292 Wisconsin Academy of Sciences, Arts, and Letters. 
divisions of this plant I have also found difficulty in destinguish- 
ing chromatic bodies in the early spirem, which I could interpret 
as chromomeres (see figs. 13, 14, 15, 17), although such collec¬ 
tions are undoubtedly present in later stages, especially after the 
spirem is split. Perhaps these bodies are present in such young 
stages as are represented in figure 17, but they may be obscured 
by the uniformity of the staining quality at this stage. Even in 
the very early split spirems no chromomeres are visible, as ap¬ 
pears from figure 19. Certain irregularly placed portions of this 
spirem stain more densely, but there are no definite chromomeres 
distinguishable. In figure 18, however, representing a nucleus 
in which the spirem is completely split, a double row of chromatic 
granules or chromomeres is apparently differentially stained as 
distinct from the linin supporting strand. In such figures and in 
the succeeding stages these granules, which stain distinct from the 
linin, even in the chromosomes of the equatorial plate, are always 
distinguishable. Whether or not they are always opposite each 
other, and whether or not during the splitting of the spirem each 
chromomere divides to form two, I have not been able to de¬ 
termine. To all appearances this is the case. I am led to this 
conclusion from the number and arrangement of the chromomeres 
in the two parts of the split spirem and especially from their po¬ 
sition in the chromosomes as they appear in division stages (see 
figs. 18, 20, 21). 
The Later Prophases 
In the stages immediately following the longitudinal splitting of 
the chromosomes, and while they are still long and much coiled 
in the nuclear cavity, a thickening of the threads occurs as shown 
in figures 18 and 19. At this stage the longitudinal split of the 
threads is very evident, and my interpretation of the split agrees 
with that of Muller (’12), namely, that the portions of the thread 
between the chromomeres splits first and that this splitting is fol¬ 
lowed by, or brings about, a splitting of the chromomeres. Numer¬ 
ous such examples as are shown in figure 18 support this view, 
rather than that of Strasburger (’07&, ’ll) that the splitting of 
the thread is initiated by the division of the chromomeres. In 
agreement with the description of Sharp (’13) for Vicia, I find 
that the longitudinally split threads or chromosomes have a gen¬ 
eral longitudinal orientation in the nucleus, making them easily 
