NATURE ADRIFT 



of the known species. If this were so, will they ever metamorphose, and if not 

 can they mature in the larval state ? Such a feat is not unknown to zoologists 

 as the larval stage of the Mexican salamander, if prevented from leaving the 

 water, retains its tadpole-like larval form, the axolotl, and can become 

 mature. We still have a lot to learn about the sea and the living things in it ! 



Conger eels do not migrate up rivers but remain as marine hsh, but they, 

 too, spawn in deep water never to return, though their spawning grounds 

 are more widespread than those of the freshwater eel. They also have a 

 leptocephalus larva. 



This chapter must close with a brief reference to small but adult fish 

 which are planktonic — this defmition excludes of course any tish like herring 

 which, although they live in the upper waters of the sea, are capable swim- 

 mers, i.e. pelagic and not planktonic. The planktonic fish are mostly small 

 deep-water fish, certainly capable of swimming and chasing their prey, but 

 generally staying within the same water mass, and being carried where its 

 movements take them. They live amongst the other species of the oceanic 

 plankton and often come to the surface at night but go down to deeper 

 water during the daytime. Some of them are grotesque shapes, vicious 

 carnivores sometimes able to eat whole fish bigger than themselves because 

 of very distendible jaws and a stomach to correspond. Although they could 

 look very frightful if they were large they are mostly measured only in 

 centimetres or inches. Some are illustrated in Plate XXXI. They often have 

 patterns of luminous organs (photophores), the pattern being very strictly 

 specific (Chapter 12) and they live and feed in a world of everlasting 

 twilight or utter darkness except for the light of their own luminous organs 

 and those of other creatures. 



And what about the sun-fish — that great but curiously abbreviated and 

 often surface-living fish? Sun-fishes can grow up to some 8 feet in length 

 and weigh about 8 cwt, they live in warm or temperate waters, and are 

 often found right at the very surface lying on their sides. When living below 

 the surface they will swim in an upright position, but why lie on their sides 

 at the surface? One suggestion is that they like basking in the sun, but it 

 seems more probable that they are feeding on the surface-floating crustaceans 

 of the plankton like Ihciiiisto (p. 72), and lying on their sides is the only 

 way of getting their mouths there. They are normally very sluggish indeed 

 and are drifted by the Gulf Stream and other currents well into the North 

 Atlantic to the west and north of the British Isles and occasionally even into 

 the North Sea, Irish Sea, Baltic and Icelandic- waters. They seem so lazy, 

 and they most certainly drift, so perhaps they, too, can be called planktonic ! 



106 



