I. INTRODUCTION. 



A certain amount of work has been done on the Norwegian Fresh- 

 water Phytoplankton. The chief contribution to our knowledge of the 

 limnoplankton of this Country is the great and valuable treatise by H. Huit- 

 feldt-Kaas, Esq. (Plaiiktoinnidcrsøgclscr i norske vande). This work deals 

 with both zoo and phytoplankton. 



The paper of Messrs. W. & G. S. West on the Scottish Freshwater 

 Plankton was published earlier than that of Mr. Huitfeldt-Kaas so that 

 the majority of the new species and varieties found in the Norwegian 

 Lakes by Mr. Huitfeldt-Kaas must be named with the names given them 

 in the paper of Messrs. West. 



1 hoped to enlarge our knowledge of the freshwater phytoplankton of 

 Norway, its geographical distribution and affinities, by examining collections 

 from various parts of the Country. — I therefore asked Mr. Huitfeldt- 

 Kaas for some samples to examine, and he \'erv kindiv submitted 38 plankton 

 collections for my inspection. 



The samples are all collected by him at \arious times. Some of them 

 have already been dealt with b}' Mr. Huitfeldt-Kaas, but most of them are 

 either horizontal samples from lakes where he has reported the vertical 

 ones or collections from lakes never examined before. 



I am pleased to be able to report that in cases where the same lakes 

 are in\'estigated b}' him, I can verify almost all the determinations. The 

 plankton material is from all parts of Southern Norway, and therefore man}' 

 interesting comparisons can be made. — From the western parts of our 

 Country 13 samples were examined, viz. 4 from Sogn og Fjordane, 5 from 

 Hordaland, and 4 from Rogaland. — From Eastern and Central Norway 

 25 collections were examined, viz. from Opland 14, from Akershus 8, from 

 Ostfold 2, and from Telemark i. 



I have had the opportunity of exchanging opinions with the well- 

 known algologist Professor G. M. Smith of Madison, Wis. U. S. A. during 

 his visit to Norway this summer. 



To illustrate the peculiarities of some characteristic collections I have 

 made use of photomicrographs. 



Professor Dr. N. Wille has \ery kindly verified some of the more 

 critical determinations and for his aid to me in preparing this paper 1 have 

 to express my best thanks. 



