Fig. 24 N'cntral viinv of :i iikmIoI of tlio mesoderm (white), hyporentodernml 

 mesencliyiiie (green) VMsofaetivc cells {yellow) :iiul enilotlielium (I'eil) of mm eniltryo 

 of four somites. Col\irnlii:i Collcclion \o. 40!), X 3(K). Roilueed ! . 



1 Anhiges of the ilors:il aorta I Position of hearl 



2 First aortic areh .'i Omphaloinesentcric vein 



3 Anlages of ventral aorta li ( )Tn|ihalomesenterie plexus 



82 



