Fig. 83. — Transverse section through the dorsal region 



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



Minot.) 



Am.y amnion. Ao.^ aorta, card.^ cardinal vein. Cho,^ chorion. Coe.^ Coe'.^ coe- 

 lom. ^c, ectoderm, endo,, endothelial heart. ^«/., entoderm, iz'., liver, mes.^ 

 mesoderm, m.ki.^ muscular heart, insth,^ mesothelium. My.^ primitive seg- 

 ment. «c^., notochord. rapk.^ raphe of amnion. 6"/. K., sinus venosus of heart. 

 Soin.^ somatopleure. Sp.c.^ spinal cord. Spl.^ sjjlanchnopleure. Ve,^ vein. K., 

 accumulation of mesodermic material about the vitelline vein. 



271 



