THE ECONOMY OF NATURE 7 



" life is not worth living, and it dies though surrounded by a 

 plentiful micro-flora of which in happier, infected circumstances 

 it avails itself without stint." 



Hence the inference has been drawn that such animals subsist 

 on the food-materials manufactured synthetically by their green 

 or yellow cells. 



In these cases other food materials may at times be tempting 

 as a kind of luxury, but for the essential purposes of reproduction 

 only special symbiotic supplies of food are of real avail. 



Even at the very lowest rung of the evolutionary ladder we 

 find Symbiosis established. As an instance, I would cite the case 

 of the bacteria. The importance of these micro-organisms and 

 in particular their symbiotic achievements, in virtue of which 

 they have become indispensable even to the highest forms of 

 life, has only quite recently been fully established. Dr. H. F. 

 Osborn, in his essays upon The Origin and Evolution of Life 

 upon the Earth, tells us that a bacteria-less earth and a bacteria- 

 less ocean would soon be uninhabitable either for plants or 

 animals, and that in all probability bacteria-like organisms 

 prepared both the earth and the ocean for the further evolution of 

 plants and animals. He instances the Nitroso Monas of Europe, 

 presumably a survival from Archezoic time, and provides an 

 interesting description of the industry and of the symbiotic 

 relations of this veritable pioneer of organic civilisation. 



For combustion it takes in oxygen directly through the inter- 

 mediate action of iron, phosphorus, or manganese, each of the 

 single cells being a powerful little chemical laboratory which 

 contains oxidizing catalyzers, the activity of which is accelerated 

 by the presence of iron and manganese. Still in the primordial 

 stage, Nitroso Monas lives on ammonium sulphate, taking its 

 energy (food) from the nitrogen of ammonium and forming 

 nitrites. Living with it is the symbiotic bacterium Nitrobacter, 

 which takes its energy (food) from the nitrites formed by Nitroso 

 Monas, oxidising them into nitrates. 



Clearly, without the primal industry of Nitroso Monas, the 

 Symbiosis with Nitrobacter would be impossible, and without 

 the succession of ever higher but similar forms of life-partner- 

 ships, the evolution of the highest forms of life would have been 

 impossible. 



The nitrates formed by the symbiotic industry of bacteria 

 are, of course, of immense value, and are practically indispensable 



