FOOP FOR YOUNG SALMONOID FISHES. 849 



sweeping away the original lots. The result was that in the case of the fibrine 

 fish the rescue effected essentially nothing, having apparently come too late; 

 but in the aquarium-cereal lot 48 were saved up to October 19, out of the original 

 100 taken out in August, or 48 per cent ; while of those left to their fate with the 

 aquarium-cereal food only 4 were saved during the same period out of 207, or 

 2 per cent. 



In the cases of the lots fed on Spratt's foods and liver on alternate days, 

 the mortality was not excessive, being only 7 per cent in the fibrine lot and 12 

 per cent in the other. 



It remains to see what effect the Spratt's foods had on the growth of the 

 fish receiving them. As none of the dead fish picked out from time to time was 

 weighed or measured, we can only note the weight attained by the survivors, 

 remarking, however, that the dead fish taken out from time to time were, judg- 

 ing by the eye, never larger than the average of lots from which they were taken, 

 and were generally smaller. All of these weighings were done in the usual way 

 in water, except the smaller numbers, 14 and less, which were weighed singly 

 on a delicate balance. The weighings showed that the 4 survivors of the lot 

 (1939K) beginning the fibrine food June 30 weighed, October 19, on the average, 

 24.1 grains (155 centigrams) and the lot (1939L) that was given liver till July 20 

 and fibrine afterwards averaged 21.7 grains (140 centigrams). These are to be 

 compared with the average weights of the fry of the two control lots (19392^ 

 and 19392^), whose average, October 9 and 10, was 72.6 grains (470 centigrams) 

 and 82.6 grains (535 centigrams), respectively; and it appears that the survivors 

 of the Spratt's food regimens had made only from one-fourth to one-third of 

 the normal growth, notwithstanding the fact that they had enjoyed from August 

 16 to October 19 a greatly enlarged area of trough room and a proportionably 

 very large volume of water. 



In growth the fish fed on Spratt's foods with liver on alternate days made 

 a growth fully up to the average of liver-fed fish, the two lots attaining 87.3 

 grains (565 centigrams) and 77.4 grains (501.6 centigrams), respectively. 



One of the most striking of the results obtained was the extraordinary 

 growth of the two "rescue" lots mentioned above — 1939K' and 1939N'; the 

 first of these, numbering at the October counting only 5 fish, had by that date 

 acquired an average weight of 15S.5 grains (1027 centigrams), and the other, 

 numbering 48, an average weight of 154.9 grains (1003.7 centigrams). These 

 weights are almost unparalleled in the station records of trough-reared fish. It 

 is more than double the weight attained by the fish of the same origin fed through 

 the season on the usual hogs' plucks, as shown in the case of lots 1939Z' and 

 i939Z^ To what shall it be attributed? So far as the comparison is with the 

 ordinary feeding we may safely say that the extraordinary rate of growth during 

 this " rescue " period is the result of the increased space accorded the rescue lots. 

 One of them (1939K') had, at the beginning of the rescue period, the i6th of 

 August, when there were 15 fish, 44 square inches of trough room per fish, and 



