47 



Ou investigation of tlie plankton-samples collected in the years 1899—11)01 

 it was found, that plaice eggs occurred in the months November — April, but in 

 November and December only in the southern parts of the Danish waters. The 

 pelagic eggs taken in November and December were all plaice eggs, smaller eggs 

 occurred even in January. 



In 1902 very exteusive investigations on the distribution of the bottom- 

 stages were carried out. The Director has discussed these investigations in the 

 Biol. Stat. Beretn. XII, and I shall therefore only give a short extract from a 

 report, which Joh. s Schmidt, who was then assistant at the Biological Station, 

 made on the investigations of the distribution of the plaice young (O group); 



" — — — — — in the beginning of September 1902 we succeeded in 

 proving the undoubted presence of specimens of the O gr. in deep water, lO'/i fm-i 

 in the Baltic, namely, S. of Møen vvith Hestehoved in the N. '/a W., on hard sandy 

 bottom \dth Mytilus, where Ave took 16 in the Danish trawl along with specimens 

 of the I group and older stages as well as a young flouuder of 24 mm. and a 

 young dab of 30 mm. In connection with this it may be mentioned that I caught 

 a young plaice of scarcely 2 inches with the Danish trawl on the 23rd of July 

 1902 in the Baltic at Kriegers Flak (9—10 fm., Møen lighthouse in W. V2 S., My- 

 tilus ground).'' 



It will perhaps be remembered, that I mentioned on p. 28 that many cod 

 young in the bottomstage were taken in 1902 to the south of Møen. I sought 

 for the explanation of this occurrence in the hydrographical conditions and showed, 

 than the salt bottom-water, which pushes from the western out in to the true 

 Baltic, must carry with it the pelagic eggs and young. It is not excluded there- 

 fore, but rather probable, that the specimens of the O group, which are now and 

 then found in the true Baltic near Møen, are brought by the current from the 

 west, though we cannot determine at what stage of development this occur.s. 



In 19015 we took one plaice .young in the Great Belt on February 26th 

 and another on March 16th. Both of these were quite small; but a pelagic young 

 plaice in which the migration of the eye had begun was sent to us at Copen- 

 hagen even in the beginning of Februar}-. This specimen was taken in the large 

 well in the working room of the Biological Station, where workmen are engaged 

 in the winter with the preparation of apparatus and where there is a lighted stove 

 each day. We took no asymmetricai young in the sea either in February or 

 in March. 



In 1903 we found a few pelagic plaice young in the true Baltic: 



D. 25—4—03. Hestehoved in W. N. W., 4\/j miles, 12'/, fm, Pelagic net on pole, 10 

 minutes: 4 plaice young, small, a few other fisli young. 



These specimens of young plaice were probably carried by the current 

 into the true Baltic, as there were no plaice eggs south of Møen in March 1903 

 (see p. 14). It appears from the "Nautisk-meteorologisk Aarbog", that in the period 

 from the 20th to 21th April 1903 much salt water (to 15.4 "/oo i° H ™- depth) 

 was carried past the Gedser Reef ligtship into the true Baltic. The plaice young 

 perhaps came with this water. 



During the (Terman investigations in 1903 Ehrenbaum and Strodtmann 

 found numerous plaice eggs in the western Baltic in February, fewer in the true 



