670 DEPTHS OF THE OCEAN 



especially conspicuous in the case of the minute young of 

 Sconibi^esox living at the very surface, the sides of which are 

 mirror-like, while the back is not black, but intensely blue. This 

 seems to correspond well to the fact that the uppermost 

 layers of the ocean, viewed from above, appear blue. A similar 

 arrangement of colour is met with in boreal waters, for instance 

 Colourings of in the colouring of the surface fish, the mackerel. The colours 

 adLpTadonsto secm SO intimately adapted to certain conditions, and the 

 advantages they offer for the purpose of eluding observation 

 are so obvious, that we can hardly avoid the conclusion that 

 these colours must be considered as the result of adaptation 

 to surroundings. 



In the surface layers most animals are colourless. The eel 

 larvae (leptocephali) are specially interesting, being indeed so 



environment. 



Fig. 491. 



Myciophum (Diaphus) rafinesquei, Cocco. Nat. size, 7 cm. 



transparent that when sorting them out of the living material 

 captured, one can only see their small black eyes ; even their 

 blood is transparent and perfectly devoid of haemoglobin. 



The surface fishes are so well known that I may merely 

 refer the reader to Plates IV. and V. One group con- 

 taining sea -blue forms is represented by the flying -fish. 

 The pilot-fish are also blue, but with some darker trans- 

 verse bars. Is this because biologically it approaches another 

 group of surface- forms, which live in the immediate vicinity 

 of drifting or floating objects ? To this group belong the 

 wreck - fish (Lirtts, Polyprion). We captured such fishes 

 swimming around a log covered with barnacles, and the 

 similarity between the colours of the fish and those of 

 the log and its Inhabitants was marvellous. The most 

 intimate adaptations to life among drifting objects are met 

 with among the animals of the Sargasso Sea (see Plates 



