304 ORGANISATION IN SPACE AND TIME 



centrating protein-like substances and others of high mole- 

 cular weight, especially at low temperatures. It is true that 

 a considerable concentration might also have been achieved 

 by the adsorption of substances of high molecular weight on 

 particles of clay, as was suggested by J. D. Bernal." This, 

 ho^vever, may lead to irreversible changes in the molecules 

 and, furthermore, they are firmly fixed to the surface of the 

 clay, while in coacervates the molecules of the compounds 

 of high molecular weight retain a considerable amount of 

 their independence and are concentrated without any par- 

 ticipation of inorganic precipitates being required. 



On the other hand, if we take processes such as gel forma- 

 tion,^^ this can only occur in the case of gelatin, for example, 

 at concentrations of 1-5 to 2 per cent because gel formation, 

 in general, only fixes the relative positions of the molecules 

 and does not give rise to any concentration of them. 



The importance of the formation of coacervates is not 

 confined to their action in concentrating organic compounds 

 of high molecular weight. Of no less importance is the fact 

 that coacervation leads to the formation of a disperse system 

 of coacervate drops with a highly developed surface separat- 

 ing it from the surrounding medium, and a definite internal 

 structure of the droplets. If coacervation merely led to the 

 formation of a continuous colloid-rich layer separated from 

 the rest of the solution, the possible part which it could play 

 in evolution would certainly be far more limited. It is 

 just because coacervation usually leads to the formation of a 

 large number of very small droplets with definite internal 

 structures that it appears to constitute an extremely important 

 stage in the spatial organisation of organic multimolecular 

 systems. • 



On the basis of many years of work Bungenberg de Jong^^ 

 has put forward the opinion that the process of coacervation 

 implies either a diminution in the hydration of the colloidal 

 particles, in their ability to retain a layer of water around 

 themselves, or else a diminution of that layer of water owing 

 to the activity of water-removing factors. The colloidal 

 particles do not, however, lose their surrounding water 

 entirely but retain those molecules of it which are firmly 



