KONGL. SV. VET. AKADEMIENS HANJJLlNGAli. BAND 35. N:i) 7. 5 



TIk' water of 35 p. rn. sallnity, E. of Scotland, Avas almost sterile. Most charac- 

 teristic species of the Avater of 35 p. m. sal. •\vere besides Halonphoera, Acanthonia Miil- 

 leri, Acaniliometron pellucidum, Plectojyhora arachnoides and Chcetoceros decipiens. Other 

 species seeiii to have migrated into this kind of water from that of 34 p. m. sal. 



The water of 34 p. m. salinity contained tripos-plankton, and this planktontype was 

 the ruling kind bet^veen Newcastle and Skagen, and most plentitul uorth of the Dogger 

 Bank, thus above the limit between the 50- and 100-metre plateaii of the bottom. 



The bank-water west of Scotland contained abundantly Coscmodiscus concinims and 

 C. radiatus, which were carried with the 35 p. m. water i-ound Scotland towards the 

 mouth of the Skagerak. The only other characteristic forms which occurred in the bank- 

 water Avere Fungella aretica (E. of Scotland) and Tintinnopsis heroidea, Biddulphia aurita 

 and Coseinodiccus polychordus (W. of Denmark). Along the Dutch coast traces merely of 

 southern neritic plankton occurred. Thus, the typical neritic plankton had not yet deve- 

 loped. In its place from the mouth of the Schelt to the West of SchlesAvig appeared 

 the copepods Teniora longicornis and Pseudoccdanus elongatus, which evidentl}' had spread 

 from the depressions of the bottom S. of the Dogger Bank and W. of the Fisher Bank. 



B. The Skagerali. The water at the two stations, where plankton Avas collected, 

 had, between the 2nd and 6th of February a teraperature betAvcen 2,i and 3, o and a 

 salinit}^ of 32 to 33 p. m., thus considerably higher thau in January. This kind of 

 water contained sparingly tripos-plankton, mixed A\-ith JTaloq)ha'ra., but the condition of 

 things soon became changed, as there appeared on the 7th of February at Måseskär 

 horeal neritic and sira-plankton in ^vater of the temperature — 0,35 and the salinity 22,72 

 p. m. This kind of plankton prevailed to the end of the month, both at Måseskär and 

 at V;\deröboda, the temperature varying from — 0,35 to — l,o and the salinity from 21,39 

 to 26,96. This kind of plankton Avas, as usually, verv poor in animals and in one sample 

 only Avere the copepods Acartia longireinis and Temora longicornis found in any amount. 

 The diatoms Avere, on the contrary, very abundant, and among them the most important 

 were the folloAvins': 



'ö • 



Biddulphia aurita, Coscinocliscus polychordiis, 



Chcetoceros debilis Skeletonem.a costatum, _ . 



' C. diadem a, Thalassiosira Nordenskiuldii, 



C. socialis, Thalassiothrix Frauenfeldii. 



March 1900. ' > 



Samples were collected ;it Måseskär and by the steamer »Svensksund» in Kattegatt 

 (at Middelgrundet and 56°33'N. r2°16'E.) and at Vinga. The temperature of the Avater 

 va-ried from 1,2 to 3 and the salinity from 25, 21 to 33,63. The plankton was everyAvhere 

 uniform, or sira-plankton, composed chiefly of diatoms. Besides the species, Avhich occur- 

 red in February (among Avhich Chcetoceros debilis, C diadema and Thalassiosira Norden- 

 skiöldii were very common) the folloAving recurred constantly in almost all samples: 



