140 IV. 14. 



of a quadruped. It differs from a quadruped, in possessing wings ; 

 from a bird in being unable to soar aloft, and in having feathers 

 that resemble hair and are useless for flight.^ On the other 

 hand it agrees with quadrupeds in having upper eyelashes,^ 

 which are the more richly supplied with hairs because the parts 

 about the head and the upper portion of the neck are bare ; ^ 

 and it agrees with birds in being feathered in all the parts 

 posterior to these. Again it resembles a bird in being a biped, 

 and a quadruped in having a cloven hoof. For it has hoofs 

 and not toes.* The explanation of these peculiarities is to be 

 found in its bulk, which is that of a quadruped rather than of 

 a bird. For, speaking generally, a bird must necessarily be 

 of very small size. For a body of heavy bulk can with difficulty 

 be raised into the air. 



Thus much then as regards the parts of animals. We have 

 discussed them all, and set forth the cause why each exists ; 

 and in so doing we have severally considered each group of 

 animals. We must now pass on, and in due sequence must next 

 deal with the question of their generation and development. 



6G7b. 



