7O EARLY EMBRYOLOGY OF THE CHICK 



in Figure 28, C. The heart here is enlarged and displaced 

 somewhat to the right of the mid-line but its fundamental 



neural plate ectoderm 

 dorsal mesoderm 



superficial ectoderm 

 neural groove 



splanchnic mesoderm 



gut immediately caudal to 

 anterior intestinal portal 



neural groove 



epi-myocardium 



somatopleure 

 ' splanchnopleure 



> somatopleure 



}- splanchnopleure 



endocardium -" gut imme diately caudal to 

 anterior intestinal portal 



epi-myocardium 

 endocardium 



dorsal mesoderm 



fore-gut 



epi-myocardi 



endocardium 



somatopleure 



- splanchnopleure 



of fusion of lateral margins of 

 anterior intestinal portal 



dorsal mesoderm 



fore-gut 



dorsal mesocardium 



ventral mesocardium 



dorsal mesoderm 

 notochord 



dorsal mesocardium 



] somatopleure 



,}- splanchnopleure 

 epi-myocardium 



splanchnopleure 



epi-myocardium 



FIG. 26. Diagrams of transverse sections through the pericardial region 

 of chicks at various stages to show the formation of the heart. For location of 

 the sections consult Fig. 27. 



A, at 25 hours; B, at 26 hours; C, at 27 hours; D, at 28 hours; E, at 29 hours. 



relations are otherwise the same as in a 29-hour embryo (Fig. 

 26, ). 



