[7] EGGS OF THE PLAICE, FLOUNDER, AND COD. 433 



servations tend to confirm them ; but I must state that, according to 

 my observations, the eggs in the ovarium show five very distinct stages: 

 (1) free, (2) mature, (3) clear, (4) large muddy, and (5) small muddy 

 eggs. Even in the immature ovarium three distinct stages can be dis- 

 tinguished, and this whole matter will have to be studied more closely. 



Earll ascertained the uumber of eggs by weighing first the entire 

 ovarium, then pieces of it, and by couhting the number of eggs in some 

 of these. This proceeding may be considered as leading to reliable re- 

 sults, as, according to my observations, the character of the ovarium is 

 very much the same in its diftereut parts, and as it would almost be im- 

 possible to count the eggs in any other way. It is, of course, possible 

 that some of the small eggs do not reach maturity, but are, especially 

 towards the end of the period, again absorbed. My observations relative 

 to this matter, however, have, so far at least, only yielded a negative 

 result. 



Earll makes the following calculations : 



Eggs. 



Cod, 75* pounds, 9,000,000 eggs, per 500 grams 160, 750 



Cod, 51 pounds, 8,489,094 eggs, per 500 grams 236, 150 



Cod, 30 pounds, 3,715,687 eggs, per 500 grams 165, 950 



Cod, 27 pounds, 4,095,000 eggs, per 500 grams 203, 200 



Cod, 22f pounds, 3,229,388 eggs, per 500 grams 190, 200 



Cod, 21 pounds, 2,732,237 eggs, per 500 grams 174, 300 



Average 188, 425 



Plaice, 9^ pounds 1, 834, 581 



Plaice, ^ pounds , 849, 315 



Plaice, 4 pounds 403, 132 



Plaice, 3-j% pounds 298, 976 



Gadus pollachius, 23^ pounds 4, 029, 200 



Gadus pollachius, 13 pounds 2, 769, 753 



The following are the dimensions of the eggs : Those of the largest 

 cod 15 millimeters, and those of the smallest cod 1.34 millimeters in 

 diameter; Gadus pollachius, 1 millimeter. No measurement is given of 

 the plaice. The specific gravity is given as varying between 1.020 and 

 1.025; but I presume that this is only an estimate based on the specific 

 gravity of the sea, for otherwise these figures would be very remark- 

 able. 



The period consumed in hatching the eggs of the cod was : At 7.5° 

 C, 13 days ; 5° C, 16 days ; at 3° C, 20 days ; at 2.2° C, 24 days ; 

 at 0.50 C, 34 days ; — 1.2o C, 50 days ; when the temperature is lower 

 the eggs perish. Some eggs develop the young fish slower; those fish 

 which are hatched first and last are not very strong. 



With a view to distinguishing with greater certainty the eggs of dif- 



* This seems to be Troy weight, therefore only 373.2 grams per pound. 



S. Mis. 46 28 



