170 A THEORY OF LIFE 



the activity of which is accelerated by the presence 

 of iron and manganese. Still, in the primordial 

 stage, Nitrosomonas lives on ammonium sulphate, 

 taking its energy (food) from the nitrogen of 

 ammonium and forming nitrates. Living sym- 

 biotically with it is Nitrobacter, which takes its 

 energy (food) from the nitrates formed by Nitroso- 

 monas, oxidising them into nitrates. Thus these 

 two species illustrate in its simplest form our law 

 of the interaction of an organism (Nitrobacter) 

 with its life environment (Nitrosomonas) " (p. 82, 

 author's italics). 



Once one has got to this stage, it is ex hypothesi 

 easy to ascend through the vegetable and animal 

 worlds and to formulate the various laws which 

 appear to have shaped the evolution of life and 

 of species. We are then " within the system," 

 but to arrive at anything worthy of the name 

 of an explanation we have first to get within the 

 system. Even then there remains over the task 

 of explaining how the system comes to be there 

 to get inside of. The writer talks of his example 

 as " the simplest form." Yet, in his own words, 

 it is a " powerful little chemical laboratory" well 

 stocked with catalysers and other potent means 

 for carrying on its work. " Simple " ! Well, 

 no doubt comparatively simple, but in reality 

 complex almost beyond the power of words to 

 describe. " A chemical laboratory " ! Yes ; and 

 one which performs most delicate operations. 

 " Well stocked with catalysers " ! And what 

 are they ? Most wonderful things which induce 

 change without themselves undergoing any ; 



