THE TROUT 57 



vice versa. The distribution of the Trout is 

 sufficient evidence that the migratory and non- 

 migratory fish are not distinct species, nor even 

 races ; there are no true freshwater fishes Roach, 

 Perch, etc. in the Hebrides, Orkneys, or Shetlands ; 

 yet in these islands every river and loch is full of 

 Brown Trout, which is only to be explained by the 

 supposition that the latter have been derived from 

 the Sea-trout, which have lost their migratory 

 instinct in different places and at different times. 



In adult Sea-trout the maxillary extends well 

 beyond the eye, and the caudal fin, when widely 

 spread, has the free edge straight or even convex. 

 The coloration is silvery, with the back bluish, 

 and with rounded or X-shaped blackish spots on 

 the upper part of the body, usually more numerous 

 than in the Salmon. The males differ from the 

 females in that the whole head, but especially the 

 snout, is longer and the jaws are stronger; in large 

 males the lower jaw is usually hooked upward at 

 the tip, especially in the breeding season, but never 

 to the same extent as in old male Salmon. A 

 comparison of the figures of the heads of old male 

 Salmon (PI. Ill) and Sea-trout (Fig. 9) and of 

 the illustrations of Salmon parr (PL IV) and grilse 

 (PI. II, Fig. 2) with those of Sea-trout (PL VI) 

 will enable the reader to form a clear idea of the 

 differences between the two species. 



Two races of Sea-trout may be recognized, 

 although in many cases it is impossible to say 

 to which race an individual fish may belong unless 

 one knows beforehand where it comes from. How- 

 ever, the Sewen (S. cambricus) of Wales, Ireland, 

 and our western coasts often differ from the Sea- 

 5 



