172 bulletin: museum of comparative zoology. 



have been published, together with the examination of the phytoplankton 

 from Lake Nyassa and Lake Tanganyika by Mr. G. S. West 1 ; and the 

 few (7) samples brought home by Dr. A. Borgert in 1904 have been 

 worked out by me in the paper mentioned above where I 2 have put to- 

 gether all the few data on the phytoplankton of Victoria Nyanza and 

 have compared them with the statements of the phytoplankton of Lake 



Nyassa 8 . 



Referring to this paper I quote some of its main results : — 



" The phytoplankton of Victoria Nyanza and Lake Nyassa bear a great 

 resemblance to each other, the dominant species being the same in both 

 lakes. Both lakes are characterized by rare tropical species, some of 

 which are common to both lakes, others of which are restricted to one 

 of them. 



" In spite of their extensive areas the lakes contain a phytoplankton 

 which must be spoken of as a pond plankton (' lac-etang ' plankton, in 

 Chodat's sense), not as a true lake plankton, and the tycholimnetic spe- 

 cies play a great part in the composition of the plankton. 



" The phytoplankton of Victoria Nyanza itself is characterized by Micro- 

 cystis, Anabaenae, Lyngbyae, Melosirae, Surirellae, Cymatopleurae, 

 Nitzschiae, numerous Protococcales, and many Desmidiaceae (especially 

 Staurastrum species) ; it is richer in species than that of Lake Nyassa, 

 especially through the occurrence of many Desmids." 



As to the seasonal changes in the composition of the plankton our 

 knowledge is too limited to say anything more definite, but in this 

 particular respect the two samples collected in February by Dr. Agassiz 

 are interesting, as compared with the samples later in the year from 

 April, October, and November; they show that the Diatoms (especially 

 Melosira) are dominant in the early spring, while later in the year the 

 Green Algae and Blue-green Algae reach their maximum. This change 

 corresponds to the normal changes in the composition of the lakes in the 

 lowland of the temperate Europe ("The Baltic Fresh-water Plankton," 

 of C. Wesenberg-Lund). 4 In my paper I have suggested something in 



1 West, G. S., Journ. Linnean Soc. London, Botany, 1907, 38, p. 81-197, 

 pi. 2-10. 



2 Ostenfeld, C. H., Botan. Jalirb., 1908, 41, p. 330-350. 



3 See Schmidle, W., Botan. Jalirb., 1899, 27, p. 229-237; 1901, 30, p. 240-253, 

 pi. 4-5; 1902, 32, p. 56-88, pi. 1-3; 1902, 33, p. 1-33; and Midler, Otto, Botan. 

 Jahrb., 1903, 34, p. 9-38, pi. 1-2; p. 256-301, pi. 3-4; 1905, 36, p. 137-205, 

 pi. 1-3. 



4 See C. Wesenberg-Lund, Plankton Investigations of the Danish Lakes. Gen- 

 eral Part, 1908, Copenhagen, p. 281, etc. 



