THE UADIATIKG ORGANS OF THE DEEP SEA FISHES. 101 



C. sloani in detail. To his statements concerning the simple organs we have 

 referred above. Tlie compound organs of this fish ('01, pp. 14, 15, Fig. 7) 

 consist, according to him, as in (J. Ixo'liatus, ul" a proximal, nearly exactly 

 spherical part, to which a I'lmnel-sliaped neck, separated by a distinct 

 incision, is attached. In the compound organs of the body the fuiuiel is 

 cut oil' obliquely where it abuts on the surface of the body. In the 

 branchiostegal organs transversely. Each compound organ consists of an 

 outer pigment layer, a reflector, a connective-tissue capsule, and a central 

 cell mass, in which three regions, an outer, middle, and inner can be distin- 

 guished. These regions correspond to the three regions in the organs of 

 C. barbalHS. Beyond the outer region gelatinous tissue is met with, occupy- 

 ing the space between its outer face and the surface of the fish. The outer 

 region is divided by connective-tissue membranes into very narrow facets di- 

 verging distally. The middle region is clearly divided into an outer portion, 

 occupied by [)olyedrical cells, and an inner portion divided into radial facets. 

 The inner region consists of railially arranged conic cells, the larger central 

 parts of which are fine grained and stainable with eosin but not with haema- 

 toxylin, whilst the much smaller peripheral portions forming about a quarter 

 of the length of each cell are readily stainable with haenuitoxylin. Each of 

 these cells contains one or two nuclei situated in the peripheral portion. 



It will be seen from this that the structure of these organs in C. tilontil is 

 very similar to that in C. barbidua. The chief dit'ferences between them are 

 the following: in C. sluaiii the facets of the outer region are narrow, the 

 middle region is distinctly divided into an outer and an inner portion, and 

 the cone cells of the inner region contain one or two nuclei; in C. barbatus, 

 on the other hand, the facets of the outer region are broad, the middle 

 region is not divided into two clearly distinct parts, and the cone cells of the 

 inner region always contain a single nucleus. 



Idiacanthus antrostomus Gilbert. 



Plate 8, Figs. 41, 43. 



This species was first described by Gilbert ('90, p. 54), later more in detail 

 by Garman ('99, p. 280). It possesses two kinds of radiating organs, one 

 without, the other with, a pigment sheath. The former are exceedingly 

 small and arranged in two large elongate groups (Plate 8, Fig. 41 u) on the 



