﻿154 William S. Marshall and Paul H. Dernehl, Cöntr. toward the Embryol. usw. 



Fig. 27. Three cleavage nuclei which, with their surrounding cytoplasm. 

 have entered the Keimhautblastem. Vergr. 800. 



Figs. 28. 29 and 30. Later stages of the same showing the cytoplasm of 

 the cleavage nuclei still separate from Keimhautblastem. Vergr. 800. 



Fig. 31. Two cleavage nuclei in the Keimhautblastem, between them. has 

 begun to recede from the egg meinbranes. Vergr. 800. 



Fig. 32. The same at a slightly later stage. Vergr. 800. 



Fig. 33. Two cleavage nuclei dividing within the Keimhautblastem, before 

 the boundaries have formed cutting off the blastoderm cells. Vergr. 800. 



Fig. 34. Three nuclei in the Keimhautblastem showing rows of vacuoles 

 between them which may be stages in formation of the boundaries separating 

 the nuclei each into a blastoderm cell. Vergr. 800. 



Fig. 35. A Single nucleus in the Keimhautblastem, showing a large vacuole 

 at either side within each of which is seen the row of granules in the form of 

 an irregulär line. Vergr. 800. 



Fig. 36. Similar to preceding, but the granules are darker and the vacuoles 

 can, with difficulty, be seen as clear Spaces at either side. Vergr. 800. 



Fig. 37. Two blastoderm cells from an egg similar to Fig. 46. Vergr. 800. 



Fig. 38 and 39. Dividing blastoderm cells. The straight line in this and 

 the three following figures represents the surface of the egg. Vergr. 1050. 



Figs. 40, 41 and 42. Dividing blastoderm cells. Vergr. 800. 



Fig. 43. Diagram showing plane of nuclear division in blastoderm cells. 

 The long straight line represents the surface of the egg; near this, the other 

 lines show axis of mitosis in cells, the short cross markings the position of 

 the chromosomes in each division. Combined from sections through one-third 

 of an egg. 



Fig. 44. Transverse section through middle of egg showing skape of 

 blastoderm cells shortly after their formation. Vergr. 110. 



Fig. 45. Transverse section through slightly older egg. Vergr. 110. 



Fig. 46. Transverse section of an egg in which the cells on the upper 

 (dorsal) surface have begun to Hatten. Vergr. 110. 



Fig. 47. Sagittal section through an egg which shows difference in the 

 blastoderm between ventral (to the left) and dorsal (to the right) surfaces; also 

 between the anterior (upper) and posterior (lower) poles. To the right the 

 cylindrical cells are shown which have begun to form the germmal band. 

 Vergr. 62. 



Fig. 48. Enlarged view of seven blastoderm cells taken from space — a — 

 in preceding figure. Vergr. 800. 



Fig. 49. Two blastoderm cells taken from space — b — in figure 48. Here 

 in each nucleus a nucleole is distinctly seen. Vergr. 800. 



Fig. 50. Amitotically dividing yolk nucleus, from an egg very similar to 

 Fig. 44. Vergr. 800. 



Figs. 51, 52 and 53. Three such nuclei. from an egg slightly older than 

 preceding. Vergr. 800. 



Fig. 54. Yolk nucleus having completed amitotic division. From an egg 

 a little older than Fig. 46. Vergr. 800. 



Fig. 55. Division completed. From same egg as Fig. 50. Vergr. 800. 



Fig. 56, 57 and 58. Yolk nuclei which have divided and show the remaining 

 Strands (connecting fibres?) and the darkened cytoplasm between the nuclei. 

 From an egg slightly older than Fig. 44. Vergr. 800. 



Fig. 59. Similar nucleus from an egg in which only three true mitotic 

 figures could be found within the yolk. Vergr. 800. 



Fig. 60. Similar nucleus from an egg nearly the same age as Fig. 45. 

 Vergr. 800. 



