Plate VI. 



Fig. 42. A portion of the anterior half of a median longitudinal section 

 from the blastoderm represented in Fig. XV. At "e" is the anterior limit 

 of the entoderm. Xl20. 



Fig. 43. A portion of the posterior half of the preceding section, x 120. 



Fig. 44. The enlarged central portion of a section from the same blasto- 

 derm as Figs. 42 and 43. Note especially the epithelial character of the 

 ectoderm, the grouping of the entoderm cells, and the granular contents of 

 the cavity. X 184. 



Fig. 45. From a median longitudinal section of an unincubated egg. It 

 shows the anterior limit of the entoderm in its forward growth. The remains 

 of the subgerminal cavity (sg) is entirely free from yolk mass, x 245. 



Fig. 4G. The central part of a longitudinal section from a blastoderm 

 taken three hours after incubation. It shows the fragmentation of the yolk 

 lying beneath the floor of the cavity. These yolk masses {m) are non- 

 nucleated. X 246. 



Fig. 47. The anterior portion of a longitudinal section from a blasto- 

 derm taken forty hours after fertilization. The remains of the subgerminal 

 cavity not yet penetrated by the entoderm (e) is full of yolk masses, some 

 of which are undergoing fragmentation ((?m). X 245. 



Fig. 48. The right side of a median transverse section taken one hour 

 after incubation. The lateral edge of the entoderm is shown at "e" and 

 the inner margin of the germ-wall at "y." The space between these two 

 points can be followed along the entire right side, showing that the fusion 

 between the lateral margin of the entoderm and the inner edge of the germ- 

 wall had not yet taken place. X 245. 



Fig. 49. The central part of a section taken through v-v' of Fig. VIII. 

 At "s" is shown a segmentation cell that has loosened and sunk down from 

 the underside of the ectoderm, x 245. 



t 



