4 P. T. CLEVE. THE PLANKTON OF THE NORTH SEA, ENGLISH CHANNEL ETC. 



Danish Peninsula, but towards Norway the tripos-plankton was interruingled with 

 Halosphcera. 



The Coscinodiscus concinnus occurred round Scotland and from Firth of Tay across 

 the North Sea towards the Danish Peninsula, where the route became forked. One branch 

 went to Skagen, another followed the Danish coast towards Heligoland. 



Of Chceto-plankton mere traces Avere found midway between Scotland and Norway. 



The changes, that arrived since December 1898, consisted thus therein, that the 

 concinnus-plankton, which then prevailed in the southern North Sea, had been forced 

 towards the Danish Peninsula and to the boundary between the 34 and 35 p. m. water, 

 and that the tripos-plankton, that in December prevailed between Scotland and Scandinavia, 

 had decreased and been partly replaced by Halosphcera-plankton. The latter kind appeared 

 already in December. 



II. The North Sea in April— May 1899. 



The state had since February been changed completely. If a line be traced on a 

 map between Newcastle and Skagen, there were found north thereof, to about 58° — 59° 

 N. a number of arctic or boreal, partly neritic forms. The chet o-plankton, that usually 

 preyails at this season between Scotland and Scandinavia, appeared first at 58° N. mid- 

 way between Scotland and Norway. South of the said line there occurred southern 

 neritic plankton, frequently intermingled with styli-pkmkton. This area was interrupted 

 from about 56° N. 4° — 5° E. towards the mouth of Elbe by a band, that contained 

 northern neritic species which seem to have spread from the depression of the bottom 

 between the Fisher and Dogger Banks. 



III. The North Sea in July— August 1899. 



The plankton, that prevailed in the greatest part of the North Sea, at least between 

 54° and 61° N., was the tripos-plankton. East and west of Scotland there occurred 

 northern neritic plankton, probably a remnant from the spring, but intermingled with 

 some styli-plankton. The plankton in the water, that occurred from the mouth of the 

 Schelde to the middle of the Danish Peninsula, belonged to the southern neritic type, but 

 contained some traces of northern neritic plankton. From Skagen to the entrance of the 

 Limfjord Iihizosolenia gracillima was met with. 



IV. The North Sea in November 1899. 



Above the 100-metre plateau of the bottom there prevailed tripos-plankton, which 

 was more richly represented in the eastern parts than along the Engiish coasts. In the 

 southern North Sea, above the 50 metre plateau, there occurred from Schelde to Skagen 

 southern neritic plankton. 



