KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 35. N:0 7. 13 



thus appeared suddenly and abundantly Rliizosolenia sti/lifonnis and some other southern 

 forms, not found or occurring only sparingly at Väderöboda, as Rliizosolenia Shruhsolei, 

 Guinardia flaccida, Chcetoceros Schuttii, Evadne spinifera; at Väderöboda on the contrary 

 the northern Pseudoca lantis elongatus and inore abundantly than at Måseskäi* tlie southern 

 Acartia Clnusii, Oithonn similis, Paracalantts parvus, Evadne Nordmani, Sagitta bi- 

 punctata. This is most satisfactorily explained by assuming that the water of the Jutland 

 Current goes straight to the station Måseskär, and that the water froin the Norwegian 

 depression appears sooner at the northern station \'äderöboda than at Måseskär. 



D. The Skagerak in August. The saniples taken at the two stations Måseskär and 

 Väderöboda had a terapei'ature varying between 16,3 and 19, 20. The salinity varied 

 between 26,84 and 20,79. 



The prevailing plankton was at both stations tripos-plankton, but at Måseskär inter- 

 mingled with didynius-plankton, as in the last month. Besides, there appeared at Måse- 

 skär Evadne Nordmani, Paracalanus parvus, Sagitta bipunctata etc, wliich ocurred in 

 July at Väderöboda and not at all or sparingly at Måseskär. 



September 1900. 



The Skagerak. Saniples of plankton were collected at Mäseskär and Väderöboda 

 only. The teniperature of the water varied from 16, o to 13, 20 and the salinity between 

 29,98 and 22, le. 



At both stations the prevailing plankton was tripos-plankton, that had remained 

 from the last month, but at the niore southern station Måseskär this kind of plankton 

 was more or less abundantly interraingled with didymus-plankton, charaterized by ChaHo- 

 ceros contortus, C. curvisetus, C. Schilttii and Skeletonema costatum, no doubt brought by 

 the Jutland Current. The total nuraber of planktonforms noted during September 

 amounted to 37. :-:i;. •. ■', •. ;> ■■:.;. ■-r-; 



October 1900. 



The Skagerak. Samples were collected at the stations Måseskär and Väderöboda 

 in water, the teniperature of which varied from 12,65 to 9.95 and the salinity between 

 27,38 and 31, 09. The plankton collected at both stations was, on the whole, very similar 

 and consisted of trijjos- and didy mus-plankton intei-mingied. The latter kind was more 

 predominant at the southern station. Måseskär. 



The number of species collected at these stations was large and had increased con- 

 siderably since the last month. It now amounted to 84 different forms. The prevailing 

 forms of the didymus-plankton were the following: . ... ,. r ,:,•,. 



Chcetoceros contortus, . Eucampia zodiacus, 



C. curvisetus, - Guinardia flaccida, 



C. debilis, ' - RMzosolenia Stolte rfotJ di, 



C. didymns, ' ' . Skeletonema costatmn. ■ 



C. Schilttii. . '. ', 



