T 



he scientific Swedish expedition 1898 lo Spitzbcrgen under the direction of Professor 

 A. G. Nathorst paid a particular interest in exploring the plankton of the sea. A great 

 number of samples were gathered, among which about 50 were collected by pumping 

 the water through a silk-net. These gatherings were all small and have been corapletely 

 examined by me both for animal and vegetable plankton. The other samples, about 100, 

 were brought up by the tow-nct, partly from the suiface and partly from raoi-e or less 

 considerable depths. As Dr. G. Aukivillius has charged himself with the examination of 

 the animals in all the tow-net gatherings, I have examined them for vegetable plankton only, 

 with the exception of the radiolarians, which offered a particular interest for my other 

 plankton-researches. 



Plankton-types. 



I proposed in 1896' to class the plankton of the Atlantic and its tributaries 

 in certain types or formations according to the association of species. For understanding 

 the following it will be necessary first to characterize briefly these plankton-types. 



I. DeslllO-plaukton (sign D). This formation rules in the warmest part of the 

 Atlantic, in the Sargasso-sea and in the equatorial current. , 



The temperature of the water containing desmo-plankton varies usually between 20° 

 and 28° and the salinity is about 36 p. m. 



The organisms belong to a great number of species, many of which are identical with 

 those of the Indian Ocean. Among the more characteristic species I can name the following: 



Animals. Planta. 



Clausocalanus furcatus, Trichodesmium, 



Corycceus longicaudis, Pyrocystis pseudonoctiluca, 



C. speciosus, Ceratium fusus var. longiseta (n. v.), 



Euchceta marina, C tripos var. flagellifera (n. v.), 



Miracia efferata, Ceratocorys horrida, 



Onccea venusta, Goniodoma acuminatum, 



Setella gracilis, Ornithocercus magnificus, 



Radiolarians (many species). Chwtoceros coarctatiis, 



C. tetrastichori , 

 Climacodium biconcavum, 

 C. Frauenfeldii (== C Jacohi Cl.), 

 Heniiaulus Hauckii. 



1 Bih. till K. Sv. Vet.-Akad. Handl. XXII, 3, N:o 5. — A treatise on the phyto-plankton. Upsala 1897. 



