58 THE SEA-TROUT 



1 may add as a further structural distinction, on the suggestion of 

 iMr. J. Arthur Button, that microscopic examination of the scales 

 shows, in most cases where the " bull trout " is not involved, whether 

 the fish in question is a salmon or a sea-trout, for, weight for weight, the 

 salmon almost invariably is the younger fish. For purposes of com- 

 parison I am able, through the kindness of Mr. Hutton, to show in one 

 plate (Fig. i6) the contrast between the scales of a grilse and those of a 

 sea-trout each of which fish weighed 4^ lb. Ihe scales respectively 

 indicate that the grilse is three and a half, and the sea-trout seven and 

 a half years old. It is possible, as I have elsewhere shown, that the 

 scales of the " bull trout " approximate closely to those of the salmon 

 in its various stages. 



Subject to the foregoing remarks it may perhaps be convenient to 

 tabulate thus : — 



The Distinctions between Salmon and Sea-trout. 



1. Weight for weight, the sea-trout is generally shorter and of more 

 sturdy build than the salmon. 



2. The gill-covers of the salmon form a true curve, those of the 

 sea-trout project backwards more or less to an apex. 



3. The eye of the salmon is set nearly in the medial line of head 

 and body, that of the sea-trout markedly above it. The pupil of the 

 salmon's eye is curiously pear-shaped. 



4. The mouth of the sea-trout is larger than that of the salmon, 

 extending backwards beyond the eye. Relatively, the maxillary bone 

 is longer than in the salmon. 



5. The salmon has generall) more branched rays in the dorsal fin 

 than the sea-trout. 



6. The posterior margin of the anal fin in the salmon tends to 

 convexity while in the sea-trout it is rather concave and projects towards 

 the tail. 



7. The tail rays of the salmon spring from a relatively broader 

 base than in the sea-trout giving the former a " wrist " by which it can 

 be securely grasped. 



