A STUDY ON TROUT AND YOUNG SALMON. 271 



curves smoothly over the eyes and precipitates itself towards 

 the nose. 



Seemngly this peculiarity is produced by the quick growth 

 of the body, the region behind the occipital part of the head 

 putting on flesh quicker than the latter. 



In the salmon on pi. II this peculiarity is only indicated. 

 In the other specimen sent me from the Bergen museum it was 

 however, more pronounced. 



In the salmon represented in PI. Ill as well as in the other 

 specimens reared in my aquarium, this feature was constantly 

 present. Also the two specimens from the University museum 

 plainly presented Iraces of the same peculiarity notwithstanding 

 that they were considerably shrivelled up from being kept for 

 years and years in spirits. 



This rounded forehead, the small short nose, the drooping 

 upper jaw and the small mouth gives a much more „beaky" 

 appearance to the face of the salmon than that of the trout. 



The arch of the forehead seems to get less pronounced, as 

 the salmon approaches the grilse stage. In a specimen 39 cms. 

 long caught in the Skagerrack off Ghristianssand only faint 

 traces of the arch are present. It seems to disappear as the nose 

 gets more developed. This seems to take place from about 30 

 cm. length and upwards. 



The difference in the length and slenderness of the tail is 

 at once obvious upon closer examination of Pis. II and III, and 

 as regards the variation of the slenderness in the two species 

 I refer to tab III and my previous comments. 



From the figures of the above-mentioned plates it will also be 

 seen that the relation between length of anal fin and length of 

 tail is utterly different in the two species. The anal fin of 

 the salmon is also proportionally smaller than is that of the 

 trout. Tab II and my comments on this table will sufficiently 

 illustrate the relation between the length of anal fin and length 

 of tail. 



