258 KNUT DAHL. 



throughout development the fish have been classified in 3 stages: 

 1) fishes of a smaller length than 16 cm. (including the largest 

 emigrating smolts, 2) fishes between 16 and 50 centimetres long 

 comprising in the case of the salmon, mainly the "missing 

 stages", 3) fishes above 50 cm. (the sizes of salmon common 



by caught). 



A == The number of scales in the oblique row of scales from the posterior 

 base of the adipose fin up to and including the scale on the lateral 

 line. 



B = The altitude of the anal fin o: the distance from the base of the 

 first ray of the anal fin to the point of the longest ray of the 

 same fin. 



C = The length of the tail, measured from the posterior base of the anal 

 fin to the sharp heel formed by the first auxiliary rays of the cau- 

 dal fin. 



D = The minimum altitude of the tail. 



This classification has been adopted mainly on account 

 of the salmon. In order to produce the correctest possible com- 

 parative representation of the alterations during development, 

 corresponding annual classes of both species ought to have been 

 compared. 'However this has been impossible. 



From the figures thus obtained I have represented graphi- 

 cally the course of the abovementioned 3 characters in the two 

 species compared. (Vide Tab. I — III). Every in these tables 

 denotes an individual examined. The Ordinales respectively 

 represent the number of scales, figures for Tail-coefficient I, 

 figures for Tail-coefficient II. From these tables it is evident: 

 1) That the scales of the salmon are larger than those of the 



trout. 



