386 Digby . — The Cytology of Primula kewensis 
40. Tischler, G. (’10) : Untersuchungen iiber die Entwicklung des Bananen-Pollens, I. Arch. f. 
Zellforschung, Leipzig, v, 4. Heft, pp. 622-70. 
41 . Zoja, R. (’ 96) : Sulla indipendenza della cromatina paterna e materna nel nucleo delle cellule 
embrionali. Anat. Anzeig., Jena, xi, No. 10, Nov., pp. 289-93. 
EXPLANATION OF PLATES XLI-XLIV. 
Illustrating Miss Digby’s paper on the Cytology of hybrid Primulas. 
All the figures were drawn with the camera lucida under a 2 mm. apochr. Horn. imm. Zeiss, 
N.A. 1*40, with comp. oc. 18. x 2,250. 
Figs. 1-6. P. kewensis (seedling form). Premeiotic divisions. 
Figs. 7-4 2 • floribunda. Meiosis. 
Figs. 43-53. P. verticillata. First meiotic division. 
Figs. 54-71. P. kewensis (type). Meiosis. 
Figs. 72-106. P. kewensis (seedling form). Meiosis. 
Figs. 107 and 108. P. kewensis farinosa. 
PLATE XLI. 
Fig. 1. P. kewensis (seedling form). Premeiotic divisions. Telophase. 
Fig. 2. Late telophase or resting stage. 
Fig. 3. Early prophase showing the stringing together of beads of chromatin. 
Fig. 4. Concentration of beads to form the chromosomes. 
Fig- 5- The chromosomes gradually become homogeneous. 
Fig. 6. Fully developed chromosomes. 
Fig. 7. P. Jloribunda. Pollen mother-cell. Resting stage between the premeiotic and first 
meiotic division. The nucleolus buds freely. 
Fig. 8. Complete resting stage. The nucleus appears empty except for a few large rounded 
chromatic masses, and some smaller chromatin granules. 
Fig. 9. Early prophase. The nuclear contents have increased owing to the continuous nucleolar 
budding. 
Fig. 10. The nucleus is considerably larger, and the chromatin granules are more definitely 
arranged on linin strands. 
Fig. 11. The linin strands tend to run parallel to one another. 
Fig. 12. The earliest stage in the massing of the granules preparatory to synapsis. 
Fig. 13. Further concentration of the granules into groups. 
Fig. 14. Synapsis. 
Fig. 15. Loosening of the synaptic knot. 
Fig. 16. Lengths of spireme come out of synapsis showing bifurcated ends. 
Fig. 17. Spireme emerging from synapsis in the form of loops. 
Fig. 18. Superficial section of loosening synaptic knot, showing ladder-like association of lengths 
of spireme. 
Fig. 19. Opening out of the loops of spireme. 
Fig. 20. Hollow spireme. 
Fig. 21. The loops of the hollow spireme withdraw from the periphery of the nucleus, the sides 
of each loop tend to approach one another and to join in places. 
Fig. 22. Closer association of the sides of each loop. Note the chromatic swelling at the 
points of union. 
Fig. 23. The associated sides of each loop form more definite figures. 
Fig. 24. Each bivalent segment dissociates itself from its neighbours. 
Fig. 25. Maximum degree of concentration of the univalent strands in the bivalent combination. 
Fig. 26. Nucleus showing some of the univalent strands approximated to form thick bivalent 
segments, whilst others still form the sides of open loops, united at intervals. 
Fig. 27. The limits of the nine bivalent segments (chromosomes) can now be identified. 
Fig. 28. The splitting apart of the two univalent chromosomes. 
Fig. 29. I.ater stage in the separation of the univalent chromosomes. 
