13 



fsh eggs, or if so ouly (juite exceptionally. On tlie other haod mimeroHS ^jelagic 

 fish eggs are found in the salt hottom-layers. This can be seen from tlie "Tabelle 

 der Fange" (Ehrenbaum uud Strodtmann 1. cit.). lu the shallower parts of the 

 true Baltic Ehreubaum and Strodtmauu took no eggs iu the vertical hauls. . Nor 

 in the deep gut N. E. ot' Boruholin, "Bornholmsdybet", 97 m. (ca. 50 fm.) did they 

 take auj- eggs iu the upper layers. It was only at depths of at least 50 m. (iu 

 May) — 60 m. (iu August), in water of at least 11. 2i 7oo saliuity*, that they found 

 the pelagic fish eggs, but as a sort of compensation in cousiderable uumbers, both 

 iu May and August. 



On the 9th of June 1904 (see Tab. I, true Baltic) we were to the east of 

 Christiansø, almost at the same place as the Germans' "Bornholm Tiefe". We 

 found there, as Ehrenbaum and Strodtmann had found in May and August 1903, 

 a cousiderable number of pelagic fish eggs in the deeper salt layers of water. At 

 a depth of 20 fathoms we repeatedly found single eggs of sprat, thougli we deter- 

 mined the salinity at this depth to be 6 — 9.9 "/„q. At 20 fathoms depth however 

 we were certaiuly very uear the boundary of the sur face- water; at 30 fathoms we 

 found 12.5 %o- 



It is clear tliat the fish eggs found in the salt water in the gut N. E. of 

 Bornholm are safe from being carried in a westerly direction by the surface- 

 current. They mav, however, if salt water pushes in from the west into the true 

 Baltic, be carried further to the east. The renewal of the water in the bottom- 

 layers N. E. of Bornholm must however be exceedingly slight*'-', as the temper- 

 ature throughout the summer is very low. In "Bornholmsdybet" Ehrenbaum and 

 Strodtmann in 1903 found a temperature of S.ib" C. at a depth of 90 — 95 m. 

 (ca. 48—50 fm.) in May, and a temperature of 3.25—3.26 C. at 90 — 95 m. in 

 August. On the 19th of June 1904 (see Tab. I) we ourselves found a temperature 

 of 4.3 '' C. at a depth of 40 — 53 fathoms.*** 



Further to the east also, in the true Baltic, fairly salt water is frequently 

 found at the bottom, but renewal takes place here and is of great importance, 

 new salt water often forcing its way in from the Sound and from the western 

 Baltic. South of Møen there is a depression in the hottom of 10 — 12 fathoms, which 

 in its northern part is in couuection with the greater depths to the east of Møen 

 (see the Chart), but is elsewhere separated from these by a ridge which extends 

 northwards from the German coast iu the neighbourhood of Darsserort. This ridge 

 is certaiuly raised but little above the level of the 10 fathoms, but in the true 

 Baltic every such deepening of the bottom however small is of importance for the 

 distribution of the pelagic organisms, as it retains some of the water which presses 

 iu from adjacent regions. Iu the Xlith Report of the Biological Station p. 16, 



* In the true Baltic we have often lound pelagic fish eggs in water-layers with a 

 salinity of ca. 11—12 ":,„. In the cases where we have determined these eggs, they have always 

 been those of the sprat. 



** See also: O. Pettersson: "Redegorelse for de svenska Hydrografiska undersokningarna 

 åran 1893—94". Bihang till K. Svensk Vet. Akad. Hånd. Bd. 19 Afd. II. Stockholm 1893. 



'** When we bring up the watersauapler fi'om the depths of the true Baltic in the 

 warm summermonths, it feels like ice to the fingers touching it, and a direct proof is thus 

 obtained of the winter cold which rules down in the deep layers. 



