Seg 



FIG. 43. THREE TRANSVERSE SECTIONS ACROSS THE CAUDAL 

 END OF THE MEDULLARY GROOVE OF A CHICK EMBRYO WITH SEVEN 

 SEGMENTS. (After Minot ) 



A, section through one of the segments. B, section posterior to the segments. 

 C, section just in front of the primitive streak. Md.gr, medullary groove; nek, 

 notochord; EC, ectoderm; mes, mesoderm; En, entoderm ; Seg. mesoblastic 



128 



