CHAPTER VII 



THE DEVELOPMENT OF THE FIFTH DAY 



THERE are no very striking features to 

 be noticed during the fifth day, the 

 changes that take place being mostly 

 the growth and development of the structures 

 that have originated during the previous days. 



The allantois is now a large and vascular 

 sac, stretching over the right side of the chick, 

 between the two layers of the amnion (Figs. 

 38, and 80, a//), and serving as the chief organ 

 of respiration. 



The yolk is completely enclosed by the 

 blastoderm, and the vascular area covers about 

 two-thirds of the blastoderm. The embryo is 

 so much curved that its head and tail are 

 almost in contact (Fig. 80). 



The splanchnic stalk is completely closed, 

 and will remain in about the same condition 

 until nearly the time of hatching : there is still 

 considerable space between it and and the 

 somatic stalk. 



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