OBJECTIONS TO THE DARWINIAN THEORY 167 



The swimming bladder of most fish — the sturgeon 



1 for example — is a closed sac lying beneath the 



vertebral column, and is used for the purpose of 



flotation, to keep the back uppermost. In many 



Fig. 29. 



B 



Diagram showing Evolution of Lung from Swim-bladder of Fish. 



A, Sturgeon ; B, Ceratodus ; C, Menobranchus ; D, A mphiuma ; 

 E, Newt ; F, Frog. 



fish it acquires a connection with some part of the 

 alimentary canal, and then becomes an accessory 

 breathing organ. 



The mud-fish, Ceratodus, of Queensland and 

 Protopterus of Africa, inhabit rivers which during 



