320 ECHIDNA AND DUCK-BILLED PLATYPUS 



eyes when the animal is grubbing in the mud. Within the mouth 

 are capacious cheek-pouches, in which food collected under water 

 can be stored until the animal rises and floats at the surface. The 

 eggs are large-yolked, and develop, so far as concerns their early 

 stages, after the fashion of the eggs of reptiles. 



It is impossible here to go into all the technical details of the 

 various anatomical points of interest concerning the Monotremes, 

 but it is interesting to note that both the Platypus and the 

 Echidna have an arrangement of the bones of the shoulder and 

 chest which resembles to a certain extent that of the lizards and 

 of the extinct ichthyosaurus ; an arrangement either altogether 

 absent, or only existing as the merest vestiges in the higher 

 Mammals. Indeed, these interesting animals not only represent 

 the lowest extant stage of evolution in the Mammals, but in 

 their anatomy preserve, more markedly than the higher Mammals, 

 traces of the far-off pedigree of their class. 



