THE FISHES OF THE FRITH OF FORTH. I53 



stead of two species only inhabiting the British waters, there are in reality seven ; 

 the characters of which depend on the structure of their internal organs, the 

 number of scales, and the form and arrangement of the lateral spots. The teeth 

 in the vomer of the migratory trout cannot be depended on as a character except- 

 ing in fishes of a certain size, for when they are eight inches in length the whole 

 vomer is armed with teeth, and when they exceed nine pounds in weight, the 

 vomer has never more than three teeth, and frequently has only one ; the num- 

 ber of teeth depending on the age of the fish. 



Salmo albus, Dr Fleming. — Hirling or Whitling. Common. In the Frith of 

 Forth never taken, owing to the meshes of the salmon-nets being too large for 

 their capture. Many naturalists, as well as most practical fishermen, consider 

 the hirling as a distinct species of trout. It is said never to exceed a foot or 

 fifteen inches in length, having a dark back, silvery sides, and a forked tail. Last 

 summer, with the view of examining these fish more minutely than had hitherto 

 been done, I remained several weeks on the banks of the Solway Frith, where I 

 had an opportunity of inspecting several hundred specimens as soon as they were 

 taken fi'om the nets. After carefully dissecting two hundred specimens, and find- 

 ing them to differ exceedingly from one another, in their anatomical structure, in 

 the number of scales, in the colour of the flesh, and in the form and arrangement 

 of the lateral spots, I came to the conclusion, that they are not a distinct species, 

 but the young of different species of trout, which, if allowed to remain uncaught, 

 would increase to six or even eight pounds in weight. 



Every British species of migratory trout less than fourteen inches in length 

 has the tail deeply forked, and, as the fish increases in size, the middle rays be- 

 come elongated, so that, by the time the fish reaches the weight of nine pounds, 

 the tail is even at the end. Colour in trout cannot be depended on as a constant 

 character, being liable to vary with accidental circumstances.* 



The natural history of the migratory trout is somewhat similar to that of 

 the salmon, but the growth of the latter fish seems to be more rapid than that of 

 the former. 



From the beginning of June to the middle of July, trout are observed to 

 leave the salt-water and ascend rivers, in search of a suitable situation to deposit 

 their spawn ; this they shed in the months of October, November, and December, 

 and when this law of their nature is fulfilled, they, like the salmon, return again 

 to the sea. In March and April the fry make their first appearance, fi^"om an inch 

 to an inch and a half in length ; in June they are found from two to three 

 inches long ; in August, September, and October, they are taken by anglers, under 

 the name of Parrs, from four to five inches in length. In December they are 

 somewhat larger, and in April and May the following year, they make their first 



* Stark in Edin. New Phil. Jour. Oct. 1830, p. 327, 

 VOL. XIV. PART I. U 



