Lewis . — The Life History of Grijfithsia Bornetiana. 665 
At this stage the tetraspore- mother-cell may be considered to be 
mature. The length of a mature mother-cell is about 20 p, the width 15^, 
and the diameter of the nucleus 7 /x. Further changes in the mother-cell 
are in anticipation of division into tetraspores. 
From this time the changes in the cytoplasm occur mainly in con- 
nexion with the vacuolar area. The vacuoles become larger and the whole 
vacuolar area presents a coarse spongy appearance. In the meshes are 
deposited numerous spheres of substance staining deeply with haematoxylin. 
There is reason to believe that these bodies are derived from the nucleus. 
As the time of nuclear division approaches, these granules become larger and 
fewer in number, so that it is possible, by noting their size and number, to 
predict in just what stage of mitosis the nucleus will be found. The 
granules seem to be analogous to the chromidial substance of Protozoa 
(see Goldschmidt, 33) and of some plants (see Tischler, 81). 
The changes in the nucleus are profound. Most striking is the 
decrease in staining capacity of the nucleolar masses. These become 
irregular in form, and at the same time fuse with one another, so that their 
number is reduced by more than half (Fig. 112). At this stage they are 
in the form of thick, curved rods, in which light and darkly staining areas 
may be discovered. Often four dark areas may be detected in each rod, 
which suggests that this stage corresponds to the formation of tetrads in the 
oocytes and spermatocytes of many animals. Coincidently with these 
changes, small granules are to be seen in the nucleus near its periphery, 
which seem to pass out into the cytoplasm (Figs. 112, 113), to form the 
granules already mentioned as occurring in the vacuolar area. 
The stage just described is considered to be the period of synapsis. 
It is of long duration, it shows a condition which does not occur elsewhere 
in the life-history, and it immediately precedes the mitoses in which 
numerical reduction of the chromosomes takes place. It differs from the 
usual type of synapsis in that no spirem or synaptic thread is formed ; but 
this is not to be wondered at inasmuch as nowhere in the life-history of 
Grijfithsia Bornetiana is a spirem produced. Perhaps the worm-like nuclear 
masses are to be considered as replacing the usual spirem stage. Somewhat 
similar conditions in the nucleus of the zygote of Spirogyra are interpreted 
by Karsten (45, p. 6) to represent the period of synapsis in this form. 
While the thick, irregular rods continue to lose their capacity for 
taking up stains, there appear scattered throughout the nuclear cavity, but 
mainly near the periphery, a number of small spherical or oval bodies 
(Figs. 1 14, 1 15). About fourteen of these bodies are usually present, though 
the number may vary within narrow limits. This is the stage of prophase, 
and the small bodies are the chromosomes. At this time traces of the 
achromatic substance of the nucleolus may be detected near the centre of 
the nuclear cavity. 
