Archegonium ; and on Spermatogenesis in Poly trichum. 1 3 1 
EXPLANATION OF FIGURES IN PLATES XIII AND XIV. 
Illustrating Mr. Walker’s paper on Polytriclium. 
The figures were drawn with the help of a camera lucida under a Leitz a objective, N. A. 
1 >32 with Zeiss comp. oc. 12, x 3,000, except Fig. 40, which was drawn under a Zeiss apo. 2 mm. 
N. A. 1-40, x 2,500. 
Figs. 1-12 were drawn from spermatogenic cells of antheridia in various stages of development, 
anterior to the last division. Figs. 13-23 refer to the last division. Figs. 24-6 show the extra 
division ; Figs. 27-42 the development of the spermatozoid. All refer to Polytrichum formosutn , 
Hedw. 
PLATE XIII. 
Fig. 1. Cell from a very young antheridium, showing nucleus and remains of chloroplasts. 
Fig. 2. Nucleus; central nucleolus, radiating threads and peripheral reticulum. 
Fig. 3. Cell containing nucleus with large nucleolus and obscured reticulum. 
Fig. 4. Cell with nucleus in the spireme stage. 
Fig. 5. Cell with nucleus in the spireme stage; early spindle fibres. 
Fig. 6. Segmentation of spireme. 
Fig. 7. Polar view of dividing nucleus, showing six chromosomes. 
Fig. 8. Metaphase in side view. 
Fig. 9. Early anaphase in side view. 
Figs. 10 and 11. Telophases ; chromatin leaving reticulum. 
Fig. 12. Daughter nucleus with outstanding particle of chromatin. 
Fig. 13. Early prophase of last division of spermatogenic nucleus; centrosomes ; chromatin 
leaving nucleolus. 
Figs. 14 and 15. Early prophases ; distribution of chromatin to peripheral reticulum. 
Fig. 16. Early spireme ; anastomosing threads still present. 
Fig. 1 7. Nucleus with nucleolus after distribution of the chromatin to the reticulum. 
Fig. 18. Anaphase of last division ; centrosomes at poles of spindle. 
Fig. 19. Telophase of last division; side view of spindle, showing detachment of chromatin 
particle from one of the chromosome groups. 
Fig. 20. Polar view of nuclei in telophase ; detached particles lying in the cytoplasm ; end-to- 
end union of chromosomes, and development of anastomosing threads. 
Fig. 21. Daughter chromosomes in telophase of last division, showing end-to-end union of five 
chromosomes. 
Fig. 22. Telophase; side view of spindle ; union of chromosomes to form a simple spireme-like 
structure ; detached chromatin particles. 
Fig. 23. Two cells after last division, lying in a common chamber with mucilaginous walls ; 
persistent centrosomes. 
Fig. 24. Prophase of abnormal extra division ; blepharoplast dividing. 
Fig. 25. Metaphase of same, showing blepharoplasts at poles of spindle. 
Fig. 26. Metaphase of same division, showing one of the blepharoplasts lying away from the 
spindle pole. 
Fig. 27. Early spermatid with blepharoplast. 
Fig. 28. Later spermatid with chromatin aggregated towards the centre of the nucleus. 
Fig. 29. Spermatid showing extrusion of chromatin from the nucleus. 
PLATE XIV. 
Fig. 30. Spermatid showing later stage of extrusion of chromatin. 
Fig. 31. Extruded chromatin in two spherical masses lying in the cytoplasm. 
Figs. 32-4. Stages in the development of the arched band. 
