CYTOLOGY OF EOCRONARTIUM MUSCICOLA 
this great difference, though two factors are evidently involved. The 
large amount of cytoplasm in the larger cells probably necessitates a 
corresponding increase in the mass of the nuclei. Also it is evident 
that the nuclei increase greatly in size as they pass into mitosis, the 
largest nuclei observed being in process of division. 
The two nuclei of a cell, when in the resting condition, usually lie 
a considerable distance apart, frequently in opposite ends of the cell. 
This is especially true of extremely long cells. When preparing to 
divide, the nuclei migrate toward the center of the cell, approach each 
other, and often come to lie in actual contact. In the majority of 
cases nuclei at this stage are of so large a diameter that it is impossible 
for them to pass each other in the thread, or to assume the side-by- 
side position typical of conjugate division. At all stages the nucleolus 
is evident as a spherical homogeneous body, staining deeply with 
safranin, and easily distinguishable from the chromatin material in the 
nucleus. The chromatin stains sharply, and in stages preceding the 
formation of the spindles is frequently contracted into a compact mass 
in one side of the nucleus (figs. 6, 7), the nucleolus occupying the other. 
In poorly stained preparations a pair of nuclei in this condition have 
the appearance of four small nuclei. When well stained the nuclear 
membranes are evident, and the two deep-staining bodies in each 
nucleus then are seen to lie in a common, hyaline nuclear cavity. 
The two nuclei pass from the resting condition into mitosis together. 
The formation of the spindles is not, however, always exactly simul- 
taneous (figs. 9-14). At all stages up to late anaphase each nucleus 
possesses a well defined membrane, and the spindle, which is intranu- 
clear, stands out sharply in the nuclear cavity accompanied by the 
nucleolus. The spindles are not necessarily parallel. Moreover they 
lie without any reference to the long axis of the cell. 
The spindle fibers stain clearly, and there is visible in some cases 
at each pole of the spindle a more deeply staining point. This is 
doubtless the centrosome, but its minuteness precludes any study of 
its structure. In certain cases it has the appearance of a short rod 
resembling that described and figured by Harper (20) in Phyllactinia. 
The writer has never seen any indication of astral rays. The prepara- 
tions examined have proved very favorable for a study of division 
stages. Equatorial plate stages are especially numerous, and in many 
of these cases it is possible to count the chromosomes with a reasonable 
degree of certainty. All the evidence accumulated shows the number 
