PLATE 7 



- r. r- 



29 



g 

 . fj 



- 







, *K :9 



**t&* 



35 



37 



36 



FIGS. 29 to 35. Photographs of serial sections through the amniotic vesicle of the twin embryo, 

 showing the ectodermic character of its wall and the investing layer of mesoderm. In figures 

 30 to 33 the region of the amniotic plate is clearly marked off. Enlarged 300 diameters. 



FIG. 36. Photograph of section through the yolk-vesicle. Enlarged 300 diameters. 



FIG. 37. Section (No. 73) through region of abdominal stalk, showing the relation of the two vesicles 

 (constituting the twin), to the larger embryo and the chorionic membrane. Enlarged 112 

 diameters. 



