1884.] Artificial Fertilisation of Herring Ova. 



459 



often carried a considerable distance before they reach the bottom. 

 It will be evident that if the eggs are shed in strong currents some 

 fathoms from the bottom, the chances of their being fertilised would 

 be considerably diminished. When the sea is rough the fishermen 

 seldom expect a good " take," they believe, in fact, that during storms 

 the herring leave the spawning ground, and if the eggs are always 

 deposited as I have described we can easily understand that this 

 might well be the case. Sometimes about the middle or near the end 

 of the spawning period the whole school disappears in a single night. 

 This generally happens during or immediately after a storm, or some 

 other disturbing cause. It may be accounted for by supposing that 

 the herring being ready to spawn, or having already begun to deposit 

 their eggs, finding the conditions on their usual spawning grounds 

 unfavourable, deserted them for banks at some other part of the coast 

 or at some distance seawards. 



A number of flat stones and pieces of sea-weed were obtained, and a 

 spawning female held over them at different distances in still water, 

 in water with gentle currents, and in water with strong currents. In 

 this way groups of eggs were obtained which mimicked in a very 

 striking manner all the arrangements of the eggs on the stones and 

 sea-weeds dredged on the Ballantrae Bank. When gently pressed a 

 beaded ribbon, consisting of a single row of eggs, always escaped. 

 When there were no gentle currents it formed conical heaps ; when 

 in a gentle current the ribbon fell in irregular loops, the elements of 

 which arranged themselves so as to form a flattened cone ; but when 

 strong currents acted on it, the ribbon was broken into fragments, 

 and only a few eggs succeeded in fixing themselves. When the 

 currents were strong, the males were seen not only to swim nearer 

 the bottom, but to expel longer ribbons of milt which reached the 

 bottom before getting dispersed, and remained visible sometimes for 

 ten minutes. On gently expressing a male under the water, it was 

 never possible to expel so fine or so short portions of milt as escaped 

 naturally, but it was extremely easy expelling a ribbon from 18 inches 

 to 3 feet in length, measuring two lines across, and one line in thick- 

 ness. Such ribbons fell to the bottom, and remained almost unchanged 

 for nearly two hours ; they then assumed a segmented appearance, and 

 in about 3^ hours had all but disappeared. 



Eggs were allowed to escape into a vessel containing fine sand, and 

 into another containing mud. The eggs after being fertilised under- 

 went the early stages of development, but, either owing to their 

 moving freely about with the sand particles, or owing to their getting 

 coated over with the sand and mud, their further development was 

 arrested. I have not yet determined finally if the development is 

 arrested when the eggs are detached, but this seems extremely 

 probable. 



