io6 



EARLY EMBRYOLOGY OF THE CHICK 



neural fold 



ectoderm of head 



somite 



intermediate mesoderm 



somatic mesoderm 



coelom 



splanchnic mesoderm 

 entoderm 



dorsal aorta 



epithelial layer of somite 



core of somite 



pronephric tubule 

 (intermediate mesoderm) 



somatic mesoderm 



coelom 



splanchnic mesoderm 

 entoderm 



D 



epithelial layer of somite 



cavity of somite 

 core of somite 

 migrating cells 



posterior cardinal vein 

 mesonephric duct 

 mesonephric tubule 

 coelom 

 dorsal aorta 



dermatome 

 sclerotome 



myocoele 



posterior cardinal vein 



mesonephric duct 

 mesonephric tubule 



dorsal aorta 

 intra-embryonic coelom 

 extra-embryonic coelom 



PIG. 38. Drawings from transverse sections to show the differentiation of the 



somites. 



A, second somite of 4-somite chick; B, ninth somite of 12-somite chick; C, 

 twentieth somite of 30-somite chick; D, seventeenth somite of 33-somite chick. 



