The caudal end of embryo No. 7802, stage 7. A detached protion of the allantoic diverticulum can be seen above. Further ventrally, the caudal end of the amniotic cavity is evident, and the clump of cells in and on its ventral aspect represents the primordium of the cloacal membrane. The umbilical vesicle is readily visible in the lower half of the photomicrograph. Section 42-2-5.