THE EARLY EMBRYOLOGY OF THE MOUSE 



19 



Maternal blood 



Ectoplacental cavity 



Chorion 



Exocoelom - 



Amnion 



Fore-gut 



Amniotic cavity 



Embryonic ectoderm 



Head process 



Squamous entoderm 



Secondary giant cell 



'" — Ectoplacental cone 



Distal entoderm 



Proximal entoderm 



Extra-embryonic 

 ectoderm 



03 Mesoderm 



AUantois 



Primitive streak 



Fig. 13.— Sagittal section of embryo of 7 days 6 hours showing completion of amnion 

 formation. Reichert's membrane omitted. Projection drawing (X200). 



