VARIED TIME OF INCUBATION. 35 



of keeping the spawning-boxes particularly clean. Should 

 any film, from the nature of the spring water, form therein, 

 it is advisable to take a hair-broom and sweep carefully 

 and lightly over the shingle daily ; and, should there be 

 anything likely to impede incubation, the flow of water will 

 carry it away. 



Upon this system, trout require only fifty days for incu- 

 bation ; jack, perch, roach and dace, forty-two days ; carp 

 and tench the same time ; and as the spawn of the two 

 last-named fish is deposited near the surface of the water, 

 they are bred in ponds, but they may be removed to 

 streams, where they thrive. In trout-streams, where the 

 water is almost all spring, it is absolutely necessary that 

 some provision should be made for feeding this fish, espe- 

 cially where there are no larvae or insects ; and this can 

 only be done by breeding coarse fish in the streams, or in 

 ponds or stews, so formed that they can be emptied into the 

 stream, or the stream be let in, and wash them out, at in- 

 tervals. In the North of Scotland, I understand that the 

 trout of some lakes and streams are in season not more 

 than two months out of the twelve, and that this is owing 

 entirely to their want of proper food ; and where this is 

 the case the larger fish prey upon the spawn-beds, or chase 

 the smaller, so that over-exertion keeps them lean and out of 

 condition. Reverse this order of things by artificial feed- 

 ing, and what is the result ? an enormous increase of pro- 



