122 Mottier . — Mitosis in the Pollen Mother-cells of 
along the nuclear membrane. With the continual condensation of the 
chromosomes and their consequent reduction in size, there is developed 
about the nucleus the weft of kinoplasmic fibres which form the multipolar 
spindle complex (Fig. 19). The nuclear membrane fades from view as 
a sharp line or boundary, and in its place there appear the kinoplasmic 
fibres. In an earlier publication the writer has expressed the opinion that 
the nuclear membrane is changed into kinoplasmic fibres, a view he still 
holds. The nucleus gradually loses its regular globular form, because of 
the encroachment of the spindle complex, and the straightening out and 
convergence of fibres to form the several poles. In short, the entire process 
of spindle formation is identical with that repeatedly described by the writer 
for other plants. 
The condensation of the chromosomes continues until the spindle is fully 
formed, at which time they have probably reached their smallest size. In 
the equatorial plate each bivalent appears usually in the form of two thick 
and somewhat rounded lumps, or they may be somewhat elongated in the 
form of rods (Fig. 22). As a rule the bivalents appear more nearly like the 
one in the centre in Fig. 22. They are generally closely crowded, and 
appear in the form of a disc in polar view. In the judgement of the writer 
twelve bivalents are present. Even with the relatively small number the 
form and arrangement make accurate counting difficult, under the most 
favourable conditions. In Fig. 21 twelve bivalents and a nucleolus are 
seen. This figure was obtained from a multipolar stage of the spindle in 
which all the objects could be clearly made out by changing the focus. 
The chromosomes that lie above others in the focus are made darker. The 
members of two of the bivalents ( a and b) are not closely applied. If each 
of these were counted as two, fourteen would be the number. I have not 
been able to convince myself that the number is thirteen as stated by 
Darling. It is either twelve or fourteen. 
In the mature spindle the poles may be pointed or broad as in 
Fig. 22. 
Anaphase and telophase . The two members of each bivalent (the two 
somatic chromosomes) now separate in metakinesis, one going to each pole. 
On their way to the poles each is seen to be split lengthwise (Fig. 23). 
This split may sometimes be observed in the equatorial plate (Fig. 22), but, 
as a rule, no indication of the longitudinal fission is noticeable at this stage, 
and not always is it very evident during the anaphase. Having arrived at 
the poles the chromosomes are almost always found closely crowded 
together, giving the appearance of a compact mass of lumps. Later they 
separate and undergo to some extent the process of reticulation or alveoliza- 
tion by which each may elongate, becoming attenuated in certain places, 
but remaining thicker in others, and the nuclear membrane is formed. The 
thicker lumps or fragments are connected with each other by means of 
