76 Appendices to Twenty-fifth Annual Report 



periods are appended. At 11.45 a.m., that is about an hour after the 

 fish were put in, and when the specific gravity was reduced to 16*4, the 

 larger of the fish was found to be lying on its side, and both exhibited 

 signs of distress. An hour later it had recovered its poise. In the 

 afternoon of the same day, when the specific gravity had been reduced 

 to 05-4, 03-2, and 02-8 (the temperature being 54-3° F.), the lice 

 were still to be observed on them. The next morning at 7 a.m., when 

 the water was quite fresh, there were still a few lice on the fish ; and 

 one or two continued to be observed on them for some days. One was 

 noted on the 4-lb. fish till the 6th July, clinging behind the anus; on 

 the following day (7th) one still clung to the shoulder of the other 

 specimen, but on Monday, 9th, all had dropped off, and a number of 

 them were found on the bottom of the tank. On the 10th the fish were 

 removed, and were found to have lost, together, about a pound in 

 weight, according to the observation of the salmon fishermen. 



The experiment shows that the parasites may cling to the fish for a 

 considerable period, in purely fresh water ; and that they differ very 

 considerably in their power of resisting its influence. From the 

 distress exhibited by the fish, and the loss of equilibrium of one of them 

 in the early part of the experiment, it appears that the change from 

 the sea water to fresh water was made too rapidly ; and the inference is 

 that the passage of a fish from the one to the other under natural con- 

 ditions would take longer, and probably much longer. 



The following table gives the particulars as to specific gravity and 

 temperature at different periods throughout the experiment : — 



Date. 



Hour. 



Sp. Gr. 



Temperature. 









c. 



F. 



2nd July. . 



10.30 a.m. 



1027-6 



11-6 



52-9 



11.45 „ 



1016-4 



120 



53-6 





12.45 p.m. 



1011-6 



12-0 



53-6 





1.45 „ 



1008-2 



12-2 



54-0 





2.45 „ 



1006-0 



12-4 



54-3 





3.45 „ 



1005-4 



12-4 



54-3 





4.30 „ 



1003-2 



12-2 



54-0 





8.15 „ 



1002-8 



12-4 



54-3 



3rd „ . 



7.0 a.m. 



10000 



12-4 



54-3 





4.15 p.m. 





13-0 



55-4 



4th „ 



7.0 a.m. 





12-8 



55 0 





3.0 p.m. 





13-2 



55-8 



5th „ 



7.0 a.m. 





13-0 



55-4 





10.0 „ 





13-0 



55-4 





2.0 p.m. 





13-4 



56-1 





4.45 „ 





13-3 



55-9 



6th „ 



7.0 a.m. 





13-3 



55-9 





10.0 „ 





13-2 



55-8 





1 2 noon 





13-3 



55-9 





4.30 p.m. 





13-3 



55-9 



7th „ 



7.0 a.m. 





13-8 



56-8 



10.0 „ 





13-2 



55-8 





1 2 noon 





14-0 



57-2 



9th „ 



7.0 a.m. 





14-6 



58-3 





10.0 „ 





14-6 



58-3 





12 noon 





14-8 



58-6 





4.30 p.m. 





15-2 



59-4 



T. Wemyss Fultox. 



