Fig. 30 Serial transverse section of an embryo of twelve somites. 2, Cells 

 derived from visceral mesoderm in process of accretion to the aorta; 3, cells of 

 sclerotome in syncytial continuity with endothelium; 7, angiocyst added to aorta; 

 a remnant of septum is still visible. 



89 



