Ventral membrane (composite) 



Dorsal membrane 



Spinal cord 



Notochord — 



Spinal cord 



Notochord 

 Dorsal membrane 

 Ventral membrane (composite)- — 



'^O 



Dorsal membrane 



i.ents 

 Spinal cord 

 Notochord (composite) 



Aorta 



Caudal vein 

 Ventral membrane 

 Spinal cord 



>rds, and d 



- 





ng in part to 



Muscle segments of principal 

 . Spinal cord 



Notochord 

 .... Aorta 

 }y^ \ Caudal vein 



Muscular tissue of defective embryos 

 Ventral membrane (composite) 



\^ 4 J Dorsal membrane of defective embryo B 



A 



Dorsal membrane 

 Muscle segments 



.Spinal cord ) aC%f 



Notochord / SV 



Ventral membrane (composite) 



Ventral membrane (composite) 



Dorsal membranes of \ 

 embryos A and BJ 



Naming of parts same as in 

 last figure. The dorsal mem- 

 branes of A and B are now 

 united. 





J. F. G. 





VII 



