- 233 — 



The curved Melosira granulatet shows an interesting adaptation 

 to the limnetic condition ; as I have given in fig. 4 the curvature is 

 so strong, that the band is like a corkscrew; the contents of the 

 cells (fig. 5) consist of about 5 chromatophores and some large 

 oildrops, the one chromatophore allways lying in the middle of 

 the cell at the connecting zone. I have taken it as f. curvata Grun. 



6 7 



Fig. 6. Dinobryon divergens Imhof, with resting spore ( 450 /i). 



Fig. 7. Ceratium hirundinella (O.F.Müll.) Schrank; slender 4-horned form ( 450 /i). 



of M. granulata, figured in V. Heurck, Synops., PL 87, fig. 18; the 

 cells are 4— 8/z broad 1 ). 



It seems strange that the Tabellaria's which are so common 

 in lakes elsewhere, do not occur at all in the sample; also, the 

 genus Cyclotella, so characteristic in Alpe lakes, is wanting. 



) I have not succeeded in finding anything concerning curved Melosira in 

 the numerous plankton- works (Lemmermann, A. Cleve, Borge, O. Müller 

 etc.), only in R. Volk, Hamburgische Elb-Untersuchung I, Hamburg 1903, 

 p. 113, the quoted form is enumerated in the table, but without any 

 remark. 



