

Not. 

 Not. Mes.-Sj^ 





Not. J J 





En. -j 2 



Figs. 1 to 11 are from Embryo VI; fig. 12 from Embryo V. All wore drawn with the aid of the camera lucida. 



Magnification X 300. 



Fig. 1. Notochord at its cephalic end. Notochordal canal is 



evident. 

 Pig. 2. Xotochord at level of first branchial pouch. 

 Fig. :i. Notochord at level of second branchial pouch. 

 Fig. 4. Notochord at level of sinus venosus. Notochordal 



canal is evident. 

 Fig. .3. Notochord over middle of yolk sac. Dorsal aorta is 



shown under the notochord. 

 Fig. 6. Notochord at posterior end of yolk sac, connected by 



neck of cells to endoderm. 



Fig. 7. Notochord over caudal end of hind gut. 



Fig. 8. Notochord over beginning of cloaca. 



Fig. 9. Notochord over cloaca at level of allantois. 



Fig. 10. Notochord over level of caudal edge of cl :al mem- 

 brane, showing remains of ncurenterie canal. 



Fig. 11. Notochord two sections before its fusion with the 

 primitive streak. 



Fig. 12. Notochord over cloaca in Embryo V, to show the. 

 remains of the neurenteric canal. ( !ompare with 

 fig. in. from Embryo VI. 



On page 40 will be found a list of abbreviations applicable to all the plates in this paper. 



