366 Labyrinthici and Holconti 



discharged per anum. In fine, the two respiratory factors 

 of the branchial apparatus have independent functions: (i) 

 the labyrinthiform, or branchihyal portion, being a special modi- 

 fication for the respiration of atmospheric air, and (2) the gill 

 filaments discharging their normal function. If, however, 

 the fish is kept in water and prevented from coming to the 

 surface to swallow the atmospheric air, the labyrinthiform 

 apparatus becomes filled with water which cannot be dis- 

 charged, owing to its almost non-contractile powers. There 

 is thus no means of emptying it, and the water probably 

 becomes carbonized and unfit for oxygenizing the blood, so 

 that the whole of the respiration is thus thrown on the branchiae. 

 This will account for the fact that when the fish is in a state 

 of quiescence, it lives much longer than when excited, whilst 

 the sluggishness sometimes evinced may be due to poisoned 

 or carbonized blood." 



Four families of labyrinth-gilled fishes are recognized by 

 Professor Gill; and to these we may append a fifth, which, how- 

 ever, lacks the elaborate structures mentioned above and 

 which shows other evidences of degeneration. 



The Climbing-perches: Anabantidae. The family of Anaban- 

 tid&, according to Gill, " includes those species which have the 



FIG. 303. The Climbing Perch, Anabas scandens Linnseus. Opercle cut away to 



show the gill-labyrinth. 



mouth of moderate size and teeth on the palate (either on the 

 vomer alone, or on both the vomer and palatine bones). To 

 the family belongs the celebrated climbing-fish. 



"The climbing-fish (Anabas scandens) is especially note- 

 worthy for the movability of the sub-operculum. The oper- 



