msth. 



Ent. 



FIG. 83. TRANSVERSE SECTION THROUGH THE DORSAL REGION 

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

 Minot.) 



Am., amnion. A a., aorta, card., cardinal vein. Cho., chorion. Coe., Coe' ., coe- 

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

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

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

 Som., somatopleure. Sp.c., spinal cord. Spl., splanchnopleure. Ve., vein. K, 

 accumulation of mesodermic material about the vitelline vein. 



2 7 I 



