THE EVOLUTION OF MAN 



ECHIDNA HYSTRIX, 



the land duck-bill, an archetype of mammal living in Australia, 

 which lays eggs like reptiles and birds, but suckles its young 

 after they have hatched. Its egg, natural size, is shown to th 

 right. 



reason. They actually lay eggs in the regular 

 way. The young is born in an egg with a parch- 

 ment-like wall, just like a young turtle or lizard. 

 But while it is hatched from this egg like a 

 young bird, it licks up the milk of its mother 

 mammal fashion. The terrestrial duckbill has 

 furthermore the method of marsupials ; it carries 

 first its egg and then its young in its pocket. 

 The aquatic duckbill, on the other hand, does 

 not use this method any more; it digs a hole in 

 the bank of a river, makes a regular nest and 

 there lays its eggs openly, just like a bird. 

 The inevitable conclusion from these premises 



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