4 P. T. CLEVE. THE PLANKTON OF THE NORTH SEA AND THE SKAGEIiAK. 



The water of the Baltic Current proved \ery variable as to the salinity. At Kalt'- 

 sund it only reached 6,94, and the plankton at that spöt contained abundantly the eury- 

 haliiie Copepods Acartia longiremis, Centropages hamattis and Temora longicornis, but be- 

 sides, some fresh-watei- species, as A sterionella gracillima, 2'(thellar{a flocculosa sund colonies 

 of a flagellate. At Marstraiid and »Tslandsbergs Hufvud» the water (15, 80 and 18,37 p. m. s.) 

 was sterile. The other saniples from the surface-water of the Baltic Current contaiued 

 a number of species, the most generally distributed of ^vhicb were: 



Copepoda. 



Acartia longiremis \ 



Centropaxjes hamatus 1 



n , ', , , } boreal, eui'vhahne forms. 



rseudocalanus elongatas I •' 



Temora longicornis j 



Oithona similis; tenaperate, eurvhaline and eurytherni. 



Ciliata. 



Ftyclioci/lis acuta.; arctic, neritic. 



Dinoflagellates. 



Ceratiiun tripos; temperate, eur\'therm, euryhaline. 

 Dinopliysis acuta; boreal. 



Chlorophyllacese. 

 Halosp>hcera; temperate. 



1 : 1 ■ j; ,,, • ;.■;'( Ti Diatomacese. 



Chcetoceros horealis; boreal and arctic. 



C danicus; temperate. 



C. debilis; arctic and boreal. 



(.'. diadoiia; arctic and boreal. 



Coscinodiscus concinnus; boreal. j 



Tlialassiothrix Fraucnfeldii; l:)oreal. . i . 



February 1900. 



A. The North Sea was in the tirst da,ys of February explored by steamers on dif- 

 ferent routes. The resiilt of the examination of the plankton-samples coUected by these 

 steamers bas been registered in Table 1. '' : ... - 



The plankton in the Ndi-th Sea -was N-er\' scarce in February as a rulc and occurred 

 in any quantity ordy abo^e the edge of the 50-inetre plateau of the Ijottom, chietiy north 

 of the Dooger Bank. 



