266 KNUT DAHL. 



their bellies and prop themselves up on their broad pectorals, 

 while the trout as a rule remain helplessly sprawling on their 

 sides< 



Respecting the size of the scales in salmon and trout be- 

 longing to this stage vide tab. 1 and my previous remarks 

 upon this subject. 



The colours and their destribution and patterns in my 

 opinion, afford considerable support in distinguishing between 

 salmon and trout in the emigration stage. 



When leaving the river in this stage of developement both 

 species possess a shiny silvery coating over the underlying fry or 

 parr-colours. This coating may be more or less pronounced, 

 the colours of the parr being more or less plainly seen 

 through or being only distinguishable at certain angles of light. 

 As a rule however, the colour patterns show very plainly. 



Generally the young salmon is more intensely silver coloured 

 than the trout and the silvery hue is mixed with a remarkably 

 beautiful mother-of-pearl tinge. 



The silvery hue of the young trout is mixed with a more 

 yellowish- sometimes copper-coloured tinge. 



The main undercolouring consists in the salmon, of a blueish- 

 green pigment. In the trout this pigment is more brownish or 

 brownish-green, with a hardly perceptible blue touch. When 

 the fishes are kept in a weak solution of formaline, the pig- 

 ment of the salmon turns blueblack, that of the trout more 

 greyish brown with a weak blueish touch. 



The distribution of the pigment is very different in the two 

 species. 



In the salmon the back is greenish blue with a few black 

 spots. This pigment reaches down the sides and the tail of the 

 fish, arranged in several (8—12) scallops or flukes contrasting 

 strongly with the pure white of the ventral parts of the 

 body. 



