VII] OF THE PARTITIONING OF SPACE 339 



And it is quite possible, also, that in the cells of a vegetable 

 parenchyma, by carefully macerating them apart, the same con- 

 formation may yet be demonstrated under suitable conditions ; 

 that is to say when the whole tissue is highly symmetrical, and the 

 individual cells are as nearly as possible equal in size. But in an 

 ordinary microscopic section, it would seem practically impossible 

 to distinguish the fourteen-sided figure from the twelve-sided. 

 Moreover, if we have anything whatsoever interposed so as to 

 prevent our twelve films meeting in a point, and (so to speak) to 

 take the place of our little central quadrilateral, — if we have, for 

 instance, a tiny bead or droplet in the centre of our artificial 

 system, or even a little thickening, or " bourrelet" as Plateau called 

 it, of the cell-wall, then it is no longer necessary that the 

 tetrakaidecahedron should be formed. Accordingly, it is very 

 probably the case that, in the parenchymatous tissue, under the 

 actual conditions of restraint and of very imperfect fluidity, it is 

 after all the rhombic dodecahedral configuration which, even under 

 perfectly symmetrical conditions, is generally assumed. 



It follows from all that we have said, that the problems 

 connected with the conformation of cells, and with the manner in 

 which a given space is partitioned by them, soon become exceedingly 

 complex. And while this is so even when all our cells are equal 

 and symmetrically placed, it becomes vastly more so when cells 

 varying even slightly in size, in hardness, rigidity or other quahties, 

 are packed together. The mathematics of the case very soon 

 become too hard for us ; but in its essence, the phenomenon 

 remains the same. We have little reason to doubt, and no just 

 cause to disbeheve, that the whole configuration, for instancef of 

 an egg in the advanced stages of segmentation, is accurately 

 determined by simple physical laws, just as much as in the early 

 stages of two or four cells, during which early stages we are able to 

 recognise and demonstrate the forces and their resultant effects. 

 But when mathematical investigation has become too difiicult, it 

 often happens that physical experiment can reproduce for us the 

 phenomena which Nature exhibits to us, and which we are striving 

 to comprehend. For instance, in an admirable research, M. Robert 

 shewed, some years ago, not only that the early segmentation of 



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