 



(l) Astronesthes niger. — In this species we find five phosphorescent j)atches of an 

 irregular glandular nature on the head, one (PL LXIX. figs. 1, d, 11, a) being situated 

 in the median line between the eyes. The other four (PL LXIX. figs. \, e, e', l\,b, c) 



