EMERGENCY RESPIRATION 



49 



Fig. 25 



Fig. 26 



Fig. 25. Fourth branchial arch in Clarias melanoderma with respiratory 

 "tree." (Bohme.) 



Fig. 26. Respiratory tree slightly enlarged (Diameter about 2 cm 'in fish 

 of 50 cm). (Bohme.) 



frogs (Das, 1928). In Plecostomus and Ancistrus (tropical 

 Siluroida) the stomach (Fig. 27) is a respiratory organ into 

 which air is swallowed and again regurgitated (Carter and 



Beadle, 1930; Carter, 1935). 

 which Cobitis (Misgurnus) is 

 the best known example, 

 more distal parts of the in- 

 testine are respiratory, and 

 the air swallowed passes out 

 through the anus. 



Finally the gas bladder 

 has been developed inde- 

 pendently in quite a number 

 of fishes either as an acces- 

 sory or as the main respira- 

 tory organ, and this would 

 appear to be the line along 

 which the pulmonary respir- 

 ation of the higher verte- 

 brates has been evolved 

 through forms related to the 

 Dipnoi. 



The criteria on which to 

 base the assumption of the 



In a number of other fishes, of 



/WrV 



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-JB" 



xm\ 



Fig. 27. Respiratory stomach of 

 Plecostomus plecostomus 20 cm long. 

 (Carter and Beadle.) 



