198 



POPULAR SCIENCE MONTHLY. 



Similar experiments were performed with the ova, to determine 

 their susceptibility to fertilization after being immersed in water for 

 various periods. The following results were obtained from one series, 

 which are typical of the others : 



The average salmon produces about 6,000 ova. In artificial propa- 

 gation from 5 to 20 per cent, cannot be spawned. These can be removed 

 only by slitting the fish open, in which case a considerable quantity of 

 blood is mixed with them. If the blood is not washed off, the fertiliza- 

 tion cannot be made complete, as many of the ova become surrounded 

 with clotted blood. But, if the blood is washed off with water, the ova 

 immediately become turgid and not susceptible of fertilization. The 

 difficulty was overcome as follows : 



Among the many experiments testing the vitality of the ova and 

 their susceptibility to fertilization under various conditions, one deter- 

 mined their reaction to normal salt solution. By normal salt solution, 

 is meant water of the same degree of saltness as the body fluids, which 

 in the case of the salmon we assumed to be .75 of 1 per cent., no 

 chemical determinations having been made. Ova were spawned into a 

 pan containing normal salt solution, and after various periods of time 

 a few were removed and spermatized in the ordinary manner, with the 

 following results: 



Time ova had been in 



salt solution. 



Minutes. 



2 

 4 

 6 



Percentage of Time ova had been in 

 fertilization. salt solution. 



Minutes. 



99 

 100 

 100 



8 

 15 

 25 



Percentage of 

 fertilization. 



99 

 97 

 86 



