TWINNING IN DASYPUS NOVEMCINCTUS 45 



Trager, while the thin-walled part of the trophoblast 

 is known as the diplotrophoblast (dtr). 



trfl 





dtr 



Fig. 12. — ^An armadillo egg (stage V) attached by the Trager to 

 uterus, and shown as if torn away at Tra. The ectoderm (ec) is a 

 hollow vesicle. The apical pole is at X. Endoderm {en) joins diplo- 

 trophoblast {dlr) in a ring (»■). The trophoderm plate {tr pi) lies within 

 the Trager collar (Tra); ectodermal layer of anmion (ec am); amniotic 

 cavity (o»»c); mesoderm (»»j); much enlarged extra-embryonic cavity 

 (ex c). (Modified from Patterson.) 



Stage V. The period of rapid growth and the estab- 

 lishment of bilaterality (Fig. 12). — During the earlier 



