2 THE STORY OF THE BIRDS 



of scene they impart an ever-welcome sense of 

 life ; whilst of all organisms they are as a class 

 the most beautiful, the most tuneful, and we 

 may even add the most widely and generally 

 interesting. The old proverb that "A bird is 

 known by its feathers" amounts to a strictly 

 scientific diagnosis of the class Aves, for feathers 

 are otherwise unknown in the animal kingdom, 

 and therefore become the most important char- 

 acteristic of a bird. There can be no reason- 

 able doubt that birds are more closely related 

 to reptiles than to any other class of animal 

 life. The close propinquity of the two classes 

 reptiles and birds was unreservedly recognised 

 by Huxley, that great comparative anatomist 

 associating both under the term Sauropsida, 

 the two combined forming one of the three 

 primary groups into which he divided vertebrated 

 animals. 



It might reasonably be thought that as birds 

 are so obviously closely related to reptiles, the 

 descendants in fact of one common ancestor 

 from which both classes of organisms (Reptilia 

 and Aves) have sprung, there would be definite 

 evidence in existence, in a fossil form, to indi- 

 cate the line of their descent. But although 

 we may be practically certain that birds and 



