THE SCALES OF SALMON 97 



ridges are few and close together. 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 



Q 



