158 
Charles E. Allen 
The number of ehromosomes appearing in the division of the androcyte 
mother cell is six; there is no reduction in number such as is described by 
the Leeuwen-Reijnvaans (1907 b, 1908) for this and other species of 
Pvlytrichum and for Mnium. That the chromosome number is the same 
in this as in previous divisions is apparent in the equatorial plate 
stage (PI. IX, Figs. 98 — 100), in the metaphases (Fig. 101), the anaphases 
(Fig. 102), and the early telophases (Figs. 109 — 116). Figures 103 — 108 
are drawn from cells which were so treated that all parts except the 
ehromosomes were practically colorless, allowing the latter to stand out 
with special distinctness; only the ehromosomes and the cell outlines 
appear in the drawings. Figures 103 — 106 show the two groups of 
daughter ehromosomes as seen in lateral views of cells in anaphase ; and 
Figures 107 a and 107 b, 108 a and 108 b, respectively, are polar views of 
the two daughter groups at a similar stage. In each case, it is plain 
that six daughter ehromosomes are moving toward each spindle pole. 
In the course of this division, differently from the previous ones, 
nucleoles do not appear until long after the reformation of the daughter 
nuclei (compare Figs. 118 — 121, PI. IX, with Figs. 62 — 65, PI. VIII); and 
when they do appear (PI. IX, Figs. 123, 124), they are smaller and less 
conspicuous than the nucleoles of androgone nuclei at corresponding 
stages. The result is that an antheridium containing newly-formed an- 
drocytes presents, with reference to the nuclei as well as to the thickness 
of the cell walls, a marked contrast to an antheridium at any earlier period 
of its development. Later, when tlic androcyte is beginning to develop 
into an antherozoid, the nuc-leole growslarger; butitremains approximately 
spherical and never becomes as large as the irregulär nucleolar mass often 
is in the earlier cell generations. 
Cytokinesis. 
The structure of the spindle during the anaphases and telophases 
(Figs. 102, 109 — 113) differs in no essential respect from what was observed 
in the divisions already described. Instead of the spindle fibers being 
plainly clustered at this period, the appearance is ratlicr, as in some of the 
later androgonial divisions, that of a small number of (mostly) coarse 
fibers. The relative thickness of these fibers is best shown in a cross 
section througli the equatorial region of a cell in anaphase (Fig. 114 &) ; 
most of the fibers, as such a section shows, are considerably thicker than 
those which were present during the prophases (Figs. 91, 92, 97). There 
can be no question, I think, that these very coarse fibers correspond to 
the clusters of fibers observed at the corresponding stages of earlier mitoses. 
