STRUCTURE OF FOUR-DAY CHICKS 



151 



in its associations. (See Chapter XI and Figures 30 and 32.) 

 The portion of the coelom which gives rise to the embryonic 

 body cavities is first marked off by the series of folds which 



neural plate 

 notochord 

 entoderm 



dorsal mesoderm 



intermediate mesoderm 

 lateral mesodenn 



lateral amniotic 



intra-embryonic coelom 

 extra-embryonic, coelom 



liver in 



ventral 



, mesentery 



right and left 

 coelom confluent 



Fig. 54. — Schematic diagrams of cross sections at various stages to show the 

 establishment of the coelom and mesenteries. For explanation see text. 



separate the body of the embryo from the yolk (Fig. 54, C, D). 

 As the closure of the ventral body wall progresses (Fig. 54, 

 E, F) the embryonic coelom becomes completely separated from 



