of the Fishery Board for Scotland. 



71 



broken into fragments, and only a few eggs succeeded in fixing them 

 selves in the vicinity of the stones and sea-weed. 



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 some- 

 times 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 thickness. 

 Such ribbons fell to the bottom, and remained almost unchanged for 

 nearly two hours, they then assumed a segmented appearance, and in about 

 3 -J 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 underwent 

 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. 



V. 



ARTIFICIAL FERTILISATION AND HATCHING OF 

 HERRING OVA. 



In referring to the artificial fertilisation of herring ova in the paper 

 presented to the Royal Society, I mentioned that the best results were 

 obtained when the natural process of spawning was as far as possible 

 followed. The plan adopted is described as follows : — 



'An ordinary wooden tub was obtained and filled with sea-water. 

 ' Into this a small quantity of milt was expressed, the male being held 

 ' completely under water while the milt escaped. A glass plate was 

 ' then held about 4 inches beneath the surface of the water, and the 

 ' female herring about 1 inch beneath the surface, and then under gentle 

 ' pressure the eggs readily escaped in the characteristic narrow beaded 

 ' ribbon, and by moving the fish over the surface of the glass either a 

 { close or an open network could be formed. At first, where one loop 

 ' crossed another, the eggs were two or more layers thick, but either 

 ' owing to the weight of the eggs or the gentle currents set up in the 

 1 water, before a few minutes had elapsed the eggs formed a single and 

 ' almost continuous layer, the network arrangement having disappeared. 

 ' The plate was then allowed to rest for two or three minutes at the 

 ' bottom of the tub and a few short ribbons of milt were again introduced. 

 1 After moving the plate once or twice across the top of the tub in order 

 ' to wash off any scales that were adhering, it was placed either in a 

 ' hatching or in a carrying box.' Fig. 6, PI. IX. shows a continuous ribbon 

 which was expressed from a living herring, and fig. 7, of the same plate 

 shows how the eggs of a similar ribbon arranged themselves to form a 

 single and almost continuous layer. 



Many thousands of eggs treated in this way on the 8th March hatched 

 out on the 26th, 29th, and 30th March — eighteen, twenty-one, and twenty- 

 two days after fertilisation, the temperature varying from 41° to 44° Fahr. 

 The method of escape was carefully studied. It was found that when 

 the eggs had been provided with a plentiful supply of pure water, the 

 embryos were extremely active — revolving within the capsule or wriggling 

 from side to side until the capsule ruptured and allowed the larval 

 herring to escape head foremost. When, on the other hand, the supply 

 of pure water had been limited, the capsule often gave way before the 

 time for hatching had arrived, and the result invariably was that the long 



