502 BIRDS. 



much of the cleverness of a bird may be traced to instinct 

 or inherited habit, there is no doubt that they are quick to 

 learn from experience, that they have good memories, and 

 that they can adapt new means to new ends. Some are 

 fond of music and quick to imitate tunes. The bower-bird is 

 an outstanding rather than an exceptional illustration of their 

 liking for beautiful things. 



General Survey of the Class. 



Order 3. Flying Birds — Carinatae — the great majority of 

 living birds. 



Order 2. Running Birds — Ratitse — only a few, the 

 Ostriches {Struthio and Rhea), the Emu {Dro- 

 mceus), the Cassowary {Casuarius), the Kiwi 

 (Apteryx), and some extinct forms. 



Order i. Saururae. Ancient extinct birds, such as Archce- 

 opteryx. 



General Characters of Birds. 



The fore-limbs are generally modified as wings capable of 

 flight ; the neck is long, the tail short. 



The epidermic exoskeleton is represented by feathers, 

 sometimes also by a few scales, but there are never any 

 scutes. 



The only skin-gland is an oil-gland or preen-gland at 

 the root of the tail. 



The pectoral muscles used in flight are generally greatly 

 developed ; in many there is a muscular gizzard ; the dia- 

 phragm is not more than incipient. 



In the brain, the predominance of cerebrum and cere- 

 bellum has resulted in displacing the optic lobes to the sides. 



The nostrils are often overhung by a sensitive cere ; there 

 is no external ear, and the connection between tympanum 

 and inner ear is by means of a columella ; the eye-ball is 

 strengthened by sclerotic ossicles, there is a well-developed 

 third eye-lid and an internal nutritive pecten. 



There are no epiphyses in connection with the bones, 



