AMPHIOXUS. 



Fig. 219. — The Development of Amphioxus as seen in 

 Sections. 



Neural Tube. 



305 



Neural Groove. 



Neural Tube. 

 Notochord. 



Trunk- sacs, 



Neural Tube, 



Neurenteric 

 Canal. 



(x\ Through D 1-2 in Fig. 218; B through E 3-4, and C through E 5-6 in 

 Fig. 218 ; D through F 7-8 in Fig. 218 ; E through H 9-10 in Fig. 219 ; and F through 

 posterior part of Fig. 221.) i/t.,. • " 



A shows the neural groove and developing mesoblastic sacs ; B and C show 

 the neural tube ; D shows the completed mesoblastic sacs ; E shows the notochord 

 completely formed ; and F shows the formation of myotome from dorsal part of 

 mesoblast and perivisceral coelom from ventral. (After Hatschek.) 



G, Longitudinal horizontal section of an Amphioxus larva. (After M'Bridk.) 



H, Horizontal longitudinal section through advanced chordula larva of Ainphi- 

 oxtcs. (After Hatschek.) 



M. 



21 



