16 



have liere only very few direct iuvestigatious, aud from Sweden none at 

 all. It would be of great importance to get such iu 1904 and the foUovv- 

 ing years. 



I presume, however, that sucli investigations from other eountries will 

 give results similar to the above mentioned, and several German iuvestiga- 

 tors, Schiemem, Ehrenhanm, and Strodtmann seem to have the same opinion. 

 But this must be confirmed by direct investigations carried on through 

 several years; and we must not be content with looking for the fry along 

 the shores iu localities similar to those where it usually occurs. It is pos- 

 sible that the fry can live and develop itself on deeper water, as, for in- 

 stance, the fry of the common dab usually does. Certainl}', I do not be- 

 lieve this to be the case; but we must be able to say that this possibility is 

 excluded by our direct investigations, as it is now, in my opinion, in the 

 Danish seas proper. 



What are the Causes of the peculiar Distribution 

 of the Fry? 



We all know that the plaice have pelagic eggs, and that the youug 

 fish go through their transformation from young ones, c. 6 — 7 mm long, 

 just out of the eggs, till they become unsymmetrical wheu they are about 

 ]1 — 14 mm, and then go to live on the flat, sandy, sunuy shores. As above 

 mentioned this takes place within the Skaw, in the months of Ma_y and 

 June. The eggs, on the other hånd, are shed from November (October, 

 Tryhom) till some time in April; but most of them, certainly, in the depth 

 of winter ("Report of the Biol. Station, IV"). We know now, from earlier 

 times {Hensen, Petersen), these eggs with embryos from all open seas within 

 the Skaw as far down as into the western part of the Baltic Sea; and 

 Petersen has them from the Baltic Sea in large numbers, south of Møen, in 

 March 1902 and Februar 27.-28., 1903, on 12 fathoms' depth, with a sali- 

 nity of 17,4 7oo and 2,5" C. March 21., 1903, we searched for eggs again 

 in the same place, but now the salinity was only 10,6 7ooi temp. 3,8° C, 

 and no eggs were found. In February we had had violent western storms, 

 therefore, probably, the salt water; the latter together with the eggs dis- 

 appeared, however, in the course of March. On the expedition of the 

 Poseidon, in February 1903, eggs were also taken in large numbers iu the 

 western part of the Baltic Sea, decreasing, considerably, in number towards 

 Bornholm; one is even stated to have been taken east of Bornholm, where 

 llie salinity was only 13,73 "/oo on the bottom. 



In all these seas we may also take plaice witli ripe spawn and milt; 

 south of Møen I have caught them many times in buge muititudes, aud 

 Tryhom ("Sveuska liydrogr. biol. Konnnissionens Skiil'ter 1", ji. 10) found 



