THE EMBRYO 



335 



Fig. 208. Fig. 209. 



Fig. 208 is a horizontal section through the stage represented by Fig. 205, 

 and shows the six pairs of mesodermic somites. 



Fig. 209 is a section through a later stage (Fig. 210) and shows the medullary 

 tube, the notochord, and the mesoderm pushing upward and downward between 

 entoderm and ectoderm. 



Fig. 210. — A later stage, showing most of the mesodermic somites completely 

 cut off from the entoderm, the notochord, and the medullary tube. 



