notochord 



Hensen's node 



primitive streak 



A PRIMITIVE STREAK STAGE 



extraembryonic coelom 



head fold 



foregut mesoderm 



notochord 



Hensen's node 



tail fold 



antoic diverticulum 



B BEGINNING OF SOMITE FORMATION 



notochord 



foregut 



serosa-^' 



Seesel's pocket 



anterior neuropore. 



posterior neuropore 



Hensen's node 



amniotic cavity 



hind brain. 



midbrain 



Rathke's pouch 



forebroin stomodeum 



amniotic cavity 



blood vessel 



D 25-SOMITE STAGE 

 Figure 9-6. Development of the gut (and ommion) in the early stages of the pig. (After Patten, 1 958) 



258 • THE VISCERA 



