THE BLACK-FIN AND ORANGE-FIN SMOLTS 213 



points I pretend not to accuracy ; still there was nothing 

 about their growth to favour the idea that they could 

 possibly, during that season at least, acquire the dimen- 

 sions of the whitling, or even full-grown finnock. A 

 subsequent capture, made at noonday, of fourteen of 

 these fish, on the same part of the coast, namely, about 

 a mile to the west of the Nairn water, aided in confirm- 

 ing this idea. I may mention, however, that in July I 

 caught fish, evidently of the same hatching, in the Nairn 

 water, on their ascent in the shape of small finnocks, 

 none of which exceeded half-a-pound in weight. Although 

 the smolts captured by me were all orange-fins, they were 

 pronounced by the tacksmaii's overseer to be salmon- 

 fry. I am convinced, however, that he was in error, and 

 led into it possibly by the fact, that by far the greater 

 portion of the smolts descending Nairn in spring are of 

 the first-mentioned description, the black-fins being 

 comparatively rare, although both salmon and grilses 

 frequent the river in considerable numbers. 



I was certainly for a long time puzzled by this expe- 

 rience regarding the slow marine growth of the orange- 

 fin in comparison with that of the black-finned smolt ; 

 the more so, that in fresh water, before the general 

 descent of the fry in April, the former is evidently of 

 quicker growth than the latter j and I concluded, very 

 naturally, that the general opinion, in respect to the 

 rapid transformation of the black-fin into the grilse was 

 quite erroneous. A circumstance, however, connected 

 with the conformation of the parr before assuming the 

 smolt garb, has urged me to come to a very different 

 conclusion. It is simply this, that in the male parr the 

 generative capacity is found fully matured ; in the female 

 parr, the roe-layers, although in an incipient state, are 

 also distinguishable. The forwardness in the case of 



