A study of Chromosomes in three species of Pseudococcus. 
51 
A definite and characteristic behavior of the spindle fibers is to be 
noted in this division. All the evidence seems to indicate that during the 
first phases only a half spindle is formed. The fibers of this are apparently 
attached only to the chromosomes of the massed group as fig. 15 shows, 
and Center at a point near one extremity of the cell. At a slightly later 
Stage the loosely grouped chromosomes are also attached to fibers, but 
these emerge from the opposite end of the cell and do not seem to merge 
at any definite point. No really complete spindle is formed and the 
impression is gained that the whole process consists in a pulling away 
of the massed group from the looser group (fig. 16 and 36). 
This division affects only the nuclear material and not the cytoplasm, 
so that, although two separate groups of chromosomes result, both are 
contained in a single cell. It is only natural to assume that this failure 
of cytoplasmic division is due in part at least to the irregularity of spindle 
fibre formation. At the same time it is necessary to remark that in Icerya 
purchasi(PiERANTONi, '13)no such irregularity is described for the spindle 
of the last division, although there also the cytoplasmic Separation is not 
completed. 
Spermatids. 
The daughter nuclei resulting from the second division are not con- 
tained in different cells, for as already indicated, no cytoplasmic division 
is effected at this time. At best the cell becomes somewhat elongated 
(fig. 18 and 37), but no trace of a constriction is ever visible. Immediately 
after the two groups of chromosomes have reached their respective poles, 
the cell again rounds up, bringing them more closely together (fig. 19). 
The massing observed in the chromosomes of one group, and the 
lack of such a relation in the sister group, remain evident for a considerable 
time. The distinction is upheld also in another way. Even while the cell 
is rounding up, one chromosome group — that which shows a looser 
arrangement — becomes surrounded by a light, aureolar area (fig. 20). 
This expands and acquires a definite outline so that the five chromosomes 
come to lie in a spherical vesicle (fig. 21). They begin to stain less inten- 
sely and become diffuse (fig. 21 und 22). All this occurs while the sister 
group of chromosomes retains its massed or circular arrangement and 
remains quiescent. At most the components of this group lose in the 
sharpness of their outline, but no such grade of diffuseness as described 
for the first named group is ever attained. However it also is finally 
surrounded by a spherical vesicle similar in appearance to that containing 
the other group (fig. 22). The chromosomes finally begin to swell, and 
although they stain intensely for some time, they become less sharp in 
4 * 
