AIR-BREATHING FISHES 141 



would be certain to mistake Salarias for it 

 unless otherwise instructed. When out of water 

 the opercular membrane is kept closely pressed 

 against the body behind the gill-opening, so that 

 the gill - cavity is temporarily converted into a 

 virtual lung-chamber. 



Other fishes which can progress out of water 

 on suitable ground without falling on to one side 

 are Anabas, C /arias, Saccobranchus, Ophiocephalus, 

 and others. These may all be designated walk- 

 ing fishes. Anabas helps itself along by means 

 of its opercular spines, Clarias and Saccobranchus 

 by their pectoral spines, Ophiocephalus by move- 

 ments of its flattened head, assisted by flexions 

 of body and tail. All of these fishes can and 

 must breathe air by means of special growths or 

 diverticula connected with the upper division of 

 the gill-cavity above the gill-clefts. Clarias and 

 Saccobranchus are both Siluroids, but the coral- 

 like dendritic appendages in the suprapharyngeal 

 chambers in Clarias are much more like the 

 lamelliform labyrinthine organs in Anabas than 

 the diverticula of Saccobranchus. If these air- 

 breathing Teleostean fishes are prevented from 

 reaching the surface in order to take the air, they 

 become drowned ; and this habitual aeropneustic 

 function of the accessory branchial organs was, 

 when first demonstrated, regarded by Professor 

 Huxley as a great fact. 1 Saccobranchus will live 



1 Rev. Barcroft Boake, " On the Air-Breathing Fish of Ceylon," 

 Journ. Ceylo?i Branch Roy. Asiat. Soc, iv., 1867- 1870. 



