4 BRITISH IRESH-WATER FISHES 



of being world-wide, must of necessity become national — 

 provincial — parochial — in its scope, as in the days succeeding 

 Aristotle. 



Further : no satisfactory understanding of the fauna, or 

 any class in the fauna, of any country can be had unless it is 

 viewed in relation to that of the rest of the world. This is of 

 special importance in dealing with fresh-water fishes, because, 

 severely circumscribed by the limits of the medium in which 

 they exist, the question constantly arises. How did such-and- 

 such a species get into certain rivers and not into others } For 

 example, the significance of the presence of the burbot in rivers 

 running eastward in England, its absence from those running 

 westward, cannot be appreciated unless the affinities of that 

 fish are understood. When it is explained that the burbot is 

 the only member of the great Cod Family known to inhabit 

 fresh water, that it abounds in the rivers of Central and 

 Northern Europe, as well as those of North America, a good 

 deal of light is thrown upon the former connection of the 

 streams of Eastern England with the great watershed of 

 the Rhine. Here, again, is the need for scientific as well 

 as for popular names. The burbot is a cod, but the great 

 Murray cod of Southern Australia is not a cod at all, 

 but a perch. 



I hope enough has been said to show that it is from no 

 delight in polysyllables that I have given the scientific names 

 in a work that lays no claim to contribute to the advance of 

 science. The utmost that I have attempted is to describe the 

 appearance, habits, and distribution of the various species, 

 partly from my own observation and, in a far greater degree, 

 from the records of trustworthy observers ; and at the same 

 time to give an accurate impression of the position of each 

 genus in the great class of Fishes. In order to do so I 

 have followed generally the classification of Dr. A. Giinther, 

 departing from it only in the case of the Salmonidde, wherein 

 close observation has inclined me to believe that too much 



