16 P. T. CLEVE, PLANKTON-RESEARCHES. 



Forms found Forms found Forms found 



in August, not both in August in February 



in February. and February. only. 



Southern oceanic 4 19 10 



Southern neritic 14 14 15 



Northern oceanic 4 29 16 



Northern neritic O 10 21 



There had thus occurred a very remarkable increase in northern neritic forms. 



March 1902. 



Not less than seven samples collected throughout the month at Måseskär and Väderö- 

 boda were examined. The plankton consisted almost exclusively of diatoms, other orga- 

 nisms occurring very sparingly. There was no noteworthy increase by addition of new 

 forms, but some of the old species increased as to the number of individuals. The sta- 

 tistics gave the foUowing result. 



Remnants from ^^ ^ 



February. ^ew. Total. 



Southern oceanic 1 li , 



Southern neritic O 2 



al 



Northern oceanic , . 3 i. , ^^o 



Northern neritic 19 3 



April 1902. 



Samples were collected at Mäseskär in the beginning and middle of the month, at 

 Väderöboda throughout the month. I have classified the forms as foUows: 



Remnants from ^^ ^ 



March. ^'ew. Total. 



Southern oceanic O 3| ,o 



I 



Southern neritic 3 7 



Northern oceanic 4 8( „„ 



(Oo 



The plankton consisted chiefly of diatoms and, besides, of Dinohryum. The most 

 common diatoms were Chcetoceros constrictus, C. contortus, C. decipiens, C. diadema, Skele- 

 tonema costatum. 



May 1902. 



Samples were collected throughout the month both at Måseskär and Väderöboda. 

 The species found in the plankton can be classified as follows: 



