LOCOMOTION 355 



action of the median fins in swimming must be regarded as 

 supplementary to that of the tail. 



Swimming is by no means the only form of locomotion in 

 vogue amongst Fishes. A few, like the Angler-Fishes (Lophius), 

 habitually use the pectoral fins for crawling about the sea-bottom. 

 The East Indian Goby, Periophthalmus, uses its pectoral fins, 

 which are bent at an angle like an elbow-joint, for hopping over 

 sandy flats left bare by the retreating tide. The Flying-Fish 

 (Uxocoetus), when projected from the water by a stroke of its 

 powerful tail, expands its large pectoral fins, and, using them 

 after the fashion of a parachute, floats through the air for con- 

 siderable distances before returning to its natural medium. The 

 " Flying Gurnards " (Dactylopterus) are also capable of short 

 aerial excursions in a similar fashion. Nor is tree-climbing 

 beyond the province of a Fish, if credit be given to the assertion 

 that the Indian " Climbing-Perch " (Ancibas scandens) uses its 

 opercular spines for ascending trees. Many freshwater Fishes 

 are known to migrate across land from one pool or river to 

 another, usually during the night. Eels do so by a serpentine 

 or wriggling motion of their long bodies, but in others the 

 pectoral fins seem to be the principal organs used for the 

 purpose, aided, it may be, by a perverted use of the tail. 



Sound-producing Organs. Contrary to popular belief sound- 

 producing or vocal organs are by no means uncommon in Fishes, 

 especially in certain families of Teleosts. It is not always easy, 

 however, to discriminate between involuntary, abnormal, or acci- 

 dental sounds, and those due to the action of special vocal organs. 

 There are, moreover, some Fishes which observations have shown 

 to utter highly characteristic sounds, although the precise nature 

 of the sound-producing mechanism is at present unknown ; while 

 other Fishes appear to possess organs which, on anatomical 

 grounds, are perhaps vocal in function, although nothing is 

 known of the nature of the sounds they emit. Here those 

 organs only will be considered which, either with certainty or 

 with some degree of probability, may be regarded as vocal struc- 

 tures. For most of our knowledge of these interesting structures 

 we are indebted to the researches of Sorensen and Dufosse. 1 



1 Sorensen, Om Lydorganer has Fiske, Copenhagen, 1884 ; Dufosse, Ann. d. 

 Sci. Nat. Ser. 5, xix. Art. 5, 1874, and xx. Art. 3, 1874. For references to earlier 

 papers see Sorensen, op. cit. 



