Development of the Nine-Banded Armadillo. 373 



ex.c. 



en 



ec 



-am. c.c. 



-V--m.p. 



777 S 



FIG. 2. A diagrammatic longitudinal section of an early stage of the Mulita. 

 ex.c., extraembryonic body cavity; en., entoderm; am.c., amniotic cavity of the 

 embryo; am.c.c., beginning of the amniotic connecting canal; c.am.c., cavity of the 

 common amnion; ms., mesoderm ',m. p., medullary plate ; i r. c., Trager cavity; tr.e., 

 Trager epithelium; (slightly modified after Fernandez). 



margins represent the entoderm of the inverted yolk-sac, while 

 the concave posterior margin is covered with Trager epithelium. 

 Between these two regions occurs a narrow zone where the vesicle 

 was attached to the uterine wall (marked X) . 



The Trager cavity (tr. c.) is situated in the concave space roofed 

 over by the Trager epithelium. While in some respects this cavity 

 is comparable to that of the rodents, yet for the most part any 

 such comparison would appear to be strained. The difficulty 

 standing in the way of pointing out any true homologies, however, 



