310 FORMATION OF THE EGG AND CHICKEN 



pronounced specializations are the definite formation of body walls 

 and a rudimentary growth of feathers. At this period the^ white 

 or albumin has practically disappeared. The beak is formed, and 

 gives the embryo a distinctly birdlike appearance. The head is 

 proportionately large, and the eyes extremely so. The body is 

 very bulky, owing to the large size of the heart and liver. The 

 legs have increased greatly in size, and the division of the extrem- 

 ities into toes is very marked. The yolk sac, while yet large, is 

 very flabby, from the absorption of nutriment. 



The feathers may be distinctly seen on the ninth day. They 

 are enclosed in a small sac, in which they grow to about one- 

 quarter of an inch in length before hatching time, but the sac is 

 not broken until then. By the thirteenth day the beak and nails 

 have taken on a hard, horny appearance. 



Motion can be discerned in the embryo on about the sixth day, 

 but it is very slight, and there is no pronounced movement of the 

 entire embryo until the fourteenth day. Up to this latter time the 

 chick has been lying with its body at right angles to the long axis 

 of the egg. Now it turns, so that the body lies lengthwise of the 

 egg, the beak in contact with the inner membrane of the shell 

 about one-quarter of the way from the large end of the egg. The 

 air cell is now much enlarged, owing to evaporation of the fluids, 

 and the additional space so formed is utilized by the chick at 

 hatching. Infrequent turning of the eggs, or weakness of the 

 embryo, will not permit the change of position on the fourteenth 

 day ; there will be what is termed a "false presentation," and, in the 

 majority of cases, the chick will not be able to get out of the shell. 



By the twentieth day the embryo will have grown so that it 

 occupies all of the egg except the air cell, the yolk will have been 

 nearly all absorbed, and what remains is drawn into the body 

 at the umbilicus (navel opening), the body walls closing over 

 the opening. This process of absorption is an important factor 

 in the early life of the chick, since it is the source of nourishment 

 until the chick can digest and assimilate feed from outside sources. 



Process of Hatching. The process of hatching is one of the 

 most striking phenomena connected with the development of the 

 young chick, and is interesting alike to the experienced and in- 

 experienced. The process is approximately as follows : 



When ready to leave the shell, which is usually on the twentieth 

 or twenty-first day, the chick tears the inner shell membrane with 

 its beak, stretches its neck, and, occupying the extra air space, at 

 once begins to breathe the air which it contained. As a result of 



