30 FISH CULTURE. 



stream without being either boiled or undergoing 

 some other process to destroy the animal and vege- 

 table life existing among it, it is impossible to pre- 

 vent insects from being placed in the boxes with it, 

 as their eggs and larvae are mixed with and laid in 

 the gravel itself. When the gravel is transferred to 

 the boxes these eggs and larvae in the course of time 

 are hatched, and many of the insects immediately 

 commence preying on the ova. Mr. Ffennel, the 

 Inspector of Salmon Fisheries, found this a very 

 considerable source of damage to the stock of spawn 

 which was deposited in the experimental boxes at 

 the Custom-house in Dublin.' The best way, there- 

 fore, to meet this evil is to boil the gravel for about 

 an hour, and then to wash it thoroughly in a sieve 

 before depositing it in the boxes. 



' Mr. Brown, in hie admirable little work on tlie "Natural History 

 of the Salmon," as elicited by the Stormontfleld operations, also 

 bears testimony to the great destruction caused amoitgst the oTa by 

 the larva of the may-fly and by certain water-beetlea. 



