12 THE AGE AND GROWTH OF SALMON AND TROUT. 

 ANALYSIS OF 75 SALMON FROM FLEKKER# AND RANDBSUND, 1909. 



and rings. Up to the present these scales have received but little attention,, 

 and they have generally been depicted and described as scales with 

 " expanded growth centres." As a matter of fact they are scales which 

 have been formed in place of those which have been lost.* As has been 

 previously pointed out, the growth rings are formed only on the outer edge 

 of the scale and on the outer surface. It is therefore evident that when a 

 scale is torn off or lost rapid growth of an indeterminate nature takes place, 

 and fills up the original scale pocket which acts as a matrix, and afterwards 

 the formation of the ordinary ring-growth takes place around the circum- 

 ference of this inner plate of indeterminate growth. From that time onwards, 

 the ordinary ring-growth proceeds in like manner to that which is being 

 simultaneously added to the other scales. At the same time the scale 

 pocket or matrix of every scale on the fish is simultaneously increasing in 

 size. It will be evident that this is the case if we examine a scale, the- 

 central portion of which has at some period of the fish's life been displaced 

 without being actually lost. The accompanying drawing (Fig. 13) shows 

 an example of this. 



The illustration shows the central portion of the scale of a full-grown 



* Attention was drawn to this point by Mr. Hutton in his last paper. 



