XVI.-ON THE OCCURRENCE AND QUANTITY OF THE EGGS OF 

 SOME OF THE FISH OF THE BALTIC, ESPECIALLY THOSE OF 

 THE PLAICE (PLATESSA PLATESSA), THE FLOUNDER (PLATESSA 

 VULGARIS), AND THE COD (GADUSMORRHUA).* 



By V. Hexsen. 



[From the Fourth Eeport o the Commission for the Investigation of the German 



Seas. Berlin, 1883.] 



By orders of the Commission I have, for four years, endeavored to 

 make observations regarding the spawn of the above-mentioned fish. 

 As regards the spawning of the cod on the coasts of Norway, we are 

 well informed by Mr. €r. O. Sars't admirable observations ; and as re- 

 gards this fish the only problem to be solved was whether the spawning 

 of the Baltic cod took place in the same manner. The same, however, 

 cannot be said relative to the plaice {Platessa platessa). A circular of 

 inquiry, addressed by the Royal Government of Schleswig to the differ- 

 ent fishery associations, elicited the most contradictory statements, even 

 as regards the time of spawning, and it became evident that not a sin- 

 gle one of the numerous answers showed a knowledge of the actual con- 

 dition of the eggs after spawning. 



In going over the literature on the subject, we find that Alex. Agas- 

 siz| has seen floating eggs of the i)laice, of which he gives a drawing; 

 and that Malm § has artificially impregnated eggs of the plaice, without, 

 however, succeeding in hatching young fish. According to Malm, the 

 eggs slowly sink to the bottom. Only at a late stage in the course of 

 my investigations was my attention directed by Professor Metzger to 

 Malm's observations. This fact probably has been the cause of reach- 

 ing my conclusions somewhat later than would otherwise have been the 

 case. 



The eggs of the plaice are, like those of the cod, transparent, have a 



* " Ueber das Vorkomnmm und die Menge der Eier ciniger Oatseefischc, inshesondere derje- 

 nigen der Scholle (Platessa platessa), der Fhinder {^Platessa vulgaris), und des Dorsches 

 {Gadus morrhua)." Translated from the German by Herman Jacobson. 



t Indherctninger til Departemcntetfor det Indre, angaaende Tomkefiskeriet i Lofoden," Chris- 

 tiania, 1869. — English translation in Report of U. S. Fish Commission, 1877. Sars' 

 work is one of the greatest achievements in this field of scientific investigation. 



tAlex. Agassiz: "Proceedings of the American Academj' of Arts and Sciences," 

 Vols. XIV and XVII, on the young stages of osseous fishes, II and III. 



§ A. W, Malm : "Bidrag till Eannedom af PleiironeJctiderncs utveckling." Svmsku Vcten- 

 skaps Akad. Handlinger, Vol. VII, 18G7 and 1868. 



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