THE EVOLUTION OF MAN 



organs compels us to consider whether we have 

 not to deal in this case with a very old inter-rela- 

 tion of things. Could it be possible that mammals 

 concealing man existed once upon a time which 

 possessed milk glands, but no external nipples, 

 and which had only one single opening for the 

 products of the urinary, sex and digestive organs ? 



There are such mammals even in our day. 

 They are known as Australian duckbills. One 

 species of them, living on dry land, called 

 Echidna, resembles a large hedge-hog and is 

 protected by strong quills. It lives in Australia, 

 Tasmania and New Guinea. Another kind, liv- 

 ing in the water and called Ornithorhynchus, 

 resembles in its pelt and habits the otter. It 

 swims very well and lives in the little rivers and 

 lakes of the Australian continent. Both duck- 

 bills are without external nipples, but they have 

 genuine milk glands. The milk percolates through 

 a sieve-like place in the skin into the mouth of 

 the young. At the same time the body of the 

 duckbill has only one single opening for the 

 products of the urinary, sex and digestive or- 

 gans. 



Injhe_ system these duckbills follow after the 

 marsupials. Neither of them has any placenta. 

 Nor do they need it, and that fpr a very good 



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