42 GREAT INCREASE OF WEIGHT IN JACK. [PART I. 



external air for the purpose of respiration. By 

 adopting this mode of carriage he never loses 

 five pounds weight out of three thousand pounds 

 transported. 



The effect which such a change has upon 

 Jack appears to be most remarkable, the increase 

 in their weight, after removal, being in some cases, 

 at the rate of not less than from eight to ten 

 pounds a year. In the year 1856, for instance, 

 Mr Maltby marked and transferred from the large 

 lake of Boilsfut to that of La Hulpe, forty-five 

 Jack, averaging one with another two pounds 

 each; none of them weighing more than three 

 pounds. In eighteen months from the time 

 when they had been thus transferred, many of 

 these same fish were caught by trolling, having 

 attained the weight of from fifteen to twenty 

 pounds, being at the extraordinary rate above 

 mentioned. 



This increase in the size of the Jack was so 

 sudden and unexpected, that nearly all the smaller 

 fish were destroyed by them, before any steps 

 could be taken for their removal. It was however 

 then effected by letting out the water, when the 

 Jack were placed in one of the smaller ponds 

 above mentioned. In this however, although it 



