B. Protistplankton. 



By E. Jm-geuseu. 



a. Plankton tables. 



In tlic following- tables r siii'iiities rare, it very rare (only one 

 or very few specimens seen), r-j- less rare, -|- frequent, +i" less 

 fi-equent. +c rather common, c common, cc very common, ccc in 

 large quantities. 



The method used for collection and examination only allows 

 reliable conclusions as to the quality, not as to the quantity. From 

 the signs used to indicate the more or less common occurrence it 

 shoidd, however, be evident which species are common or go to 

 make up a considerable part of the plankton. It is, however, 

 always to be remembered that the signs are only based upon a sub- 

 jective judgment, not upon exact counting. 



As a general characterization of the plankton — which for all 

 stations, the sea off Vesteraalen (Yttersiden) perliaps excepted, is to be 

 considered more or less unmixed coast plankton (neritic p.) — it may 

 be stated that the Peridinæa in the winter season are predominant 

 in (luantity, together with Halosphæra, while the Diatomaceæ and 

 likewise the Tintinnodea are of less frequent occurrence. This state 

 is at once changed in the spring (about 'A 1899, in 1900 "A), 

 when a few species of Diatomaceæ suddenly appear in large quanti- 

 ties, and remain for a considerable time at least more than one 



month, how long cannot be seen from the samples collected, as it 

 was too early in the year, when the last samples were taken. During 

 this time the other plankton is very much reduced in quantity, 

 excepting Phæocystis, which species seems to have its optimum 

 just in this period. The Peridinæa occur far less abundantly than 

 earlier, not only in relation to the large masses of Diatomaceæ, but 

 also absolutely. 



This phenomenon, that might truly be named the inflow of 

 Diatomaceæ, is a well known phase also in the development of the 

 more southern coast plankton (see L. (= Literature, at the end of 

 this essay) 1). Ostenfeld and Gran (L. 2 and 3) have also men- 

 tioned it, and try to explain the causes. It is an interesting fact 

 that most of the leading species are identical, both in the northern 

 and in the southern intioAV of Diatomaceæ, on the extensive coast 

 of Norway. Yet there are some few species characteristic of the 

 northern, that seem to be entu-ely wanting in the southern, especially 

 Fragilaria oceanica, partly accompanied by F. cylindrus, and Chceto- 

 ceros fureellatus (besides some other, less predominant species). 



As to quality the northern plankton is decidedly poorer than 

 the southern, especially is this the case with the Tintinnodea. 



