No. 643] 



ORTHOGENESIS IN BACTERIA 



109 



seems that we must admit that orthogenesis does exist 

 there. But if, on the other hand, progressive changes 

 like those in question must also be in the direction of pro- 

 ducing a more advanced form of organism, we are con- 

 fronted by a quandary resulting from a lack of an ac- 

 cepted definition for the term advanced.^' 



The argument that bacteria do not at all lend them- 

 selves to appraisal as regards evolution by the standards 

 applying to the higher organisms is, perhaps, not sound 

 as shown again by the researches of Lohnis, which I have 

 just cited. The objection to viewing bacteria in a man- 

 ner similar to the higher organisms because no sexual 

 reproduction is known among them is removed by Lohnis ' 

 observations, which indicate that something akin to a real 

 conjugation of cells does occur in the bacteria. His stri- 

 king monograph in the Memoirs of the National Academy 

 should be read and studied by all those who seek new 

 light on the origin and nature of bacteria. 



Another point of view which I believe may be intro- 

 duced into this discussion with some justification results 

 from a broad comparison of natural phenomena gener- 

 ally. In the inanimate world, we are confronted by the 

 evolution of substances in series in which the first mem- 

 ber of the series is simple and by small accretions be- 

 comes progressively more complex in the succeeding 

 members of the series until very complex materials are 

 finally built up. We are all well acquahitod with the 

 seriation showing progressive complexity in the hydro- 

 carbons beginning with methane and going up : in tlic car- 

 bohydrates beginning with formaldehyde and going up; 

 in the proteins beginning perhaps with amino acids and 

 going up. Such examples of progressive seriation may 

 be multiplied ad libitum. Why, therefore, should it not 

 be possible that similar series should arise in the progres- 

 sive evolution of bacteria through certain forces as yet 

 largely unkno^\Ti which cause accretions of characters, so 

 to speak, to occur in bacteria through their being ren- 

 dered more complex and complicated by the influence of 



