MEGALOPS 145 



fact that the arteries which supply the lungs of 

 Dipnoi and the air-bladder of some other fishes 

 (e.g., Polypterus) and the lungs of all air-breathing 

 vertebrates from the Amphibia onwards, arise as 

 branches of the fourth afferent branchial arteries. 

 But Burne J has shown that the accessory branchial 

 diverticula or air-pouches of Saccobranchus, which 

 penetrate the body musculature throughout the 

 greater part of the length of the trunk from the 

 gill-cavity to the tail, lying above the transverse 

 processes on either side of the vertebral column, 

 are also vascularised from the fourth afferent 

 branchial artery on each side ; but these air- 

 pouches co-exist with a true air-bladder. We 

 have, in fact, in this case a very delicate example 

 of vascular convergence. 



The air-bladder of the estuarine Clupeoid fish 

 Megalops cyprinoides, common in Ceylon, is pro- 

 vided on its inner surface with an abundance 

 of spongy, vascular, alveolar proliferations which 

 are especially dense just behind the large orifice 

 by which it communicates directly, without the 

 intermediation of a pneumatic duct, with the 

 oesophagus immediately behind the gill - clefts 

 dorsally ; it is not vascularised from the branchial 

 arches, but this species can live for a long 

 time after capture, an uncommon feature in the 



1 R. H. Burne, " On the Aortic Arch System of Saccobranchus 

 fossilis? Journ. Linn. Soc. Zool., xxv., 1894, pp. 48-55. 



K 



