STRUCTURE OF FIFTY-HOUR CHICKS 



97 



are also termed secondary optic vesicles in distinction to prim- 

 ary optic vesicles, as they are called before the invagination. 

 The formerly capacious lumen of the primary optic vesicle is 



visceral furrow 1 



myelocoele 



auditory vesicle 



dorsal 



aorta 



pharynx 



mandibular arch 

 aortic arch I 

 dorsal aorta 



nyelencephalon 



ant. cardinal v 



pharyn 



visceral cleft II 



duct of Cuvier _ 

 dorsal aorta 



diocoele 

 ventral aorta 



lens 



sensory layer of retina 



;ment layer of retina 



diencephalon 



extra-embryonic 

 coelom 



region of choroid fissure 

 pharyngeal pouch I 



ndocardium of 

 bulbo-conus arteriosus 

 epi-myocardium of 

 ventricle 



somatopleure 

 splanchnopleure 



fore-gut 



intra-embryonic coelom 



dorsal mesocardi 

 sero-amniotic raphe 



telline vessels 

 extra-embryonic coelom 



eural crest 



dorsal aorta 



post, cardinal 



extra-embryonic coelom 



intra-embryonic coelom 

 omphalomesenteric vein 



lateral amniotic fold 



B 

 C 



mesonephric duct 

 mesonephric tubule D 



E 



mid-gut 



fold 



E 



itelline vessels 



mesonephric duct *" 



mesonephnc tubule 



PIG. 36. Diagrams of transverse sections of 55-hour (ao-somite) chick. The 

 location of the sections is indicated on an outline sketch of the entire embryo. 



practically obliterated in the formation of the optic cup. What 

 remains of the primary opticcele is now but a narrow space be- 



7 



