182 



ON THE INTERNAL FORM AND 



[CH. 



the chromosomes, which had at first been apparently repelled 

 from the poles towards the equatorial plane, should then be spht 

 asunder, and should presently be attracted in opposite directions, 

 some to one pole and some to the other. Remembering that it is 

 not our purpose to assert that some one particular mode of action 

 is at work, but merely to shew that there do exist physical forces, 

 or distributions of force, which are capable of producing the 

 required result, I give the following suggestive hypothesis, which 

 I owe to my colleague Professor W. Peddie. 



As we have begun by supposing that the nuclear, or chromo- 

 somal matter differs in permeability from the medium, that is to 



Fb 



Fig. 54. 



say the cytoplasm, in which it Ues, let us now make the further 

 assumption that its permeabihty is variable, and depends upon the 

 strength of the field. 



In Fig. 54, we have a field of force (representing our cell), 

 consisting of a homogeneous medium, and including two opposite 

 poles : fines of force are indicated by full lines, and loci of constant 

 magnitude of force are shewn by dotted lines. 



Let us now consider a body whose permeability (/x) depends 

 on the strength of the field F. At two field-strengths, such as 

 Fa, Ff,, let the permeability of the body be equal to that of the 



