THE OCEAN FEEDING-GROUNDS 93 



North Sea, between Bergen in the east and Bodo 

 in Iceland in the west, the waters are inhabited by 

 a host of copepoda belonging to the family of the 

 Calanidae. The Calanidae form distinct zones, which 

 exhibit no solution of continuity, constituting an un- 

 broken cycle. There are three zones : the zone of eggs 

 and lanrae, the zone of young fish, and the zone of 

 reproductive adults. This, says M. Damas, "indicates 

 that the species maintains itself by the existence in these 

 regions of a circulatory current, which periodically carries 

 with it a certain proportion of the individuals scattered 

 over the surface of the ocean, and carried onward by the 

 perpetual movement of the waters. The existence of a 

 central and special plankton zone is a new proof of the 

 existence of this rotatory circulation. The well-known 

 example of the Atlantic Ocean and the Sargasso Sea 

 shows that this instance is not unique." Thus the 

 complete cycle of the life of the pelagic species is 

 connected with the complete cycle of the currents, and 

 this double cycle is the symbol of the rigid correspondence 

 between the species and its habitat. 



Professor Cleve has attempted to establish planktological 

 charts from data afforded by the various currents. He 

 distinguishes several separate regions in the North Atlantic. 

 All the eastern quarter of the Atlantic (including the 

 waters of France, England, Spain, and Ireland) is 

 populated by diatoms of the genus Thalassiosira. The 

 western quarter (the waters of the United States, Canada, 

 Newfoundland, Greenland, and Iceland) is peopled with 

 diatoms of the Rhizosolenia family, while to the east of 

 Iceland are found diatoms of the genus Thalassiothrix. 

 The North Sea also exhibits several planktonic areas : 

 firstly an urn-shaped area, of which the foot rests upon 

 the Flemish coast, while the sides touch the north of 



