656 Beer. — Studies in Spore Develop7nent. III. 
round the nucleus. In Fig. 39 the nucleus has shrunk slightly, so that the 
relation between nuclear membrane and extranuclear spindle fibres is seen 
unusually well. 
Very soon, however, the nuclear membrane disappears and the rather 
confused tangle of chromosomes lies among the spindle fibres, which are 
now both intranuclear and extranuclear in origin. At first the chromo- 
somes do not appear to be quite free from one another, but soon they free 
themselves and arrange their long axes parallel with the long axis of the 
spindle. They are now long, thin, smooth structures (Fig. 40). The spindle 
in many cases is multipolar diarch in origin (Fig. 40), but in other instances 
it is clearly multipolar polyarch (Fig. 41). In either case, however, it 
always becomes bipolar later on (Fig. 43). The nucleoli may remain 
entangled among the chromosomes or they may pass out at once into 
the surrounding cytoplasm. 
Owing to their close arrangement during the prophase the individual 
chromosomes are usually rather difficult to study satisfactorily at this stage, 
but in a few favourable cases it was observed that some at least of the 
chromosomes were longitudinally divided (Fig. 42). Soon, however, the 
chromosomes arrange themselves upon the equator of the spindle, and then 
it is easily possible to repeatedly observe the longitudinal split in their sub- 
stance (Fig. 43). The daughter chromosomes separate from one another 
during the anaphase, and in Fig. 44 these chromosomes are seen to have 
reached the poles of the spindle and are there closely grouped together 
with their free ends directed towards the equatorial region. A nuclear 
membrane develops round each group of daughter chromosomes, but 
certain of the longer chromosomes still protrude for a time beyond the 
general surface of the nuclei (Fig. 45). A little later the protruding 
chromosome-extremities are retracted, and the nucleus presents a smooth 
outline (Fig. 46). The substance of the chromosomes becomes dispersed 
along the anastomotic connexions which develop between them, so that the 
outlines of these bodies are gradually lost to view. No distinct vacuolation 
of the substance of the chromosomes could be seen, but the slender character 
of these bodies makes observation of this point very difficult. 
One or two nucleoli make their appearance in each nucleus at this time. 
The nuclear division is followed by cell division, and four spores are 
produced which are at first completely unprotected by a distinct membrane. 
The nucleus of the young spore soon after cell division has been completed 
contains one or two distinct nucleoli and a reticulum in which the outlines 
of the chromosomes have been quite lost to view. 
A little later, when the spores of a tetrad are just becoming separated 
from one another by the intrusion of tapetal cytoplasm, the nuclear reticulum 
has become slightly coarser and more chromatic than before, but the most 
striking difference between the nuclei at this stage and those at a somewhat 
