DEEP-SEA FISHES. 17 



increased acuteness of sense organs other than the eyes ; some again 

 are uniformly phosphorescent or have special luminous organs on 

 the head or in series along the body. 



Most are of a pale green or blue colour when caught (see 

 coloured sketches 980 and 981), but they rapidly turn black; it 

 is for this reason that the coloration of many of the models shown 

 is blackish. Some deep-sea fishes are colourless and gelatinous in 

 appearance (e. g. Aphyonus, 974). In those which are coloured 

 the coloration is mostly uniform, without spots or bands, and without 

 the belly being paler than the back and sides. A few are silvery 

 (e. g. Lepidopus, 971). 



Many fishes obtained from great depths come to the surface in a 

 damaged condition owing to the expansion of the gases in the 

 tissues of the body when relieved from the great pressure to which 

 they are subjected at the bottom of the sea. For this reason few 



Fig. 5. — A Deep-sea Fish, Maiacosteus mdicus. 

 (From Boulenger, Camb. Nat. Hist, vii, 1904, after Giintlier.) 



are suitable for exhibition, and most of the specimens shown in 

 Cabinet-case 44 are models, some of them enlarged, made to 

 present as nearly as possible the appearance that the fishes would 

 offer in their natural state. 



Most of the deep-sea fishes are known by a few specimens only, 

 and, being rare, they have no popular names. 



Aulostomatumorpha (984) is a curious fish in. whichalmost the 

 whole of the skin of the head is phosphorescent ; in Maiacosteus 

 (979, and fig. 5) there are two photophores or luminous organs 

 situated below and behind the large eye; in Ipnops (976) the eyes 

 are wanting and the top of the broad, flat -head is occupied by a 

 pair of large photophores, which nearly touch one another in the 

 middle line. 



c 



