70 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, and yet continued to inhabit the same waters within 
eee the narrow confines of this island. Probably the 
cernua). ruffe 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 14 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. dorsal fins, 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 preoperculum, 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 
