Piate 3. 



Maturation and Fertilization of Ovuni of Peltogaster curvatus. 



ep ovarian epithelium. p.bl first polar body. p.b2 second polar body, sg segmentation spindle. 

 spi first maturation spindle. sp2 second maturation spindle. q? spermatozoon or male pronucleus. Q female 

 pronucleus. 



Fig. 1. Section through a piece of ovary of Peltogaster curvatus, ceitain of the eggs having already begun 



the maturation process. X 650. 

 Fig. 2. Longitudinal section through the first maturation spindle, showing tetrads. X 1300. 

 Fig. 3 and 3a. Longitudinal sections through the first maturation spindle (metaphase). X 1300. 

 Fig. 4 and 4a. Longitudinal section through the first maturation spindle (metaphase, spindle having rotated). 



X 1300. 

 Fig. 5 and 5a. Transverse section through equatorial piate of first maturation spindle (metaphase). X 1300. 

 Fig. 6. Formation of second spindle immediately after telophase of first. Whole preparation. x 650. 

 Fig. 7. Equatorial piate of second spindle (sp2) with 14 chromosomes. Transverse optical section of whole 



preparation. X 1300. 

 Fig. 7 a. Egg at same stage as Fig. 7, but left in sea water to separate chromosomes. X 1300. 

 Fig. 8 and 8a. Transverse section through second maturation spindle (metaphase). X 1300. 

 Fig. 9. Second maturation spindle (sp2), travelled away from lst polar body [pbl) (metaphase). Whole 



preparation. X 650. 

 Fig. 9a. Second maturation division (late telophase); first polar body [pbl) placed on egg envelope and de- 



generating. Optical section. X 650. 

 Fig. 10. Fertilization, spermatozoon ((jf) having just entered and lying alongside female pronucleus. Section. 



X 1300. 

 Fig. 11. Passage of pronuclei ((jf and Q) to centre of egg. lst polar body stili attached to egg envelope, 



2nd polar body lying within it. Optical section. X 650. 

 Fig. 12. Passage of pronuclei to periphery of egg. Section. X 650. 

 Fig. 13. Growth and further passage of nuclei. Optical section. X 325. 



Fig. 14. Two pronuclei arrived at periphery near 2n<i polar body. Whole preparation. X 325. 

 Fig. 15. Same as 14. Section. X 650. 



Fig. 16. A case where lobation of nuclei shown in 15 has led to division into three nuclei. Section. X 650. 

 Fig. 17. Formation of aster for first segmentation division, and of spireme in nuclei. Section. X 1300. 

 Fig. 18. First segmentation division (anaphase). Section. X 1300. 

 Fig. 19. First segmentation division (metaphase). Whole preparation. X 325. 

 Fig. 20 and 20a. First segmentation division (metaphase). Section. X 1300. 

 Fig. 21 and 2 la. First segmentation division (telophase). Section. X 1300. 

 Fig. 22. First segmentation division (late telophase). Section. X 1300. 



