EC. 



Cho. 



msth. - 



Ent. 



FIG. 83. TRANSVERSE SECTION THROUGH THE DORSAL REGION 

 OF A CHICK EMBRYO WITH ABOUT TWENTY-EIGHT SEGMENTS. (After 

 Minot.) 



Ant., amnion. Ao., aorta, card.* cardinal vein. Cho., chorion. Coe., Coe' ., coe- 

 lom. EC.) ectoderm, endo., endothelial heart. ./., entoderm. Z,/., liver, mes., 

 mesoderm. m.At., muscular heart, msth., mesothelium. My., primitive seg- 

 ment, nch., notochord. raph., raphe of amnion. Si.V., sinus venosus of heart. 

 Sow., somatopleure. Sp.c., spinal cord. S//., sp^lanchnopleure. Ve., vein. K, 

 accumulation of mesodermic material about the vitelline vein. 



271 



