TWINNING IN DASYPUS NOVEMCINCTUS 57 



Vitelline blood vessels, arranged somewhat as in the 

 area pellucida and area opaqua of the avian egg, are 



Fig. 18. — Armadillo egg showing that the primary embryos (II 

 and IV) are in advance of the secondary embryos (I and III). The 

 primary placenta as Trager is becoming displaced by the secondary 

 true placenta, which is covered with villi, or short finger-like processes 

 (see stage X). (Redrawn from Newman and Patterson.) 



very characteristic features of this stage; no blood is 

 found in this vitelline area and no vitelline circulation 



