174 THE TROUT 



hatching-house, and leave the running water to per- 

 form the work of incubation. If your hatchery is 

 thoroughly secure against intruders, it is not necessary 

 to close the lids of the boxes. The tray-covers will 

 afford sufficient protection against a stray mouse. 



Your labours during the hatching stage will not be 

 very arduous. You must, however, inspect the boxes 

 daily to make sure that the water is continuing to flow 

 properly, and to remove any dead eggs. A bad egg is 

 easily recognised by its milk-white colour, and unless 

 it is quickly taken out, the ova which lie in contact 

 with it will decay, and, if the mischief is not arrested, 

 a form of fungus called byssus will eventually appear 

 and spread devastation far and wide. The injurious 

 effect of a rotting trout egg in a hatching-box has been 

 aptly compared to the mischief which one decaying 

 peach will communicate to the good fruit which lie 

 close to it in the same basket. 



In the old days, when the ova lay concealed from 

 view under gravel, it was very difficult to ensure the 

 removal of every dead egg. Byssus was then a real 

 danger, but with a modern system of incubation on 

 trays or grilles none of the eggs can long escape 

 observation ; nor should the scourge of byssus ever 

 afflict you except as a penalty for very serious 

 neglect. 



