630 EEPOET OF COMMISSIONER OF FISH AXD FISHERIES. 



I therefore examiued the condition of spring spawn when kept in A'ery 

 cold water with the following results : 



For this year's experiments I used full-grown fish which had been 

 caught with hook and line near Bappeln, on the Schlei (Duchy of Schies- 

 wig), on the 26th of April. Milt and roe were ejected by these fish into 

 porcelain dishes the verj^ moment they were taken out of the water, with- 

 out exercising any pressure. The temperature of the water at the time 

 these fish were caught was 8o.4 0. (47.12° F.), the saltness midway 

 between the surface and the bottom 1 per cent, (specific gravity =1.0070 

 at 17'^.5 C. = 03.5° F.). The artificial impregnation was, as in former cases, 

 accomplished in porcelain dishes, which during the journey to Kiel were 

 often supplied with fresh sea- water, which was kept at the above-men- 

 tioned temperature. 



The diameter of the eggs, altough they came from different fish, only 

 varied between 1.22 and 1.37 millimeters. On closer examination it was 

 found that nearly every egg had been imi>regnated and that their nor- 

 mal development had begun. 



The following experiments were made with these impregnated eggs : 



1. A number of eggs were placed in the open water of the Bay of Kiel, 

 whose temperature at this time was 11-12° C. (51.8°-53.0° F.), and whose 

 saltness near the surface was 1.40 per cent. These eggs were left in the 

 water till the young fish were hatched. 



2. Some eggs were likewise hatched in the open water of the Bay of 

 Kiel, but after having been impregnated, they were from the 2d to the 5th 

 day after this had taken place put in water whose temperature was only 

 2° 0. (35.6° F.), in order to learn the influence of cold water on scarcely 

 developed eggs, and likewise to see what would be the result of suddenly 

 placing them in colder water. 



3. Eggs which for eight days had been in the water of the Bay of 

 Kiel with a temperature of 11-12° (51.80-53.6° F.), and whose develop- 

 ment had almost been completed, were suddenly placed in water whose 

 temperature was only 2° (35.6° F.), in order to ascertain the power of 

 resistance to cold of eggs which were near being hatched. 



4. One-fourth of all the eggs were, immediately on their arrival at Keil, 

 placed in water whose temperature was only 2° (35.0° F.), where they 

 were left, to retard their development as much as possible. 



5. Finally, some eggs were placed in still colder water, in order to 

 ascertain the degree of cold which becomes destructive to herring-eggs. 



A uniform temperature suitable for these purposes can easily be ob- 

 tained by using wooden boxes similar to refrigerators, especially if these 

 boxes are carefully surrounded by non-conductors of heat. The water 

 used in these experiments was salt water from the Bay of Kiel. In all 

 the experiments the water was changed once a day and fresh water put 

 in the vessels after being reduced to the desired degree of coolness. 



At as low a temperature as 2° C. (35.6° F.) it seems quite easy, even 

 without taking any special precautionary measures, to keep herrmg-eggs 



