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 
