THE ALLIES OF THE FROG 



347 



The mud puppy, or water dog {Nectu'rus Fig. 177), lives 

 permanently in the water and never loses its gills. This 

 form is the most primitive of present-day amphibians. The 

 adults are more than a foot in length. 



Toads and Frogs. The members of the order Anu'ra (Gr. 

 an-, "without"; our a, "tail") undergo a well-marked 

 metamorphosis. From eggs they hatch as tadpoles, and 



Fig. 177. Necturus in an aquarium 

 Photograph by Elwin R. Sanborne, courtesy of the New York Zoological Society 



later change to the adult condition by the development 

 of legs and the gradual absorption of the tail (Fig. 175). 

 Many examples of peculiar breeding habits are known. 

 The female of a Brazilian species of tree frog (Hy'la fa'ber) 

 lays her eggs within a circular wall of mud which she con- 

 structs on the bottom of a shallow pool of water. Within 

 this nursery the tadpoles develop, unless liberated by the 

 rain or other accident. Several species lay their eggs on the 

 leaves of trees above the water, into which the young fall 

 when hatched. The male of the obstetrical toad of Europe 

 (Al'ytes obstet'ricans) winds the eggs around his legs, and, 

 seeking a safe place, guards them till they hatch. In a 



