1 6 WALLACE. 



EXPLANATION OF PLATE IIL 



Fig. I. Longitudinal median section of blastoderm shown in PI. II, Fig. 6. 

 X 100. per. ^= periblast. 



Fig. 2. Cross-section of the same. X loo. 



Fig. 3. Cross-section of rim at anterior pole of stage shown in PI. Ill, Fig. 9. 

 X 160. 



Fig. 4. Cross-section of rim in lateral region of stage shown in PI. Ill, Fig. 9. 

 X 160. 



Fig. 5. Longitudinal section through axial thickening of stage shown in 

 PI. II, Fig. 9. X 160. 



Fig. 6. Cross-section of rim at anterior pole of blastoderm shown in PI. II, 

 Fig. 8. X 160. 



Fig. 7. Cross-section of rim in lateral region of blastoderm shown in PI. II, 

 Fig. 8. X 160. 



Fig. 8. Longitudinal median section through embryo and lip of blastopore at 

 stage shown in PI. II, Fig. 5. X 160. A'.r'. ^ Kupffer's vesicle; /. ^lip of 

 blastopore. 



Fig. 9. Enlarged view of blastoderm in which the germ-ring is beginning to 

 disappear at the anterior pole. X 45. (Drawn by Mr. Hayashi.) 



