785 



Öfversigt af Kongl. VeteDskaps-Akademiens Förhandlingar 1899. N':o 8. 

 Stockholm. 



On the seasonal distribution of some Atlantic plankton- 

 organisms. 



By P. T. Cleve. 



(Communicated 1899 October 11.) 



During the years 1898 and 1899 a very considerable number 

 of plankton samples have been collected by the kind assistance 

 of the officers on many Dutch, English and French oceanliners, 

 by the Swedish corvette, the Freya, by the Swedish arctic expe- 

 ditions as well as by whalers in the arctic ocean. Collections 

 have, besides, regularly been made at Westraannaö (S. of Ice- 

 land), the Färöes, the Shetlands and the Azores. By the recent, 

 very valnable report of Ostenfeld ^) on the plankton in the 

 Northern Atlantic my observations have been considerably am- 

 plified in a most welcome way. By this addition of data it 

 becomes possible to follow in detail and raonth for month the 

 distribution of many plankton-species. As it will be a long time 

 before I have arranged and corabined all the numerous obser- 

 vations, I will here report about sorae few results of the plankton 

 investigations, which seem to me to be of considerable interest 

 to hydrography. I will in this paper treat of the seasonal dis- 

 tribution of some arctic or west-atlantic forms, which constitute 

 my plankton-types chceto- and ^WcAo-plankton. The species, 

 of which the former type principally consists, the Chcetoceros 

 decipiens, will first be examined as to its geographical distribu- 



^) Iakttagelser over Overfladvandets tenaperatur, saltholdighed og plankton paa 

 isländske og grönlandske skibsrouter i 1898 foretagne under ledeise af C. F. 

 Wandel bearbeidede of Martin Knüdsen og C. Ostenfei.d Kbn., 8:o 1899. 



