The Salmon 69 
the number of rings one must be careful to remember that while grilse 
and salmon are in fresh water no addition to the number of rings takes 
place. On examining the scale carefully where the new rings join on 
to the old, we find a dark line round the plain part of the scale. This 
is where the new ring begins. 
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Fic. 65.—10]bs. 19th February 1907. 
During winter, when the fish is in the sea, the rings become con- 
tracted, and this is caused, I think, by the food-supply becoming scarcer 
during the cold weather. This dark mark must not be confused with 
the dark mark that is made while the fish is in fresh water, caused 
by the breaking of the scales, which takes place every time the 
fish returns to fresh water, and is afterwards clearly shown on the 
scale. It is, however, seldom seen more than three times. Every 
