THE ALLIES OF THE FROG: AMPHIBIA 341 



resembling frogs' eggs, though the jelly-like mass which sur- 

 rounds them is more opaque. The young keep their gills for 

 a considerable period, and one species, called the axolotl 

 (Amblystoma tigri'num, Fig. 169), found from New York to 

 California and Mexico, may even breed in the gill-bearing 

 larval stage. These immature forms live in the water, grow- 

 ing to be eight or nine inches long, or, in exceptional cases, 

 even larger, and may continue in this condition for years, with- 

 out ever changing to the adult form. An observer who has 



FIG. 169. Photograph of Young Axolotl. Reduced. (By H. V. Letkemann) 



had opportunity to study axolotls in their native habitat says 

 that the change to the adult condition is hastened by abun- 

 dance of food, and by the partial drying up of the water and 

 consequent increase in temperature of the water which remains. 

 Like some other amphibians these salamanders can regen- 

 erate lost limbs. This, according to Professor Gadow, of Cam- 

 bridge, England, takes place more certainly and quickly the 

 younger the animal is. In one case quoted by this authority 



