Eugene Howard Harper 37 



Fig. 10. Vertical section. Pronuclei and surroundings. <^ pron. at left. 

 From two sections. Time, 11.50 P. M. x 400. 



Fig. 11. Vert, section, showing pronuclei. Time, 10.15 P. M. X ^00. 



Fig. 12. Vert, section, showing pronuclei and surroundings. Time, 10.40 

 P. M. X 200. 



Fig. 13. Vert, section, showing segmentation nucleus and surroundings. 

 Pair of sperm nuclei at left. Time, 12 P. M. x 200. 



Fig. 14. Horizontal section, showing first cleavage spindle and surround- 

 ings. Position in oviduct at constriction between upper portion and shell 

 gland. Time, 10.30 P. M. x 200. 



Fig. 15. Horizontal section, showing first pair of cleavage nuclei and sur- 

 roundings. Combination of two sections. Time, 12 P. M. X 80. 



Pi6. 16. Horizontal section showing first pair of cleavage nuclei at begin- 

 ning of second division and surroundings, n, nucleus; f, first furrow. Posi- 

 tion in shell gland of oviduct. Time, 1.00 A. M. x 80. 



Plate III. 



Fig. 17. Horizontal section through nucleus of ovarian egg (Fig. 2D;, 

 showing group of chromosomes, a, pair of dyads; 6, refractive substance In 

 vesicular mass. X 2000. 



Fig. 18. Group of chromosomes in equatorial plate from a mature ovarian 

 egg. Same stage as Fig. 5, but from a different egg. X 2000. 



Pig. 19. Group of chromosomes in equatorial plate of first polar spindle, 

 showing central spindle granules. From same egg as Fig. 6a. X 2000. 



Pig. 20. Vertical section, showing first polar spindle. Central spindle gran- 

 ules present as in 19, but not drawn. Egg clasped by funnel of oviduct. Time, 

 8.50 P. M. X 2000. 



Fig. 21. Vert, section, showing second polar spindle, not completely formed 

 and first polar body. One chromosome not in equatorial plate. Combination 

 of two sections. Time, 8.55 P. M. x 2000. 



Fig. 22. Vert, section, showing second polar spindle and first polar body. 

 See Fig. 8. X 2000. 



Fig. 23. Vert, section showing second polar spindle and first polar body. 

 Chromosomes are separating. Combination of two sections. Time 8.15 P. M., 

 X 2000. 



Fig. 24. Second polar spindle. See Fig. 9. 



Fig. 25. Vert, section, showing polar body, and egg nucleus as a fused mass 

 of chromosomes. Combination of two sections. Time, 10.45 P. M. X 2000. 



Fig. 26. Vert, section, showing polar bodies, egg nucleus without definite 

 membrane, inner sphere enlarged. Combination of two sections. Time, 8.55 

 P. M. X 2000. 



Fig. 27. Vert, section, showing completely reconstructed egg nucleus and 

 polar bodies. Time, 8.30 P. M. X 2000. 



Fig. 28. Horizontal section showing first cleavage spindle in prophase. 

 Chromosomes not drawn into equatorial plate. See Fig. 14. x 2000. 



Fig. 29. Spindle from cell of blastoderm about fifteen hours after fertili- 

 zation. Chromosomes not all shown, x 2000. 



Fig. 30, Sperm nucleus from 2-cell stage of the egg. In prophase of divi- 

 sion. X 2000. 



