260 KNUT DAHL. 



The material measured by me however, has not been large 

 enough to allow of this method. 



The abovementioned facts seem to me to show clearly, that 

 any characteristic body relation in these two species might have 

 been treated in the same manner and would have yielded similar 

 curves of variation. By way of example we have now seen 

 how some specific characters apply to the species in general. 



I have previously given prominence to the fact that the above- 

 mentioned investigations are not intended to establish characters 

 which might be expressed by figures or formulae and separately 

 employed in determining the species of a given individual. In 

 itself, this would be unnecessary, because the accurate specific 

 distinction of all the individuals on which these tables are 

 prepared, must needs have been known previous to my investi- 

 gations on the variation of the different characters in the 

 two species. 



Thus none of the characters investigated, has separately 

 been fundamental to my distinction; but. the sum total of these, 

 in addition to many other characters I have before called „habitus" 

 has in all cases enabled me to distinguish the two species. 



Supposing that we tried to determine the species of an 

 individual solely by means of one of the 3 characters whose 

 variai ion has been investigated, e. g. the scale fugure. By 

 examining table I we find, that an absolutely certain determination 

 is in a large number of cases possible. Just as large a propor- 

 tion however, leaves room for doubt. 



If we examine table II (Tail-coefficient I) we find that a fish 

 belonging to the youngest group is only in about half the cases 

 with certainty determined by the value of Tail-coefficient I. 



As regards the two older groups it will be seen that the 

 curves run almost quite separated. Consequently the species of 

 a fish may in the great majority of cases be determined solely 

 by the value of this character, when the fish is not smaller 

 than 16 cm. in fact neither a parr nor a smolt. 



