THE SCALES OF SALMON 107 
redds or destroy the eggs in the early and delicate 
stages. If these high tributaries, where in many 
cases the finest spawning grounds are to be 
found, are not occupied by the spring fish, it some- 
times also happens they are not occupied by the 
quick running summer fish which follow, and at the 
same time it is well known that the available lower 
spawning grounds are not infrequently occupied by 
successive runs of late fish, so that to some extent 
one set of spawners undo the work of fish which 
have preceded them by turning up gravel already 
protecting eggs. 
The kelts of the spring fish by getting away down 
stream at an early date have also a better chance 
of reaching the sea before the time at which salmon 
disease makes its worst appearance. Such kelts 
should be respected and carefully handled by any 
into whose hands they may fall. Like the bread 
cast upon the waters, they will return after many 
days. 
The observations of Mr. Hume Patterson * on the 
subject of salmon disease show that it is possible for 
an apparently healthy fish to be infected by the 
real cause of salmon disease—the bacillus salmonis 
pestis—since, if the fish has been previously diseased 
in fresh water, a sojourn in the sea, although it kills 
saprolegnia ferax, does not kill the bacillus. His 
observations also show, however, that the entrance 
of the bacillus to the tissues of the salmon is most 
readily gained when fish are injured and sickly. 
The organism itself has been found in river water, 
+ “ The Cause of Salmon Disease,” Fishery Board for Scotland, 1903. 
