172 FISHING GOSSIP. 
on either side of the. upper jaw before the eye, are 
very long, nearly extending to the tail ; the other four 
are much shorter, and arranged in pairs on the chin. 
Both jaws and palate are armed with broad bands of 
small, closely-set teeth, which give to the bones a 
rasp-like appearance. The eyes are very small, and 
a thin, more or less transparent skin passes over them, 
so that the perception of light must be very limited. 
When we recollect that the water of the rivers 
and lakes inhabited by the wels is generally coloured, 
it is evident that only a few rays of light can pene- 
trate to the depth where the fish chooses its lurking- 
place. Now in fishes which inhabit dark places or 
great'depths, we find the organ either extremely large, 
as in nocturnal animals, in order to collect as many 
rays of light as possible, or quite rudimentary. The 
latter is the case with the wels, but this fish is pro- 
vided with a compensatory organ in the barbels sur- 
rounding its mouth, especially those of the upper 
jaw, which can be moved voluntarily in every direc- 
tion; and anybody who has had the opportunity of 
observing one of these fishes in an aquarium, must 
have been struck by the constant and peculiar motion 
of these barbels, which is very similar to that of the 
common aquatic worms known by the name of 
Senuris. When the fish moves about leisurely, it 
uses them constantly, feeling its way with them. 
Therefore these barbels have the double purpose of 
