METHODS OF INVESTIGATION. 13 



salmon. We see the two years comparative poor growth in fresh water, 

 and surrounding the second winter-band a few of the broad rings are shown 

 which were formed in the richer feeding ground of the sea during the first 

 summer after migration. Shortly before the innermost winter growth was 

 completed, during the first year of life in fresh water, the scale must have 

 been pushed backwards and sideways, and thus displaced from its original 

 position. The posterior edge of the scale has been worn away or re-absorbed, 

 and has, as it were, adjusted itself to the shape of the original scale pocket 

 or matrix. In that portion of the matrix left empty by the displacement 



FIG. 13. Salmon, 70 cm. long, 3'9 kilos. Mandal, June 29, 1909 (magnified). 



of the scale we see that no regular ring- formation has taken place, but it 

 has been filled up by growth of an undefined and indeterminate nature, 

 corresponding to the blank space previously occupied by the anterior 

 portion of the scale. Outside this growth ring-formation has proceeded 

 in the normal manner. If the scale had been lost the whole of the 

 space within the matrix would have been filled with indeterminate and 

 abnormal growth. 



The occurrence of such scales is not, however, of importance, provided 

 that one is aware of their existence, and care is taken to select for examination 

 only such scales as have perfect centres. 



