Fig 24 Ventral view of a model of the mesoderm (white), hyperentodermal 

 inpsonchyme (green) vasofactive cells (yellow) and endothclium (red) of an embryo 

 of four somites. Columbia Collection No. 409, X 300. Reduced J. 



1 Anlages of the dorsal aorta 4 Position of heart 



2 First aortic arch "> Omphalomesenteric vein 



3 Anlages of ventral aorta <'> Omphalomesenteric plexus 



82 



