XVI 



INTRODUCTION 



giant reptiles known as the Dinosaurs corresponds 

 marvellously well with that of a modern bird, only 

 in the reptiles the foot-bones had not become welded 

 to form a cannon-bone. So much, then, for the 

 evidence from the skeleton, for the present. 

 The arrangement of the blood-vessels, the struc- 

 ture of the eye, ear, organ of smell, and brains, are all 

 on the reptile plan, and so also are the organs of re- 

 production. Similarly, the microscopic structure of 

 the growing feather in the embryo, or unhatched chick, 

 shows that it is really an extremely elaborate reptile 

 scale, and is formed on a plan quite different from 

 the hairs of mammals. 



But, it may be urged, it is all very well, and it may 

 be quite true, to say that because the reptiles and the 



birds have so much 

 in common, there- 

 fore they must be 

 related. But why 

 should we assume 

 this? One of two 

 courses is open to 

 u s. Either w e 

 must believe that 

 birds were, as used 

 to be held, special- 

 ly created, or that 

 they have in- 

 herited the char- 

 acters which they 

 hold in common with reptiles from a common ancestor 

 which had the characteristics which distinguish rep- 



FiG. 3. — The first known bird. 



