\ -TEXT-BOOK OF EMBRYOLOGY. 



Chorionic villi 



Chorion 



Mesoderm 

 of chorion 



Blood vessel 



FIG. 77. Medial section of human embryo shown in Fig. 76. von Spee, Kollmann. 



Ecto- 

 Mesoderm derm Primitive groove 



Ectoderm 



Parietal mesoderm 

 Visceral mesoderm 

 Entoderm 

 FIG. ?&. Transverse section through primitive streak of embryo shown in Fig. 76. von Spee. 



Parietal mesoderm Primitive groove 



Visceral mesoderm Primitive fold 



Entoderm 

 FIG. 79. Transverse section through primitive groove of rabbit embryo, van Beneden. 



