CHICK EMBRYO OF TWENTY-SEVEN SEGMENTS 



71 



folds now forms the outer layer of the chorion and the inner layer of the amnion. The meso- 

 dermal folds of the amnion have not united. 



Spinal cord 

 Mes. segment 



Dorsal aorta. 



Mesenchyme 



Common . 

 card- vein 



Entoderm 

 Myocardium 



.ndothelium 

 or heart 



Fig. 59. — Transverse section through the sinus venosus and common cardinal veins of a fifty-hour 



chick embryo. X So. 



Chorion 



Notochord 

 Dorsal aortcc 



. Foreput 



L. vitelline 

 vein 



Splanchnic 

 mesoderm 



Post card. 

 Vein 



Splanchnic 

 mesoderm 



Liver 

 anlage 



Fig. 60. — Transverse section through the anlage of the liver of a thirty-six-hour chick embryo. X So. 



Section through the Anlage of the Liver (Fig. 60) . — In this section the cavity of 

 the fore-gut is narrow, the gut being flattened from side to side. Ventrad there are evaginated 

 from the entoderm two elongate diverticula which form the anlages of the liver. On either side 



