TRANSACTIONS OF SECTION D. 629 



ia the theory by pointing out that the material visible structures of the polar 

 stars and spindle were not the abstract, ' lines of force ' of Faraday and Clerk- 

 Maxwell, but material 'chains of force' of more permeable substance than the 

 rest of the field, held in position by the stresses radiating from the unlike poles. 

 This is in brief a statement of what we may call the ' heteropolar hypothesis.' On 

 the other hand, Rhumbler. Butsehli, and Leduc put forward the view that the 

 spindle was due to diffusion currents centred on its poles. The two former 

 failed to realise that diffusion currents centred on two like poles (two sources, 

 or two sinks to use Clerk-Maxwell's metaphor, taken from stream lines) could not 

 produce the spindle, but the anti-spindle or crossed figure, just the same as two 

 ' like ' magnetic or electric poles. Leduc, when he realised that the centrosomes of 

 the animal cell were 'like' in respect to osmotic phenomena, immediately tried to 

 show that the cell spindle was no true spindle, but a mock one, formed of two 

 asymmetrical spindles touching by their wide ends. But the figure obtained in 

 his models was, unlike the cell spindle, discontinuous across the equator. Never- 

 theless, it had the effect of inducing Gallardo to try to get better models. 

 Gallardo, like others, was impressed by two facts : (1) the centrosomes diverge as 

 the spindle grows; (2) Lillie had shown that the chromosomes bear a positive 

 electrostatic charge and must repel each other. 



The answer to (1) is that in many cases the centrosomes show the effects of a 

 bodily pull exercised by the cytoplasm ('cytoplasmic traction' of Hartog). This 

 is well shown in the enormous cell-figures of Ehynchelmis, where the centrosomes 

 actually give way under the contrary pulls; and in several worms and molluscs, 

 where the whole figure is spirally twisted, proving that the pull is accompanied 

 by a twist. Moreover, the separation of the poles during the process of karyo- 

 kinesis is not universal, as noted and figured by Kostanecki and figured without 

 remark by Yatsu. 



The answer to (2) is that Pentimalli has shown that while the living chromo- 

 somes migrate towards the anode of a constant current, the achromatic spindle 

 is not affected in the same way, but only yields to the mechanical push exerted 

 by the chromosomes. 



Gallardo has sought to model electrically the spindle between like poles, with 

 two closely apposed broad inductors of one sign to represent the ' equatorial 

 plate,' and two small poles of the opposite sign for the centrosome. It is 

 impossible in this way to represent the interzonal fibres between the two disceding 

 groups of chromosomes in anaphase. 



His last model is what we may term an osmoto-electrolytic model. His field is 

 of mucilage; the centro-poles are drops of solution of acid fuchsin, his equatori;)] 

 band of (basic) brilliant green ; while the indicators are powdered (basic) fuchsin 

 dusted on the surface of the gum, which leave behind a comet-like trail of red as 

 they travel away from the central band to either pole. The central band itself 

 tends to split, and its two halves are united by cross bands of green solution 

 which simulate in position and in outward bulge the interzonal bands; and this 

 gives a most striking character to the model. If two like poles are united by 

 tenacious threads their lateral repulsion and their tenacity result in a good 

 geometrical spindle, as is shown in the electrostatic model figured by the author; 

 but if these threads are severed they at once assume the direction of the anti- 

 spindle, and this is the crucial point. 



The absolute proof of the opposite polarity of the two centrosomes is to be 

 found in the growth of the spindle by inflection and coalescence of rays growing 

 out from the centrosomes. In some cases the spindle is actually formed ab initio 

 in this way. 



Gallardo has stated that no spindle can be formed in the absence of chromo- 

 somes, and this is essential to his view. But the spindle in the animal cell every- 

 where is free from chromosomes at first; and several cases may be cited, besides 

 Bonnevie's, of the formation of full-grown spindles without any equatorial plate. 



Since it is demonstrated that the cell-spindle is homopolar with respect to 

 osmosis, currents, electrolytic, or electrostatic force, magnetism is out of the 

 question, we may conclude that mitokinetism is a new force unknown so far outside 

 the living cell. 



