Fig. 23. — Colored plate drawn by Miss Katharina Hill, artist of the De- 

 partment of Anatomy of the University of Chicago, from an enlargement 

 of Fig. 25, photomicrogi-aph from section 153. The embryo shown in this 

 plate is di'awn after section No. 155, because in it the yolk sac, embryonic 

 shield proper, allantois and allantoic duct are best seen. 



All. S.— Allantoic stalk. 



C. A. — Cavity of amnion. 



Can. F. — Fine fibrin threads and leucocytes (early canalized fibrin). 

 Cho. M. — Chorion mesoderm. 



D. C. — Decidua capsularis. 

 Exoc. — Exocoeloni. 



Gl. — Gland space (ei)ithelium partly preserved). 



Mat. Bl. S.^ — Large cystic gland spaces filled with blood. 



S. v.— Yolk sac. 



Syn. — Syncytium. 



Tr.— Trophoblast. 



