60 Overton. — On the Organization of the Nuclei in the 
Fig. 14. Chromosomes from equatorial plate, showing method of separation: — 140, 14 b. 
Lateral view of chromosomes during metaphase. 14 c. Later metaphase, longitudinal split in each 
daughter chromosome evident. 14 d. Metaphase with the four parts of the chromosomes entirely 
separated at their outer ends. % 
Fig. 15 a. Spindle with chromosomes in anaphase. Each chromosome may be seen as being 
two-parted as it passes to pole. 
Fig. 15 b. Single two-parted chromosome in anaphase. 
Fig. 16. One pole of spindle, chromosomes crowded together at pole. 
Fig. 17. Polar view of daughter nucleus ; chromosomes somewhat distributed in linin substance. 
Fig. 18. Polar view of homeotypic division spindle, showing arrangement and form of 
chromosomes. 
Fig. 19. Homeotypic division figures, one spindle viewed laterally and the other from the pole. 
Fig. 20. Pollen grain showing prochromosomes as single unpaired chromatic bodies. 
PLATE TIL 
Richardia ajricana. 
Fig. 1. Very young pollen mother-cells, showing linin intervals and linin framework. 
Fig. 2. Early synaptic contraction stage ; prochromosomes and linin somewhat more distinctly 
parallel. 
Fig. 3. Synaptic contraction still more advanced. Distinct parallel arrangement of elements. 
Limits of prochromosomes not distinct. 
Fig. 4. More complete contraction stage. Chromatin rather more uniformly distributed in the 
spirem. 
Fig. 5. Complete contraction stage. Nucleole entangled in the mass. Elements compactly 
massed. 
Fig. 6. Complete contraction stage. Nucleole not entangled in the mass. Threads distinctly 
parallel. 
Fig. 7. Synaptic mass loosening up. Bivalent chromosomes and linin intervals distinct. 
Fig. 8. Still more complete post-synaptic bivalent spirem. Chromosomes and linin intervals 
distinct. 
Fig. 9. Showing structure of prochromosomes: 9 a. Chromatin grouped in dense masses in 
parallel linin threads. 9 b. Chromatin spread out along linin. Two parallel series of chromatin 
masses visible in linin. 9 c. Chromatin masses still more scattered along linin. 
Fig. 10. Nearly homogeneous chromatic post-synaptic spirem. 
Fig. 11. Completely distributed post-synaptic spirem. Bivalent chromosomes and linin intervals 
distinct. 
Fig. 12. Portions of the bivalent post-synaptic distributed spirem. 12 a. Showing limits of 
individual bivalent chromosomes. 12 b. Segmentation of post-synaptic spirem. 
Fig. 13. Early diakinetic stage. Chromosomes widely scattered in nuclear cavity. 
Fig. 14. Single chromosomes from various diakinetic stages : 14 a. Usual parallel double rods. 
14^. Same with each component somewhat contracted. 14 c. The two components crossed, forming 
an X -shaped figure. 14^. Same with components attached nearer one end. 14 £. Parallel double 
rods slightly separated. 
Fig. 15. Late diakinetic nucleus. Chromosomes all in form of short double rods. 
Fig. 16. Diakinetic chromosomes showing four-parted structure: 1 6a. Each component of 
parallel double rods shows longitudinal splitting. 16 b. Each component of X-shaped figure shows 
longitudinal splitting. 1 6 c. Each component shows longitudinal splitting. Parts separated to form 
distinct double V-shaped figures. 
Fig. 17. Late diakinetic chromosomes: 17 a. Two components placed end to end. 17 A 
Parallel double rods : usual arrangement. 17 c. Components attached at middle with ends separated. 
X-shaped figure. 
Fig. 18. Multipolar spindle stage becoming bipolar. Arrangement of chromosomes also shown. 
Fig. 19. Side view of equatorial plate stage showing chromosomes in late metaphase as early as 
anaphase. 
Fig. 20. Polar view of equatorial plate, showing the sixteen chromosomes in different planes. 
