I 20 
Walker. — On Abnormal Cell fusion in the 
by delicate threads, which pass from the spireme to the cytoplasm. In 
some cases the spindle fibres are seen to be connected with elongate 
structures, probably the remains of the chloroplasts, which often partly 
invest the nucleus at this stage (Fig. 5). Later, when the spindle is clearly 
present, it is seen in most cases to possess blunt poles about which are often 
seen aggregations of irregular particles (Fig. 9). 1 In the last division, how- 
ever, the spindle fibres converge upon a single centrosome-like particle. 
The segmentation of the spireme to form the chromosomes is rarely found 
in the preparations, but it was observed in the nucleus of an early spermato- 
genic cell from which the stain had been removed from all parts except the 
spireme (Fig. 6). This mode of treatment was generally followed, owing 
to the greater clearness which it imparts to the chromosomes. *A.ccording 
to J. and W. van Leeuwen-Reijnvaan, the chromosomes in Poly trichum are 
derived by the breaking up of the nucleolus into fragments, each fragment 
becoming a chromosome. 
The number of chromosomes is six, and they are approximately 
of the same size and of a broad V shape (Fig. 7). No indications were 
observed of the three pairs of chromosomes of different sizes, described 
by J. and W. van Leeuwen-Reijnvaan in this species of Poly trichum. The 
chromosomes become arranged upon the spindle and lie flat in the equatorial 
plane with their ends outwards. A careful search discovered one case only 
where indications of longitudinal fission of the chromosomes could be 
observed (Fig. 8). The appearance of some of the chromosomes in Fig. 9 
suggests that the separation takes place first at one end. One of the inner 
pairs of daughter chromosomes seen in the above figure and also those in 
Fig. 18 seem to have separated first in the middle region. The sliding apart 
of the daughter chromosomes and their passage to the poles are probably 
rapidly effected, as these phases are of unusual occurrence in preparations 
showing very numerous nuclei in a state of division. 
During the last division, while the daughter chromosomes are travelling 
to the poles, a relatively large deeply stained particle becomes detached 
from one or both of the chromosome groups ; occasional dividing nuclei 
also occur which have reached the telophase without detaching these 
bodies. Fig. 19 shows this chromatin particle as it appears in a side view 
of the spindle, and Fig. 20 as seen in two polar views. As Fig. 19 indicates, 
this body appears to separate as a viscid drop of matter from a chromosome 
which lags a little behind the rest. J. and W. van Leeuwen-Reijnvaan 
1 Since writing the present account of the division of the nucleus in Poly trichum, a recent 
contribution upon this subject by C. E. Allen (1) has come into my hands. This observer deals in 
detail with the organization of the spindle, and describes certain polar plates and polar particles, 
named by him ‘ kinetosomes upon which the spindle fibres are inserted. The observations made 
during the present investigation upon Polytrichum formosu?n lead to the conclusion that Allen’s 
‘ kinetosomes ’ are derived from the chloroplasts which are received by the early spermatogenic cells 
when these become differentiated from the wall-cells. 
