108 BRITISH SPORTING FISHES. 
No member of the migratory or non-migratory 
Salmonide will spawn either upon mud or sedi- 
ment. But, unfortunately, they do this sometimes 
ere the deposit is thrown down. Then what 
ensues? Protect the stream as you will from 
heron, duck, and waterfowl, and from 1,000,000 
eggs with which the stream is spawned, not more 
than a very small percentage of fry will come forth, 
The spawning-beds of rivers must be pure and 
clean, else no successful hatching can take place. 
Where solid matter is held in suspension over a 
spawning-bed the eggs are suffocated, and any few 
that may escape usually turn out to be deformed 
fish. This is owing to the clogging of the outer 
wall of the cell-sac, which interferes with the equal 
absorption of oxygen from the water. Therefore, 
where this sort of pollution exists, the absolute 
extinction of trout is certain at no very distant 
date. 
Of late years disease has played terrible havoc 
in some of the best northern streams. In one 
river I could name, scarcely a fish can be caught 
which does not show in some way marks left 
by disease—want of tail, partial loss of fins, 
white patches on the skin, where the fungus has 
previously grown. That numbers of the fish 
attacked do survive there can be no question; 
and that the disease may be prevented at the cost 
of a few fish I have but little doubt. In these 
