468 WILSON. 



PLATE XIV. 



[Figs. 11-17, 20 from life; 18, 19, 21, 22 from preparations.] 



Fig. II. The same egg shown in Figs. 3, 4, 5, immediately after completion of 

 the third cleavage (2 h. ^tZ inO- 



Fig. 12. The same seven minutes later. 



Fig. 13. Fourth cleavage, from the upper pole (3 h. 21 m.). 



Fig. 14. The same egg; end of the fourth cleavage (3 h. 30 m.). 



Fig. 15. Fourth cleavage; posterior view, showing origin of the first somatoblast 

 {N. megalops). 



Fig. 16. Fourth cleavage, from the right side (2 h. 40 m.). 



Fig. 17. The same egg, nearly in the same position, in the sixteen-celled stage 

 (2 h. 55 m.). 



Fig. 18. Optical longitudinal section of sixteen-celled stage. 



Fig. 19. Beginning of the fifth cleavage, from the upper pole; primary micro- 

 meres preparing for their second spiral division (r/i Fig. 14). 



Fig. 20. Twenty-two-celled stage, immediately following the last, from the upper 

 pole. First division of X, formation of the two posterior tertiary micromeres fi, d^ 

 (3h.58m.). 



Fig. 21. Rear view of same stage. Division of X, spindles of ^, d^. 



Fig. 22. The same embryo, from the left side. 



