of the Fishery Board for Scotland. 



289 



T have elsewhere shown* that at the last stages of the maturation of 

 plaice eggs in the ovary the absorption of water by the eggs is enormous, 

 amounting to at least two- thirds of the volume of the contents. Thus, in 

 the 654 cubic centimetres of eggs produced by the female, No. 2, at least 

 536 cubic centimetres is represented by water absorbed not long before 

 the eggs are extruded, and which is secreted by the fish. So in the other 

 case ; about 572 cubic centimetres of the 857 cubic centimetres of eggs 

 represents water absorbed. 



Both the plaice were kept in the tanks after the conclusion of spawning. 

 On 9th May, no further eggs having come from the plaice in No. 2 since 

 the 23rd of April, and spawning being clearly over, she was killed and 

 examined. The length was the same, 46*5cm., and the weight was 21bs. 

 8|oz. (11 39 8 grammes), showing a loss of 14oz., or 396 grammes. 



At the same time, the other plaice (No. 5) was also weighed. It was 

 21bs. 6|oz. (1083 grammes), showing a loss of 8|oz., or 234 grammes. 

 The measurement was a little less, viz., 46'7cm. 



This fish was put back with the males into the tank, but no further 

 spawning occurred. On 13th May she weighed 1119 grammes, and was 

 still 46 - 7cm. ; on 21st May the weight and length were the same, so that 

 recovery was slow. 



The loss in weight above referred to does not represent anything like 

 the weight of the eggs spawned. Among those of No. 2 it was found 

 that 56 cubic centimetrea weighed 53 grammes, so that the total weight 

 of the 654 cubic centimetres spawned would be about 619 grammes, or 

 223 grammes more than the loss of weight of the fish. 



In the other plaice (No. 5) 6-7 cubic centimetres of eggs weighed 6*65 

 grammes, and the total weight of the whole quantity of 857 cubic centi- 

 metres would be about 850 grammes, or 616 grammes in excess of the 

 loss of weight of the fish. 



The difference is accounted for by the water secreted and absorbed 

 as the eggs mature ; also, no doubt, by the absorption of water by the 

 muscles and tissues of the fish after spawning, the increase of weight in 

 No. 5 after the 9th May being probably due to this, since no food was 

 eaten. 



When the first plaice (No. 2) was killed, on 9th May, the ovaries were 

 found to contain a large quantity of spawn. When put into sea-water 

 all went to the bottom within a few minutes, and the disc was chalky 

 white, and in many cases wrinkled and irregular. They represent the 

 eggs which the fish is unable to get rid of at the end of spawning, and 

 which disintegrate and are absorbed. The quantity amounted to 43*95 

 cubic centimetres, of which 3*75 cubic centimetres contained 1482 eggs, 

 or 395 2 per cubic centimetre. The estimated number of eggs thus 

 retained in the ovaries and destroyed was 17,369, or over 10 per cent, of 

 the number spawned, which indicates a very considerable loss. 



The ovaries of the other plaice were in the same condition, slightly 

 swollen, tumid, and soft. 



* Ibid., p. 14. See also p. 145. 



T 



