MITOSIS (KARYOKINESIS) 23 
the chromosomes and become attached to them, one or 
more sets from each pole being fastened to each chro- 
mosome. In some way, perhaps by the contraction of 
these fibrillae, the chromosomes are brought to lie at the 
equator of the spindle, forming the so-called equatorial 
plate. The chromosomes are of various shapes, like rods, 
or resembling the letters J, V or U, more frequently the 
last two. Usually the faint longitudinal split which 
first became visible during the spirem stage is quite dis- 
tinct. As the fibrillae attached to the chromosomes con- 
tinue to contract the latter are torn in two along the line 
of this longitudinal split, one half being dragged toward 
each pole. When these daughter chromosomes, as they 
are called, reach the two poles they soon join to each other 
end to end and form spirem threads similar to those 
formed before the cleavage into chromosomes (the di- 
spirem stage). ‘These elongate and finally form a long 
tangled thread along which the chromatin begins to 
assemble in lumps and which soon forms short lateral 
connections to make the typical nuclear reticulum. In 
the meantime the nuclear membrane has appeared 
around each daughter nucleus and the nucleolus has made 
its appearance. The kinoplasmic fibrillae around the 
centrosome gradually disappear in the plants with cen- 
trosomes, while in plants without centrosomes they dis- 
appear in about the same way that they. appeared, or in 
the higher plants take part in the formation of the sepa- 
rating membrane. In this latter case the spindle fibrillae 
seem to increase in number until they occupy the whole 
width of the cell. At the equatorial plane a little knot 
appears on each fibrilla. The fibrillae contract and as 
they shorten the knots increase in size until by the con- 
tact of the knots with each other a thin membrane (of 
kinoplasm) is formed which separates the protoplasm of 
