8 



THE ANATOMY OF VEETEBRATED ANIMALS. 



lesces with the vitelliiie membrane, to foi-m the Chm-ion 

 (Fig. 3). 



Fig. 3. 



Fig. 3. — Later stages of the development of the body of a Fowl thau 

 those represented in Fig. 2. — E, embryo at the third day of incuba- 

 tion ; ff, heart ; h, eye ; i, ear ; k, visceral arches and clefts ; /, m, 

 anterior and posterior folds of the amnion which have not yet united 

 over the body; 1, 2, 3, first, second, and third cerebral vesicles ; la, 

 vesicle of the third ventricle. — F, embryo at the fifth day of incuba- 

 tion. The letters as before, except n, o, rudiments of the anterior 

 and posterior extremities ; Am, amnion ; All (the allantois, hanging 

 down from its. pedicle ) ; Um, umbilical vesicle. — G, under-view of 

 the head of the foregoing, the first visceral arch being cut away. 



Thus the amnion incloses the body of the embryo, but 

 not the umbilical sac. At most, as the constricted neck, 



