Ectoderm 

 Amniotic cavity 



Ccelom 



Trophectoderm 

 *' Archenteron 

 Entoderm 



Mesoderm 



Ectoderm of embryo 



Ectoderm of amnion 



Allantois 



D 



Body stalk 



Amniotic cavity 



Ectoderm of embryo 

 Cavity of amnion 

 Mesoderm of 



Trophectoderm amnion 



Yolk sac Ectoderm of 

 chorion 



Entoderm Cavity of yolk 

 sac 



Splanchnic Entoderm of> 

 mesoderm y ifc sac 



Extra-embry- Mesoderm 

 omc ccelom O f yo i^ sac 

 Extra-embry- 

 onic C02lom 



Chorionic meso- 

 derm 

 Trophoderm 



Mesoderm 

 of chorion 



Chorionic villi 



Fig. 12. Four diagrams of early human embryos (based on figures of Robinson and 

 Minot). A, Hypothetical Stage; B, Bryce-Teacher Embryo (modified); C, Peter's 

 Embryo; D, Graf Spec's Embryo. From Prentiss and Arey, Embryology. By permission 

 of W. B. Saunders and Co. 



