i INTRODUCTORY 5 



apparatus— means higher temperature, comparative, 

 superiority to external conditions, greater vitality, 

 and greater enjoyment of life. And the changes from 

 first to last have not been additions of new organs, but 

 adaptations of existing materials. 



The differences between a bird and a reptile are so 

 striking, they lie so much on the surface, that we are 

 in danger of seeing the differences only and passing 

 over the resemblances, some of which arc obscure and 

 require a minute knowledge of anatomy. But there is 

 no reason why the pedigree should be taken on trust. 

 Much of the evidence that enables us to trace it is 

 easily intelligible. 



After trying to make clear the development of the bird 

 from reptile ancestors, I shall go on to describe (1) his 

 structure in more detail and the work done by the 

 different organs, (2) what cannot be dissociated from 

 his structure, his life and habits. 



