302 LILIAN SHELDON. 



Fig. 8. — Two ovarian ova of P. capensis of April; in one the nucleus 

 and nucleolus are still present, in the other both have disappeared, and the 

 ovum lies loose in its follicle. Fol. Follicle. Nl. Nucleolus. Nu. Nucleus. 

 0. S. Egg-shell. Fed. Peduncle. 



Fig. 9. — Ovarian ovum of April of P. capensis shortly before the nucleus 

 disappears, shovfing its peduncle and follicle. Fol. Follicle. Nu. Nucleus. 

 0. S. Egg-shell. Fed. Peduncle. Magnified 600 diameters. 



Fig. 10. — Ovum of P. capensis shortly after it has passed into the 

 uterus ; the nucleus is absent ; a small prominence on the surface is present, 

 which may be the point of entrance of the spermatozoon. Magnified 600 

 diameters. 



Fig. 11. — Section of an ovum of P. capensis. The male pronucleus is 

 just formed ; the nucleus is in the spindle stage, preparatory to budding off 

 the first polar body. Fron. (^. Male pronucleus. Hu. Nucleus. Magnified 

 600 diameters. 



Fig. 12. — Ovum of P. capensis, in which the nucleus is again present 

 after its disappearance in spindle form. The spindle is seen in transverse 

 section. Magnified 600 diameters. 



Fig. 13. — Ovum of P. capensis, in which the nucleus is in the spindle 

 stage after budding off the first polar body. Nu. Nucleus. F. b. 1. First 

 polar body. Magnified 600 diameters. 



Fig. 14a and b. — Two sections through an ovum of P. capensis. 



Fig. 14a shows the nucleus and the second polar body, which has just 



been budded off. 

 Fig. 14^ shows the male pronucleus lying in the centre of the ovum. 

 The sections from which the two figures are drawn are separated by 

 twelve intervening ones. F. b. 2. Second polar body. Fron. ^. Male 

 pronucleus. Nu. Nucleus. Magnified 600 diameters. 

 Figs. 15 — 20. — Consecutive stages, showing the changes undergone by the 

 nucleus in the formation of the polar bodies. Zeiss, oc. 2, Reichert's J^th 

 oil. imm. 



Fig. 15. The nucleus in spindle stage, before the formation of the first 



polar body. The chromatin forms an equatorial plate. 

 Fig. 16. The equatorial plate is divided into two bands. (This is in the 



formation of the second polar body.) 

 Fig. 17. The chromatin bands are completely separated, and are approach- 



ing the ends of the spindle. (From P. Balfouri.) 

 Fig. 18. The chromatin lies at the ends of the spindle-fibres. 

 Fig. 19. The first polar body is just separating from the ovum, the spindle- 

 fibres are still visible in the polar body. P. b. 1. First polar body. 

 Fig. 20 a and b. Two sections slightly removed from one another, show- 

 ing the resting condition of the nucleus after the formation of the 



