198 How to obtain it. 



excessive numbers in cases of hybridization. Otherwise, the 

 affected fish are not numerous, and as there seems to be nothing 

 infectious about it, it is not to be much dreaded. I have tried 

 many experiments with it, and out of a large number of fish whose 

 sacs were carefully punctured only one recovered. Seth Green 

 was also successful in performing the same operation, but I 

 question whether anything is gained by it beyond the knowledge 

 that it can be done, as such fish will probably never live to grow 

 up, owing to inherited weakness of constitution. 



A few others among the alevins will also die from constitu- 

 tional weakness, although they may not have developed the "blue 

 swelling." They are, however, like any other weakly animals, 

 ready to develop anything that surrounding circumstances may 

 favour, and amongst others will often exhibit inflammatory 

 symptoms. Sometimes they are attacked by fungus (sapiolegnia). 

 Every precaution ought to be taken to guard against it, and this 

 being done, fungus ought to be unknown amongst alevin trout. 

 The great safeguard to be employed is the same as for the eggs; 

 have all woodwork that comes in contact with the water well 

 charred. One of the worst features of fungus amongst young trout 

 is that it frequently attacks the best fish. Next to uncharred wood, 

 nothing is so likely to .bring it on as dirty hatching or rearing 

 boxes. These should always be kept perfectly clean. I have 

 already pointed out the necessity for this during the period of 

 incubation, and repeat the warning now as it is of the utmost 

 importance. 



A very sharp look-out should be kept, and should fungus 

 make its appearance from any cause, an application of sea water 

 will do good. Where this is not easily obtainable, a dose of 

 chloride of sodium or common salt will prove beneficial. Or a 

 piece of rock salt may be placed in the water at the intake. It 

 will have the effect of making it slightly saline, and this kills the 

 germs of the fungus and also the plant itself. The amount re- 

 quired depends so much upon surrounding circumstances that it 

 is difficult to lay down any fixed rules as to quantities, but for 

 a hatching box twelve feet long by nine inches wide, five or six 

 pounds of common salt is not at all too much. It may be in- 

 troduced by simply placing it in the inflowing current. Of course 



