EMBRYO AND EMBRYONIC MEMBRANES 221 
Rate of Growth of the Allantois. As the embryo lies on its 
left side, the allantois grows out on the right side of the embryo 
(Figs. 127 and 130 A) and unites with the chorion about the 
one hundredth hour. It then spreads rapidly as a flattened sac 
over the embryo, increasing the extent of the fusion with the 
77. C—-- 
ALE 
Fic. 130. — Diagrams showing the relations of the allantois, 
represented by the tinted area, at different ages. (After 
Hirota.) 
Alb., Albumen. Alb. S., Edge of albumen-sac. All. V., 
Allantoic vein. am. C., Amniotic cavity. S.-Am., Sero-amni- 
otic connection. Y.S., Yolk-sac. 
A. At uel hours showing only the amniotic cavity and al- 
lantois x ‘ 
B. At 44 hours, showing only the amniotic cavity and al- 
lantois x 1.2. 
C. At 192 hours; the entire yolk x .66. The dotted out- 
line represents the amniotic cavity. 
D. At214hours. The entire egg after removal of the shell, 
x .66. The albumen mass is at the left; the albumen-sac is be- 
ginning to form. 
chorion, hence of its outer wall pari passu. At the end of the 
fifth day it covers more than half of the embryo (Fig. 130 A); 
at the end of the sixth day the embryo is entirely covered by 
