450 



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



the rotation of the plane of polarisation of light in bisulphide of 

 carbon under the action of magnetic force. Of the results obtained by 

 Gordon and Becquerel, differing by about 9 per cent., our preliminary 

 measurements tend rather to confirm the former. 



III. " On the Natural and Artificial Fertilisation of Herring Ova." 

 By J. Cossar Ewart, M.D., Regius Professor of Natural 

 History in the University of Edinburgh. Communicated 

 by The President. Received March 19, 1884. 



It is well known that for centuries herring have been in the habit 

 of congregating on inshore banks around the coast of Britain in order 

 to deposit their spawn. 



In 1862 the Royal Commission (of which Professor Huxley was a 

 member) appointed to report on the trawling for herrings on the 

 coast of Scotland, arrived at the conclusion that herring visit our 

 shores for this purpose twice a year, some shoals arriving during the 

 autumn, while others make their appearance during the winter. The 

 herring which spawn during the autumn (and which at another time 

 I shall endeavour to show differ from the winter herring) chiefly 

 frequent banks on the east coast, while the herring which spawn 

 during winter are most abundant on the west coast. 



Of the west coast spawning-grounds, the Ballantrae Bank, which 

 lies off the coast of Ayrshire, is one of the most important and is 

 certainly the most famous. To this bank herring are known to have 

 resorted for at least 200 years, always bringing in their train 

 numerous codfish, whiting, and sometimes shoals of dogfish, por- 

 poises, and dolphins, and while on the bank they have afforded an 

 abundant harvest to the fishermen of the surrounding districts, and to 

 the flocks of gannets and gulls which people Ailsa Craig. 



The herring fishery being one of the most important industries in 

 Scotland (the autumn fishery engaging nearly half- a- mil lion people, 

 and being worth in good years about 2,500,000Z. sterling), there has 

 been since 1809 a Board specially charged with guarding its interests. 

 This Board (formerly known as the Board of Fisheries, but since 

 1882 as the Fishery Board for Scotland) in 1862-63 endeavoured, 

 under the direction of Professor Allman (then a member of the 

 Board), to gain some information as to the habits of the herring, and 

 more especially as to the nature of the spawn and the spawning 

 grounds. Since 1863 little has been done in this country by way of 

 continuing these experiments until last autumn, when the new 

 Fishery Board, recognising the importance of the investigations so 

 ably initiated by Professor Allman, appointed a Committee of its, 



