300 Vertebrate Embryology 



membrane, but in the placental animals it is a 

 much more important structure, and takes an 



AX 



cx 



EK 



FlG. 96. A RABBIT EMBRYO AND FtETAL APPENDAGES AT THE END 

 OF THE TWELFTH DAY. THE EMBRYO IS REPRESENTED IN SURFACE 

 VIEW FROM THE RIGHT SIDE ; THE YOLK-SAC AND FCETAL MEMBRANES 

 ARE SHOWN IN MEDIAN LONGITUDINAL, OR SAGITTAL SECTION. THE 

 HIND-LIMB AND PART OF THE TAIL HAVE BEEN REMOVED TO ALLOW 

 THE YOLK-STALK AND ALLANTOIC STALK TO BE FULLY SEEN. (From 



Marshall, in part after Van Beneden and Julin.) X8. 



AX, amnio tic cavity, between the inner or true amnion and the embryo. 

 <?, CX, extra-embryonic part of the ccelom or body-cavity. , epiblast. E\ 

 ectoplacenta, or thickened part of the epiblast from which the placenta is formed. 

 EK,, epiblastic villi. //, hyppblast. M, mesoblast. SI, sinus terminalis. TA^ 

 cavity of allantois. KS", cavity of yolk-sac or blastodermic vesicle. 



