22 



OUR DOMESTIC BIRDS 



FIG. 10. Egg before exclusion and partially 

 excluded chick 



purpose. In about thirty-six hours from the beginning of incuba- 

 tion it will be found that the germ has turned red, and little red 

 veins radiate from it somewhat like the legs of a spider. For 



several days the egg 

 is quite translucent 

 and the yolk shows 

 plainly. As the 

 germ grows, the 

 contents of the egg 

 become clouded and 

 dense, and the air 

 space at the large 

 end of the egg is 

 clearly defined, the 



density being greatest near it. From the time that the egg be- 

 comes dense, observations of development must be made by 

 breaking one or more eggs daily or every few days, according 

 to the number available for observation. 



The embryo grows until it fills the egg. The mere application 

 of heat to the egg has gradually transformed that little germ 

 and the yellow and white of egg 

 into bones, flesh, skin (and, in 

 some cases, down), and all the 

 organs of a living creature. 

 When the embryo has filled the 

 shell, it lies curled up, usually 

 with the head at the large end 

 of the egg and the beak almost 

 touching the shell, at about one 

 third of the distance from the FlG< . Light Brahma (day old) 

 large to the small end of the 



egg. At the point of the beak of the young bird on the curved 

 tip of the upper mandible is a small horny scale. Without this 

 scale it would be hard for the embryo to break the shell because it 



