132 SYMBIONTICISM AND THE ORIGIN OF SPECIES 



only the simplest known organisms, but it is possible that they 

 represent the survival of a primordial stage of life chemistry. 

 These bacteria derive both their energy and their nutrition 

 directly from inorganic chemical compounds, such types were 

 thus capable of living and flourishing on the lifeless earth even 

 before the advent of continuous sunshine and long before the 

 first chlorophyllic stage (algae) of the evolution of plant life. 

 [Osborn.] 



The next stage in organic evolution involved the pro- 

 duction of variations in the primordial bacterial strains. In 

 this connection, Osborn suggests a possible mechanism by 

 which this could occur, on the basis of studies on Nitroso 

 monas which lives on ammonium sulfate and produces 

 nitrites, and Nitrobacter which lives symbiotically with it 

 (bacteriological symbiosis). The Nitrobacter utihzes the 

 nitrites and produces nitrates. It is reasonable to assume 

 that early in this bacterial evolution chlorophyl-bearing 

 bacteria or blue-green algae arose, perhaps by a process of 

 bacterial fusion or under the influence of extrinsic factors. 

 It must be emphasized again, that bacterial organisms are 

 readily modified by environmental influences. It is not 

 known if these modifications are permanent, or under what 

 circumstances they may become permanent. On account of 

 the importance of starch in the world today, it is thought 

 that chlorophyl-bearing organisms arose very early in 

 evolution, and hence from practically the beginning of 

 Ufe on the earth, chlorophyl-containing organisms have 

 been the ''food factories." 



The next important stage in organic evolution witnessed 

 the introduction of "organized cells" — the cellular animals 

 and plants. The simplest representatives of both of these 

 groups are composed of a single cell. The problem then 

 resolves into a determination of the nature of the origin of 

 the first true cells in evolution. (We are using the term 

 "cell" to include only such units as have an organized 



