THE RADIATING ORGANS OF THE DEEP SEA FISHES. 179 



facets are nearly straight throughout the whole of their length. As we 

 approach the proximal part of the facet we find these cells curving away 

 more and more from the walls of the facet so that their free ends come to 

 lie more or less obliquely (Plate 7, Fig. 34 sc). Finally they are situated 

 nearly transversely, the cells arising from the different sides interlacing 

 axially. 



In the sections one often finds a circular structure of considerable size 

 (Plate 7, Figs. 34, 35 o) in the centre of the facet. Sometimes it appears as 

 an empty space, and is perfectly colorless and structureless ; sometimes it 

 has — in sections stained with acid-fuchsin — a bright red color and then 

 one occasionally notices traces of a granular structure within it. The tissue 

 surrounding the circle often shows a fine radial structure (Plate 7, Figs. 34, 

 35). I have not been able to ascertain the real nature of these circles and 

 their coronas with any degree of certainty. The circles seem to be the 

 expression of spherical spaces lying between the cells, and the radial 

 structure surrounding them might be due to the fact that the slender inner 

 terminations of the spindle cells abut vertically on this sphere. 



The organ is rich in blood vessels. These follow the facet walls and 

 can often be traced for a considerable distance. 



The gelatinous tissue (Plate 7, Figs. 34, 37 gl) mentioned above is com- 

 posed of a gelatinous ground substance traversed in all directions by exceed- 

 ingly slender spindle cells. It passes into the connective-tissue membrane 

 overlying the reflecting layer. A thick granular lamella or cushion (Plate 7, 

 Fig. 37 gr) underlies this gelatinous tissue and separates it proximally from 

 the reflecting, and distally, where this is absent, from the pigment layer. 



As mentioned above, the anteorbital radiating organ differs in some 

 respects from the others. It appears to be much larger and measures 

 1.5 mm. in diameter. Closer examination shows that it is a duplex organ 

 composed of two, each similar to the other radiating organs of the fish. 

 These two organs point different ways and are enclosed in a common pig- 

 ment sheath which has the shape of a curved tube open at both ends. The 

 two orifices of this tube lie in the surface; one is oblique, directed upwards 

 and forwards towards the eye, the other vertical, directed straight down- 

 wards. The spherical parts (inner regions) of the two organs occupy its 

 central, the paraboloidal parts (middle and outer regions) and the gelatinous 

 and granular tissue the terminal portions of the tube. These two joined 

 organs throw their radiation in different directions, one into the field of 



k 



