18 THE ACCLIMATISATION 



five weeks the apparatus was fitted up. It 

 was a distinct improvement on the former, 

 but as it was discarded in the finally suc- 

 cessful case, its principal features need only 

 be noticed. One set of trays, containing 

 ova laid on gravel, was hung on gimbals, 

 and another large svsdng tray contained the 

 remainder. A constant supply of water 

 was made to flow over these at the rate of 

 500 gallons a day, with power to increase 

 the quantity to 2000 gallons by means of a 

 force-pump, and the whole body of water 

 could be changed every fourth day. The 

 ova were expected to hatch on board ship, 

 and it was at least hoped that the supply of 

 water would last long enough. Cumbersome 

 as the apparatus was, it was the best that 

 could be devised at the time ; but Mr. Youl 

 determined to make an experiment which, 

 since it practically solved the problem of 

 exporting the ova safely, is of the highest 

 importance. A pinewood box, an inch 

 thick and about 11 in. by 8 in. by 6 in., per- 

 forated at top, bottom, and sides, to allow 

 the free passage of water, was imbedded in 



