564 Dr. M. Hartog. | Dec. 1, 
Consequently, as I have shown elsewhere,* the model does not justify the 
theory of its author. His apparent triaster is founded on the same error. 
Though the scope of the present study is essentially limited to the 
achromatic figure, I must say a few words on the chromosomes. If we 
represent the split chromosomes by strips of charcoal-iron, we find the 
distribution of the magnetic chains corresponds to those of the cell-figure, 
and may hence infer that the chromosomes are permeable to mitokinetic 
force, and consequently susceptible to its induction. The result of this is 
that two adjacent segments will be the seats of like charges, and repel one 
another: any slight movement that brings the two sister segments so that 
they are respectively nearer opposite poles, will tend to separate them by the 
effects of this induction, and the segments will then recede from one 
another. As they do this, any chain connecting the segment with the nearer 
pole will shorten and thicken. It thus simulates the behaviour of a muscular 
fibre, but differs in that it shortens up to nothing, 2.¢., it is taken up into the 
centre of force or disappears into the cytoplasm: such fibres have been 
termed “tractive” fibres par excellence. 
J have begun a series of experiments using aggregations of magnetic matter 
free to move in a viscid medium to represent the chromosomes and diffused 
dust to form the spindle fibres. Here we can see the magnetic chains 
attached to the aggregates move up as the aggregates move towards the poles ; 
we cannot call such shortening magnetic chains “ tractive,” and have no right 
to ascribe this function to the corresponding fibres in the cell. But my work 
on the models of the chromosomes is too inchoate for me to do more than 
indicate the lines on which it is shaping. I should add that in 1898 I 
definitely wrote:—“The splitting of a viscid thread is one of the most 
difficult mechanical feats to accomplish. Suppose, then, that there is a 
certain polarity about the granules of chromatin, through which, after their 
division, they tend to recede from their fellows as far as possible: through 
this they will determine a splitting of the filament on which they are 
$ As 
ae OVA: 
The name I have given to the dual force we have just studied may 
perhaps be criticised on the ground that, as “karyokinetic force” is a more 
or less familiar word to cytologists, there was no need to invent a new term. 
* ¢ Arch. Entwickl.,’ vol. 19, 1905. 
+ “Nuclear Reduction and the Functions of Chromation” (‘ Nat. Sci. vol. 13, and 
‘ Biol. Centr.,’ vol. 18, 1898). Ralph S. Lillie has developed similar views, and regards 
the force as definitely electrostatic. ‘On Differences in the Direction of the Electrical 
Convection of certain Free Cells and Nuclei,” ‘Amer. J. Physiol., vol. 8, January, 1903 ; 
see also ‘ Biol. Bull.,’ vol. 4, 1903. 
