346 SCIENCE PROGRESS 



involved in complete karyokinesis with cell-division to one 

 force, we must regard even the simplest cases of mitosis as 

 the resultant of two actions at least of different character : 

 (a) the bipolar mitokinetic force, and (b) the homopolar traction 

 of the cytoplasm on the centrosomes. 1 



We have now seen that the only adequate explanation of the 

 mitotic figure is that it is a strain-figure under a dual force or 

 polarised stress, and that the threads obey the same laws as 

 flexible chains of force in an electrostatic or magnetic field ; and 

 we pass to the chromosomes, which are but lightly dealt with 

 in the P.R.S. I have made experiments which show that the 

 chromosomes can be represented in a magnetic field by floating 

 chains of iron beads; that two parallel chains of magnetisable beads 

 at the equator tend to separate and to recede to opposite poles, 

 but if nearer the one pole they are both attracted to it and diverge 

 as they come to it. Now Mme. Boveri has shown that when the 

 assemblage of split chromosomes known as the equatorial plate 

 is formed nearer to the one pole of the cell spindle, all the half- 

 chromosomes pass to that pole, diverging much more strongly 

 as they approach it. This result, which could be predicted as 

 the necessary action in a dual field of force, is totally inexplicable 

 in any other way. 



Again, if we float on mercury two chains of steel beads, 

 magnetised so that their like poles are all in the same direction 

 across one another, or if we take chains of cork balls, each 

 containing a steel rod magnetised in the same way, and float 

 them in water crossing one another about the middle of the 

 chain, they will diverge into an X ; if they be attached at both 

 ends, they will diverge into an ellipse, with its long axis parallel 

 to that of the field ; if they are attached at one end and cross 

 in the middle, they will take the form of a CC- The same 

 would occur if the magnetised steel beads were replaced by 

 soft iron beads, lying in the field of two opposite magnetic 

 poles. Now all these associations are reproductions of figures 

 shown by the pairs of split chromosomes as they lie about the 

 equatorial plane of the spindle still attached by remnants of 

 the viscid nucleoplasm or linin, before this bond finally gives 

 way under the stresses of the field, and leaves each daughter 



1 A detailed discussion of the various processes involved in normal mitosis, 

 with a full refutation of the single-force hypotheses, will appear shortly, in English, 

 in the International Edition of the Rivista di Scietiza. 



