VIVIPAROUS AMPHIBIANS 39 



eggs in crevices, has its young hatched perfect — active 

 and leaping. 



The Mexican axolotl (Figs. 20 and 21) shows a 

 peculiar form of suspended growth. If all the con- 



FiG. 21. — Axolotl [Amblystoma tigrinum), adult. 



ditions be not fair, it will cease to grow, and spend 

 the rest of its Hfe in the tadpole state, reproducing its 

 young in this immature state while in the water, and 

 these young are capable of either becoming land- 

 haunters, by losing their gills, or remaining always 

 aquatic. It is probable that other blunt-nosed sala- 

 manders do the same, or they may make the change 

 the second year and not the first. 



In the obstetric frog (Fig. 22), which wraps the 

 string of eggs about his legs, the tadpoles are hatched 

 in water, but they have no gills. 



There is a number of nest builders among the 



