242 Rickett.—Fertilization in Sphaerocaapos . 
the first stages of degeneration. This, together with the sporadic occurrence 
of the granules in the cytoplasm, suggests that the whole phenomenon may 
be artificial or pathological in nature. 
It is the fourth phase which seems to correspond with most of the 
stages of fertilization in Liverworts observed by other workers. 
Fifth Phase. 
* 
It was seen in the consideration of Phase 4 that there is a great varia¬ 
tion in the time of occurrence of particular stages relative to the time after 
flooding. This variation now becomes even more marked, so that, although 
the next set of changes occupies roughly the next 20 hours (to 66 hours 
after flooding), this time may vary very greatly. 
The male nucleus, as mentioned above, apparently undergoes a contrac¬ 
tion, and appears once more as a small mass of granules surrounded by a clear 
area (PL IV, Fig. 14). It is probable that this condition is usually preceded 
by the open reticulate condition, since the majority of the cases of this phase 
was found in the same series (C) as afforded most of the instances of the 
reticulate condition. 
The characteristic change in the female nucleus during this phase is the 
organization of chromosomes. The first indication of a change is that the 
chromatic substance, heretofore (in most cases) densely massed in one part 
of the nucleus, begins to spread out or unravel slightly, and becomes collected 
in several large masses and a larger number of smaller ones, which in their 
shape and position with respect to one another suggest that a continuous 
thread or spireme is being formed—or at least a series of chromosomes or 
short threads arranged roughly end to end. The substance of these groups 
of material is still a mass of fine granules and delicate coiled and twisted 
threads. The rest of the nuclear cavity is not entirely clear, for much of 
what seems to be the same stainable material is scattered through it, often 
in the form of a very delicate and rather regular reticulum bearing granules 
at the points of junction of the threads. Some slight indications of the 
beginnings of these changes can be seen in P'ig. 13 ; the chromatic substance 
is still densely massed in the centre of the nucleus, but within it can be dis¬ 
tinguished some more massive bodies arranged roughly in chains. In the 
nucleus represented in Fig. 14 an apparently continuous spireme has been 
formed. The outline of the latter is rough, and it is not homogeneous in 
structure. In many cases it seems to be continuous with the delicate reti¬ 
culum which fills the rest of the nucleus. A nucleolus is not recognizable 
at this stage ; if present, it does not differ from other structures of the nucleus 
either in form or in reaction to the stain. In Figs. 16 and 17 the spireme has 
apparently segmented into chromosomes ; the outlines of the latter are much 
smoother than that of the spireme shown in Fig. 14. In Fig. 17 the X-chromo- 
