324 



THE MAMMALIAN EMBRYO. 



[CHAP. 



ing medullary folds (Fig. 105 C, ae). Where this promi- 

 nence becomes first apparent the epiblast and hypoblast 



A SERIES OF TRANSVERSE SECTIONS THROUGH THE JUNCTION 

 OF THE PRIMITIVE STREAK AND MEDULLARY GROOVE OF 

 A YOUNG GUINEA-PIG. (After Schafer.) 



A. is the posterior section. 



e. epiblast ; m. mesoblast ; h. hypoblast ; ae. axial epiblast of 

 the primitive streak ; ah. axial hypoblast attached in B. and 

 C. to the epiblast at the rudimentary blastopore ; ng. me- 

 dullary groove ; /. rudimentary blastopore. 



