338 Cleland.— The Cytology and Life-history of 
threads. After a time, however (Fig. 34), the individual threads begin here 
and there to show signs of thickening, and it is soon evident that with this 
gradual thickening there is a corresponding decrease in the length of the 
reticulum, the meshes becoming larger in size and the threads fewer in 
number. This process is often attended by a knotting at the points where 
two strands cross (Fig. 35). As the threads thicken they become quite 
granular, with definite bodies scattered all along them. At this point the 
threads show parallel arrangements (Fig. 36), and it is probable that an 
association of the threads, in pairs takes place. I have noted no. marked 
contraction of the thread system comparable to the stage of synapsis or 
synizesis in higher plants. From now on, the threads of the spireme 
present a much more even, smooth, and striking appearance, becoming 
thicker, while the total length markedly decreases. The spireme is double 
its former thickness and possibly represents a fusion of the male and female 
chromatic elements in the nucleus (Fig. 37). At the intersections of the 
threads, thickenings begin to form as knot-like structures. These knots 
grow larger, and at the same time the portions of the thread system 
connecting them become more and more attenuate until finally it can be 
seen that they are breaking here and there as they become too thin to hold. 
The process is one of condensation of chromatic material to form individual 
chromosomes, accompanied of course by their separation. The final result 
of this process is a set of eight bodies which are rather oblong in shape and 
quite large, and almost entirely separated from one another (Fig. 38). 
These are bivalent chromosomes, the paired members of which are to be 
segregated by the first mitosis in the carpogonium. The two portions of 
these bivalent chromosomes then separate (Fig. 39), and the result is a set 
of eight pairs of single chromosomes standing apart in the nucleus and 
forming a very clear stage of diakinesis (Fig. 40). My observations are 
thus in accord with the account of Kylin for Nemalion and of Svedelius for 
Scinaia in placing chromosome reduction at the first division of the zygote 
nucleus. 
Diakinesis seems to be of rather short duration. The paired chromo- 
somes soon become arranged in the equatorial plate and a spindle is formed. 
Polar structures are developed during the later prophase stages prior to 
diakinesis, but are not easily seen since they appear merely as slightly 
denser areas in the cytoplasm. That they are distinct bodies, however, is 
shown by such conditions as are pictured in Fig. 41, in which a slight 
amount of shrinkage has occurred, leaving the polar structures separated 
from the surrounding cytoplasm. The details of spindle formation were 
not observed. 
The metaphase of the first mitosis is intranuclear (Fig. 42), although 
the nuclear membrane breaks down very soon after the equatorial plate is 
formed. The nucleolus is present during metaphase as an empty-looking 
