FISHES. 



woven. .The rest of the inner 

 surface of the air-bladder re- 

 ceives its blood, not from the 

 red bodies, but from normally 

 ramifying vessels. This kind 

 of rete mirabile or "vaso- 

 ganglion" is found in the 

 Perch and Ga;doids; it is 

 generally distributed in closed 

 air-bladders, but also some- 

 times observed in air-bladders 

 with pneumatic duct. In 

 Anguilla and Conger two 

 similar vaso-ganglia are situ- 

 ated at the sides of the open- 

 ing of the pneumatic duct. 



Whilst the air-bladders 

 of some GaTwids, anatomi- 

 cally as weU as functionally, 

 closely adhere to the Teleo- 

 steous type, that of Amia is 

 more cellular and lung-like in 

 its interior than the Teleo- 

 steous air-bladder, and Polyp- 

 terus approaches the Dipnoi 

 not only in having a laterally 

 divided air-bladder but also 

 in its pneumatic duct entering 

 the ventral side of the oesopha- 

 gus. The air-bladder of the 

 Dipnoi possesses still more 

 the anatomical characteristics 

 of a lung and assumes its 

 functions, though, as it co- 

 exists with gills, only perio- 



