PLATE IV 



EXPLANATION OF FIGURES 



40. The dorsal view of a vesicle in a rather advanced stage of development. 

 The embryos measure 155 mm. from tip to tip. The dorsal notch, d.n., although 

 extending down to near the meddle of the vesicle, does not completely separate 

 the lateral placental discs. X f 



41. Dorsal view of a vesicle showing the difinitive condition of the placenta. 

 The placenta is divided into two lateral discs, each of which is distinctly bilobed. 

 The notch between the two lobes of the left lateral (on right) disc is clearly shown 

 in the photograph (n.l.l.). The discs are united to each other both on the dorsal 

 and ventral side by placental bridges, the one on the dorsal side (d.b.) being the 

 narrower. The original arborescent villi at the cervix end have greatly degen- 

 erated, and have become reduced to flat, blunt knobs. The embryos in this vesicle 

 are about 210 mm. from tip to tip. X \. 



42. Right lateral view of a uterus showing a dorso-ventral bilobing. Embryos 

 are 48 mm. long. X |r. 



43. Ventral view of a pear-shaped uterus, which contained embryos measuring 

 52 mm. This and the preceding uterus show two of the several forms that have 

 been observed. X \ 



