36 THREE CRUISES OF THE " BLAKE." 



are groups of four and five stalked organs, more or less cup- 

 shaped, the surrounding skin deeply pigmented. The function 

 of these side organs is probably tactile, or they may serve some 

 special purpose at the great depth at which these fish live. 

 Analogous organs have been described in the head of the blind 

 cave fish. It may be that the side organs are phosphorescent, 

 like those of the scopelids. These side organs also recall the 

 sense organs of embryo fish. The respiratory apparatus is 

 unique among bony fishes. There are air-breathing slits, and 

 the water which enters the buccal cavity escapes by a small open- 

 ing in front of the rudimentary pectorals. The " Blake " took 

 specimens of this fish in 898 fathoms. It also occurs between 

 389 and 1,467 fathoms. 



Of the selachians, few representatives have as yet been 

 brought to light by deep-sea explorers, nor is it to be expected 

 that such large forms should be captured by the methods 

 hitherto employed, although, as has been stated, a regular fish- 

 ery for deep-sea sharks (Centrophorus) has existed from time 

 immemorial off the coast of Portugal. A species of skate was 

 taken by the " Blake " in 233-333 fathoms. Scy Ilium and Spi- 

 nax also occur below 200 fathoms (Centroscy Ilium Fdbricii 

 down to 671). Only three species of selachians at all special- 

 ized for deep-sea life have as yet been found, unless perhaps we 

 except Chlamydoselachus, the frilled shark, a representative of 

 the devonian selachians, which is found off Japan, where it pro- 

 bably is an inhabitant of deep water. This is one of those in- 

 teresting persistent types, like the Australian Ceratodus and the 

 American ganoids : the gar-pike and mud-fish. The Japanese 

 shark has the teeth of an ancient devonian type, and the em- 

 bryonic characters of the lowest orders of recent sharks. 



The lamper eel (Petromyzon marinus) and hag (Myxine 

 glutinosa) have both been dredged below 500 fathoms. 



