44 BRITISH FRESHWATER FISHES 



growth seen in a transverse section of the stem of 

 a woody plant ; during the summer the Salmon 

 feed more freely and grow more rapidly than in 

 the winter, and the scales increase in size by the 

 addition of a number of rings which are rather far 

 apart, whilst the winter growth is represented by 

 fewer rings closer together ; when the fish are in 

 fresh water the scales do not grow, but their edges 

 become more or less worn and irregular, especially 

 at the shrinkage in girth which follows the spawn- 

 ing, and when the kelts reach the sea and scale 

 growth recommences, the irregular line of the 

 former edge is usually clearly seen and is called 

 the spawning-mark. 



In order to show the application of this method 

 I give on PI. V figures of the scales of a Smolt 

 (A), a Grilse (B), and a Salmon which had spawned 

 in the season previous to its capture (C). In all 

 three it will be noticed that in the exposed posterior 

 part of the scale the lines of growth have disappeared 

 or are inconspicuous, whilst the remainder is mapped 

 out more or less distinctly into broader zones of 

 summer growth and narrower zones of winter 

 growth. The smolt scale (A) is from a fish 

 caught in May, and shows the rings formed during 

 two complete summers and winters, and the third 

 summer's growth just beginning. That of the 

 grilse (B), from a 3 -lb. fish taken in July, is less 

 highly magnified, and shows the great increase 

 caused by a summer and winter's sea-feeding 

 (between the points marked 2 and 3) and by half 

 a second summer in the sea (external to 3). 



The third scale (C) is from a 20-lb. Salmon 

 captured in March ; this fish spent two years in 



