III.1 



THE NOTOCHORD. 

 Fig. 20. 



iMIB^^ 



61 



Transverse Section through the Embryonic Eeqion op the 

 Blastoderm of a Chick at the time op the formation 

 op the notochord, but before the appearance op 

 THE Medullary Groove. 



ep. epiblast ; hy. hypoblast ; ch. notoohord ; me. mesoblast ; 

 yk. yolk of germinal wall. 



Fig. 21. 



Transverse Section op a Blastoderm incubated for 

 18 hours. 



The section passes through the medullary groove mc, at some 

 distance behind its front end. 



A. Epiblaat. B. Mesoblast. C. Hypoblast. 



m.o. medullary groove ; m.f. medullary fold ; ch. notochord. 



