KONGL. 8V. VET. AKADEMIENS HANDLINGAR. BAND 36. N:0 8. 21 



Seasonal distribution of tiie plankton-organisms. 



In the foUowing account of the species noted in 1901 and to August 1902 I use 

 the signs o for not found, r for rare, + for not rare and c for common. For the sta- 

 tions Måseskär and Vsderöboda I use the signs M. and V. Whore these signs are followed 

 by three of the above signs the first relätes to the beginiiing, the second to the middle 

 and the third to the end of the month. In case only one or two such signs are appointed 

 to M. or V. it denotes that plankton has not beeu collected throughout the month, and 

 the signitication will be understood by consulting the text for the respective months. 



The signs R. Sg denote Smögen-Rarasö and Nh Norsholrn Lighthouse. 



All data reläte to plankton collected at the surface, in case no notes indicating the 

 depth in metres (m.) follow. 



For the sake of shortness I note at the end of each form whether it is to be con- 

 sidered as belonging to styli-plaiikton {S), Tricho-plankton {T), Tripos-plankton (7);), 

 Southern neritic or Didymus-plankton (Nm.), Northern neritic plankton (iVs.), and Arctic 

 neritic plankton (iY^.). The neritic kinds of plankton frequently contain in the North 

 Sea interraingled forms belonging to the two first named oceanic types. Data under the 

 heads »Norw.» and »Atl.» have been borrowed from Gran's latest paper. 



Leptocardii. 



imphioxus lanceolatus Yarkel. Larv^. — 1901 August, W. of Jutland, 55° — 56° 



N. 7°— 8° E. Skagen 20—25 m. r. — Nm. 



Åppendicularia. 



Fritillaria borealis Lohmann. — 1901 Ajjril, Y. + ro. November, W. of Schleswig, r. 



1902 February, Vinga, 85 — 50 m. r. May, Sparingly west of Sylt, more abundant 

 along the west coast of Jutland, from 56°18' N. to Skagen. M. roa. July, the fjords, r 

 in the deeper waterstrata. — Ns. 



Oikopleura dioica Fol. — 1901 January, Y.+oo. May, V. rrr. M. oor. June, 

 M. c + +. July, M. + + 0. August, from the mouth of the Scheldt to Skagen and from W. 

 Scotland to S. Norway, whole Skagerak, not rare. September, V. c. M. + oo. October, 

 V. r. +. M. rr +. November, N.W. of Dogger bank and W. of Denmark r. V. r + o. De- 

 cember, V. + + 0. R.Sg. r. 



1902 May, sparingly in the mouth of the Scheldt and in the area 55°44' N. 0°37' 

 E., 56°24'N. 0°40'W. and 56°10' N. 2° E. Y.orr. June, Y or +. July, central Skagerak r. 

 M. + CO. V. + + +. The fjords +. — Nm. 



