634 EEPORT OF COMMISSIONER OF FISH AND FISHERIES. 



size, it could be proved that the decrease of the yolk is invariably ac- 

 companied by an increase of the embryo. The young fish were meas- 

 ured, with the following result: 



Millimeters. 



After 7 to S days from the time they left the egg 4.7 to G.O 



After 11 to 12 days from the time they left the egg 5.2 to 6.6 



After 20 days from the time they left the egg 6.0 to 6.9 



After 28 to 35 days from the time they left the egg 6.1 to 7.2 



If these results are compared with those which are given m the report 

 of the commission, for young fish hatched from autumn eggs from Kor- 

 soer (Denmark), it will be found that these last-mentioned fish were con- 

 siderably longer. Their length varied between 5.4 millimeters, when the 

 time of development was shortest, and 8.8 millimeters, when it was longest. 



II. — INFLUENCE OF NORTH SEA "WATER ON HERRINGS' EGGS FE03I THE 



BALTIC. 



In order to ascertain the influence of the water of the Xorth Sea^ — 

 which contains more salt than that of the Baltic — on the eggs of the 

 Baltic herring, I took some eggs which had been impregnated, on the 

 26th of April, at Cappeln, on the Schlei (a fiord of the Baltic), on the 

 following day to the aquarium of the zoological garden in Hamburg. 

 The iSTorth Sea water used in this aquarium at this time only contained 

 3.25 per cent, salt, and its temperature was 12° G. (53.6° F.). Here the 

 Baltic water was gradually mixed with the North Sea water, so that the 

 eggs were not exposed to the full degree of saltness till after forty-eight 

 hours. On the 7th of May the first young fish were observed swimming 

 about freely, and during the succeeding days they were followed by 

 others. The time of development was therefore very nearly the same 

 as in Baltic water of the same temperature. The day when the eggs 

 were taken to Hamburg was unfortunately very hot, and as the eggs 

 were not evenly distributed, but were placed several layers deep at the 

 bottom of the vessel, the larger number of them spoiled. But the fact 

 that the remaining ones reached their full development about as fast in 

 the North Sea water as in that of the Baltic, shows that the saltness of 

 the water does not exercise any very marked influence. There were no 

 arrangements in the Hamburg aquarium for raising the fish, and this 

 first experiment therefore only proves that the eggs of the Baltic spring- 

 herring can develop in the North Sea, leaving it an open question 

 whether the young fish hatched from these eggs can live and grow to 

 maturity in tlie North Sea. 



III. — RAISING YOUNG HERRINGS FROM ARTIFICIALLY-IjIPEEGNATED 



EGGS. 



As far as I know, no one has succeeded in artificially raising young 

 herrings. ]\Iy own numerous experiments in this direction invariably 

 failed, because the eggs began to mold, and because no suitable food 



