INTRODUCTION 



xui 



Thus, then, we ask. How have the birds come by 

 these distinguishing characters? The answer to this 

 question has been supplied partly by the anatomist 

 and partly by those who have spent their lives in read- 

 ing the riddles of the rocks. Let us take the anato- 

 mist's evidence first. According to him, the peculiari- 

 ties which distinguish the bird have been derived from 

 reptiles, and this is nowhere more evident than in the 

 skull. As in the reptile, it joins the neck by a single, 

 rounded boss of bone; while in the mammals (the 

 great class to which we ourselves belong, the class dis- 

 tinguished by the body covering of hair, and the fact 

 that the yoimg are suckled) the skull joins the neck 

 by two such bosses. In the form of the backbone 

 and of the hip-girdle, and in the structure of the legs, 

 birds also agree with the reptiles. To state in full 

 the evidence on which these conclusions are founded 





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2"-'' KoiA/ opflNKce. 3o/i/£S 



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Fig. I. — Bones of the foot and ankle of a young fowl, show- 

 ing THE separate ELEMENTS THEREOF. 



