XXII.-PAPERS RELiVTING TO PRACTICAL FISH-CULTURE. 



A— METHOD OF TREATING ADHESrVE EGGS OF CERTAIN 

 FISHES, ESPECIALLY OF THE CYPRINID^E, IN ARTIFICIAL 

 PROPAGATION. 



By Rudolph Hessel. 



[TranslatioD.] 



Offenburg, Germany, May 3, 1872. 



lu giving the following instruction for hatcbing the eggs deposited 

 by certain fish in the summer-time, I thought it best to select the species 

 of Cyprinidce, with adhering eggs, for my communication. Such eggs are 

 of larger size compared with those of the other Gyprinidm, and thus the 

 manipulation of impregnation and the observation of the progressing 

 changes are much facilitated. Besides this, it is a fish of great value for 

 table-use and for feeding other fish, and is, in all probability, (though I 

 do not know with certainty,) already introduced into your country, so 

 that you will have no difficulty in procuring male and female specimens 

 for your hatching experiments. 



The carp have adhering eggs, and with reference to this peculiarity, 

 the mode of impregnating and the arrangement of my hatching-appa- 

 ratus are based. 



I presume if you cannot obtain any carji, other Cyprinidoi with ad- 

 hering eggs might be substituted ; even the percoid Perca JIuviatilis, 

 (Linne,) which has adhering eggs, would do, as my apparatus is adapted 

 for any fishes of this habit. 



I can highly recommend the modus operandi^ as it has been full3" tested 

 by many experiments, provided that your water has similar constituents, 

 is free from contamination by industrial establishments, is of moderately 

 elevated temperature, and, especially, is not infested with spores of 

 the confervoid, {Leptomitris clavatus.) With some care, you will have 

 favorable results, but my directions must be strictly followed. You 

 are fully acquainted with the Cyprinus carpio and its habitat, and 

 therefore I need not detail my observations made in different parts of 

 Europe during the last twenty years, beyond remarking that it occurs 

 in many of the larger rivers of Midtj|| Europe — the Rhine, Vistula, 

 Elbe, Danube, &c. — and in many lak" It is especially adapted for 

 ponds, and most of the German villages and estates have ponds where 

 both carp and pike occur together, their propagation being left to 

 uatnre. It is remarkable that car[> thrive equally well in sea-water, 

 even attaining better quality and larger size than in fresh. I have fre 



