304 Cardiff: Synapsis and reduction 



Explanation of plates 12-15 



All figures were made with Spencer 1.5 mm. objective and Leitz ocular, and 

 camera lucida. The original drawings were reduced one halt in reproduction. Ex- 

 cept where otherwise indicated the magnification of the figures is X 2 3°°- 



Acer platanoides 



Figure I. Early mother-cell. Sectional view, only, of nucleus ; chromatin at 



periphery of nucleus. 



Figure 2. Mother-cell showing increase in chromatin and formation of threads. 



Parallel threads, a. 



Figure 3. Later stage of mother-cell nucleus ; threads parallel at a and b. 



Figure 4. Nucleus of mother-cell. 



Figure 5. Mother-cell ; several pairs of parallel threads preparing for synapsis. 



Figure 6. Presynaptic nucleus a little later than figure 5. 



Figure 7. Paired chromatin threads from a presynaptic nucleus. 



Figure 8. Paired presynaptic threads. 



Figure 9. Paired presynaptic threads. 



Figure 10. Paired presynaptic threads ; moieties in 

 one in close contact, apparently twisted upon each other. 



Figure 11. Portion of presynaptic nucleus. 



Figure 12. Pair of threads just previous to synapsis . 

 chromomeres in contact and apparently fusing ; linin portion 

 of thread not yet in contact. Slightly greater magnification 



than other figures. 



Figure 13. Presynaptic mother-cell; threads con- 

 tracting at one side of nucleus with nucleolus ; moieties much 

 closer together; cytoplasm becoming more dense in neigh- Figure 12 



borhood of nucleus. 



Figure 14. Contraction of chromatin threads just previous to close synaptic knot ; 



parallel fusing of threads evident in looser portion of knot. 



Figure 15. Synapsis ; projecting end of thread showing bivalent character. 



FIGURE 16. Chromatin threads just leaving synapsis ; chromomeres no longer evi- 

 dent, but thread homogeneous throughout. 



FIGURE 17. Portion of postsynaptic nucleus showing threads disentangling from 



synapsis. 



Figure 18. Postsynaptic nucleus just after threads have left knot ; bivalent char- 

 acter of threads. 



Figure 19. Shortening and thickening of postsynaptic threads. 



FIGURE 20. Stage a little later than figure 19, showing beginning of transverse 

 division. 



Figure 21. Bivalent chromosome just after transverse division. 



Figures 22 and 23. Stages showing shortening and thickening of chromosomes. 



Figures 24-32. Bivalent chromosomes of prophase of first division ; various stage 

 in shortening and thickening. 



*These text-figures are inserted to illustrate the differentiation into linin and chromatin 

 in the presynaptic threads, a character which the plates failed to show. 



