KNUT DAHL. 



lateral line. Small black spots are scattered over the back and 

 the sides of the body. 



The dorsal fin has the colour of the back. 



The adipose fin as a rule is orange-coloured. 



The caudal fin is as a rule yellowish-brown, semi-transparent. 



The anal fin is mostly yellowish-brown with blackish fore- 

 part and a creamy streak along the first ray. 



The ventral fins are whitish-yellow-brownish and the pectoral 

 fins have the same yellowish-brown, semi-transparent colour as 

 the caudal fin. 



The different colours however, may vary a good deal ac- 

 cording to the locality. 



Even the size will afford some aid in distinguishing the 

 two species in the emigration-stage, the salmon according to my 

 experience in northern rivers only exceeds 13 cm. in length in 

 one case in a hundred, while the trout in this stage not rarely 

 reaches 18—20 cm. in length. (Vide Tab. IV and V). 



f. Description of young salmon in the oceanic stage, 

 compared with trout of the same size. 



After the young salmon have left the rivers the characters 

 gradually undergo considerable changes. 



This is also the case with the trout, although the changes 

 in this species are not quite as great as in the salmon. 



Judging from my aquarium experiments these changes 

 cannot be said not to occur when the fish reaches any certain 

 or fixed length. They are evidently dependent on the time of 

 emigration, no matter whether the fish belongs to the largest 

 or to smallest of the sizes peculiar to the emigration stage. 



Only gradually and during a long lapse of time do the fishes 

 lose their juvenile characters. Thus one may very well meet 

 salmon individuals of the same size, some presenting many 

 juvenile characters, while others of the same size may present 



