Development of the Nine-Banded Armadillo. 421 



20 



21 



Fig. 20. A section taken through the connecting canal, which is seen to be com- 

 posed of two layers, ectoderm on the inside and mesoderm on the outside, and is 

 loosely connected with the mesoderm of the yolk-sac wall. X 143. 



Fig. 21. A section taken through the tip of the medullary plate. This is the first 

 section that shows the anterior end of the protochordal plate of Hubrecht. Note 

 that there are a few scattering mesoderm cells (?ws.) that have wandered in between 

 the plate and the ectoderm. X 143. 



Fig. 22. A section taken through the belly-stalk at the level of the mouth of the 

 allantois {al. ) . The cavity of the posterior amnotic process {p.am.c. ) does not cover 

 more than one-half the width of the section. The mesoderm of the belly-stalk 

 extends laterally to form wing-like processes. These are the belly-stalk 

 bands {b.b.) through which the umbilical blood vessels pass to the Trager. X 143. 



