388 
Digby . — The Cytology of Primtila Hybrids. 
Fig. 71. Embryo-sac mother-cell. Prophase of first meiotic division, showing nine chromosomes. 
Fig. 72. P. kewensis (seedling form). Synapsis. Note budding of the nucleolus. 
Fig. 73 * Hollow spireme ; large round masses of chromatin lie within the meshes. 
Fig- 74* Thfe chromatin masses become absorbed, and an association between univalent portions 
of spireme begins to be seen. 
Fig- 75* The thin strands of spireme, carrying beads of chromatin, lie parallel to one another 
and fuse in places. 
Fig. 76* The paired univalent segments form definite bivalent combinations, the future bivalent 
chromosomes. 
Fig. 77. The univalent segments become beaded. 
Fig. 78. The limits of the beaded chromosomes can now be distinctly seen. 
Fig. 79. Two of the bivalent chromosomes may be joined together. 
Fig. 80. The chromosomes tend to lose their beaded character. Note two bivalent chromosomes 
are joined together. 
Fig. 8r. The univalent chromosomes thicken, and become more homogeneously chromatic. 
Fig. 82. Slightly later stage in which the chromosomes are more definite, some being still 
beaded whilst others are concentrated. 
Fig. 83. The univalent chromosomes begin to contract. The quadrivalent chromosome is most 
apparent. 
Fig. 84. The contracted chromosomes once more become beaded. 
Fig. 85. Contraction proceeds, resulting in an extremely beaded condition of the chromosomes. 
Fig. 86. Same stage as Fig. 85. The large chromosome is to be seen. 
Fig. 87. The chromatin of the beads diffuses throughout the linin, and the chromosomes 
increase in size. 
Fig. 88. The chromosomes become more homogeneous. 
Fig. 89. Typical diakinesis. The bivalent chromosomes resemble dyads, the quadrivalent 
chromosome a tetrad. 
Fig. 90. Same stage as Fig. 89. 
Fig. 91. Some shapes adopted by the quadrivalent chromosome. 
Fig. 92. Droplets of nucleolar material attached to the chromosomes. 
Fig. 93. Chromosomes going on the spindle. Note the quadrivalent chromosome. 
Fig. 94. Equatorial plate of the first meiotic division. The quadrivalent chromosome is 
separating into its univalent segments. 
Fig. 95. The bivalent chromosomes are beginning to separate into their univalent parts. The 
quadrivalent chromosome is still a ring. 
Fig. 96. Polar view of an equatorial plate of the first meiotic division, showing eighteen chromo- 
somes. 
Fig. 97. Passing of the univalent chromosome to the poles. Note the separation of the chromo- 
somes of the quadrivalent union. 
PLATE XLIV. 
Fig. 98. The chromosomes approach the poles. 
Fig. 99. Polar view of an aster of the first meiotic division, showing the eighteen chromosomes. 
Fig. 100. Early telophase. 
Fig. 101. The chromosomes begin to separate and a nuclear limiting membrane appears. 
Fig. 102. Later telophase. The chromosomes are all distinct and separate. 
Fig. 103. Interkinesis between the first and second meiotic divisions, showing the split chromo- 
somes. 
Fig. 104. Embryo-sac mother-cell. Prophase of the first meiotic division. The chromosomes 
are all separate from one another. Note seventeen chromosomes and one in the next section. 
Fig. 105. Embryo-sac mother-cell. Equatorial plate (in two consecutive sections). All the 
chromosomes are of the same size, and there is no quadrivalent combination. 
Fig. 106. Embryo-sac mother-cell. Polar view of equatorial plate, showing the eighteen 
chromosomes. 
Fig. 107. P. kewensis farinosa (varietal origin). First meiotic division. Polar view of aster, 
showing eighteen haploid chromosomes. 
Fig. 108. P. kewensis farinosa (hybrid origin). Premeiotic prophase, showing thirty-six diploid 
chromosomes. 
