A STUDY ON TROUT AND YOUNG SALMON. 



Two courses of reflection have in this connection strongly 

 asserted themselves. 



One has forced me to effect the strongest possible control 

 as to the correctness of my specific determinations. 



The other has urged me to endeavour by positive results 

 to illustrate the real habitat of the young salmon in the missing 

 stages. 



When I have not been able to find those stages of the 

 salmon, which a number of other scientists have described, this 

 fact would clearly seem to contain a contradiction fatal to the 

 correctness of my investigations, and this chain of thaught 

 caused me to begin with no small amount of trouble. 



When I laid before me a collection of salmonids, it was 

 by no means difficult, the works of systematical authors (f. ex. 

 Liljebofg) in my hand, closely to distinguish the young of 

 salmon and trout up to 16 cm. in length. No more did the 

 distinguishing between salmon and trout above 45 — 50 cm. in 

 length occasion the least difficulty. However, if I laid before 

 me fishes between 24 — 40 cm. in length, I found to my great 

 astonishment that they ad libitum might be determined as sal- 

 mon or trout and that on the strength of the printed descriptions 

 by the different authors. In other words mere judgement appa- 

 rently had to decide. It also seemed to me as if mere judge- 

 ment must have formed the base of the diagnostic description. 



I laid before me seperate series of these two species in their 

 different stages avaibable to me In one species i. e. : the 

 trout, I could follow it through its developement through all 

 sizes from 10 — 40 cm. and more. In the salmon, quite contrary 

 to the trout, the series was broken at 16 cm,, and could not 

 be continued befoj'e a length of 45 cm. was reached. 



Those very pregnant characters, distinguishing the young 

 of the salmon (parr and smolts) from those of the trout, were 

 found suddenly at 16 cm. length to cease. 



