THE COMMON TROUT. 305 



it is very marked) ; jaws nearly equal ; the posterior extremity of 

 the maxillary reaching beyond the orbit. Teeth sharp and stout, 

 slightly curved inwards ; about thirty in the upper jaw, twenty-four 

 in the lower, twelve on each palatine, ten on the vomer, and eight 

 on the tongue. Scales small and adherent ; flesh white ; caeca forty- 

 two.* Number of fin rays — 



1st D. 14 ; P. 13 ; V. 9 ; A. 11 ; C. 18 ; « Vertebrae 56." 



Trout are liable to much variation as to colour,-f- which 

 seems greatly to depend on the situation and the waters 

 they are accustomed to inhabit. Thus if one of these fish 

 be taken from a small burn, running over a peaty soil, 

 shaded by high banks, or overhanging trees, it will be 

 found almost invariably of small size, seldom exceeding the 

 weight of half a pound ; with the head large in proportion, 

 the belly, back, and sides, of a dark colour, and in some 

 instances assuming a perfect black. If taken from a river 

 overgrown with weeds, and flowing through a mossy dis- 

 trict, it will be found marked with large black spots, placed 

 in a pale circle, the back dark, and the sides shaded with 

 green. But when newly taken from a translucent stream, 

 which glides over a sandy or gravelly soil, it is found to be 

 exquisitely beautiful ; the head and back of an olive brown, 

 the spots clearly displayed, and the sides tinged with the 

 most brilliant orange and gold. It is perhaps owing to these 

 variations in colour, that many species of trout are said to 

 exist. k< One cause of the variation is the difference of food, 

 and, according to every information we possess, those which 



• In those trout which inhabit highland streams, I have never found the 

 number of caeca to exceed forty-six, the average number being forty-two. 



+ See Observations and Experiments on the Colour of Fishes, by Dr Stark, 

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



In the Tweed I have frequently observed a singular variety of trout, 

 which is considered by the fishermen as the young of the bull-trout. Ge- 

 neral length about eight inches; vomerine teeth nine ; pectorals of an orange 

 colour ; anal pure white ; anterior part of the dorsal with a dark band (as 

 in S.fario) ; and the extremity of the caudal fin is margined with black. It 

 is found in the month of May in company with the you n g of the migratorv 

 species. 



VOL. VII. U 



