198 



A HISTORY OF FISHES 



modified to form elongate feelers {cf. p. 79), these are also 

 supplied with an abundance of tiny sense organs. They 

 frequently occur in fishes living at considerable depths, in which 

 the eyes are feebly developed, and undoubtedly compensate 

 for the loss of vision. In the Southern Chimaera or Elephant- 

 fish {Callorhynchus) a remarkable membranous appendage hangs 



Fig. 78. — BARBELS IN OCEANIC FISHES. 



A. Eustomias bituberatus,xl ; b. Head of Eustomias temso7n,x i-h ; c. Head of 

 Eustomias silvescetis,X if ; d. Head of Photonectes intcrmedius,X2 ; E. Head of 

 Chirostomias pliopterus, X i J. (After Regan and Trewavas.) 



from the snout: its exact function is a little obscure, but it is 

 believed to be connected in some way with the sense of touch. 

 The last of the sense organs to be considered is the series of 

 organs collectively known as the lateral line or mucous canal 

 system, structures beheved to be the seat of a sense peculiar to 

 fishes. The external appearance of the lateral line in different 

 fishes has been previously described in considering the scales 

 {cf. p. 100), and it was pointed out that the series of external 

 pores or of tube-bearing scales are only the outward and visible 



