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NUCLEAR OSMOSIS AS A FACTOR IN MITOSIS. 141 
we see them in the mature spindle. Moreover, these fibrils attach themselves to 
opposite sides of each bivalent chromosome, and the sheaf on one side is approximately 
equal to that on the other. The difficulties here presented are quite obvious. In the 
first place, an explanation is needed to account for the actual attachment of the free 
ends of these fine, delicate, in-growing fibrils to the chromosomes, and if they do so 
attach themselves, this implies a selective power either on the part of the fibrils or of 
the chromosomes both in regard to numbers and position of attachment. 
Another series of difficult interpretations is to be found in reference to the 
coalescence of the cones of the multipolar stage which results in the bipolar figure. It 
will be remembered that the apices of the cones may be some distance apart, but it is 
believed that they eventually approach one another at opposite points. Such approach- 
ment and coalescence impliesa movement. Such a movement would necessarily be through 
the undifferentiated reticulum of the cytoplasm. It should be remembered that certain 
of the apices of the cones are so far apart that they pass through an angle of 45° in the 
accomplishment of this fusion. In this connection Professor Farmer calls attention to 
the aggregation of the nuclein-charged linin beneath the points of origin of the cones, 
and he sees in this an indication that there exists a causal connection between the two 
phenomena ; and just as the chromatin at this early stage appears to determine the 
formation of the four or more poles, so now the chromosomes again appear to be the 
active agents in effecting the resolution of the quadripolar into a bipolar arrange- 
ment. But just how this is brought about Professor Farmer does not explain. The 
fact is, the idea of approachment and eventual coalescence of the cones has been 
based upon appearances only. A careful search of the literature and of my own 
preparations has failed to reveal the slightest indication that the cytoplasmic reticulum 
has been in any way disturbed by such a coalescence. No real evidence has been 
recorded to show that an approachment of the cones really occurs. I shall attempt to 
prove in the following pages that the idea of a lateral movement and coalescence of 
the cones is a misconception. 
Perhaps the most striking feature of the whole mitotic process is the constancy and 
uniformity of the equatorial plate in the metaphase. Here the chromosomes always 
arrange themselves in the same plane at the equator of the spindle. This plane 
constitutes a dividing line between two series of fibril-sheaves which extend in 
opposite directions and generally converge at the poles. It is this constant position 
of the chromosomes which gives the spindle its character. Up to the present no 
adequate explanation has been offered to account for the factors concerned in the 
arrangement of the chromosomes in this peculiar fashion which results in so striking 
a feature of mitosis. To say that the equatorial plate is due to electrical conditions 
only confuses the issue, at least until more is known of such electrical conditions 
and their influence upon protoplasmic bodies. It is just as profitable to say that 
it is due to cell-polarity, the determining factors of which are unknown so far as the 
vascular plants are concerned. 
