The Mechanics of Mitosis 29 



ity in or on the surrounding aqueous solution. Moreover, since 

 this aqueous solution contains inorganic, ionized salts it must be a 

 conductor of electricity, and the positive charge must be distrib- 

 uted over the whole solution. Any localized positively charged 

 area in the electrolyte, except for the supposed "double layer" 

 around each charged particle seems, consequently, unlikely. 

 Lillie has encountered a similar difficulty in accounting for the 

 configuration of the chromosomes. They ought not only to be 

 repelled from the astral centers but also to migrate toward the 

 boundary of the equatorial plate. This latter thing they do not do, 

 and Lillie is therefore again obliged to make the assumption of a 

 localized positive inter-astral region. 



There is, however, another force which might well come into 

 play here, which so far as I know has not been mentioned in this 

 connection before, and which involves none of the objections 

 urged against the electrostatic explanation. I refer to the mutual 

 repulsions and attractions, exerted by bodies pulsating or oscil- 

 lating in a fluid medium. We owe our knowledge of this branch 

 of hydrodynamics chiefly to the two Bjerknes, father and son.** 

 They have shown that bodies pulsating or oscillating synchro- 

 nously in a liquid attract or repel one another dependingon whether 

 they pulsate or oscillate in the same or opposite phase. Further- 

 more, these bodies set up lines of flow in the liquid, real hydro- 

 dynamic lines of force, which simulate exactly the lines of force 

 in magnetic or electric fields. The sign of this force is, however, 

 in general, just the reverse of that in electric or magnetic fields. 

 Bodies pulsating synchronously and in opposite phase repel each 

 other, although the form of the field they produce is identical with 

 that between unlike magnetic poles which attract each other. Simi- 

 larly, two spheres oscillating synchronously and in the same phase 

 , repel each other, although they too produce a field like that 

 between opposite magnetic poles. The following experimentally 

 derived figures, taken from Bjerknes' text-book, illustrate this 

 identity of form and reversal of sign in the electric and hydrodyna- 

 mic energies: 



^ See Hydrodynamische Fernkrafte, v. Bjerknes; 2 vols. Leipzig, J. A. Barth, 1902. 



