REPORT ON THE DEEP-SEA FISHES. 307 



whilst the dorsal stern-chasers or the solitary dorsal stern-chaser, which are invariably 

 directed backwards, probably serve for purposes of defence, inasmuch as a strong ray of 

 light shot forth from the stern-chaser may dazzle and frighten an enemy which is in hot 

 pursuit of fi Scopelus. 



e. Development. 



According to Emery' these organs are enclosed between two scales, one forming the 

 light-reflecting layer of spicules below the cup-shaped portion, and the other a lens 

 on the surface above it. 



All these organs examined by me are destitute of a lens, and only covered by a very 

 thin epithelium. 



As these organs, with the exception of the dorsal stern-chasers, are always found in 

 two more or less continuous lateral rows, they seem to be in some way connected with the 

 slime-canal system. 



It may be supposed that the stern-chasers have been developed in the skin inde- 

 pendently of the lateral slime-canal. 



The development of the complex organs with coalesced proximal portions from 

 isolated ones, has been referred to above. 



5. Regular ocellar projecting organs. 



a. Distribution. 



These organs have been only found in Xenodermichthys nodulostis. 

 They differ in a remai-kable manner from all other forms, and no organs similar to these 

 liave been previously described. 



They are found segmentally placed in rows on the sides of this fish. 



b. Structure. 

 These organs appear as oval bodies, attached to the fish only by a small portion of 

 their base, and they project freely beyond the surface, differing in this respect from all other 

 analogous organs. Each organ is oval, about two and a half times as long as high, slightly 

 flattened, and broader than high. One end is slightly wider and covered by a thick layer 

 of pigment. This is directed dorsad, and is accordingly under ordinary circumstances 

 turned upwards, while the other end is slightly narrower and looks downwards, being 

 situated ventrally. This end is only covered by a thin transparent epithelium. The 

 organ is about 2 mm. long and 1 mm. wide ; it is attached (PI. LXXIII. fig. 50) to the 

 surface of the fish by a peduncle near its upper end, and apparently pendent from the 

 base of attachment. 



' C. Emery, Mittheil. ans d. zool. Station xii Neapel, I'd. v. 



