'434 REPORT OF COMMISSIONER OF FISH AND FISHERIES. [8] 



ferent species, and to comparing them with each other, I have endeav- 

 ored to obtain average figures relative to the measurements, but iii doing 

 this I encountered innumerable difiBculties. By measuring eggs which 

 had not yet been impregnated, I found that as a rule they are ellip- 

 soids, and not globes. In measuring such eggs, it is not absolutely cer- 

 tain whether one measures the long or short axis. Moreover it is nec- 

 essary to measure a considerable number of free eggs, which is a very 

 tiresome i)rocess. It would be better if the average diameter could be 

 gained from the weight, numbers, and specific gravity ; but the exceed- 

 ingly tender nature of the eggs became an insurmountable obstacle 

 when I attempted to measure in this manner eggs which had not yet 

 been impregnated. 



The freshly laid eggs lie in a liquid which may well be designated as 

 Liquor folliculi, as it probably originates in Graf's follicles. This liquid 

 has less specific gravity than the eggs, and has, therefore, to be exam- 

 ined separately. As the shell of fresh eggs when exposed to the air is 

 very apt to burst, partly through the weight of the eggs, no method 

 could be found to weigh the eggs in a dry condition. The liquid would 

 have to be removed by washing the eggs, which would cause them to 

 swell and possibly produce transudation, thus changing the original 

 character of the eggs. The eggs, after having been laid in salt water 

 undergo A^ery considerable changes. After a while they become so hard 

 that they can be rolled between the fingers, and their presence among 

 other matter brought up from the water can easily be ascertained by 

 the touch. Eggs which have not been impregnated do not become so 

 hard, because after awhile they begin to dissolve. For 14 days, how- 

 ever, and even longer, their shape remains well preserved, and, com- 

 pared with fresh eggs, they seem hard. The hardening process, in or- 

 der to become perfect, requires one day. But I have not followed this 

 process closely, and must mention this circumstance because afterwards 

 my attention was directed to a very striking observation made by Mr. 

 Earll. He says, on page 721 : 



" It was found desirable to leave the eggs for fully half an hour to- 

 gether with the milt ; and sometimes a longer time was required to make 

 them quite hard." 



Earll, therefore, seems to assume, as a well known fact, that fish-eggs 

 harden in consequence of impregnation. If there are any facts relative 

 to this subject in literature, they must have escaped me. Hitherto I 

 have considered the hardening process as owing to the effect of the water, 

 and the gases contained in it ; which is undoubtedly correct as regards 

 the hard crust found on many eggs. If impregnation by itself cause a 

 hardening of the eggs, this must be considered as a fact not yet suffi- 

 ciently noted and examined by science. 



As regards eggs which had not yet been impregnated I have, in the 

 following manner, endeavored to obtain approximately correct data : I 

 first determined the specific gravity of the liquid, then that of the eggs 

 in the liquid. Thereupon the weight of a certain known number of eggs 



