KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 57- N:0 7. 



55 



similar differences; we are thus led to make also the somewhat higher temperature of 

 c. + 2° to + 3°, ruling in February 1914, or a repulsion by the huge Baltic water-masses, 

 responsible for the slight prospering. The great maximum of Gran was found 

 at 0° to 1°. 



MM 



i 1 .'. 1 'i 



TOlW 



•: " 







1 











mct 





+ '»V^^ 



10 



l 



5JW 



il, - ., 



4Tos 







i 







■ 10 

 30 



-40 



50 

 CO 







100.000 



•JUV.OUO 



300.UUO 



400.000 



600,000 



600.000 



Fig. 2. Thalassiosira Nordenskiöldii. S Skag. 0. 15. II. 1912. 



The spring-development of Leptocylindrus is equally very dependent on light. 

 If the two following diagrams of the frequency of that species in April 1913 at the stations 



mel 

 10 



Fig. 3. Thalassiosira Nor- 

 denskiöldii. S. Skag. 0. 

 25. II. 1914. 



Fig. 4. Leptocylindrus danicus. S. Skag. 0. 26. IV. 1913. 



Skag. and Extra II be compared, it will be found that the maximal number per 1, 

 obtained at Extra II, is about twice as large at as S. Skag. 0, where mighty quantities 

 of too fresh and unmixed Baltic Water fill the uppermost 25 metres. 



Fig. 5. Leptocylindrus danicus. S. Extra II. 20. IV. 1913. 



Influence of salinity. 



A careful study of the small and isolated water -samples, that can be taken from 

 any depth whatever with a water-bottle, has no doubt proved a proper salinity to be of 

 greater import ance for a multiplying, at least, of phytoplanktonts, than may have been 

 generally admitted hitherto. As a matter of fäet, a great many species are found in waters 



