THE SCALES OF SALMON 97 
ridges are few and closetogether. The result is that 
each summer and each winter leaves its indelible 
trace on the scale. 
In the case of the salmon the same is true, and in 
addition there are periods when, through the for- 
saking of the sea for fresh water, where no regular 
nourishment of the body takes place, a complete 
cessation of scale growth results. Also, when 
spawning has taken place, with its consequent 
shrinkage of the body girth in the kelt, a record— 
called the “spawning mark ”—is stamped upon the 
scale, due in part to the apparent fraying of the 
scale edges and in part to the healing or mending 
of their frayed edges when feeding is recommenced. 
The spawning mark is therefore analogous to the 
“scar tissue” of pathologists. 
But there is in all cases a certain irregularity in 
the amount of growth, due directly to the varied 
amount of feeding. Even parr and smolts show 
differences in the number of ridges added at similar 
times. A parr growing in a river which flows through 
richly wooded country, and which has water of a 
comparatively high temperature, receives many more 
chances of food than the parr growing in the rocky 
stream of some cold mountainous district. Never- 
theless, the number of ridges in each period of 
life is found to be the safest guide to the under- 
standing of the growth, the separation of summer 
and winter areas being at the same time clearly kept 
in view. 
In Mr. Johnston’s second paper (loc. cit.) several 
tables are given showing the number of lines of 
G 
