262 



ZOOLOGY 



only of the yolk and for some time after hatching the yolk 

 mass hangs as a lump on the under side of the embryo. 

 Very early a deep groove, bounded by a pair of folds, 

 arises on the edge. This groove is large in front (Fig. 

 245, />). It forms the beginning of the brain and spinal cord. 

 The feathery gills and the beginnings of the appendages 





SS^L 



Fi<i. 246. Pipa americana. Female with young in pits on its back. 



next sprout out, while the trunk continues to elongate and 

 assume the form of a young salamander (Fig. 245). 



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 



