460 Prof. J. C. Ewart. On the Natural and [Mar. 27, 



Amongst questions still to be settled are the following : — 



How long does the female require to shed all her ova, and does it 

 escape in thick ribbons when she is in an exhausted condition ? 

 When the sphincters are relaxed in a dead fish the spawn escapes in 

 rounded cords about three lines in diameter. 



How long after death are the eggs capable of being fertilised ? 

 Eggs were successfully fertilised during the autumn from a herring 

 taken from the stomach of a cod immediately after it was caught. 



How long does the male require to discharge its milt ? And how 

 long do the sperms retain their fertilising power ? I have found that 

 in 1J hours the sperms cease moving, and that ribbons of milt 

 from herring dead 12 hours remain for several days unchanged, the 

 dead sperms being unable to separate from each other, and diffuse 

 themselves through the water. 



When at Ballantrae I noticed that the trammel-nets secured often 

 more males than females* Is this partly owing to the males swimming 

 somewhat higher than the females, and partly owing to the males 

 taking longer to shed their milt, and hence remaining longer on the 

 spawning-ground ? It may be found that while the females discharge 

 all their spawn in three or four days the males require nearly double 

 that time to get rid of their milt. Mr. Wilson, fishery officer at 

 Girvan, at my request, made a number of experiments with ripe 

 herring. He found that on opening a female herring after as much 

 spawn as possible had been expressed by the hand about a fourth of 

 the roe remained, while on pressing a ripe male in the same way 

 about a third of the milt remained, and he observed that it was more 

 difficult to express the milt than the roe. Mr. Wilson states in answer 

 to other queries : (1) That the ripest fish are caught in the trammel- 

 nets, while most of the unripe fish are obtained in the drift-nets ; 

 (2) That at the end of the fishing season at least there are about 

 three males taken for every two females, indicating not necessarily 

 that the males are more abundant than the females, but rather that 

 the males remain longeron the spawning-grounds. Boeck states more 

 females are caught at the beginning of the fishing season, which agrees 

 with our observations in the Moray Firth. Mr. Wilson believes that 

 herring prefer quiet water free from strong currents when spawning, 

 and that when the weather is fine, the herring remain long upon the 

 bank, and deposit their spawn leisurely, but when there are strong 

 currents they either hurry the spawning process, or disappear into 

 deeper water. 



IY. The Artificial Fertilisation and hatching of Herring Ova. 



Hitherto, herring ova when wanted for artificial cultivation have 

 usually been obtained in the following way. The herring was 

 removed from the water and gently pressed along the abdomen so as 



