livinq port of cell 

 food material, yolk 



fertilization of ovuro 



fertilizotioo in opper oviduct 

 ovary with immature eqqs 



fully formed "eqq" in 

 qostrula staqe 



shell 



endodcrm 



yolk 



choloza 



white 



proorTDnion 

 ectoderm of head 



forequt border, 



neural fold 

 neural qroove 

 notochord 

 somite 



primitive streak - 

 vascular area — 



incubated 35 hours Surface view 



proomnioo 



forebrain 



forequt 

 midbrain 



bindbrain 

 heort 



vitelline vein 



neural tube 

 somite : 



notochord 



© ^~W 



-neural groove 

 ^neural fold 



.primitive streak 



Fig. 23-4. Fertilization and early embryology of the chick. The egg is fertilized internally and by the time it is laid 

 the embryo is in the gastrula stage. After 33 hours of incubation several regions that will become organ systems 

 are laid out. 



