igG A HISTORY OF FISHES 



and therefore immovable; further, it has no delicate membranes 

 comparable to those of the tongues of higher vertebrates. It is 

 true that the barbels, lips, mouth, and palate are richly suppHed 

 with tiny sense organs, but it is more than likely that these 

 are concerned with the sense of touch rather than with that 

 of taste. A curious cushion-like organ, richly supplied with 

 nerves, found on the palate in the Carps and related fishes 

 {Cyprinidae) , may perhaps be connected with the perception of 

 this sense. 



The sense of touch seems to be highly developed, and a 

 number of special organs have been evolved in connection with 

 it. The whole of the epidermal layer of the fish's skin is provided 

 with small sense organs scattered irregularly over the head, 

 body, and fins. They are present in the Cyclostomes, Selachians, 

 and Bony Fishes, but in the Lung-fishes [Dipneusti) are confined 

 to the region of the cavity of the mouth, and there is reason 

 to believe that they gave rise to the taste-buds found on the 

 tongue in higher vertebrates. These dermal sense organs may 

 take the form of tiny buds, with which are associated the fine 

 end-branches of nerves, or of small pits with specially sensitive 

 cells hidden away in their depths. Their function is to receive 

 impressions or sensations from the outside world, such as a 

 change in temperature, or a feeling of the proximity of food 

 or of enemies, and to set up nervous impulses which convey 

 these sensations to the brain. 



Although, as already remarked, such organs are scattered 

 over every inch of the body, they tend to be specially abundant 

 in the organs known to be connected with the sense of touch. 

 Of these the most important are the barbels or feelers, which 

 may be thread-like or flattened, long or short, smooth or with 

 corrugated or roughened surfaces. They are generally to be 

 found in the region of the mouth, but are also developed on the 

 lower surface of th'e throat and on the chin. In the Cod [Gadus) 

 there is a single short barbel below the chin (Fig. 770), in the 

 Drums [Sciaenidae) there maybe several in this position (Fig. 77A). 

 In the Gat-fishes (Siluroidea) the barbels are always arranged in 

 pairs round the mouth, the largest being connected with the 

 maxillary bone of the upper jaw and freely movable at will 

 (Figs. 34k; 41 d; 77B, etc.). They vary a good deal in size 

 and form in this group of fishes, sometimes being even longer 

 than the fish itself. There can be little doubt that they aid in 

 the search for food in waters which are so muddy that eyes 

 would be of little use. In the Sturgeon {Acipenser), another 



