POSTERIOR 



ANTERIOR 



PRE-CHORDAL PLATE 



,N0TOCH0RD NEURAL ECTODERM 



Fig. 213. Sagittal sections of blastoderms shown in figure 212A-G, with corresponding 

 letters, showing migration of presumptive organ-forming areas. (See also fig. 179.) (B) 

 Dorsal lip is shown to left. (H-M) Transverse sections of embryo of Squalus acanthias, 

 similar to stages shown in 212F and G, for Scy Ilium. (H) Section through anterior 

 head fold. (M) Section through caudal end of blastoderm. H-M original drawings 

 from prepared slides. 



443 



