A STUDY ON TROUT AND YOUNG SALMON. 261 



Examination of the 3rd relation as represented in tab. ITI 

 (Tail-coefficient II) will yield a similar result. 



None of these relations detached from the others whose 

 course has just been described, or from the other, „habitus"- 

 characters of the fish suffice as a fundamentally safe diagnosis 

 embracing all cases. 



If however the course of these 3 relations of form or 

 character is examined in the isolated individual, they will be 

 found, if compared with other characteristics, to present a valuable 

 support to specific determination. 



The youngest group (below 16 cm.), belongs to the stage, 

 where these 3 relations are most similar in the two species. 

 However, other body relations yield destinctions so pregnant 

 and so easily observed, that there never is any doubt as to 

 which species the individual in question belongs. 



An examination of the large number of individuals by 

 means of which the tables (I — III) on the two older stages, have 

 been constructed, has shown that the same individuals never 

 cause the curves to meet or overlap each other in regard to all 

 three characters. As I have mentioned above, the tables show, 

 that the salmon has large scales (small scale-figure) small anal 

 fin in relation to the tail (tail longer than anal fin) and a 

 very slender tail, while these characters in the trout are just 

 the opposite. 



When the tables now show that the amplitudes of the 

 variation of these characters in the two species overlap each 

 other, we are not justified in inferring, that there needs must 

 exist individuals of the salmon species which in themselves unite 

 all the lowest values of the salmon curves or trouts possessing 

 all the highest values of the trout. The curves thus do not shew 

 that salmon exist which e. g. possess 15 scales, Tail-coefficient I 

 0,90 (anal fin longer than tail) and Tail-coefficient II 1,30, or a 

 short and thick tail. No more do they show that trout exist 

 which e. g. possess 14 scales. Tail- coefficient I 1,0 or an equally 



