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



31 



S. Skag. 8 



S. 



Skag. 9 



S 



. Alsbäck 



S. Smörkullen 



XI 



O. 



p 



t» 

 ■*» 



a 

 3 



5 



m 



a 



a 



< 



Organisms 



total 



numbers 



to 



B 

 03 



E 



C 



Organisms 



total 



numbers 



m 



S 

 03 



5 



Animals 



Organisms 



total 



numbers 



m 



a 



a 



s 



00 



| 



c 

 < 



Organisms 



total 



numbers 





4,330 



1,680 6,010 



44,440 



180 



44,620 





















10 



80,370 



2,440 82,810 



114,840 



2,730 



117,570 















20 



150,C50 



1,650 152,300 



117,000 



2,400; 119,400 



364,500 



1,400 



365,900 









30 



195,650 



1,000 



196,650 



61,900 



2,900 



64,800 















40 



130,230 



850 



131,080 



104,200 



250 



104,450 



44,320 



500 



49,820 



33,900 



300 



34,200 



50 



89,200 



850 



90,050 



95,250 



920 



86,170 















60 



323,050 



700 



323,750 



90,200 



920 



91,120 



9,560 



400 



9,960 



4,660 



240 



4,900 



80 



64,400 



150 



64,550 



201,060 



650 



201,710 















100 



26,380 



130 



26,510 



58,450 



50 58,500 



9,450 



100 



9,550 ' 









150 



7,580 



20 



7, 6" Kt 



6,340 



80 



6,420 















200 



1,870 



10 



1,880 



7,720 



3o 



7,750 















300 



590 





590 





















Summary: A striking feature of this spring-series of 1913 is the great predominanee 

 of the diatoms. Some characteristie spring-forms are at the end of their maximum, as is 

 shown for the Chaetoceras by their frequent or, for Ch. dioderna, total passing into the 

 sporal stage. Diatoms are now present in a maximum surpassing 100,000 pro 1 at all 

 stations of the section, but the mighty vegetations are not formed by the same leading 

 species in all parts of the Skager Rak. In the south-eastern part, Leptocylindrus is the 

 all-dominating species; in the deeper, northern waters, the small Chaetoceras sociale is 

 by far the most numerous one. These two chief constituents of the vegetation ask for 

 quite different kinds of water. Leptocylindrus likes a more outfreshed water, as that of 

 the Kattegat and is thus confined to the undermost layers of the Baltic Current, 2 Chae- 

 toceras sociale comes from the opposite side in deeper layers of Atlantic water under the 

 Baltic Current. It has now its maxima up to 200,000 — 320,000, at so great a depth as 

 60 — 80 m; t hanks to the spores. 



It is, however, worth remarking, that in spite of this general sinking by means of 

 spore-formation, there could nowhere be noted any sedimentation wortli mentioning. 

 At S. Skag. 0, the frequency is no doubt much raised for Chaetoceras sociale in the verv 

 bottom-layer, but this is the effect of the unmixed Atlantic water penetrating here only 

 as a thin bottom-cover. 



Series IV. August lth- 3rd 1913. 



Compared to the previous series, this one was incomplete, as it comprises samples 

 only from the stations Skag. 6 — Skag. 9, that is from the Central and Northern Skager 



1 106 m. 



2 The verv surface-water is poor in plankton. 



