MANUAL OF FISH-CULTURE. 47 



hours 4,400 eggs were obtained, of which only 58^ per cent were capable 

 of fecundation. In one instance eggs taken from a dead fish and kept 

 until the morrow before milting remained so far in normal condition 

 that 12i per cent were fecundated. In another case 400 eggs from a 

 fish that had been dead 15 hours failed totally; and the same result 

 was obtained with 2,200 eggs taken from four specimens killed two days 

 before. 



The same experiments atford evidence as to the result of keeping eggs 

 for various periods of time after they are taken from the fish, and 

 eggs exposed to the air and guarded against contact with water appear 

 to keep better than in the organs of a dead fish. Thus, 200 eggs were 

 kept in a pan without water for 12 hours after they were taken from 

 the fish, and the application of milt then resulted in the impregnation 

 of 90 per cent; of 200 eggs kept in the same way for 30 hours and then 

 treated with fresh milt, 87 J per cent were impregnated ; and of 100 eggs 

 kept 4 days and then treated with fresh milt, 12 were impregnated. 



Milt taken from a living male and kept in an open dish for several 

 hours retains its powers fully, but experiments with milt from dead fish 

 have given almost wholly negative results. Numerous experiments 

 show that if eggs are merely covered by water, without effort to secure 

 intermixture or the washing off of the mucus that envelops them when 

 pressed from the organs of the mother fish, their susceptibility to fecun- 

 dation may not be seriously affected by immersion 5 or 6 minutes; but 

 if the eggs are stirred, so as to facilitate the washing off of the mucus 

 and the access of pure water, immersion for 1 or 2 minutes may pre- 

 vent impregnation. 



When thoroughly diluted with water the milt speedily loses its 

 power, the effect being very marked at the end of 30 seconds; diluted 

 with the mucus that accompanies the egg, it will remain effective for a 

 long period. Where water has been carefully excluded, milt has been 

 used successfnlly after the lapse of 12 hours with landlocked salmon, 

 and this would probably hold with eggs of all kinds of salmon and 

 trout. This propert}^ of the mixed mucus and milt has been utilized 

 in impregnating masses of eggs when there is a scarcity of males, as 

 sometimes occurs toward the close of the spawning season. In strain- 

 ing the mixed mucus and milt from the pan of eggs, the lower strata, 

 which are richer in milt than the upper, should be especially secured 

 and the mixture kept in a convenient receptacle. The upper strata of 

 the mixture should not be used, as the milt settles to the bottom. 

 Fresh milt should always be preferred when obtainable. 



The eggs are washed as soon as the milt is thoroughly diffused among 

 them, and this can hardly be done too speedily for the milt to act. A 

 careful record of certain lots of eggs that were washed in special haste 

 for experimental purposes shows that they were as well impregnated 

 as those exposed to the action of the milt for a considerable period. 

 Prolonged exposure to the milt has beeu found to affect the health and 

 development of the embryo unfavorably. 



