stage shown in
figures 104 and 105 is a later one than that just described. Here we
have again a continuous spireme connected with the element _x_, making
it seem improbable that the bivalent chromosomes are really separated in
the bouquet stage. Figure 106 gives some of the variations in form of
the combined nucleolus and element _x_. The last of the five figures was
taken from a giant cell containing at least twice the usual amount of
chromatin. In one giant cell four unusually large combinations of this
kind were found, and a corresponding amount of chromatin in the spireme.
In figure 107 one sees the spireme divided into segments still joined by
linin bridges. In figure 108 similar segments may be seen, one of them
showing a longitudinal split. The element _x_ is present, but the
nucleolus has disappeared. In many cases the split, if it appears at
all, closes quickly and the chromosome bends in U-shape, as in figure
109, plate IV. This figure also shows two centrosomes (_c_). In other
cases the split persists as in figure 110 and leads to the formation of
crosses of a tetrad character (figs. 111, 112, 113), as in
_Stenopelmatus_ and many other insects. Figures 114 to 117 show later
stages of the U-shaped chromosomes. Perfect rings are rare. All sorts of
variations are seen, broad and narrow U-shapes, rings split at one point
or the opposite points, a U split at the bottom (fig. 114), pairs of
parallel rods (fig. 115), and occasionally rods constricted in the
middle and showing a longitudinal split in each half, as in figure 116.
Figure 117 shows different views of the split rings. Apparently all of
these forms straighten out so that the two components of the bivalent
chromosome stand end to end as dumbbells or compressed crosses in the
metaphase of the first maturation spindle (figs. 123-125). The element
_x_ remains concentrated and more or less spherical in form. Figures
118-122 are equatorial plates, with _x_ absent in figure 120, in the
same plane as the 11 other chromosomes in figure 119, far to one side in
figure 118, and near one pole of the forming spindle in figure 122. It
is also shown in various positions with regard to the spindle in figures
123 to 126 and 128 to 132. In figure 125 it is apparently double, and
again in figure 129. In figure 130 one lagging chromosome shows the dyad
nature of the products of the division of the tetrad. In this form
there can be no doubt that reduction occurs in the first s