198 THE RADIATING ORGANS OF THE DEEP SEA FISHES. 



one should say that the radiation — supposing that a radiation is really 

 emitted from it — is produced by the nerve branches themselves and that 

 the paratagential cells are merely packing. 



These organs of Bassozetus resemble the basal part of the radiating discs 

 of Halosaurus to be described below and so one might suppose that the 

 superficial layer of cylindrical cells there present also occurs here but has 

 been lost post mortem. It must however be remarked that no trace of a 

 previous presence of such a cell layer could be made out in transverse sec- 

 tions of the radiating discs o^ Bassozetus nasiis. 



LeUCiCOrUS luSCiOSUS Gannan. 



Plate 3, Figs. 10-13. 



This species has been described by Garman ('99, pp. 148, 361, Plates 38, 74, 

 Fig. 1). After removing the semitransparent skin of the head the radiating 

 discs underlying it are exposed to view. They appear as roundish white 

 spots 1.5-3 mm. in diameter overlying the bones of the skull. They are 

 remarkably hygroscopic. If one places one of the discs preserved in alcohol 

 in water it rapidly increases in size and swells to the bulk of a pea. On 

 each side of the head there are 3 maxillary, 4 orbital, 2 ethmoidal, 3 fron- 

 tal, 7 occipitoparietal, 4 mandibular, and 5 opercular radiatiug discs. 



These organs are similar to, but in their finer structure more highly 

 differentiated than, those of Bassozetus nasus described above. A very stout 

 nerve (Plate 3, Figs. 11, 12 n) enters the disc from the side and extends, as 

 in Bassozetus, to its centre without decreasing in thickness. Besides this 

 main disc nerve there are other smaller nerves (Figs. 11-13 n'), which 

 enter the disc in a similar manner. In some cases it appeared as if the latter 

 connected different discs with each other. Numerous large blood vessels 

 (Figs. 11-13 b) are met with. These chiefly extend from two opposite 

 sides towards the centre of the organ and here, bending abruptly at nearly 

 right angles, and ramifying, form a vascular ring of rhomboid al shape. From 

 this ring numerous branches are given off towards the interior which supply 

 the central part of the disc. These blood vessels form a dense superficial 

 reticulation (Fig. 13). 



The large main disc nerve extends through the basal part of the disc and 

 terminates in the centre of the rhomboidal space surrounded by the blood- 

 vessel ring. Here it abruptly divides into numerous branches all diverging 



