482 SOME RESULTS OF THE INTERNATIONAL FISHERY INVESTIGATIONS. 



by the great oceanic streams. In the Norwegian sea occur enormous 

 numbers of the copepod crustacean Calanus Jininarchicus. This animal 

 has its home in the colder sub- Arctic regions, and does not, like so 

 many other planktonic organisms, reach the Norwegian sea from the 

 Atlantic. In the spring of the year the adults are brought to the south 

 by the current which flows to the south-east of Jan Mayen and Iceland 

 — the East Icelandic Polar stream. Eeaching the region of the Faeroe- 

 Iceland channel, spawning takes place, and the young are then carried 

 to the north along the coasts of Norway by the Atlantic north-flowing 

 stream. In these waters the young calani, living among immense 

 quantities of diatoms, peridinians, and other forms of plankton life, 

 grow and form the great shoals of Calanus jininarchicus which charac- 

 terize these waters. It is the salt water of the Atlantic stream which, 

 to some extent at least, favours the spread of this crustacean. 



The precise manner in which changes in temperature and salinity 

 affect the abundance of planktonic organisms is, of course, very 

 obscure. In many cases the connexion is doubtless an indirect one. 

 We know that in the sea the larger animals prey upon the smaller, and 

 that the ultimate food organisms are the diatoms (and other organisms 

 with a similar method of nutrition). That is to say, every living animal 

 in the sea depends, in the long run, on the diatoms, which form the 

 "pastures of the sea." A cod, for instance, may feed on dabs and 

 hermit crabs (it may feed on anything, but we take these as favourite 

 foods). Now the dab will feed on shellfish, and the hermit crab on 

 (say) small fishes or worms. The shellfish will feed on diatoms (among 

 other things), and the small fish and worms perhaps on microcrustacea, 

 and the latter on diatoms. Every chain of food animals in this sense 

 terminates in the diatoms. If then it can be shown that these 

 organisms are closely affected by hydrographic changes in the sea, we 

 make a distinct step in proving the dependence of many biological 

 phenomena on hydrographic ones. Now we are still far from possessing 

 all the data necessary for proving this connexion, but I may refer to a 

 most stimulating paper by Brandt,* which goes a long way in providing 

 the information required. In the periodical cruises of the German 

 International research vessel Poseidon samples of sea water were 

 collected, and these were subsequently examined by the German 

 chemists working under the International organization for the quantities 

 of ultimate food-stuifs contained in them. The ultimate food-stuffs are 

 nitrogen compounds (ammonia, nitrites, and nitrates), silicic acid, plios- 

 phates, and some other substances. It is upon these that diatoms (and 

 consequently all other life in the sea) depend. The amount of nitrogen, 

 in the above form, in the sea is very small (not more than about 0'2 



• Brandt, Rajjpts. et Proc.-vcrb., vol. iii. app. D, 1905. 



