122 Steil. — A p agamy in Nephr odium hirtipes, Hk. 
extending part way across the cell. Hence when a new wall is produced it 
extends frorp. the wall of the cell to the concavity of the nucleus (Figs. 30, 
3 T 3 2 > and 33, PL VI). 
Fig. 32, PL VI. presents some evidence that if spindle fibres are formed 
during the division of the nucleus they may sometimes wholly or partially 
disappear before cell-wall formation. On the left-hand side of the figure 
the new walls are present, but on the other side no indication of such walls 
is observed. Fig. 33 was drawn from the same sporangium. Such figures 
are very infrequent and suggest that complete nuclear and cell divisions may 
occur in rare instances. It would be difficult to conceive how Fig. 33 could 
represent the result of a fusion of two sporogenous cells and their nuclei. 
The whole figure represents clearly a single cell, and the portions of it have 
been produced by an incomplete cell division just described. Such a cell 
could be formed from one similar to a , Fig. 25, PL VI. 
It appears, therefore, that the eight sporogenous cells undergo not only 
an incomplete nuclear division but also in some instances an incomplete cell 
division. That nuclear and cell divisions are not completed, except possibly 
in very rare instances, was determined by counting the sporogenous cells at 
various stages of development. Many spore mother-cells during the resting 
stage of the nucleus, synapsis, the heterotypic and the homotypic divisions, 
and spores showed evidences of incomplete division (Figs. 33, 34, PL VI, and 
Figs. 39, 43, 49, 50, 51, and 52, PL VII). Hence there can be no question 
that cell and nuclear divisions rarely, if ever, occur during the first eight- 
celled stage of the sporogenous cells. 
Except in the sEape of the cell or its nucleus, nothing unusual was 
observed in the structure or behaviour of the sporogenous cells after the 
incomplete division just described. The nucleus and the cell increase con- 
siderably in size, and unless there is a well-developed spindle produced, and 
a partial division of the cell occurs, the majority of the cells and their nuclei 
finally become approximately spherical. A comparison of the sizes of the 
resting nuclei before and after the incomplete divisions shows that they are 
considerably larger at the latter stage. While the nuclear material is still in 
the form of a reticulum, it recedes gradually from one side of the nuclear 
membrane. A continuous spireme appears to be formed as the nucleus 
passes into synapsis. Fig. 35, PL VI, represents an early stage in this con- 
tinuous spireme thread. The compact synaptic mass that finally appears 
pressed against the membrane on one side of the nucleus includes the 
nucleolus, which seems to persist during the contraction stage (Fig. 36, PI. VI). 
When the spireme emerges from synapsis, radiating portions of the thread 
extend to the nuclear membrane on the side opposite that at which the con- 
traction took place. During the synaptic period the cytoplasmic portion of 
the mother-cell, where the synaptic mass is present, is very thin. After 
synapsis the cytoplasm of the mother-cell gradually grows to a nearly 
