112 L. DONCASTER. 



of fertilisation, but when unfertilised they may continue to 

 develop at least as far as the blastoderm stage. 



Birmingham University; 



November, 1906. 



EXPLANATION OF PLAT 10 8, 



Illustrating Mr. L. Doncaster's paper on " Ganietogenesis 

 and Fertilisation in Nematus ribesii." 



All Cgures are drawn with an oil-immersion lens, but are not exactly on 

 the same scale. Those illustrating spermatogenesis are more highly magnified 

 than the remainder. All represent Nematus ribesii except figs. 12, 13, 

 14. 



Fig. 1. — Conjugation of male and female pronuclei. Three polar nuclei 

 near the edge of the egg. 



Figs. 2, 3, 4. — " Polar proioplusm " of fertilised eggs showing chromo- 

 some groups derived from polar nuclei. 



Fig. 5. — Nucleus of spermatogonium. 



Fig. G. — Spermatogouial mitoses, (a) Metaphase, side view; (b) Fqu- 

 torial plate. 



Fig. 7, a, b, c. — Spermatocyte: three prophases of hetcrotype mitosis. 

 (a) Showing 8 chromosomes ; (b and c) Pairing to form 4 double chromatin 

 masses. 



Fig. 8. — Heterotype mitosis, equatorial plate, (a) Pole view; (b) Side 

 view. 



Fig. 9, a, b. — Heterotype anaphases. 



Fig. 10. — Homotype. (a) Pole view of equatorial plate ; (b, c) Anaphase, 

 side view. 



Fig. 11. — Spermatid. 



Fig. 12. — Young oogonium, N. lac tens. 



Figs. 13, 14. — Stages of growth of oogonium, N. lacteus pupa. 



Fig. 15. — Oogonial mitoses, larval ovary, (a) Pole view; (b) Side view. 



Fig. 16, a — r. — Mitosis in ovary sheath witli more than 8 chromsomes. 

 (a) Equatorial plate, pole view ; (b, c) Similar stage seen from side and 

 obliquely ; (d, e, f) Anaphases. 



