352 H. B. POLLAED. 



Fig. 2. — " Schematic" representation of braiu — ectoderm (blue), mesoderm 

 (red), and endoderm (yellow) — viewed from below. First day. 



Fig. 3. — "Schematic" representation of braiu. Third day. The struc- 

 tures are represented also as cut in halves in the middle line vertically. 



Fig. 4. — Model of brain at fifth subsequent day. Left half viewed from 

 inside. Commissures represented in red. 



Fig. 5. — Sagittal section of anterior end of embryo of first day. (x 450 

 approx.) 



Fig. 6. — Transverse section through same region. Slightly oblique. 

 ( X 450 approx.) 



Fig. 7. — Transverse section through optic stalks. Slightly oblique. ( X 450 

 approx.) 



Fig. 8. — Transverse section behind optic stalks. Slightly oblique, (x 450 

 approx.) 



Fig. 9. — Transverse section through the eyes. Slightly oblique, (x 450 

 approx.) 



Fig. 10. — Transverse section behind the eye. Slightly oblique, (x 450 

 approx.) 



(Figs. 6 — 10 are from the same embryo.) 



Fig. 11.— Sagittal section through eye and ear. Third day. 



