114 



COMPAEATIVE ANATOMY 



SOMATOPLEURE 

 AMNION CAVITY\ 



EXTRA-EMBRYON 

 COELOM 



SEROSA fcHORION 



AMNION 

 COELOM 



A. 



AMNION CAVITY 

 AMNION 



SEROSA 



FOETAL PLACEf^JTA 

 ALLANTOIS 



ENTERON 

 BRAIN 



COELOM 

 YOLK-STALK 



YOLK 



ALLANTOIC 

 STALK 



SPLANCHNOPLEURE 



Fig. 84. — Diagrams illustrating the development of the amnion and allantois. 

 The upper Figure (.4), a cross section of an earlier stage, shows the amniotic folds rising 

 above the embryo. The lower Figure (B), a longitudinal section of a later stage, shows 

 the allantois as well as the completely closed amnion. In most mammals the fused 

 allantois and serosa (chorion) form the foetal placenta. Ectoderm in diagram is striped, 

 mesoderm stippled in black, endoderm stippled in white. 



