STREETER 



Campbell Art Co. 

 Elizabeth, N. J. 



FIGS. 17 to 22. Sketches of selected cell groups found in the chorionic villi, which are interpreted 

 as blood-vessels in a progressive series of developmental stages. In figure 22 is shown the 

 relation of the endothelium to the surrounding stroma. Enlarged 600 diameters (approx.). 



FIGS. 23 to 28. A similar series of angioblastic cell-groups found in the wall of the yolk-sac. In 

 this series the endoderm is shown as the upper and the mesoderm as the lower layer. 

 Enlarged 600 diameters (approx.). 



