676 Journal of Agricultural Research vol. vi, no. 18 



As our earlier observations indicated that an extended study would 

 lead to still more interesting results, we have resumed our work. A com- 

 parative study of 24 Azotobacter cultures and 18 strains of other bac- 

 teria now revealed the fact that those wide morphological differences 

 first observed with Azotobacter are by no means restricted to this one 

 group of bacteria. Similar variations occurred with all cultures tested, 

 and under suitable conditions they will occur with all bacteria generally. 

 The importance of these wide morphological variations, however, is mate- 

 rially increased by the fact that they are connected with no less consider- 

 able variations in the physiological qualities of those organisms. There- 

 fore, not only for diagnostic and systematic purposes are these facts of 

 fundamental importance but also for all other lines of research in agricul- 

 tural and medical bacteriology. 



The quite unexpected character of the results obtained seems to 

 justify a preliminary discussion of the facts and problems involved. 

 Of course, at the present time it is neither our intention to furnish all 

 those numerous details which are necessary to obtain a full knowledge 

 of these heretofore practically unknown facts, nor do we want to col- 

 lect all the widely scattered observations from a voluminous literature 

 which will not only give some interesting support to our new viewpoint 

 but which also, in their turn, will sometimes find their full explanation 

 there. At present we merely wish to inform agricultural and also medical 

 bacteriologists about these newly discovered facts and to ask for their 

 cooperation. 



It is beyond question that progress in bacteriology has been severely 

 checked by the widespread inclination to consider as not worth studying 

 or as some uninteresting "involution form" all that sort of bacterial 

 growth which does not fit exactly into the conventional conception of a 

 very simple and constant character of the species. Even modern stand- 

 ard works assert, for instance, that the branched type of Bacillus radicicola 

 represents an "involution form" not capable of further propagation. 

 However, nitrogen fixation takes place only when these branched forms 

 develop, which unmistakably proves their full virility; and there is no 

 lack of exact results which show conclusively that suitable conditions 

 always allow a new development from these branched forms. 



Undoubtedly a somewhat more scientific study of such "abnormal" 

 forms would long ago have revealed the fact that the life cycles of the 

 bacteria are no less complicated than those of many other micro-organisms. 

 Indeed, numerous items in the bacteriological literature, for instance, 

 show that the formation of gonidia and the budding of bacteria have 

 been observed quite frequently. Yet again the authoritative statement 

 that bacteria multiply exclusively by fission apparently has been suffi- 

 cient to prevent thorough research in this direction, and the credulous 

 adherence to "standard methods" unfortunately explains only too well 

 why the turning point in the life cycles of the bacteria has been com- 



