8o 



THE BIOLOGY OF TWINS 



corpus luteum as a means of distinguishing between 

 multiple births and polyembryony should omit to furnish 

 this information. 



Fig. 33 



Fig. 34 



Figs. 33 and 34. — ^Two stages in the development of the egg of the 

 armadillo Euphractus (Dasypus) villesus (from Fernandez), showing 

 how each of the individuals shown in Fig. 32 appears before they fuse 

 membranes. In Fig. 33 the single embryo has formed at the lower pole, 

 as in Dasypus (cf. Figs. 13 and 14), but only one primitive streak 

 arises. In Fig. 34 the single embryo has grown backward, as in Dasypus, 

 to the upper pole, where placentation has occurred. 



The Peludo shows us typical armadillo development 

 unobscured by polyembryonic processes, and on that 

 account should throw light on the mechanics of poly- 

 embryony. A comparison of the earHest known stages 

 of the development of the Peludo and those in Dasypus 

 may be made by examining the diagram of Fernandez 



