THE RADIATING ORGANS OF THE DEEP SEA FISHES. 175 



tion as " polygonal," meaning perhaps polyedric. The latter are, as it has been 

 described above of A. hjcliims, also in A. hmdgjjmnus, smaller than the former. 

 Handrick found blood vessels but no nerves in the middle region. The ex- 

 tent of the gelatinous tissue occupying the distal part of the cone is dif- 

 ferent in the different organs ; it is absent altogether in the anteorbitals. 

 In this region a loose network of connective tissue with large nuclei ex- 

 tends, the interstices being occupied by a gelatinous substance ('01, p. 58). 



According to this, the latest paper on A. hemigt/mnus, the radiating organs 

 of this fish seem to have very much the same structure as those of A. lychnus. 



Sternoptyx obscura Gar man, 



Plate G, Figs. 86, 37. 



This species was described by Garman ('99, p. 232, Plate 53, Fig. 1). 

 The radiating organs are, as in Argf/ropelecus If/clums, very conspicuous. 

 There are on each side 2 opercular (Plate 6, Fig. 26 op), 5 branchiostegal 

 (br), 10 ventrothoraic (vt), 3 ventral (ve), 3 anterior lateral (al), 3 poste- 

 rior lateral (pi), 3 anal (a) and 4 ventrocaudal organs (vc). As in Argyrope- 

 lecus lychnns all these groups form rows in which they lie close together. 

 The 20 ventrothoracic organs of the two sides are joined to form a medial 

 crest protruding from the ventral side of the fish. The inner regions of 

 the internal parts of these organs are joined and form a continuous mass. 

 The axes of all the organs enclose very small angles with the outer surface 

 and thus lie nearly paratangentially. The 2 opercular of each side are 

 oblique, directed downwards and backwards, all the others more or less 

 vertically downw'ards. 



Besides these organs observed by me, Garman ('99, p. 233) mentions a 

 silvery area below the eye which he thinks may be a rudimentary suborbital 

 radiating organ. 



The structure of the organs is apparently the same as in Argyropckcus 

 Igchmis. In some of them, however, chiefly in the ventrothoracic organs 

 (Plate 6, Fig. 27), the proximal part of the pigment sheath (p) is thicker 

 and the middle and outer region together are much less extensive than 

 in that fish. These appear here (1 and s) as a rather thin, oblique, lenticular 

 body separating the extensive gelatinous outer mass (gl) from the cellular 

 inner region (g). Traces of stratification could also be detected in the 

 outer region. 



