GENERAL FEATURES 



53 



be very suggestive if the sea-trout of any other rivers were discovered 

 in their spots to reproduce at spawning time the typical pattern of the 

 spots of the non-migratory trout of the district. Such a fact, if 

 estabHshed, would suggest that the variety of marking of the sea-trout 

 is mfinite just because the variety of marking of trout is infinite, or, in 

 other words, that the fish are really one species whereof some are 

 migratory and some non-migratory. 



The sea-trout, in common with the salmon and trout, has what 

 scientists call a fusiform body " moderately elongate and compressed," 

 as Mr. Regan puts it, " deepest at or in advance of the middle of the 

 length and tapering posteriorly." It possesses the same number of 

 fins as salmon and trout do, and they are similarly placed in relation 

 to each other (Fig. ii). 



The first dorsal fin projects from the ridge of the back midway 

 between head and tail. In direct line with it and midway towards the 

 tail is the second dorsal fin, generally called the adipose fin, the 

 distinctive badge of all the family SalniomdcB. The caudal fin, or tail 

 fin, with practically equal lobes above and below the middle line, 

 completes vertically the posterior extremity of the body. The anal 

 fin projects vertically downwards and, in the sea-trout, backwards, 

 immediately behind the vent. The pelvic fins, which used more 

 commonly to be called the ventral fins — and perhaps might still be so 

 called with advantage — are set midway on the belly, as a pair, imme- 

 diately below the first dorsal fin, and springing beside each of these is 

 a little rudimentary, or, it may be, an aborted fin, making four fins in 

 this group. The pectoral fins, having their origin on each side of the 

 gullet behind the gill-covers, complete the number of ten fins which 

 salmon, sea-trout and trout possess in common. 



One mav revert to Mr. Regan's scheme of classification for such 

 special structural features as characterise the genus Salmn ; but in manv 

 matters of unscientific import salmon, sea-trout and trout bear so much 



