276 Allen.— The Spermatogenesis of Poly trichum juniperinum. 
of the blepharoplast, it must push in between the blepharoplast and the 
apical body ; but of such an intrusion there is no indication. 
Whether the nucleus, as a result of its elongation, finally extends to 
or beyond the posterior end of the blepharoplast, I have not been able 
in most cases to determine. As will appear more fully later, the blepharo- 
plast, except for its short anterior portion, usually becomes indistinguishable 
while the nucleus is still in the early stages of extension. Rarely (as in 
Pig s * 4 5 an d 46) the blepharoplast is visible as a distinct body until a quite 
late period. In Fig. 45, representing an androcyte, the posterior portion 
of whose nucleus is towards the observer, the anterior end of the blepharo- 
plast is seen close to the apical body in the upper end of the figure ; it can 
be traced in the preparation from which the drawing was made, along the 
anterior half of the nucleus (not shown in the figure), and then along the 
posterior half of the nucleus, which, with the corresponding part of 
the blepharoplast, appears in the drawing. The posterior tip of the nucleus, 
and perhaps also that of the blepharoplast, are hidden from view by the 
limosphere. Fig. 46 shows a different view of an androcyte found in 
the same antheridium. In this case also the blepharoplast can be traced 
nearly the full length of the nucleus. The anterior portion of the blepharo- 
plast, apparently extending beyond the end of the nucleus, is shown, and 
what seems to be the posterior end of the blepharoplast appears near the 
upper edge of the figure, in close contact with the nuclear membrane. 
Here it appears that, just as the blepharoplast extends beyond the nucleus 
anteriorly, posteriorly the nucleus extends beyond the blepharoplast. 
The nucleole usually remains conspicuous until the later stages of 
nuclear elongation (Figs. 43, 45). Thus far there has been no decrease in 
the bulk of the nucleus ; rather, to judge from appearances, the opposite 
has happened, for, as the figures show, the nuclei in process of elongation 
often seem much larger than those of young androcytes (compare, e. g., 
Figs. 31, 37 , and 38, PL XVI, with Figs. 14-20, PI. XV). Some of the apparent 
increase in size is due to the fact that as the nucleus is elongating it also 
flattens itself against the plasma membrane, thus, in certain views, giving 
an exaggerated impression of its bulk. Allowing for this source of error, 
however, it seems true that the progressive change in shape of the nucleus 
thus far described is actually accompanied by an increase in its size. 
When the nucleus has reached nearly or quite its final length 
(Figs. 43, 44, 47, PI. XVI), a portion of it still remains comparatively thick. 
Now ensues a period (Figs. 45, 46, 48-55) during which the diameter of 
the nucleus (and consequently its volume) is considerably diminished, not 
only in the region that has thus far remained thick but in its slenderer 
portions as well. Until this time the reticulate structure of the nuclear 
contents has persisted. The diminution in volume which now occurs 
seems to involve the extrusion of the nuclear sap. As a result, the 
