FIG. 13 





STURGEON 



AND MANY 



TELEOSTS 



LEPIDOSTEUS 

 AND AMIA 



ERYTHRINUS 



CERATODUS 



POLYPTERUS 



AND 

 CALAMOICHTHYS 



LEPIDOSIREN 



AND 



PROTOPTERUS 



REPTILES 

 BIRDS 



MAMMALS 



Figs. 13-19. — Air-bladder of fishes, shown from the front and sides. Cf. p. 

 264. .^. Air- or swim-bladder. AD. Airduct. Z). Digestive tube. (After WILDER.) 

 13. Sturgeon and many Teleosts. 14. Amia and Lepidosteus. 15. Erythrinus, a 

 Cyprinoid Teleost. 16. Ceratodus. 17. Polypterus and Calamoichthys. 18. Lepi- 

 dosiren and Protopterus. 19. Reptiles, birds, and mammals. The diagrams illus- 

 trate the paired or unpaired character of the organ, its varied mode of attachment 

 to the digestive tube, and the smooth or convoluted condition of its lining mem- 

 brane. 



22 



