Development of the Nine-Banded Armadillo. 419 



NOTE Figs. 16-23 represent a series of transverse sections taken through various 

 regions of an embryo from the same vesicle as that shown in fig. 13. 



FIG. 16. A section taken through the anterior end of the medullary plate. The 

 most important feature of this section is the thickening of the entoderm to form 

 the "protochordal plate" of Hubrecht, p.p.h. X 130. 



FIG. 17. A section taken through the medullary plates at a point lying half way 

 between the fore end of the head process and the anterior tip of the embryo. The 

 entoderm is distinct from the mesoderm, which is scarcely more than one cell thick. 

 X 130 



