700 Journal of A gricultural Research vol. vi, No 18 



same manner, in all probability analogous results may be expected with 

 all species of bacteria. 



All bacteria studied live alternately in an organized and in an amor- 

 phous stage. The latter has been called the "symplastic" stage, be- 

 cause at this time the living matter previously inclosed in the separate 

 cells undergoes a thorough mixing either by a complete disintegration 

 of cell wall, as well as cell content, or by a "melting together" of the 

 content of many cells which leave their empty cell walls behind them. 

 In the first case a readily stainable, in the later case an unstainable 

 "symplasm" is produced. 



According to the different formation and quality of the symplasm the 

 development of new individual cells from this stage follows various lines. 

 In all cases at first "regenerative units" become visible. These increase 

 in size, turning into "regenerative bodies," which later, either by germi- 

 nating or by stretching, become cells of normal shape. In some cases the 

 regenerative bodies also return temporarily into the symplastic stage. 



Besides the formation of the symplasm, another mode of interaction be- 

 tween the plasmatic substances in bacteria cells has been observed, 

 consisting of the direct union of two or more individual cells. Thi9 

 "conjunction" seems to be of no less general occurrence than the process 

 first mentioned. The physiological significance remains to be studied. 



All bacteria multiply not only by fission but also by the formation of 

 "gonidia"; these usually become first regenerative bodies, or occasion- 

 ally exospores. Sometimes the gonidia grow directly to full-sized cells. 

 They, too, can enter the symplastic stage. The gonidia are either lib- 

 erated by partial or complete dissolution of the cell wall or they develop 

 while still united with their mother cell. In the latter case the cell wall 

 either remains intact or it is pierced by the growing gonidia, which be- 

 come either buds or branches. 



Some of the gonidia are filterable. They also produce new bacteria 

 either directly or after having entered the symplastic stage. 



The life cycle of each species of bacteria studied is composed of several 

 subcycles showing wide morphological and physiological differences. 

 They are connected with each other by the symplastic stage. Direct 

 changes from one subcycle into another occur, but they are rather rare 

 exceptions. The transformation of spore-free into spore-forming bacteria 

 seems to be dependent on the conditions acting upon the symplasm and 

 regenerative bodies. 



The discovery of the full life cycles of bacteria may be helpful in many 

 directions. Systematic bacteriology now can be established on a firm 

 experimental basis. Physiological studies will win considerably in con- 

 formity and accuracy when connected with morphological investigations 

 along these new lines. Several problems in general biology are brought 

 under more promising aspects. Agricultural bacteriology and medical 

 also will derive much benefit. 



