FIELD BOOK OF PONDS AND STREAMS 



em and eastern ones, these salamanders transform typically, 

 their lungs develop, their gills shrink, and they finally climb 

 out on land as air-breathing adults. But in other regions 

 such as western Texas and the southwest, and under certain 

 conditions, the larvae continue to grow to full adult size with- 

 out changing their form or losing their gills and are known as 

 axolotls (Fig. 290, 2). 



Although these axolotls appear like overgrown lar\^ae, their 

 reproductive organs mature, the females lay eggs and the 

 males deposit spermatophores containing sperm cells which 

 fertilize them. Generations of such axolotls may follow one 

 another for a long time if their surroundings remain the same, 

 but a sudden change of climate or lack of water may shift 

 their course of life. Then their gills shrink and they trans- 

 form into ordinary air-breathing adults whose offspring will 

 lose their gills and transform into t3^pical adults. This cycle 

 may be repeated over and over till conditions change again. 



Size. — Length of adults 7 to 8 inches. 



Range. — The entire United States and southern Canada; 

 rare in the eastern states, especially in New England ; abund- 

 ant in the western and southwestern United States where the 

 axolotl form is often treated as a separate species. 





Fig. 291.- 

 ma opacuni. 



-Adult marbled salamander, Amhysto- 



;6o 



