KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 32. N:0 7. 13 



Clueloceros didymus 1 n t ■, ■ ■, ■, ^ ■ -, 



p Qj-ff-- were lound during the whole period. 



Rliizosolenia stj/liformis, whole of August, contiriues to the end of the year. 



D. From September: 



Calanus finmarchicus. Biddulphia mobilensis. 



*Corycceus anglicus. *Ch(Btoceros densus. 



*Labidncera WoUastonii. *Rliizosolenia calcar avis. 



Evadne spinifera. R. semispina. 



Acanthometron quadrifolium. R. setigera. 



Ceratium tripos var. longipes. Stephanopyxis turgida. 



Those marked * arrived p robably from the southern North Sea, the others with 

 the Scottish current. 



The following, euryhaline animals appeared more or less abundantly, especi;illy in 

 the fjords: 



Acartia longiremis. 



Centropages h a matas. 



Pseudocalanus elongatus. 



Teviora longicornis. 



Temorella affinis. 



These may be considered either as coraing with the outfiowing Baltic water or as 

 stationary in the fjords. The Pseudocalanus and Temora may however also have fol- 

 lowed the Scottish current. 



As stated above, the arctic and northern forms have almost completely disappeared. 

 Biit an interesting exception occurred. Mr. Gunnar Andersson, who hauled in the middle 

 of July south of Hven in Öresund, found there a surface stratum, containing Acartia 

 bifilosa A. longiremis, Temorella affinis, Aphanizomenon and Nodularia spmmigena, all 

 Baltic forms, but below that stratum near the bottom (or about 40 metres from the sur- 

 face) a plankton remarkably similar to that, which pi-evailed in the Skagerak in the spring. 

 C/uetoceros borealis var. Brigthivellii, abundant in the Skagerak in the winter 1896 — 97, was 

 also very coramon in the bottom-plankton. There remained thus during the height of summer 

 in Öresund, a remnant from the winter and the spring, below the outfiowing Baltic water. 



yth Period. October 19*^ to the end of the year. Tripos- and southern neritic 

 planktons now prevail as before, but, in addition, northern forms in the company of 

 species from the Scottish current begin to arrive. The plankton becomes thus very com- 

 plicated. 



I consider that the following species belong to the southern neritic plankton: 



Euterpe acutifrons, found first ^^/x. 



Eucampia zodiacus, ^®/x. 



Proto pedata, ^^/xi. 



Rliizosolenia robusta, ^^/xi. 



Bacteriastrum varians ^Vix in Skagerak, the "/is at Måseskär. 



Tomopjteris helgolandica, Vxu (has possibly been carricd by the Scottish current). 



