HOW BACTERIA ARE NAMED AND IDENTIFIED 45 



known among the fungi. Such, for example, may well be the rough (R) 

 and smooth (S) types described for manj' bacteria, possibly the filterable 

 stages noted by many authors, the so-called G types, etc. It is evident that 

 an adequate description of any species of bacterium should include a de- 

 scription of each of these stages in the cyclical development wherever such 

 is proved to exist. In all other cases in botany and in zoology which 

 involve growth stages or cycles one stage has been chosen and designated 

 as the mature or adult or perfect stage. In ferns, for example, names and 

 classifications are based largely upon the sporophytic generation, in insects 

 upon the adult or imago, in the rusts upon the stage in which the teleuto- 

 spores are produced. There has been no international agreement as to 

 what stage should be thus designated for the bacteria. Beyond doubt, it 

 would be the stage which is most easily cultured and studied in the la|3ora- 

 tory, the stage with which we are best acquainted in the laboratory. It 

 might easily happen in bacteria (as it has with fungi) that two different 

 stages of the life cycle of single species have been described and named as 

 separate species. When the mistake has been discovered, the name given 

 to the mature or perfect stage is the one that is accepted. In general the 

 descriptions given in the present volume are those which may be regarded 

 as belonging to the perfect stage. Unfortunately it is not yet possible 

 accurately to group the stages in many of the bacteria that have definite 

 growth cycles. 



It is desirable frequently to designate the stage with which one is working. 

 This may be done by some conventional sjinbol, as S (smooth tj'pe), G 

 (filterable stage), etc. 



(b) How should one designate variants which differ in some minor re- 

 spects from the tj'pe, but which do not constitute growth stages? For 

 example, the species Bacillus subtilis normally produces endospores. Sup- 

 pose that an asporogenous race is derived from such, agreeing with the 

 parent culture in all respects, but showing no tendency to revert to spore 

 production. What such an organism should be called is a matter of judg- 

 ment. It might frequently be designated as an asporogenous strain, or 

 more technically if one desires as a variety. It might be termed, for 

 example, Bacillus subtilis var. asporus. In other cases such expressions as 

 Diplococcus pneumoniae Type 1, or the Rawlings strain of the typhoid bacil- 

 lus may be used. 



Unfortunately there is no general agreement upon the exact significance 

 which the word "strain" should have in bacteriology. It is recommended 

 that it refer merely to source, e.g. the Rawlings strain of Eberthella typhosa, 

 and that it be never used to connote a biological character. This would 

 not prevent such expressions as "a non-motile strain of Salmonella suipes- 

 tifer". but it would make erroneous a statement to the effect that the A 



