642 FISHES. 



now be considered to be fully acclimatised in Tasmania and 

 New Zealand, and with but little protection may be expected 

 to bold tbeir own in the freshwaters of those colonies. Whe- 

 ther the acclimatisation of the Salmon will be in the end 

 equally and permanently successful, remains to be seen. The 

 true S. salar is not subject to variation, and is very sensitive 

 to any change of external conditions, and to every kind of 

 interference with its economy. The fourth species, with 

 which attempts of acclimatisation in Southern Australia have 

 been made, is a migratory Salmon from the Sacramento river 

 in California. This experiment is still in progress, and be- 

 lieved to be promising of success. It will be a most curious 

 problem to ascertain, how much the original characters and 

 habits of those species will be affected by their transference 

 to so distant a part of the globe. At present it would be too 

 hazardous to offer an opinion on this point, especially as it is 

 a fact that numerous cross-breeds have been introduced into, 

 and reared in, Tasmania, which must more or less interfere 

 with the characters of the pure breeds. 



It is apparent, from the foregoing remarks, that the dis- 

 tmction of the various species of Salmonidse is a matter of 

 considerable difficulty, and that there is scope for great 

 diversity of opinion. At any rate it is only by a close, long- 

 continued study, and constant comparison of specimens of 

 various ages and from various localities, that one is enabled 

 to find a guide through the labyrinth of confusing variations. 

 However, it is a significant fact that the very same characters 

 by which we are enabled to distinguish European species 

 occur asjain, thou2:h in an exaggerated form, in American 

 Salmonoids (which everybody will admit to be of distinct 

 species), and therefore our faith in them necessarily becomes 

 strengthened. In accordance with acknowledged principles 

 in zoology, forms which differ from their congeners by a com- 

 bination of two or more of constant characters, are to be 



