386 Fertilization and Early Development of Pigeon's Egg 



Plate IV. 



Fig. 31. Pair of sperm daughter nuclei. See Fig. 13 at left. X 1000. 



Fig. 32. Sperm nucleus in prophase of division. X 2000. 



Fig. 33. Sperm nucleus in division; shows chromosomes splitting. A ves- 

 icular refractive body and a yolk granule at right. X 2000. 



Fig. 34. Anaphase of division of sperm nucleus in polar view, lighter 

 gioup of chromosomes are in different plane, x 2000. 



Fig. 35. Late anaphase of division of sperm nucleus. Figures 30-35 are 

 all from the same egg. x 2000. 



Fig. 36. Vert, section through blastoderm about fifteen hours after fertili- 

 zation. Shows nuclei free in the yolk at the edge of the blastoderm. One 

 nuclear nest is shown, x 120. 



Fig. 37. Similar to above. A " giant nucleus " is present in yolk. X 120. 



Fig. 38. From same egg as above. Shows an area in which two groups 

 of chromatic staining bodies lie. a, chromatin vesicle; ft, refractive body; c, 

 yolk. X 2000. 



Figs. 39 a, b, c, d, e. Nuclei in yolk showing amitosis. X 1000. 



Fig. 40. Surface view of germinal disc showing first furrow and accessory 

 cleavage beginning at one side. Time, 12.20 A. M. x 10- 



Fig. 41. Surface view of four-cell stage, showing accessory cleavage. Time, 

 3.15 A. M. X 10. 



Fig. 42. Surface view of 8-cell stage with accessory cleavage. Time, 2.10 

 A. M. X 10. 



Fig. 43. Surface view of eight-cell stage. Accessory cleavage not shown. 

 Time, 3.55 A. M. x 10. 



Fig. 44. Surface view of sixteen-cell stage. Accessory cleavage not drawn. 

 X 10. 



Fig. 45. Surface view of sixteen-cell stage. Daughter nuclei are visible 

 in a whole mount of the disc and are shown in the drawing. Accessory 

 cleavage not drawn. The boundary represents the margin of the inner zone 

 of the germinal disc, x 20. 



