10 P. T. CLEVE, PLANKTON-RESEARCUES. 



March 1901. 



From Vilderöboda four samples collected in the course of the month were received. 

 but from Måseskär one only collected at the end of the month. The plankton contained 

 scarcely ariy animals or dinoflagellates and consisted chiefly of ärctic and boreal diatoms 

 isira-plankton). The forms noted may be classified as follows: 



Eemnants from ,^ „ 



February. ^'^^"- T"*^^- 



Southern oceanic O O \ „ 



Southern neritic . . '. 3 O I 



Northern oceanic 4 O ( ^^ 



Northern neritic 19 5 1 



The three forms classified an southern neritic are Lauderia annulata, Leptocylindrus 

 danicus and Nitzschia seriata, perhaps rather boreal forras. 



The Norwegian expedition under Bidencap (see Geax's paper, quoted above) collec- 

 ted samples of plankton in the area between Beeren Island and Norway. I have rear- 

 ranged the data, published by Mr. Gran, as for February, but omitted litoral forms and 

 radiolaria. Of 42 forms not less than 38 occurred in February off the west coast of 

 Norway. The same kind of plankton occurred then in the early spring along the whole 

 coast of Norway from 63° to 74° N. 



Compared with the plankton of the Skagerak the difference is striking, four forms 

 only common to the Skagerak and the coast of Norway. That is owing to the fact that 

 the tripos-plankton remained west of Norway, but had in the Skagerak been replaced by 

 siVa-plankton. 



April 1901. 



Four samples were collected at each of the stations Mäseskär and Väderöboda, 

 dui'ing the month. The plankton contained a number of arctic and boreal forms from 

 the preceding month, but many of the forms in March died out and were replaced by 

 new boreal forras and not a few of southern origin. The same statistics as used above 

 gave the followjng result: 



Remnants from 

 March. 



Southern oceanic O 7 



Southern neritic 3 9 



Northern oceanic 4 12 



Northern neritic 18 11 



New. Total. 



19 



45 



Mr. Gran has in his paper »Das Plankton des Norw. Nordmeeres» p. 154 published 

 the result of his exaraination of plankton collected in April 1901 at 69° N. 14° — 18° p]. 

 The plankton had a remarkable resemblance to the plankton that occurred in March in 



