22 PROTOPLASM AND PLANT CELLS 
matin granules spreading themselves out along the thread 
until it is of even thickness. The thread rapidly shortens 
and thickens, eventually becoming a thick, more or less 
distinctly spirally arranged thread (spirem stage). At 
the same time the nucleolus has been growing smaller or 
less distinct and soon disappears entirely. In the spirem 
thread there often becomes visible at this stage a split for 
its whole length. However, it does not separate along 
this split as yet. In the mean time outside the nucleus 
there begin to appear in the cytoplasm immediately 
surrounding the centrosomes fine lines, or fibrillae (of 
kinoplasm), which appear to center at the centrosome and 
extend from it in all directions but especially toward the 
nucleus. In the plants which have no centrosomes there 
appear near the poles of the nucleus tangled masses of 
fine fibrillae which in some cases form a sort of cap at each 
pole or even may entirely surround the nucleus. From 
this tangled mass the fibrillae gradually untangle them- 
selves somewhat and finally lie in the form of a cone at 
each pole, with the apex away from the nucleus. In the 
forms with centrosomes one of the latter lies at each apex, 
often surrounded by radiating fibrillae which may reach 
out even to the cell wall. Where the mass of fibrillae 
comes in contact with the nucleus the nuclear membrane 
disappears and soon after vanishes at all other points 
also. The fibrillae push into the nuclear cavity. Inthe 
meanwhile the spirem thread breaks transversely into a 
number of segments called chromosomes, the number 
being constant for all vegetative nuclei of a given species 
of plant. Two sets of kinoplasmic fibrillae can now be 
recognized. Some push through the nuclear cavity until 
they meet and unite with similar ones from the other pole, 
forming a spindle-shaped structure commonly spoken of 
as the nuclear spindle. Other sets of fibrillae push toward 
