CONSIDERATIONS INFLUENCING CLASSIFICATION 5 



It is true that the chemoautotrophic organisms are able to Hve on simple 

 inorganic foods that were, in all probability, available to living things under 

 early conditions in the development of the earth. However, it does not necessarily 

 follow that chemoautotrophic forms are the only ones that could have existed 

 in the beginning. It seems even more reasonable to assume that early living 

 forms developed a pigment like chlorophyll that enabled primordial bacteria to 

 utilize the sun's energy in synthesizing organic matter. Such photosynthetic 

 pigments are found in purple or green bacteria. These photoautotrophic forms 

 could have existed on the simple foods available when life began as readily as 

 could chemoautotrophic forms. 



In either case, it is necessary to assume that living protoplasm, with its com- 

 plex enzymatic systems, existed before primordial bacteria, which utilized 

 inorganic materials as food. In other words, complex proteins had to be in 

 existence before either chemoautotrophic or photoautotrophic bacteria of the 

 types now found on the earth could exist. 



Even if it is granted that photoautotrophic living things were primordial, it 

 must also be granted that when the existence of such organisms is postulated 

 we are not starting with the beginning of life itself. So little is known about the 

 possibility of living proteins (protoplasm) developing out of inorganic com- 

 pounds that speculation regarding this development has brought but very little 

 information that is factual. 



In the present edition of Bergey's Manual, the classification used has been 

 rearranged on the assumption that the photoautotrophic bacteria extant today 

 presumably are the living organisms that are most nearly like the primordial 

 types of bacteria. 



In support of this thought it should be kept in mind that the earliest living 

 forms must necessarily have been free-living forms, not saprophytes nor parasites. 

 This being the case, forms such as viruses that are very tiny in size and therefore 

 necessarily of a simple structure ought not to be regarded as primitive just 

 because of a comparatively simple structure. The viruses are adapted to life 

 within living protoplasm, and they represent an extreme degree of specialization 

 to a parasitic existence. They are known as organisms that invade the living cells 

 of higher plants and animals, including man. The latter are the living things 

 that were latest in development in geological time. Viruses could not have existed 

 before their host plants and animals were developed. 



The term "viruses" ought not to be used for the hypothetical, very tiny, 

 free-living primordial organisms that must have existed before primordial 

 bacteria. Some investigators feel that such organisms may still exist in some as 

 yet unrecognized form. 



It is not surprising that a great development has taken place in outline clas- 

 sifications since bacteriologists first tried to develop such classifications to express 

 the possible relationships of the organisms with which they have worked. While 

 O. F. Mueller (Animalcula infusoria et Marina. Hauniae. 1786) and C. G. Ehren- 

 berg (Die Infusionsthierchen als vollkommende Organismen. Leipzig, 1838) made 



