138 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



their existence when they would otherwise be exposed to 

 innumerable enemies in the surface waters of the ocean. 



But it cannot be too emphatically stated, and widely 

 made known, that sea-fish hatcheries ought not to be 

 merely for the purpose of hatching young fish and then 

 setting them free in the sea. Hatching and rearing of 

 fish is the end to have in view, and scientific men who 

 have charge of fish hatcheries will not be content till 

 they have succeeded in rearing into young fish, at a 

 reasonable cost, a large proportion of the fry which they 

 can now hatch from the eggs by the million. Professor 

 G. 0. Sars first showed how the eggs of an edible fish 

 (the Cod) could be hatched in small numbers as a labora- 

 tory experiment ; Dannevig in Norway and the U.S. Fish 

 Commission in America have devised the apparatus and 

 technique by which it has become possible with very slight 

 mortality to hatch out such eggs on an industrial scale 

 by hundreds of millions. The next advance must be in 

 rearing. At present practical difficulties block the way, 

 but the Fishery Board for Scotland has had some success 

 with Plaice, and the French at Concarneau with the Sole, 

 and we cannot doubt that further investigation and 

 experience will show us the best methods to pursue. It 

 is at institutions like this at Port Erin, where a Scientific 

 Laboratory is combined with the Hatchery (fig. XXXII.), 

 that experiments in feeding and aeration can be carried 

 out which will eventually lead us to the successful rearing 

 of the young fish that we now hatch and distribute as fry. 



It is evident, from questions that have been asked by 

 those who have seen the hatching in progress, that some 

 information as to the life-history and habits of the young 

 plaice may be a useful addition to this guide. 



The average size at which the female plaice becomes 

 mature in our seas is about fourteen to fifteen inches ; 



