3 1 8 Mo li ter . — The Development of the Heterotypic 
vary greatly in size, and which are arranged into a spirem. When such 
conditions as Figs. 19, 20, and 21 are found in preparations showing no 
evidence of poor fixation, the only conclusion that can be drawn is that the 
presynaptic thread consists of a single row of chromomeres. There is no 
evidence that two distinct spirems are present prior to the first contraction, 
or synapsis. 
From Synapsis to the Loose or Hollow Spirem. 
Podophylhim. As stated in the foregoing, the period of synapsis 
represents probably the longest pause in the entire mitotic process. 
During the same, the cells and their nuclei may increase somewhat in 
size, although extensive measurements were not made to determine the 
amount, as this was not considered of very great importance. 
The first indication of a loosening of the contracted mass is seen in 
the extension into the nuclear cavity of loops of the spirem, and the 
beginning of the rounding off of the pollen mother-cells at the corners 
(Fig. 6). In the section from which this figure was taken, some of the cells 
showed the first signs of rounding up. When the loosening of the spirem 
has once begun, the process seems relatively rapid, as the enlargement of 
the anther is also rapid, so that the pollen mother-cells are soon separated 
from each other, in some instances rather widely. As soon as the balled- 
up thread begins to loosen, some of the loops or portions of the thread 
which project into the nuclear cavity are seen to be double, that is, two' 
rows of granules or chromomeres may be made out in them (Fig. 6). The 
double row of chromomeres is not everywhere distinguishable, for in many 
of such free portions of the spirem only a single row can be recognized. In- 
exceptional cases the halves of the thread diverge for a short distance, so 
that it seems that the linin thread is also double, but, as a rule, the linin 
seems undivided. The writer wishes to emphasize the fact that neither in 
Podophyllum nor in the other plants to be described further on, are the 
chromomeres all of the same size, nor are they all exactly paired (Fig. 6). 
In a comparatively short time, the contracted mass distributes itself some- 
what uniformly within the nuclear cavity, and the pollen mother-cells 
round off, secreting their own rather thick and characteristic cell-walls. 
This stage is shown in Fig. 7. In nuclei less densely stained, the two rows 
of chromomeres imbedded or held in the linin can be clearly observed. 
In exceptional cases the halves of the spirem may diverge in places, 
showing clearly the longitudinal fission of the spirem. In Podophyllum , 
the separation of the halves is the exception (Fig. 7). Following this 
stage, the spirem thickens somewhat and probably becomes a little shorter, 
but the contraction or shortening is very much less than has hitherto been 
assumed. The result is a smooth chromatin spirem, arranged in rather 
regular turns, and in which, as a rule, no indication of a longitudinal fission 
