602 



chamber, into which the pneumatic duct opens near the anterior end. 

 The epithelial lining of this swim-bladder is differentiated into a "red 

 gland", situated in the anterior end of the organ and around the en- 



oes 



Fig. 1. Diagram of the salmon swim-bladder. A anterior end of oesophagus. 

 oes oesophagus, pnd pneumatic duct, sb swim-bladder. 



trance of the pneumatic duct, while a "rete mirabile" lines the re- 

 maining portion of the swim-bladder wall (Corning, op. cit.). In Fun- 

 dulus and Menidia the pneumatic duct is not retained by the adult, but 



oes 



Fig. 2. Diagram of the carp swim-bladder. A anterior end of oesophagus, oes 

 oesophagus, pnd pneumatic duct, sb swim-bladder. 



otherwise the swim -bladder in these fishes does not appear to differ 

 essentially from that in Esox. There is no "oval" or partition in these 

 swim-bladders. 



sb 



oes 



Fig. 3. Diagram of the swim-bladder in the pickerel (Esox). A anterior end of 

 the oesophagus, oes oesophagus, pnd pneumatic duct, rd red gland, sb swim-bladder. 



The swim-bladder of the eel (Fig. 4) represents another type. It 

 consists of a large, fusiform chamber, into which the pneumatic duct 

 opens at the left side near the middle (Corning, op. cit. ; Jacobs, '98). 

 The duct is remarkable in that it dilates to form a chamber of con- 

 siderable capacity, which communicates with the oesophagus only by a 

 very minute aperture. The epithelial lining of these structures shows 



