Development of the Nine-Banded Armadillo. 369 



y. s. w. 



Fig. 1. Outline camera drawing of a transverse section through a pregnant 

 uterus measuring about 15 mm. long by 14 mm. wide. Line D-V is drawn from 

 the points lying at the middle of the dorsal and ventral sides of the vesicle. It 

 divides the section of the vesicle into halves. Embryos I and II lie in the left 

 hand half, and III and IV in the right hand half, a.a., line of attachment of the 

 amnion to the vesicle; e.;;., a small extra chorionic vesicle, which is not fused 

 with the larger one; i.l., intestinal loop; l.s., lymph sinus between the wall of the 

 vesicle and the uterine mucosa, um. X 9. 



the two pairs of embryos and their placental areas from each 

 other. There may be a secondary shifting of the positions of the 

 various amniotic sacs, so that in the definitive condition one may 

 find the upper embryo of the right hand pair occupying the doi'sal 

 position, which in the great majority of cases is occupied by the 

 upper left hand embrj^o. Such a shifting might easily occur at 

 any time before the walls of the various amnia fuse firmly with 

 the chorion, a process that does not occur until a late period of 

 gestation. Previous to this time each amnion is attached to the 

 chorion only along a meridional line, an attachment that would 

 permit the whole sac to swing almost as readily to one side as to 



JOURNAL OF MORPHOLOGY, \OL. 21, NO. 3. 



