16 KENDALL: NEW ENGLAND SALMONS. 



As concerns the three recognized series of western trouts, i.e., the cut-throat, steelhead, 

 and rainbow series, it is observed that with a few exceptions, which may prove the 

 rule, thej^ are distinguished in at least three waj^s: (1) geographically; (2) habits; (3) by 

 number or size of scales, and to some extent by (4) number of vertebrae. 



In Europe a similar situation exists in the series commonly designated the salmon, 

 the sea trout, and fresh-water trout series. With these series similar difRculties have 

 confused ichthyologists. Many species of sea and fresh-water trouts have been de- 

 scribed and as many times relegated to synonymy. Some have regarded all trout, whether 

 marine and anadromous or perfectly fresh-water forms, as constituting a single species. 

 Others, whUe so regarding them, are compelled to admit that the sea trout differ more or 

 less according to locaUty, and that there are northern and southern forms of fresh- 

 water trout, which they designate in their terminology as Salmo fario and Salmo 

 ausonii. Even Smitt (1893-1895), who regards the salmon, sea trout, and fresh-water 

 trout as one species, indicates specific distinctions between the salmon and sea trout, 

 as he does between two forms of Salvelinus, in 'Salmo alpinus' and 'Salmo salvelinus.^ 



The structural characters of the sea trout are evidences of its differential advancement, 

 and its restriction to certain coastwise, western European range is evidence in favor of 

 previous isolation of some nature with which its differential characters were associated. 

 If the isolation was geographical the present coincidental geographical range of the 

 salmon can be accounted for only by assuming a later encroachment of either the 

 salmon or trout within the range of the other, and the most natural assumption is that 

 the adventitious form is the salmon. In whatever manner it may or may not be ac- 

 counted for, it is obvious that, in accordance with accepted views of descent they were 

 not developed in exactly the same environment and probably not in the same geographi- 

 cal range. 



On the Atlantic coast of North America the situation is somewhat different from that 

 of the other regions discussed. Of the genus Salmo, so far as known, there are only two 

 series, comprising the anadromous, marine salmon and the fresh-water forms commonly 

 called landlocked salmon and ouananiche. Anticipating a discussion which appears in 

 a subsequent chapter, it may be stated here that in my opinion the so-called, 'fresh- 

 water' salmon is just as distinct and almost as easilj' distinguished from the sea salmon 

 as are the trouts of Europe from the sea salmon; furthermore among the fresh-water 

 salmon there are forms, or species, if you please, just as distinct from each other as are 

 some of the trouts of Europe from each other. In fact, it is more difficult to distinguish 

 certain forms of fresh-water salmon from 'Loch Leven' trout in this country, than it is 

 to distinguish the former from the marine form of the salmon. 



Those who hold that all the different forms of a trout of a region, as for example 

 Europe, constitute but one comprehensive species, attribute the differences shown by 

 them to an unstable quality, supposed to be characteristic of salmonoid fishes, which 

 they term 'plasticity.' 



