may be derived from the Scottish current. To aid us in ascertaining what forms are 

 due to one or the otlier origin we have a considerable number of observations for the 

 year 1897. M. Ostenfeld of Copenhagen has published^ a valuable report on the plankton 

 coUected thi'oughout the year on the routes: Shetlands — Iceland and Shetlands — Greenland. 

 I have also exarained a series of samples from Plymouth, for which I am indebted to the 

 kind assistance of Mr. Allén, the director of the marine biological laboratory in that town. 

 Another set of samples has been obtained from the Dutch marine laboratory at Helder 

 and I take this opportunity of thanking Dr. P. Hoek, the director of the laboratory. 

 The Swedish Andrée-Expedition to Spitzbergen has brought home materials contributing 

 to the knowledge of the state of the plankton along the Norwegian coast and at Spitz- 

 bergen.^ 



All these materials will be discussed in the following pages. 



1. Nortli Sea January— February 1897. 



From my paper: »A treatise on the phytoplankton of the Atlantic and its tributaries» 

 I quote the following summary: 



1. Tripos-plankton. This kind characterises water with a salinity of 35 p. mille 

 and a temperature of 6°, which extends east of Scotland, above the 100 metre plateau. 

 Eastwards the salinity becomes lowered by the admixture of water from the Baltic 

 current. 



2. Concinnus-plankton. Outside the tripos-region and above the 50 metre 

 plateau Coscinodiscus concinnus and Halosphcera viridis occur abundantly, and it is 

 easily seen on the map in my above-mentioned paper that these forms have spread with 

 the Scottish current. The salinity of the water with this plankton is as a rule about 34 

 p. mille, but is influenced by the admixture of the Continental water. The plankton with 

 Coscinodiscus concinnus ^vas predominant also at Plymouth, and it seems probable that 

 it had been forced out of the North Sea during the abnormal meteorological state 

 that prevailed at that time of the year. 



The region between the Shetlands and Iceland was, to judge from the report of Osten- 

 feld, exceedingly poor in plankton in January and February, containing only a few rare 

 specimens, doubtless remnants from past epochs. 



3. Tricho-plankton. Skagerak was covered by a thin sheet of water from the 

 Baltic current, which had spread över a mäss of water with a salinity of 34 p. mille and 

 a temp. of about 6°. The prevailing plankton in the water last named was thricho- 

 plankton, which we may assume to have come through the deep Norwegian fissure, 

 probably from the western Atlantic. 



' lagttagelser över overfladvaadets temperatur, saltholdighed og plankton paa isländske og grönlandske 

 skibsrouter in 1897. Copenhagen 1898. 8°. 



2 Bih. t. K. Sv. Vet. Ahad. Handl. XXIII. 2. N:o 4, 



