326 ANATOMY OF VERTEBRATES. 



Such an organisation of a fold of skin bordering the mouth as 

 implies the tactile faculty is rare in Fishes ; the Cyfjrinoids 

 exemplify it, and more especially many of the Indian species : 

 also the marine family of Labroids. In the Sturgeon the lip has 

 numerous papillas, and more minute papilhe occur on the lips of 

 many fresh-water fishes. In tlie Eels the upper lip is richly 

 supplied by the fifth nerve, and the upper lip of the Lepidosiren 

 is papillose. The soft skin of the sucking-lip of the Lamprey is 

 well supplied with a reticulate arrangement of sensitive filaments 

 from the fifth ; its margin is papillose, fig. 277. The associated 

 pectoral and ventral fins, forming the sucker in the Lnmp-fishes, 

 have a texture of the applied surface, which seems adapted to 

 receive impressions from the part it touches, whereby the fish 

 may ascertain its fitness or otherwise for the application of the 

 anchorintr orsan. 



The pectoral fins seem to be applied occasionally to explore the 

 nature of the bed of the water inhabited by the fish ; and in the 

 Gurnards ( Tru/Udce) three soft flexilile rays are detached from the 

 fin, like fingers, fig. 82, and the large nerves supplying them have 

 cjano'lionic enlargements at their origins. The filiform radial 

 appendages of the Pulynemidce, and the prolonged ventral fins of 

 Osjjhromenus, Trichogaster, and other Labyrinthibrauchs, and of 

 the Ophidiida3, enter into the present class of organs. The 

 barbules are long, slender, pointed processes of the skin, either 

 median or in pairs: the former arc limited to the imder jaw, as in 

 the Cod ; the latter may be developed from both jaws, and are 

 called, according to their position, ' prcmaxillary,' ' angular,' 

 ' nasal,' &c. They are commonly found in the grovelling fishes, 

 such as the Sheat-fishes, Loaches, Barbels, Sturgeons, tig. 123, A, 

 or in the parasitic Myxines, fig. 248. The nerves supplying the 

 barbules are large and derived from ganglionic di^•isions of the 

 fifth pair. A Cod, blind by absence or destruction of both 

 eyeballs, has been captured in good condition ; and it may be 

 supposed to have found its food by exploring with the symjihysial 

 barbule, as well as by the sense of smell' The sublingual fila- 

 ment of many UrdnoscopincE, and the rostral tentacle of Malthe 

 and Haheuta-a,^ may also exercise a tactile faculty. The limbs 

 of Lepidosiren, fig. 100, have the general form rather of organs 

 of exploration than of locomotion. 



The scalcless condition of the skin in Batracliia makes it more 



' xcriii. p. 72. 



■' CLXXiv. iii. p. 'M\. The homologous organs in Lo,,hh,s scorn to act as bail, to 

 attract small (ishcs. 



