July, 1922] CLELAND OENOTHERA FRANCISCANA * 403 
It is not until late interkinesis that the irregularity in the shape of 
the chromosomes begins to give place to a definiteness of form. Shortly 
before the disappearance of the nuclear membrane preparatory to the 
homoeotypic mitosis, it becomes clear that the chromosomes have split, 
and that the halves are swinging around in such a way that they cross. 
Oftentimes they bend over one another in a very interesting way (fig. 34), 
at other times they remain straight. In either event, the general appear- 
ance is that of a Maltese cross. 
The Homoeotypic Division 
The spindle for the homoeotypic mitosis begins to develop shortly 
before the nuclear membrane breaks down. Here again a very prominent 
multipolar spindle is formed, which later becomes bipolar. The chromo- 
somes, which lie scattered in the cytoplasm after the disappearance of 
the nuclear membrane, become very short and are clearly paired. They 
are brought to the equatorial region (fig. 35) and are separated, and seven 
chromosomes pass to each pole in an entirely regular way. The two 
figures lie at opposite sides of the cell, with their axes in a majority of 
cases in the same plane, though this position is not constant (fig. 35). 
The granddaughter nuclei are constituted in much the same manner 
as were the daughter nuclei. The seven chromosomes lie at first very 
close together, and become surrounded by a vacuole whose outer boundary 
becomes the nuclear membrane. The nuclei grow rapidly and pass quickly 
into a resting state in which all trace of the individual chromosomes is 
lost. The process of expansion of the chromosomes is very clear and 
can easily be followed (figs. 36-38). Each chromosome begins to lengthen 
out and becomes a thread, which loses in diameter as it gains in length 
(fig. 36). Each of these threads may attam a length equal to, or greater 
than, the diameter of the nucleus. As each chromosome lengthens, it can 
be seen that very delicate strands begin to extend out from it in every 
direction, and these threads, coming from the various chromosomes, meet 
and fuse, forming a very delicate reticulum. We have then at this stage 
seven prominent threads, joined together by a loose network of very delicate 
ones (fig. 37). The contents of the original threads then pass out in vary- 
ing degree into the more delicate strands, so that in time it becomes im- 
possible to tell where the original chromosomes lay (fig. 38). After the 
material is thus rather thoroughly distributed, and the nucleus has reached 
the resting condition, it is seen to possess a loose reticulum, dotted over 
with chromatin particles of various sizes, and also one to several nucleoli, 
which have arisen as in the daughter nuclei. It is especially to be noted 
that there is no indication of a splitting of the chromosomes during this 
period. The process seems to be one purely and simply of expansion- 
increase in length of the original bodies, formation of branch threads by 
an outflowing of liriin material, and distribution of the chromatin contents 
