356 THE FIRST ORGANISMS 



as the first result of the directed evolution of our original 

 systems. 



The origin of the capacity of the systems 

 for self-preservation and growth. 



The second step forward in the same direction was the 

 emergence of systems which could not merely preserve them- 

 selves, but could also grow, increasing their mass by drawing 

 substances from the external medium. As was pointed out 

 in the previous chapter, the stationary state of open systems 

 is maintained constant, not because the free energy of the 

 system is at a minimum as in thermodynamic equilibrium, 

 but because the system is continually receiving free energy 

 from the surrounding medium in an amount which compen- 

 sates for the expenditure of free energy within the system. 

 In such chemical open systems as the coacervate drops of the 

 primaeval ocean would seem to have been, the intake of free 

 energy was mainly due to the entry into the drop of organic 

 compounds which were relatively rich in energy and which 

 underwent some sort of chemical reaction within the drop. 

 When chemical reactions are taking place, however, closed 

 and open systems differ from one another in that in the 

 former equilibrium is characterised by the reaction occur- 

 ring at the same rate in both directions so that, in the nature 

 of things, there can be no increase in mass. In open systems 

 in the stationary state, on the other hand, the rate of the 

 reaction is considerably greater in one direction than in the 

 other, and it follows that there may exist in them a co- 

 ordination of processes leading to an increase in the mass of 

 the system. Such systems enjoyed an undoubted advantage 

 in the process of directed evolution and therefore, owing to 

 the action of ' selection ', they came to occupy a predominant 

 position in the general extension of organised formations. 



In the absence of any appropriate experiments, even with 

 models, one cannot say anything definite about the nature 

 of such growth in our original systems. They might have 

 become larger in the form of uniform layers of coacervate, 

 but they might also have become divided into separate drops. 



