H. C. Williamson 101 



There is the question of how much milt the ova require. The most 

 common method of spawning sahnon eggs is to bathe them in the milt, 

 water being added after a short time. Jousset de Bellesme states that 

 "the robustness of an organism would depend in great measure on the 

 number of fecundating elements which entered the egg." There would 

 however appear to be a danger from water which was excessively laden 

 with milt. I have observed a white deposit of milt in the interstices of 

 the eggs, and that would no doubt prove to be a source of danger 

 through its decay. 



The spawn on glass plates is easily handled ; but when the eggs have 

 been attached to gravel satisfactory results have also been obtained. 

 Such spawn is conveniently incubated in a box having a sieve bottom. 

 The water finds issue through the bottom after passing among the 

 gravel. If the box is now and then lifted and then pressed down into 

 the water an effective change of water is secured. 



There is a reasonable expectation that naturally spawned herring 

 ova could be dredged during February, or March, at Ballantrae Bank, 

 Firth of Clyde, and it seems likely that such spawn would stand transport 

 better than the artificially spawned ova. The spawn secured in this 

 way would probably not be newly deposited, still development might 

 be thereafter retarded sufficiently for the object in view. 



Some herring ova, after incubation at from 37° to 40° F. for 19 days, 

 had embryos in an advanced stage. The eggs were then treated with 

 water of 33-8° to 37° F. The first larva appeared on the 30th day, and 

 hatching proceeded for the next 12 days. Eggs left at the original 

 temperature hatched in from 23 to 36 days. In another case the spawn 

 began to hatch on the 20th day ; the temperature of the water had been 

 38° to 44-5° F. Thereafter the temperature was lowered, and the larvae 

 hatched out daily till the 41st day. All the eggs in a batch do not hatch 

 out simultaneously; there have occurred, during the experiments, 

 intervals of 5 to 21 days between the appearance of the first larva and 

 the last to hatch. 



There is another alternative method of obtaining the spawn; that is 

 to arrange, if possible, that the herrings spawn in confinement. Ewart^ 

 described the spawning of herrings in Rothesay Aquarium. 



^ Ewarfc, C, "Natural History of the Herring." Plates. 2nd Ann. Report Fisheries 

 Board for Scotland. 188.3, p. (il. 



