A 



B 



Ectoderm 

 Amniotic cavity 



Ccelom 



Trophedoderm 

 A rchenteron 



Enloderm 

 Mesoderm 



Ectoderm 



Ectoderm of amnion 



Allantois 



Trophectoderm 

 Yolk sac 



Ectoderm of embryo 

 A mniotic cavity Cavity of amnion 



Mesoderm of 



a m a ion 

 Ectoderm of 

 chorion 



Entoderm Cavity of yolk 

 sac 



Splanchnic Entoderm 

 mesoderm yo ik sac 



T-l ,f J. 



j ^y ^lj\liQ.~CiflOF \ ~ \ff ^flflf}'}}? 



onic ccdom of yolk sac 

 Extra-embry- 

 onic caslom 



Choriomc meso- 

 derm 



~Trophoderm 



Mesoderm 

 of chonon 



Chorionic villi 



FIG. 12. 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 & Co. 



