A STUDY ON TROUT AND YOUNG SALMON. 



Although the nose region of the trout is longer, and the eye 

 pushed further back, the upper jaw as a rule reaches a good 

 deal further back than tot he posterior edge of the pupil, 

 in many cases even further back than the posterior edge of 

 the eye itself. Thus a perpendicular line drawn from the poste- 

 rior margin of the pupil downwards will in nearly all cases cut 

 the posterior part of the upper jaw. 



The form of the upper jaw is also somewhat different in 

 the two species, that of the salmon being considerably broader 

 in proportion to its length and generally more finely rounded at 

 the posterior margin than is that of the trout. If the heads of 

 the two fishes are seen from above, it is at once obvious that 

 the forehead of the trout is broader than that of the salmon, 

 the forehead of the latter being shorter and more pointed. 



All fins, excepting the adipose fin, are at this stage larger 

 in the salmon than in the trout. 



The size of the caudal fin and the pectorals is specially 

 conspicuous, the caudal fin of the salmon possessing consider- 

 ably longer and more finely pointed flukes than that of the trout. 



The pectoral fins of the salmon exceed by far those of the 

 trout in size, being longer as well as broader. If the pectoral 

 fin is folded along the side of the fish, its posterior point will 

 in the salmon be as a rule situated a little in front of or right 

 below the anterior edge of the dorsal fin, and it will often reach 

 even further back. Thus if a perpendicular line is drawn down- 

 wards from the anterior base of the dorsal fin, this line will as a 

 rule touch or cut the pectoral fin. In the trout this fin is stri- 

 kingly shorter. 



This difference causes the two species to act quite differently 

 on dry land. 



If a bucket of water containing living specimens of the 

 two species is poured out on a sloping deck, the fishes when 

 left dry will act quite differently. The salmon will all turn on 



