THE FROG 



345 



front (Fig. 323 h). It forms the beginning of the brain and 

 spinal cord. The feathery gills and the l)eginnings of the ap- 

 pendages next sprout out, while the trunk continues to elon- 

 gate and assume the form of a young salamander (Fig. 323 h). 





Fig. .324. — Pipa americana. Female with young in pits on its back. 



Families of Anura. — Of the Anura there are eight or ten 

 times as many species as there are of the Urodela. They are 

 distributed into nearly a score of families. Of these a few of 

 the more interesting deserve to l^e mentioned. 



The South American Pipa (Pipidae) is noteworthy because 

 of the habit which the female has of brooding its young in 

 pits of the skin on its back (Figs. 324, 325). 



