THE RADIATING OKGANS UF THE UEKi' SEA EISIIES. 183 



This tissue is rich in blood vessels. The radiating organ proper, tliat is, the 

 mass of cells (pc) which probably emit the radiation, lies in tlie middle of 

 tliis connective tissue. It is pear-shaped, the tliiiiner end extending outward 

 and downward. The cells composing it are llattened and extend parallel to 

 the surface of the body. The protoplasm is quite transparent and each cell 

 contains a large granular nucleus. The blood vessels form a fine-meshed 

 capillary network (b) on tlie surface of this cell mass, but do not penetrate 

 into its interior. 



Radiating organs of this kind seem to be rare in fishes. Somewhat simi- 

 lar ones have been described by Emery ('84, p. 473) from the ventral series 

 of Scopelus duiujatus. 



Chauliodus barbatus Gannau. 



Plate S, Figs. 38-40 ; I'late U, Fiss. 43-40. 



Tliis species has been described by Garmaii ("'JO, p. 271, Plate K, B'igs. 2, 

 2 a). The radiating organs are very numerous. Three diffeieiit kinds of 

 them can be distinguished. The differences between these are considerable 

 and clearly discernible with the naked eye. Some of the organs are simple, 

 some composed, as in the fishes described above, of an inner spherical and an 

 outer paraboloidal part. The simple ones again are either uncovered or 

 provided with a pigment sheath. I have designated these three kinds of 

 organs accordingly as simple organs without pigment sheath, simple organs 

 with pigment sheath, and compound organs with pigment sheath. 



The simple radiating organs without pigment sheath appear as very 

 small whitish dots. They are arranged in groups of from 4 to 16. These 

 groups are scattered over the medial part of the ventral surface (Plate 8, 

 Fig. 39 u) and also occur in great numbers on other parts of the surface, 

 chiefly on the back of the iish. 



The simple organs with pigment sheath appear as dark spots 300 /x in 

 diameter. They are scattered in great numbers over the whole of the sur- 

 face and seem to be most numerous on the sides of the head just behind the 

 eyes (Plate 8, Fig. 38 x). In the barbel there are 8 of these organs 

 (Plate 8, Figs. 38-40 Ba). 



The compound organs with pigment sheath are lustrous, elongated, 

 about 1mm. long and 600 jx broad. Of these organs there are on each side 1 

 anteorbital (Plate 8, Fig. 38 ao), 1 suborbital (Fig. 38 so), 18 branchio- 



