22 



the above vessel. On April 6th, 364,250 plaice fry were 

 set free on the way to the off-shore grounds between 

 Lancashire and the Isle of Man. On April 9th, 90,000 

 flounder fry were distributed about the same locality as 

 the last, making 3,318,910 in all. 



Besides bringing in the eggs, the steamer also, on 

 various occasions, collected numbers of nearly mature 

 fish, chiefly plaice and flounders. These were kept alive 

 in our tanks, where the eggs were shed as they became 

 ripe, and the majority of them were fertilised. The 

 emission and fertilisation of these eggs, which always 

 took place in the dark, went on in the tanks probably 

 much in the same way as under natural conditions in the 

 sea. The eggs rose to the surface and were carried along 

 by the water, which was allowed to overflow into a floating 

 collecting box, where they were retained, and afterwards 

 transferred to the hatching apparatus. The subsequent 

 incubation of these eggs and hatching out of the larvae was 

 accompanied by a nmch smaller mortality than in the case 

 of the eggs obtained by the steamer. The fry hatched 

 out from these eggs numbered 78,000 plaice and 90,000 

 flounders (included in the 3,318,910). 



When the spawning period of the sole approached, 

 special visits were made to the off-shore grounds to collect 

 mature fish, which were brought in and kept alive in the 

 tanks. In the course of a few days some of them began 

 to shed their eggs, which rose to the surface and were 

 collected from the overflowing water. On being submitted 

 to microscopic examination it was found, however, that 

 not a single egg was fertilised. Various attempts were then 

 made to biing about fertilisation by dissecting the male 

 fish and squeezing up the reproductive organ amongst the 

 eggs, but all attempts failed owing probably to the imma- 

 turity of the male fish. 



