som 



ng 



som 



som 



Fig. 7, A and B. Two Later Stages in the Development 

 of Amphioxus, showing the elongation of the embryo in the 

 antero-posterior axis (o p), and formation of the somites 

 (som) ; neural groove (ng) and neural tube (nt ) ; ect, ecto- 

 derm; mes, mesoderm; ac, alimentary canal. (After Hatschek.) 



Fig. 8. Caoss Section of Amphioxus Larvae in Successive 

 Stages of Development. A, through a larva similar to 7 A; 

 B and C, of a larva similar to 7B; D, of a still older larva, 

 ect, ectoderm; ent, endoderm; mes, mesoderm; ch, notochord; 

 np, neural plate; gc, gastrocoel; ac, alimentary canal; coel, 

 coelom. 



