CLASS amphibia: oedee ueodela. 183 



Mg. 310. Mg. SU. 



THUm crimtm. Newt or Triton. SirSOon licMnoides, Axolotl. J. 



Amphipneusta. — The Double-breathing Amphibians 

 present anomalous forms, which are of interest on account 

 of the apparent permanency of their gills. Among them are 

 the Siren, or Mud-eel, of the Carolina rice swamps, the Axo- 



Fig. SIB. 



Protlus anguinus. 



loti of the Mexican lakes, and the Proteus, which inhabits 

 certain caves in Austria, and has only rudimentary eyes. 

 Eecent investigations suggest a doubt whether they are. not 

 merely the larvae of other animals whose life history is not 

 yet fully known.* 



furnish the most convenient means for observing the circulation of the blood. Plac- 

 ing the little creature in a vial, with a pocket-lens the globules may be seen chasing 

 one another as they go out through the arteries and return by the veins. 



* As they have tuft-like branchiae besides lungs, they have been thought to illus- 

 trate the general law that the " tvansient embryonic stages of the higher members of 

 any division of the animal kingdom are often represented by the permanent condi- 

 tion of its lower members." 



