180 THE RADIATING ORGANS OF THE DEEP SEA FISHES. 



vision and the other downward, neither inward nor backward, as Garman 

 ('99, p. 245), who also noticed that this organ differs in structure from the 

 others, seems to think. 



Cyclothone acclinidens Garman. 



Plate 6, Figs. 38-30. 



This species has been described by Garman ('99, p. 247, Plate J, Fig, 4), 

 whose statements concerning the radiating organs are, on the whole, in 

 accordance with my observations ; in his figure (4), however, 2 opercular and 

 5 posterior lateral organs are drawn which do not exist and which Garman 

 himself does not mention in his description. The other organs are repre- 

 sented in the figure as lateral whilst they are in reality situated on the ven- 

 tral side of the body. 



The radiating organs are very small, only 700 fx in diameter, and are 

 destitute of reflectors. On account of their insignificant size and want of 

 lustre, they are far from conspicuous and not easy to make out. There are 

 on each side 10 branchiostegal (Plate 6, Fig. 29 br), — Garman ('99, p. 247) 

 gives their number as 13 — 13 ventrothoracic (Figs. 28, 29 vt), 3 ventrome- 

 dial (Figs. 28, 29 ve), and 16 ventroanal (Figs. 28, 29 a) radiating organs. 



All the organs seem to have the same structure. They are approxi- 

 mately spherical and enclosed in a pigment sheath which forms over three 

 quarters of a sphere and encloses them on all sides except where they abut 

 on the surface of the fish. A straight line drawn through the centre of the 

 sphere and the centre of the more or less circular superficial orifice of the 

 pigment sheath is vertical to the surface of the body. 



The pigment sheath (Plate 6, Fig. 30 p) is composed of cells containing 

 dark brown pigment granules. It is very stout. Its inner surface is pretty 

 smooth, the outer covered with irregular protuberances. Within the pig- 

 ment sheath a connective-tissue membrane (Plate 6, Fig. 30 c) is met with. 

 Near the surface this splits up into two membranes, one covering the mass 

 of radiating cells proper on the outer side (Plate 6, Fig. 30 cr) the other 

 forming a thick superficial cell layer (Plate 6, Fig. 30, 1 and cd). 



Three zones can be distuiguished in the organ : an inner^ occupying 

 about three quarters of the whole sphere, an intermediate, and an outer. 



The inner zone is composed of a mass of large polyedrical cells and 

 enclosed in a connective-tissue capsule. The part of this capsule which 

 covers the radiating cell mass inwardly and laterally and separates it from 



