202 SYMBIOGENESIS 



and yet they do not assume the unduly fixed condition usually 

 characterising solids. The absence of power to unite together 

 in polar arrangement leaves these atoms with a certain freedom 

 of relative movement which makes them sensitive to small 

 forces, and produces plasticity in the aggregates composed of 

 them." 



They are specially fitted, as he further points out, for 

 plastic purposes, which would indeed remind us that a peculiar 

 importance must attach itself to the fact that the force of 

 surface-tension is of particular dominance in the plastic world 

 of the colloids. Surface-tension makes for economy of form 

 and is an important basic factor in the "objective " elements 

 of beauty and of utility. So much so, that we may say that 

 normally, when by itself, in the plastic state, every aggregate, 

 every cell, every organism, is tending not only to perform 

 work, but also to become a work of art in itself, which is also 

 saying, in other words, that it is endeavouring to be free from 

 impeding impurities, i.e., healthy (surface-tension, as a matter 

 of fact, has the effect of drawing out all over the surface any 

 impurities that may settle on it). 



The importance of the plastic unicellular stage, 

 allowing, inter alia, of the entanglement and separa- 

 tion of suspended impurities, through which every organism 

 in its ontogenetic development has to be passed for 

 purposes of rejuvenescence, of health, and of work, may 

 thus again be seen as greatly enhanced. The evolution of 

 colloidity itself, as already surmised, may thus perhaps 

 be viewed as a symbiogenetic compromise achieved by life 

 in the solution of the combined problems of pure physical 

 existence Spencer's required compromise between fluidity and 

 solidity and of the constant preservation of a healthy, i.e., 

 duly balanced, economic and physiological basis of evolving 

 life, consisting of a great complexity of life-purposes, requiring 

 adequate relations in its various inorganic and organic ramifi- 

 cations. The requirements of at least three mechanisms, as it 

 were, have to be satisfied in this symbiogenetic compromise: 



