ROGER G. PERKINS 123 



a gram+to gram — by the use of suitable chemicals. Winslow quotes Wolf as re- 

 porting "a considerable number of temporary modifications and some permanent in- 

 heritable ones stimulated by exposing bacteria to the action of chemicals. White and 

 dark-red strains were thus produced from a normal B. prodigiosus, the resulting modi- 

 fications breeding in each case true to their new type." Winslow calls these changes 

 "impressed variations," and further on says: 



The fact that all cells are potentially reproductive removes any bar against the inherit- 

 ance of acquired characteristics. Again, the absence of sexual reproduction must operate to 

 preserve variations which arise from within or without .... with fission as the normal mode 

 of reproduction every variation which can arise can be handed on unchanged; .... there are 

 sharp limits to the variability even of the bacteria, and for practical purposes we find the 

 larger groups quite constant in their general properties .... in part at least I am inclined 

 to believe that this is due to the direct or selective action of similar environmental conditions. 



Since we are dealing not only with variables, but with variables in a group of or- 

 ganisms susceptible to permanent and hereditary change, we must select as most im- 

 portant those characters which as nearly as possible approach constants, and which 

 seem least susceptible to these permanent changes. One method of approach is well 

 exemplified by the work of Winslow (1906) in his study of the Coccaceae, and the 

 work of Hucker (1924) in a similar study. Believing that improvement might result 

 from a statistical analysis of a variety of characters in the hope of determining cor- 

 related groups, these extensive and painstaking studies were undertaken. The fact 

 that the authors are often in marked disagreement shows that the method of pro- 

 cedure, while suggestive, is as yet unsatisfactory. 



We must not forget that the actual number of bacteria described is but a small 

 fraction of those which exist. This is of course true in botany and zoology as well. 

 Stiles (1927) states that there are hundreds of thousands, possibly millions, of genera 

 and species still to be given technical baptismal certificates. Aldrich (1927) quotes 

 Horn as saying; "Whoever as an entomologist looks into the future knows full well 

 that we are steering into a shoreless sea, no matter whether he estimates the total num- 

 ber of insect species at three, ten or fifteen millions. In the near future any beginner 

 will be greyheaded before he has caught up with what is already known." Although we 

 have not quite reached this status with bacteria, partly because the details of struc- 

 ture and other characteristics are so much less complex, it is already practically im- 

 possible for anyone to be an expert in all the lines of bacteriology, and especially in 

 their finer taxonomic relations. The student in medicine interests himself in the non- 

 pathogenic forms only in their relation to the pathogenic (many early classifications, 

 such as Fliigge, were of pathogens only), and even neglects the organisms relating to 

 those diseases of animals that are not transferable to man, to say nothing of those 

 which cause disease in plants, while the veterinary and the plant bacteriologists are 

 similarly exclusive. It is only very recently that the workers on filterable viruses have 

 appreciated that the botanist, the zoologist, and the medical biologist are working on 

 an identical problem and that in their combined effort may lie the key to success. 



Students of the non-pathogenic organisms naturally tend to the study and iso- 

 lation of those groups which have economic relations with soil values, with fermen- 

 tations, with decompositions, and consider all others as merely annoying contami- 



