226 



EMBRYOLOGY. 



Fig 132.— Five diagrammatic figures illuatrating the development of the foetal egg-memtranes 

 of a Iffammal, after Kolliker. 

 fig:iires 1 to 4 the embryo is represented in longitudinal section. 

 ^1) Ovum with zona pellucida, 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 amniotic folds, the amniotic sac and the serous mem- 

 brane are formed, and the allantoiB makes its appeai'ance. 



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

 embryo, in which the oral and anal openings hav^ arisen. 



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



aUantois has become applied to the serous membrane on all sides, and has grown into it» 

 villi. The serous membrane from this time forward takes the name of chorion. The cavity 



