D. 



'uriiig the ycar 1900 saiuples of plankton were collected ragularly, 3 to 4 tiines a 

 inonth, at Måseskär (or about 58° Lat N.) and Väderöboda (or about 59° Lat N.), on 

 the west-coast of Sweden, in the North Sea, four timcs (February, April, August, No- 

 vember) by stearaers on different routes and, besides, occasionally, by the Government- 

 steamer »Svensksund» in the Skagerak and, in July-August, by a tishing boat off the 

 Shetlands. 



The following account contains the results obtained by the microscopical analj^sis 

 of the samples and has been coinpleted by hydrogi-aphical data, cominunicated by Pro- 

 fessor S. O. Pettersson. 



January 1900. 



Samples were collected at Måseskär (1 sample), at Väderöboda (3 samples) and by 

 the steamer Svenksund on the route Vinga, Marstrand, Lysekil and Dröbak (mouth of 

 Christiania Fjord). ]\Iost samples were collected from the surface water of the low sali- 

 nity characterizing the Baltic Current, but at Dröbak a sam[)le was hauled from the depth 

 of 30 m. in water of 34 p. m. salinity, so also at 57° 59' N. 11° 14' E. from 90 m. The two 

 samples from the water of 34 p. m. salinity were vei-y different, and the temperature of 

 the water was also different, viz. 7,46 at Dröbak, but 4,45 in the central Skagerak. 



The plankton from Dröbak had a niore oceanic character, but the plankton from 

 Skagerak contained about the same species as the Baltic Current at that season, as will 

 be seen from the followinsr list: 



HoUö-Vinga| IJröbak 

 Ö7° 59' N. (Christiania' 



iri4'E. 



Temp. 4,45. 



Sal. 3i,s5. 



90 m. 



fjord) 



Temp. 7j 



Sal. 34,2, 



30 m. 



Calanus finmarchicus . . . 

 Centropages hamatus . . . 

 Microsetella atlantica . . . 



Oithona similis 



OncEea minnta 



Pseudocalanus elougatus . 

 Temora longicornis .... 

 Acanthometron pelluciduni 

 Plectophora arachnoides . . 

 Codonella Tcntricosa . . . 

 Ceratium longipcs .... 



C. macroceros 



C. tripos 



Peridiniam depressum . . 

 P. divergens , . 



Gronyanlax spinifera . . . 

 Biddulphia aarita .... 



B. mobilensis 



ChEEtoceros debilis .... 



C. decipiens 



C. diadema 



Coscinodisous polychordus. 



C. radiatns 



C. stellaris 



Ditylum Brigthwellii . . . 

 Rhizosolenia setigera . . . 

 Thalassiosira gelatinosa . 

 Thalassiothrix Francnfeldii 

 Halosphaera 



Hollö-Vinga, Dröbak 



fu° 59' N. (Christiania- 



iri4'E. fjord). 



Temp. 4,45. i Temp. 7,46. 



Sal. 34,3.v Sal. 34,56. 



90 m. 30 m. 



I 



r 



r 

 r 

 + 



rr 

 r 

 r 



