age 



[9] EGGS OF THE PLAICE, FLOUNDER, AND COD. 435 



with liquid iu air. Finally I measured the eggs of the same fish, and 

 from all these observations I determined their true weight and their 

 specific gravity. 



The mature eggs of three female cod each weighing 1^ pound, were 

 placed on filters, in order to obtain the liquid. It is ad\isable for this 

 purpose to remove the ovary from the fish, to open them, and let the 

 eggs run out into a vessel. In this manner more eggs, and generally 

 ones in a better condition, are obtained than by squeezing them out, 

 which process is also apt to let other secretions mingle with the eggs. 



The specific gravity of this liquid, as determined by the picknometer, 

 was 1.01115, at a temperature of 8.7° C. The specific gravity of a quan- 

 tity of eggs, with liquid, of the same fish was 1.01542, at a teu)perature of 

 7.2° C. Nine hundred and sixty-one of these eggs weighed 1.9038 grams. 



To find the relative quantity of the liquid, the diameter of these eggs 

 had to be ascertained. In order to avoid their i^ressing against each 

 other, they were placed iu the remainder of the filtered liquid, and 

 after 23 measurements the maximum diameter was found to be 1.4119 

 millimeters, the maximum 1.5099, and the average 1.4375. The aver- 



volume of an egg | '^ f?^ = vol. | = 0.5236 multiplied by 2.9705 = 



1.5553 cubic millimeters. The above mentioned 961 eggs, therefore, had 

 a volume of 1494.6433 cubic millimeters. 



As the specific gravity of the eggs with the liquid had been 1.01542, the 

 volume of the above 1.9038 grams eggs with liquid was 1.9038 divided by 

 1.01542=1.8749 c. c. ; subtract from this the volume of the 961 eggs, 

 which is 1.4946, and the volume of their liquid is 0.3803 c. c. 



Calculating the percentage on the quantity of eggs in these three 

 fish, we find, that of the total quantity of matter discharged from the 

 ovaria 79.72 per cent, was egg substance and 20.28 liquid. 



As this mixture had a specific gravity of 1.01542, and the liquid a 

 specific gravity of only 1.01115, the specific gravity of the eggs, at a 

 temperature of 8.3° 0., is found to be 1.01664. The equation from 

 which this result is obtained would be the following {x standing for the 

 specific weight of the eggs) : 



79.72.r+20.28x 1.01115= 100 X 1.01542. 



It must be observed, however, that small difterences in the micromet- 

 ric measurement change the results considerably. Careful measure- 

 ments of 23 eggs, from a cod weighing 9 pounds, showed the large 

 diameter to be 1.502, and the small diameter 1.457 millimeters. Calcu- 

 lated from these figures the volume of the ellipsoid was found to be 

 1.6703 cubic millimeters, and from this, the average diameter of the 

 globe of the egg 1.4721 millimeters. If I use this diameter for the above 

 calculation I find per 100 volumes eggs 85.61 per cent, egg substance and 

 14.36 per cent, liquid. The specific gravity of the eggs by themselves, 

 is, therefore, 1.016165. The fourth decimal, therefore, shows already 

 difterences. Other experiments show that the quantity of liquid is not 

 always the same; but the above mentioned 20 per cent, is probably to 



