15G 



HABITS OF BIRDS. 



On the ninth day the bones begin to be formed, 

 appearing in the form of hard bony joints, the middle 

 of the thigh and leg-bones, according to Scarpa, 

 becoming yellowish. These form the rudiments of 

 the bony ring of the sclerotic, resembling a circular 

 row of the most delicate pearls. At the same period 

 the marks of the beautiful yellow vessels on the yolk- 

 bag begin to be visible. 



On the tenth day the muscles of the wings are 

 seen completely formed, and the germs of the feathers 

 appear enlarging. Scarpa up to this period could 

 observe nothing hard, but a yellow wrinkling of 

 beautiful network*. 



An Egg as it appears ten days after incubation. 



On the eleventh day the arteries begin to be 

 distinct, those which were previously at a distance 

 from the heart now joining and cohering to it. It 

 * Zool, Journ, ii, 433. 



