REPORT ON THE DEEP-SEA FISHES. 309 



of the skin (PI. LXXIII. fig. 49). Ducts leading from the slime-canals of the skin to the 

 outer surface pass through it, and form loops in the fibrous tissue, which is apparently 

 quite transparent. It seems not improbable that the contents of these ducts are 

 luminous. 



6. Regular ocellar covered organs. 

 a. Distribution. 



These organs are found in Haloscmrus macrochir and other species of Halosaurus. 

 They invariably form one single row on each side of the body, overlying the large lateral 

 slime-canal. The scales of the lateral line are, in these fishes, "much larger than the rest 

 and form a conspicuous row on each side. They are covered by membranes. Each 

 scale bears a transverse vertical ridge on its outer side, and behind this ridge a conspicuous 

 spindle-shaped whitish organ is situated, which is 1 mm. broad and from 2 mm. to 3 mm. 

 long. The ends are extended to form fine points. The long axis of the organ is vertical. 



J>. Structure. 



a. General. 



The large scales of the lateral line overlap about one-third or less, and appear slightly 

 curved, S-shaped in longitudinal section. Outside, the row of scales is covered by two 

 membranes, the outer one of which appears pretty continuous and attached particularly 

 above, and loose only partially on the lower margin. The inner one extends from ridge 

 to ridge of the successive scales (PI. LXXIII. fig. 61, r). The lateral slime-canal is situated 

 below these scales and sends l)ranches up between them, which extend on the outer side of 

 the proximal, anterior portion of each scale (PI. LXXIII. fig. 61, e). The space between 

 the slime-canal and the scales is filled with a peculiar tissue (PI. LXXIII. fig. 63, c), and 

 this extends outwards so as to fill the spaces between the scales; this tissue will be 

 described below. At the sides of the slime-canal meandriform gland-tubes are met 

 with (PI. LXXIII. figs. 50, h, 59). The whole of the immersed portion of the scale is 

 covered by a pigmented membrane (PI. LXXIII. fig. 61, m). Between the pigment coat 

 iind the tissue underlying the scales a highly refracting membrane is observed. Just 

 liehind the transverse ridge a peculiar, apparently phosphorescent organ is attached out- 

 side to the middle of the scale ; this is spindle-shaped and upright, and measures 1 mm. 

 in width and 2 to 3 mm. in length in the vertical direction, being about 0"4 mm. high 

 (in spirit specimens). Below this phosphorescent organ the scale is perforated by a 

 conical canal leading outwards and backwards (PL LXXIII. fig. 61, t). The nerves 

 and bloodvessels which supply the organ pass through this canal. The phosphorescent 

 organ itself has a radiating structure. 



