THE EVOLUTION OF MAN 



into this first third of the so-called Trias period. 

 Most of the discoveries consisted of teeth, but 

 neither of the two duckbills now living has any 

 teeth. They are called duckbills because their 

 toothless jaws are covered with a horny skin 

 giving them the shape of bird's bills. The 

 aquatic species especially has a genuine duck 

 bill. 



However, one fine day the biogenetic law once 

 more came to our rescue. A young duckbill de- 

 velops in its first stages a sort of milk teeth, hav- 

 ing the early characteristics of molar teeth. No 

 teeth of any other living or extinct animal cor- 

 respond to the form of these teeth of the young 

 duckbill with the sole exception of those fossil 

 teeth of the saurian age. Hence we conclude 

 that the toothless bills of the duckbills, in spite 

 of the fact that they look so queer in a mammal, 

 do not represent an ancient heritage. They are 

 rather a newly acquired character, an adapta- 

 tion, which these surviving Australians have ac- 

 quired during the long period that has elapsed 

 since then. Their ancestors in the saurian age, 

 who were at the same time the genuine ancestors 

 of the higher mammals, had teeth, and these are 

 the very teeth which we now find in a fossil state. 

 These ancient duckbills with teeth, as one might 



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