302 



STUDY OF YOUNG CHICK EMBRYOS. 



Seg 



En 



FIG. 173. CHICKEN EMBRYO WITH SEVEN SEGMENTS. 



Three transverse sections across the caudal end of the medullary groove: A, Section through one of the seg- 

 ments ; B, Section posterior to the segments ; C, Section just in front of the primitive streak. Md.gr, 

 Medullary groove, nch, Notochord. EC, Ectoderm, tries, Mesoderm. En, Entoderm. X 2 3 diams. 



