Development of the Mammal 299 



SI 



layers form what is called the false omnion, or 

 serous membrane, or chorion (Fig. 38), 



In the chick the chorion is merely a thin 

 membrane that lies close against the inner-shell 



TA 



CF 



CP 



BM 



FlG. 95. A MEDIAN LONGITUDINAL, OR SAGITTAL, SECTION 

 THROUGH A RABBIT EMBRYO AND BLASTODERMIC VESICLE AT THE 



END OF THE NINTH DAY. (From Marshall, in part after Van Beneden 

 andjulin.) Xio. 



AN, tail fold of amnion. A A", proamnion. BM, mid-brain. C, extra- 

 embryonic part of the coelom or body-cavity. CP, pericardia! cavity. E, epi- 

 blast. E', thickened epiblast by which the blastodermic vesicle is attached to 

 the uterus (from Marshall). EK, epiblastic villi. GF, fore-gut. GH, hind-gut. 

 G T, mid-gut. //, hypoblast. A/, mesoblast. S r , sinus terminalis. 7>l,allan- 

 tois. F5, cavity of yolk-sac, of blastodermic vesicle. 



