LIFE WITHOUT OXYGEN in 



need no sunlight. Some are fixed but others are free swimming 

 organisms. But whereas only a few of the bacteria and practi- 

 cally none of the plant forms— the case of the Schizophyceae is 

 still rather doubtful '—are able to assimilate gaseous nitrogen,, 

 it is among the anaerobic bacteria that the most typical nitrogen 

 fixers are found. 



Consider the implication. The anaerobic organism is evidence 

 of the fact that gaseous oxygen is not essential to the synthetic 

 changes which accompany life. It is only as we rise in the 

 scale of life that the need of oxygen becomes obvious. On the 

 other hand, the capacity of assimilating nitrogen exists only in 

 the lowest forms and as we ascend the scale is very quickly 

 lost. Considering how essential the element nitrogen is in the 

 chemistry of life and the established non-essential character 

 of gaseous oxygen, we seem driven to the conclusion that the 

 most primitive and therefore the earliest form must have been 

 a nitrogen fixer to which a supply of uncombined oxygen was 

 immaterial. 



It is true that Bacterium Clostridium (Past.), the best studied 

 of the organisms that assimilate nitrogen, requires for its 

 nutrition a supply of glucose, 2 that is to say an organic product ; 

 whilst forms are known, like Nostoc, among the Schizophyceae,. 

 which are able to fix at least minor quantities of nitrogen in an 

 entirely inorganic culture medium, that is to say they do not 

 require a ready-made supply of complex organic carbon com- 

 pounds. It is for this reason that the Nostoceae have been 

 regarded by some as the more primitive form. 3 Euler observes : 



" We have herewith every reason to seek among the 

 Schizophyceae the earliest inhabitants of the earth. Further 

 support for this assumption is derived from repeated observa- 

 tions that these algae are always the first colonists on sand, 

 bare and humus soil and the like. A celebrated example is 

 that afforded by the Nostoceae, which Treub found as the 

 earliest germinants on the sterile soil of Krakatoa, after the 

 famous catastrophe." 



But the ability to assimilate carbon from its simplest- 

 inorganic compounds, the carbonates, not only from carbon 



1 Heinze, Cent.f. Bakt. II. Bd. xvi. 



2 For an excellent review of Winogradski's work, cf. Jost, Pflanzen physiologie > 

 2te auf. 1908 ; also in English translation. 



3 Euler, I.e. Bd. ii. p. 140. 



