Mnium affine var. ciliaris ( Grev .), C.M. 
445 
Resting Stages and Prophase in the Antheridial Tissues. 
It may be well to speak briefly of the condition of the earlier cell 
generations in the antheridium. The cells are somewhat larger in the 
young antheridia than those found in the mature condition. Compare 
PI. XXI, Fig. i with Figs. 8, 9, and 10. Much growth, however, takes place 
as the cells of the later generations have not diminished proportionately in 
size, in comparison to the number of divisions which have occurred, neither 
do the cell-contents seem to grow depleted. (Cf. Fig. 1 with Fig. 10.) The 
cytoplasm is finely granular, sometimes showing a tendency to form more or 
less flocculent masses (Fig. 1). Again, it may be observed very evenly 
distributed throughout the cell without any noticeable lumps or flakes 
(Figs. 3, 4, 5, and 6 ). The appearance of the antheridium from which the 
latter figures were drawn suggested most excellent fixation ; however, it may 
also be true that the flocculent nature of the cytoplasm shown in Fig. 1 may 
be a natural condition and not an artifact. I have observed that in the 
deeper tissues, in those cells nearer the base of the antheridium where the 
fixing fluid does not penetrate so quickly and with as great strength as it 
does nearer the tip, frequently, although not constantly, there is a tendency 
towards vacuolization. The clear central part of the nucleus around the 
nucleolus is larger, with the chromatin network collected nearer the nuclear 
membrane, while the cytoplasm tends to collect in lumpy masses nearer the 
plasma membrane. A careful study was made with these facts in mind in 
an endeavour to give here representative figures. 
A nuclear membrane is clearly present during the resting stage. The 
contents of the nucleus consist of a very conspicuous deeply staining and 
relatively large nucleolus surrounded by a clear region, which separates the 
nucleolus from a peripheral chromatin network (Figs. 1, 2, and 3). Walker 
reports practically the same condition in the resting cells of Poly trichum, 
but also describes and figures delicate threads connecting the nucleolus with 
this reticulum. The writer was not able to observe these threads in Mnium . 
The chromatin network is often partly obscured by a very finely granular 
substance, which appears usually during active conditions of prophase. 
This may be material which at other times, either earlier or later, may be 
represented in the substance of the nucleolus or chromatin and is at this 
particular stage in a transitional condition. At least it is quite clear that as 
the nucleus prepares to divide the nuclear network becomes more prominent, 
the lumps tending to draw out along the connecting threads (Fig. 3), form¬ 
ing eventually a distinct spireme (Fig. 4). During this process the nucleolus 
gradually loses its affinity for the stains (Figs. 1, 2, and 3) and finally 
is lost sight of altogether (Fig. 4). It is interesting to note that as the 
nucleolus apparently loses material the chromatin is most densely aggregated 
