[11] 



EGGS OF THE PLAICE, FLOUNDER, AND COD. 



437 



of 1 pound and an average length of 30 centimeters. The specific 

 gravity of the liquid was 1.01022 at 7.5° C, and of the eggs with the 

 liquid 1.01430. After having been weighed and counted, the weight of 

 one egg with the liquid belonging to it was 3.3C3 milligrams. The 

 average diameter of the egg, calculated from 30 measurements, was 

 found to be as follows : long axis, 1.76163 millimeters ; short axis 1.71686, 

 the minimum, 1.608; and the maximum 1.804. The volume would, there- 

 fore, according to these figures, be 0.0027188 cubic centimeters. The 

 mass of eggs taken from the ovarium was therefore composed of 82 

 parts eggs and 18 parts liquid, and the specific gravity of the eggs by 

 themselves 1.01557 at 4o.5 C. 



These eggs, when thrown into salt water had a specific gravity of 

 1.01496 at 6.80 C=1.0136 at 7.5° =1.78 per cent. salt. It does not ad- 

 mit of a doubt, that these eggs had begun to swell, for the difference 

 of weight between the eggs from the ovary and the eggs from the 

 water is very considerable. Taking the specific gravity of the swelled 

 egg, calculations show its volume to be 0.003081 c. c. at 7°, it weight 

 3.127 millimeters, and its average diameter 1.801 millimeters; whilst 

 calculated on the basis of the original volume of the egg, it is only 

 1.732 millimeters. Comparisons made between the average measure of 

 eggs taken from the sea, and eggs taken from a fish will not lead to 

 absolutely certain results, but if the eggs are thrown into salt-water, a 

 comparison of those eggs which have not yet been very much developed 

 will be tolerably exact. It is of some interest to embryolgy to know that 

 the eggs swell, considerably, so that they increase 11 per cent, of their 

 volume and 4 per cent, of their diameter ; the shell of the eggs is so thin 

 that their swelling cannot be 0.07 millimeters. Unfortunately I neglected 

 to make the necessary investigation of more devejjoped eggs, which 

 would of course require a considerable number of eggs. It would be 

 interesting to know whether the small fish of the Baltic have as large 

 «ggs as the great fish of the ocean. 



The specific gravity is, as we know, of peculiar importance as regards 



the Baltic. Our monthly reports show the following data as to the 



saltness of the water of the Baltic, at same depth, in the Bay of Kiel 



near Friedrichsort : 



Percentage of saltness in deep water. 



