33 o SCIENCE PROGRESS 



Again, Meves and others have suggested that the fibres from 

 the one centre push the chromosomes across the equator to 

 the other. The continuity of some of the fibres in certain cases, 

 and of all of the fibres in others, is equally valid against this 

 view ; which lacks all probability, moreover, since the threads 

 are certainly flexible, and quite unfitted for the role assigned 

 to them. 



These grossly mechanical forces we may call " linear " forces, 

 unchanging in intensity along the line of push or pull. We 

 leave them, and now pass to a more subtle group, the "centred" 

 or " Newtonian " forces. With these the action radiates from 

 a centre, and in a uniform medium changes in intensity 

 inversely as the square of the distance from the centre. Of 

 these are gravity, electrostatic force, magnetism, molecular 

 osmotic attraction ; and obeying similar laws are radiant 

 energy, the flux of heat either from a calorifer or towards 

 a refrigerator, the steady flow of liquid, either from a source 

 or toward a sink, and the molar flow of osmotic currents. 

 Gravity reveals no trace of bipolarity : for "negative gravity" 

 and its effects we must turn aside from the facts of Nature to 

 the imaginative pages of Frank R. Stockton ; and the effect 

 of a second gravitating body is obtained by arithmetical 

 summation. The other phenomena admit centres of opposite 

 sign, whose joint effects are their algebraical sum : positive and 

 negative electricity, north- and south-seeking magnetism, 

 calorifer and refrigerator, source and sink of stream-lines, 

 centres of greater and of lesser osmotic concentration than 

 the medium. 



Numerous attempts have been made to explain what we have 

 called "mitokinetic force" or " mitokinetism " as a centred 

 force, and to refer it to one of the well-known centred forces 

 enumerated above. Thus Biitschli and Rhumbler refer it to 

 osmotic diffusion, Stanislas Leduc to osmotic currents, Frank 

 Lillie and Gallardo (in his recent works) to electrostatic 

 displacement. 



The theory of the distribution of " centred " or " Newtonian" 

 forces in a uniform medium was worked out geometrically 

 by Faraday : unwilling to admit of gravity and magnetism 

 acting at a distance, he introduced the conception of a strain 

 in the medium (which might be substantial or ether), by which 

 the stress radiating from the centre was transmitted along 



