.226 



EMBRYOLOGY. 



Fig 132. Five diagrammatic figures illustrating the development of the total egg-membranes 

 of a Mammal, after EOLLIKER. 

 figures 1 to 4 the embryo is represented in longitudinal section. 



(1) Ovum with zona pelhicida, blastula, embryonic area, and embryonic fundament. 



(2) Ovum iu which the yolk-sac and the amnion are beginning to develop. 



(3) Ovum in which, by the fusion of the araniotic folds, the amniotic sac and the serous mem- 

 brane are formed, and the allantois makes its appearance. 



(4) Ovum with serous membrane, which has developed villi, with a large allantois and an 

 ombryo, in which the oral and anal openings have arisen. 



(5) Diagrammatic representation of a young human,ovum, in which the_vascular layer of the 



allantois has become applied to the serous membrane on all sides, and has grown into ita 

 vilii. The serous membrane from this time forward fekcs the name of chorion. The- cavity 



