Plate II. 



Fig. 15. Posterior end of an oblique section from a blastoderm taken 

 thirty-four hours after fertilization, or seven hours before laying. The 

 yolk is cracked and as a result granules are found in the cavity (c) just 

 posterior to the dorsal-lip. Sec text for description, and also Fig. VIII. 

 X 339. 



Fig. IC— Posterior end of a section taken through y-y'. Fig. VITT. The sec- 

 tion ends with a thin free marghi. x 259. 



Fig. 17. Posterior end of a section slightly to the right of the one repre- 

 sented in Fig. 14. It shows how a considerable cavity may develop beneath 

 the margin before invagination begins, x 259. 



Fig. 18. Anterior third of a section taken in the plane passing through 

 CR of Fig. XI. The thinning-out is in the last stages, and at the points 

 marked "s" a few cells have loosened and sunk down. Otherwise the sub- 

 germinal cavity contains no nucleated cells — only large yolk masses are 

 present, some of which are disintegrating (dm). See text for description, 

 and also Figs. 35 and 36. x 259. 



Fig. 19. Posterior third of the same section as preceding, w, union be- 

 tween the deeper cells of the dorsal-lip and the entoderm. See text and 

 Figs. 35 and 37 for description, x 259. 



Fig. 20. Anterior part of a section taken in the plane passing through 

 FH of Fig. XII. Three large degenerating periblastic nuclei are shown 

 {pn), and at "y" are the cells whicli constitute the inner margin of the 

 germ-wall. The zone of junction is too far to the left to be seen in the 

 figure. X 259. 



Fig. 21. Posterior part of the preceding section. See text, x 259. 



