TOUCH 211 



the chin of such fishes as cod, haddock and, among fresh- 

 water fishes, the barbel. In some fishes there is more than 

 one barbel on the chin, and in others there may be a pair, 

 or several pairs, on the upper lip and snout as well. Among 

 fresh-water fishes the British loach has six barbels on the 

 snout, and the catfish of continental waters has two very 

 long barbels on the snout and four shorter ones on the 

 lower jaw. In some of the deep-sea fishes the barbels reach 

 a fantastic length and may be longer than the body. Barbels 

 are obviously of great importance as touch-organs to fishes 

 that live in turbid water, or at great depths of the sea, or 

 that feed mostly at night, but they are also one of the 

 most used organs in some fishes that live in clear water. 

 It is a fascinating sight to see red mullet in an aquarium 

 using their barbels. Under the chin of these fish there are 

 two rather long barbels which can be folded away under 

 the lower jaw so that they cannot be seen when the fish is 

 swimming in mid water but can be brought out to project 

 slightly forwards below the chin when the fish is seeking 

 food at the bottom. They are very mobile and assuredly 

 very sensitive ; the fish moves them about rapidly, gently 

 touching everything below it as it explores the shingle and 

 sand. They are moved about by muscles, but the exact way 

 in which they function does not appear to have been re- 

 corded. In use the part between the fish and the bottom 

 appears to be rigid, although it has no bone in it, but the 

 part in contact with the bottom is soft and moulded to the 

 shape of the objects it touches. If the fish moves nearer the 

 bottom more of the barbel becomes soft ; if it moves away 

 more of it becomes rigid. The mechanism by which this 

 change is attained must be of some complexity. 



In the invertebrates with naked bodies the sense of touch 

 is generally distributed all over the skin, but there is also 

 often a concentration of touch-receptors on feelers and 

 tentacles of different sorts which nearly always occur at the 

 head end. Most of the aquatic worms, the snail-like molluscs, 

 and a host of other creatures are thus provided. In the 

 crustaceans, the insects, and the other animals with jointed 

 body-armour, there are one or more pairs of feelers, or 

 antennae, often of great length, as in the crayfish. These 



