

DEVELOPMENT OF THE FETAL MEMBRANES AND THE PLACENTA 57 



The Umbilical Cord and Body-stalk. The umbilical cord (Fig. 28) attaches 

 the fetus to the placenta; its length at full time, as a rule, is about equal to the 



false amnion or serosa 

 \ 



FIG. 29. Diagram of a transverse section, showing the mode ol formation of the amnion in the chick. The amniotic 

 folds have nearly united in the middle line. (From Quain's Anatomy.) Ectoderm, blue; mesoderm, red; entoderm 

 and notochord, black. 



Umbilical 

 cord 



Chorior 



Placenta 



Amnion 



Umbilical 

 cord 



Yolk-sac 



Vitelline 

 duct 



FIG. 30. Fetus of about eight weeks, enclosed in the amnion. Magnified a little over two diameters, 

 from stereoscopic photographs lent by Prof. A. Thomson, Oxford.) 



(Drawn 



