THE INSTABILITY OF THE HOMOGENEOUS. 415 



until it is of the consistence of cream) be poured on a piece 

 of paper, the surface of the varnish will shortly become 

 marked by polygonal divisions, which, first appearing round 

 the edge of the mass, spread towards its centre. Under a 

 lense these irregular polygons of five or more sides, are seen 

 to be severally bounded by dark lines, on each side of which 

 there are light-coloured borders. By the addition of matter 

 to their inner edges, the borders slowly broaden, and thus 

 encroach on the areas of the polygons ; until at length there 

 remains nothing but a dark spot in the centre of each. At 

 the same time the boundaries of the polygons become 

 curved; and they end by appearing like spherical sacs 

 pressed together; strangely simulating (but only simulating) 

 a group of nucleated cells. Here a rapid loss of homogene- 

 ity is exhibited in three ways: First, in the formation of 

 the film, which is the seat of these changes; second, in the 

 formation of the polygonal sections into which this film di- 

 vides; and third, in the contrast that arises between the 

 polygonal sections round the edge, where they are small 

 and early formed, and those in the centre which are larger 

 and formed later. 



The instability thus variously illustrated is obviously 

 consequent on the fact, that the several parts of any homo- 

 geneous aggregation are necessarily exposed to different 

 forces forces that differ either in kind or amount ; and be- 

 ing exposed to different forces they are of necessity differ- 

 ently modified. The relations of outside and inside, and of 

 comparative nearness to neighbouring sources of influence, 

 imply the reception of influences that are unlike in quantity 

 or quality, or both; and it follows that unlike changes 

 will be produced in the parts thus dissimilarly acted upon. 



For like reasons it is manifest that the process must re- 

 peat itself in each of the subordinate groups of units that 

 are differentiated by the modifying forces. Each of these 

 subordinate groups, like the original group, must gradually, 

 in obedience to the influences acting upon it, lose its balance 



