4i8 



EYCLESHYMER. 



EXPLANATION OF PLATE XXIL 



Figs. 1-4. Successive phases in closure of neural folds of Amblystoma (X 15). 

 Figs. 5-8. Successive phases in closure of neural folds of Rana palustris show- 

 ing the infolding of the optic pits, and the formation and extension of the oral 

 and olfactory grooves (X 15). 



Figs. 9-1 i. Successive phases in closure of neural folds of Necturus, showing 

 formation of optic vesicles (X 10). 



Fig. 12. Transverse section through dark areas shown in Fig. 5 (X 120). 



Transverse section through same areas as shown in Fig. 6 (X 130). 

 Transverse section through same areas as shown in Fig. 7 (X 100). 

 Transverse section along line 15 in Fig. 10 (X90) 

 Transverse section along line 16 in Fig. 11 (x8o). 

 Transverse section along line 17 in Fig. i (X 100) 



