54 THE SEA-TROUT 



of a general resemblance to one another that occasionally it happens 

 that doubts arise as to the species of an individual. It may therefore 

 be of some service to put on record here such marks of structural 

 distinction between the species as have been found to be generally 

 constant and more or less easily recognisable. To contrast, then, 

 S. salar with 5. tniita : — 



" Of characters which distinguish Salmon from Trout," Mr. Regan 

 says, differentiating broadly, it will be observed, between salar and 

 India, " we may note that the dorsal fin has usually more rays (lo, 

 exceptionally 9, to 12 branched rays in the Salmon, 8 to 10, excep- 

 tionally II, in the Trout), and that the scales on the tail are larger, in 

 an oblique series from the posterior edge of the adipose fin downwards 

 and forwards to the lateral line numbering 10 to 13 in the Salmon, 13 

 (exceptionally 12) to 16 in the Trout." These figures, Mr. Regan 

 explains, are based on an examination by him of more than a hundred 

 examples of each species, and he states that these numerical differences 

 are of special importance because they are not subject to change with 

 the growth of the fish. It may occur to the reader that if the salmon's 

 branched rays range between 9 and 12 and the trout's between 8 and 1 1, 

 any fish that possesses 10 may, for aught anybody can tell, be either a 

 salmon or a trout, especially if it has at the same time 13 scales in the 

 oblique line indicated, which, according to Mr. Regan, either species 

 may have. But of course there are other features which help to supply 

 corroborative evidence, in doubtful cases, for one opinion or the other. 



" In a Salmon," continues Mr. Regan, " the tail is more constricted 

 at the base of the caudal fin than in a Trout, and consequently the 

 anterior caudal rays form more of a shoulder, so that a Salmon does not 

 slip through the fingers when grasped round the caudal peduncle, but 

 a Trout usually does; the caudal fin is more or less emarginate, or in 

 large specimens truncate, or even rounded, but is usually more distinctly 

 notched than in Trout of the same size." 



