726 DEPTHS OF THE OCEAN 



and from winter to summer. Any one who has examined 

 the quantity of organisms obtainable in silk nets at different 

 seasons in boreal waters will know the magnitude of these 

 changes. I may cite some of my own results from the coast 

 waters of Norway. 



During my winter cruises in the sea between northern 

 Norway and Spitzbergen and 240 miles west of Tromso, the 

 sea was everywhere found to be so poor in organisms from the 

 surface down to 100 fathoms that we had to drag our nets for i|- 

 or 2 hours before we perceived any organisms at all on the silk 

 cloth of the nets. In February I made a haul in the Westfjord 

 (Lofoten) with an 8-feet hoop-net from 200 metres to the 

 surface, and caught only 380 specimens of Calanus Jinmarchicus, 

 although perhaps 1000 tons of water were filtered by 

 the net. On the loth of April a haul was made on the 

 bank off Tromso (Svendsgrund), with the same net and from 

 100 metres to the surface, when 2356 specimens of Ca/anus 

 were taken. Another haul yielded 16,420 specimens of 

 Calanus, and a third about one litre of Calanus. This obvious 

 increase in their numbers continued during spring, and on the 

 ist of June in the Altenfjord a lo-minutes' haul with a i-metre 

 net at the surface yielded so many individuals of Calamts, that 

 their weight, after squeezing off the water, amounted to o*8 

 kilogram, — a weight corresponding to at least two millions of 

 individuals. In July some hauls with the 8-feet net were made 

 in the Norwegian Sea, generally from 200 metres to the 

 surface, and as a rule 200 or 250 c.c. of Calarms were taken, 

 mainly consisting of Calamts finmarchiais. These hauls 

 indicate the characteristic features of the occurrence of minute 

 crustaceans in boreal waters : the poverty of winter, the 

 abundance of summer. 



Gran and Damas have continued these investigations during 

 the cruises of the " Michael Sars," at the same time taking up 

 the study of the life-history of Calamts JimnarcJiiats. Gran 

 arrived at the conclusion, now confirmed by more recent 

 investigations, that the life-cycle of this species is annual. 

 During winter only adult animals are met with. They breed 

 in spring, and the young pass through five larval stages ; in the 

 sixth stage they assume the shape of the adults. From a detailed 

 study of the material collected in the nets Damas attempted to 

 draw a chart showing the spawning places, arriving at the con- 

 clusion that spawning does not take place to any important extent 

 in the fjords, nor on the coast banks, but principally above the 



