PHYSICS OF SEGMENTATION. I 2 I 



The negative results obtained with KCl indicate that it is the H 

 and not the Cl ion that is effective. Two views of the way in 

 which this ion acts are conceivable. First, an interpretation we 

 have referred to previously, it may be that only the H ions penetrate 

 the membrane, either because of i/s specific chemical nature or 

 because of their greater diffusion velocity ; or, second, that, with 

 no penetration occurring, the cytoplasmic membrane simply at- 

 tracts the H ions to the surface. 



Both views however present difficulties if the H ions are con- 

 sidered to have a purely inductive (physical) action. The first 

 view in its very genesis, because, firstly, unless the surface is 

 negative all the time it is hard to understand why the positive 

 ions should even be attracted to it, much less penetrate it ; if, on 

 the contrary, it is at first positive they would not reach it, being 

 repelled, unless their velocity of diffusion overcame this repul- 

 sion ; but secondly, because if penetration does occur it is difficult 

 to understand how at least many of the ions can reach the 

 nucleus from which point possibly to, in turn, induce negative 

 charges at the surface ; for cytoplasm and H ions are like- 

 charged ; these would, however, tend to cause a repulsion of 

 cytoplasmic particles and therefore an increase in pressure. The 

 second view meets with objections because, with no penetration 

 occurring, it is difficult to understand also here why, firstly, if the 

 surface is not yet negative before mitosis, either H or any other 

 kations should be attracted, or, secondly, if the surface is nega- 

 tive at all times and the cytoplasm positive, so that the surround- 

 fhg H ions may induce further negative surface charges, why 

 the H and not other kations as well should be effective. That 

 they are might seem to be explained by the comparative diffusion 

 velocity of H, K and Cl ions (H is 313, Cl 65.9, K 63.8) ' from 

 which it might be assumed that the K ions are not effective be- 

 cause with them the Cl ions while in the case of HC1 the H ions 

 have the greater comparative velocity. But this explanation 

 would not hold good for explaining positive results with Ca(NO. j ) 

 on A nipJi itritns- for the diffusion velocity of Ca, is 62, that of 

 NO 3 6s. 3 



1 Hober, loc. cit., p. 7 2 - 



2 Fischer, Am. Join: of Physiology, VII., III. 

 3 Hober, loc. cit., p. 191. 



