lug. 



•:>.'^ 



Transverse section of an embryo of fo\U' somites at the level indioateil 

 Cohunliia Collection Xo. 409, slide ">. row 6, section 15, 

 .sevci':il annyocysts are in co!itact but tlicir Inmina are 



by leader 3 in figure 24. 

 X300. Reduced ,;. Tin 

 not continuous. 



1 Aorta 



2 Juxta-neural line 



3 Quintal anlag(^ 



\'asofactive cells attached (o jiixla- 

 neuial vessel; this (deft-like lu- 

 men is not continuous with that 

 of the vessel 



Fig. 26 Ventral view of a model of the mesoderm (w'hite), mescnehynie (green), 

 vasofactive cells (yellow) and endothelium (red) of an embryo of eight somites. 

 Cohnnbia Collection Xo. 530, X 300. Reduced J. 



1 Doisal aorta 



2 Omphalomesenteric vein 



3 Omphalomesenteric plexus 



4 Projections of visceral mesoderm 



which later be<'ome conne<'ted 

 with the aorta 



5 Position of heart 



84 



