PLATE 4 



EXPLANATION OF FIGURES 



4 Herzog embryo, slide M, sect. 147. Chorion and base of body-stalk, to 

 show irregularity of the coelomic surface, the partial mesothelial layer, and the 

 funnel-shaped ingrowths (/.). The chorionic ectoderm has shrunken away, leaving 

 naked the chorionic mesoderm, at the bottom of the drawing, and the stumps of 

 two villi (wz7.). Coe., coelom; a, unlined space; 6, angioblast cord. X circaSOO. 



5 Herzog embryo, slide M, sect. 143. Angioblast cord in chorion, part of a 

 net. Notice the clear-cut extra-intimal space. X circa 800. 



8 Grosser embryo, slide 3, row 8, sect. 3. Vessel from the body-stalk, to 

 show delamination of endothelium and formation of extra-intimal space. X circa 

 800. 



11 Minot embryo, H.E.C. no. 825, sect. 27. Cross section of a strand of the 

 net in the chorion to show a small angiocyst. X circa 540. 



472 



