9 6 



EARLY EMBRYOLOGY OF THE CHICK 



narrowed optic stalks. The invaginated layer of the optic cup 

 is termed the sensory layer because it is destined to give rise 

 to the sensory layer of the retina. The layer against which 



prosencephalon 

 choroid fissure 

 Rathke's pocket 



ventral aortic root 



anterior intestinal 

 portal 



roots of omphalo 

 mesenteric artery 



mesencephalon 



cut ectoderm 



met encephalon 



anterior cardinal vein 

 myelencephalon 



neuromere of 



myelencephalon 

 auditory vesicle 



aortic arches 1. 11,111. 

 pharynx 



duct of Cuvier 

 posterior cardinal vein 

 dorsal aorta 



omphalomesenteric veir 



cut spianchnopleure 

 cut somatopleure 



om phalomesenter ic 

 artery 



posterior intestinal 

 portal 



FiG. 35. Diagram of dissection of chick of about 50 hours. (Modified from 

 Prentiss.) The spianchnopleure of the yolk-sac cephalic to the anterior in- 

 testinal portal, the ectoderm of the left side of the head, and the mesoderm in 

 the pericardial region have been dissected away. A window has been cut in 

 the splanchnopleure of the dorsal wall of the mid-gut to show the origin of the 

 omphalomesenteric arteries. 



the sensory layer comes to lie after its invagination is termed 

 the pigment layer because it gives rise to the pigmented layer 

 of the retina. The double-walled cups formed by invagination, 



