4 THE AGE AND GKOWTH OF SALMON AND TEOUT. 



power, as will be seen with, a microscope by using different methods of 

 illumination. 



This difference in the appearance of the summer and winter growth on 

 the scales can be easily seen by examining them at different seasons of the 

 year, but I considered it advisable to investigate the scales of parr of 

 known age. 



From the State Hatchery at Haugsund I obtained examples of parr 

 hatched in April, 1907, reared there and finally killed in the middle of 



FIG. 2. Parr 13 cm. Haugsund. 

 Hatched April, 1907. Killed 

 middle of December, 1908 

 (magnified). 



FIG. 3. Parr 13 cm. Haugsund. 

 Hatched April, 1907. Killed 

 middle of December, 1908 (mag- 

 nified). 



December, 1908. These fish had, therefore, lived for two summers and a 

 portion of the second winter. The accompanying figures (Figs. 2 and 3) 

 show the scales of two of them. It will be seen that the structure of the 

 scales corresponds fully with the seasons during which the fish have lived. 

 In the centre of each we find a growth-zone, consisting of relatively unbroken 

 broad rings corresponding to the first summer. Surrounding this we find a 

 band of narrow branching rings depicting the slackened rate of growth 

 during the first winter. Then again surrounding this inner core we find 

 similar growth-zones corresponding with the second summer and half of 



