A critical study of the cytology of Crepis virens. 
145 
Fig. 73. In one bivalent segment the univalent lengths are completely separate, 
whilst in the other they are joined at their ends to form a loop. 
Fig. 74. Complete secondcontraction. The hoinogeneous bivalent loopsshowno sign 
of their duplex character, their component univalent segments being closely associated. 
Fig. 75. Complete second contraction, the segment in the south part of the nucleus 
has di\aded into its two univalent lengths; a chromatic swelling marks their point of 
Union. 
Fig. 76. The coming out of second contraction. Two bivalent loops shovr traces 
of Separation of the univalent segments. 
Fig. 77. Loosening of the second contraction. Some of the portions are concen- 
trated, whilst others show indications of the Separation of the univalent segments. 
Fig. 78. Shows the sorting out of the segments as they come out of second con- 
traction. There is great diversity in their appearance. In some cases the univalent 
segments have separated along their lengths, and have but to condense to form the 
bivalent chromosomes. True fission in the substance of the univalent segment is to 
be seen in the segment situated in the left portion of the nucleus. 
Fig. 79. A nucleus which has just come out of second contraction. The separat- 
ing univalent strands, owing to their extremely viscous character, are drawm out pro- 
ducing a very confused appearance. 
Fig. 80. As the univalent segments separate, they gradually become concentrated. 
Even at this stage it is impossible to distinguish the limits of the three chromosomes. 
Fig. 81. As concentration proceeds the individual chromosomes can be recognised. 
Fig. 82. The three bivalent chromosomes. 
Plate X. 
Fig. 83. Equatorial plate of the first meiotic divLsion. 
Fig. 84. The passing of the chromosomes to the poles, at which the small chro- 
mosomes are the first to arrive. 
Fig. 85. The arrival of all the chromosomes at the spindle poles. 
Fig. 86. Close association of the chromosomes in anaphase. 
Fig. 87. Anaphase of the heterotype division with apparently five chromosomes 
probably due to the transverse Segmentation of two of the chromosomes. 
Fig. 88. The chromosomes have separated out and are dividing into their longi- 
tudinal halves. In the upper nucleus the identity of the three chromosomes is still 
maintained, whilst in the low’er it is partly obliterated. 
Fig. 89. Further stage in the dissolution of the chromosomes. 
Fig. 90. Homotype division: showing the reconcentration of the chromatic 
segments and the elongation of the cytoplasm at right angles to the plane of the prevnous 
spindle. 
Fig. 91. Concentration of the chromosomes, but the limits of the three chromo- 
somes are as yet not clearly defined. 
Fig. 92. Polar view of the equatorial plate of the homotype diAÜsion. 
Fig. 93. The passing of the chromosomes to the poles of the homotype dmsion. 
Fig. 94. Late anaphase of the homot 5 q)e di\nsion showing the Separation of the 
chromosome segments. 
Fig. 95. Telophase of the homotype division. The remains of the chromosomes 
may be recognised either as homogeneous chromatic portions, or as paired beads, or 
the portions may show fission in their substance. 
Archiv f. Zollforschnng. XII. 10 
