7 BRITISH FRESH-WATER FISHES 



resembles the common and more powerful perch in so many 

 respects that the puzzle is how it ever became differentiated, 

 The Ruffe, an d yet continued to inhabit the same waters within 

 ^ Q narrow confines of this island. Probably the 

 ru ff e is of more northerly origin than the perch, 

 having had its dimensions restricted by more rigorous 

 climatic conditions, which have left a stamp upon the little 

 creature so permanent as not yet to have yielded to more 

 temperate surroundings. Yet if that be so, it is perplexing 

 to note that the ruffe is not found in those parts of Great 

 Britain where the fauna retain most traces of Arctic experience, 

 for it is unknown in Scotland and the north of England, 

 neither has it a home in Ireland. Yet is its range far more 

 northerly than that of the perch, for the ruffe is not found in 

 Southern Europe, but abounds in Scandinavia, Russia, and Siberia. 

 In the last-named territory it attains its greatest dimensions, 

 sometimes measuring, it is said, as much as eighteen inches in 

 length, and weighing ij lb., whereas in England it scarcely 

 ever reaches six inches in length, and more commonly measures 

 but three or four. The largest British specimen whereof I 

 can find precise record was one taken near Shepperton by 

 Mr. J. H. Keene weighing just 5 oz. May we not, then, 

 consider the ruffe as hypothetically an Arctic perch, a survival 

 of more severe climatic conditions than now prevail in regions 

 which have since been colonised by the more robust genus ? 



In general form the ruffe bears a marked resemblance to 

 the common perch. It has a similar hog back, carrying a 

 Outward spinous dorsal fin. But whereas the perch has two 

 appearance. d orsa ] fi nSj one spinous, the other soft, these are 

 united in the ruffe, the forward portion being usually sup- 

 ported by fourteen sharp spinous rays, the posterior by a dozen 

 soft rays. The praeoperculum, or foremost gill-cover, differs 

 from that of the perch in a remarkable feature, the border 

 thereof being armed with ten or a dozen divergent spines ; 

 while the operculum, or posterior gill-cover, ends in a single 



