
1904.] The Dual Force of the Dividing Cell. 561 
We can model this by putting a heap of heavy, coarse powder just in front of 
the poles, or by cementing to the glass a small disc of charcoal-iron in the 
corresponding place, especially if we cement a larger disc immediately over 
the pole (fig. 15). I also figure a “monaster” from Boveri, where the 
centrosome has broadened out, but failed to divide (fig. 12). Its magnetic 
model is thus obtained: a blunt crescent of charcoal-iron is cemented over 
the pole of a single magnet to represent the centrosome, and a small disc in 
its concavity represents the nucleus (fig. 13). From the correspondence of 
the distribution of the chains of force, we must infer that the nucleus, or at 
least the nuclear wall is highly permeable to mitokinetic force. This is a very 
good illustration of the value of our method of studying by models, in 
enabling us to gain an insight into the laws of the cellular field. 
XIV. 
We are now sufficiently familiar with the essential conceptions of the 
theory ; and can profitably examine in detail how far such forces as osmosis,. 
surface-tension, etc., could be used to explain the cell-figure. Thanks to the 
careful researches of Vejdowsky and Mrazek on the most favourable object. 
known, we are aware that the osmotic and surface-tension actions at the two: 
cell-centres are of exactly similar character. They appear (a) to be limited 
to the immediate neighbourhood of the centrosomes, (b) to have for their 
object the nutrition of these, and (¢c) not to be transmitted toa distance. The 
first-formed rays, indeed, seem different in their behaviour to the later ones, 
and to have no kinetic action, no inductive results on those of the opposite 
poles. Were there any action at a distance the field produced must resemble 
that of two “ like” magnetic or electrostatic poles. For if “like” centres act 
through a permeable medium, (1) a particle free to move under their 
influence, if on the axis joining them or its prolongations, will tend to move 
along that straight line to the nearer one if the force be one of attraction, 
away from it if it be one of repulsion; except that if it be at the centre of 
figure (assuming that the forces are equal in magnitude) it will stay there. 
Thus the line drawn through the poles is a “ line of force.” (2) Any point on 
the equator, or plane bisecting the interpolar axis at right angles, will tend to 
move to (or from) the centre of figure; so that every line on the equator 
passing through the centre is also a line of force. (8) The remaining lines of 
force all diverge from the poles, and are convex to the interpolar axis. The. 
figure of the distribution of the lines of force in such a field we may call the 
“anti-spindle” or “crossed field.” Thus the formation of a spindle is. 
impossible between two poles of “like ” or of undifferentiated character. 
As stated above Leduc has demonstrated this for diffusion-currents of 
