302 



STUDY OF YOUNG CHICK EMBRYOS. 



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

 Medullary groove, nch, Notochord. Ec, Ectoderm. »«, Mesoderm. En, Entoderm. ■ 250 dianV 



