CHANGES IN THE EGG. 95 



the chick is within the amnion. Motion 

 commences on the sixth day ; ossification, 

 or the commencement of bones, on the 

 ninth ; and at the same time the marks of 

 the elegant yellow vessels on the yolk-bag 

 begin to appear. 



On the fourteenth day the" feathers begin 

 to be seen, and if the chick is taken out of 

 the egg it will now open its mouth, as if 

 for air. 



On the nineteenth day it is able to utter 

 sounds, and on the twenty-first or second 

 breaks the egg. This latter process is ef- 

 fected in a systematic manner. The chick 

 lies in the shell, with its feet and tail to- 

 wards the smaller end ; the head is bent 

 down under the wing, with the bill project- 

 ing up on a level with the inner surface of 

 the shell. When the chick is sufficiently 

 developed, it forces its bill through it. At 

 each successive stroke the body is turned 

 partly round, so that a circle of fractures is 

 formed ; but before this is completed, the 

 shell usually gives way. The inner mem- 

 brane is sometimes very thick, and the 



