326 DAN H. JONES 



This dealt with the viability, thermal death point and formation 

 of involution forms in four varieties of azotobacter under 

 observation. 



The studies with these strains of azotobacter were continued 

 for a short time longer, attention being directed more particularly 

 to the disintegration of mother cells with the liberation of the 

 gonidia-like granules and their subsequent development, and 

 numerous photomicrographs were taken of these phenomena. 

 Unfortunately, these studies were interrupted in the latter part 

 of 1914 and were not resumed until the summer of 1919. 



In the meantime Lohnis and Smith published in the Journal 

 of Agricultural Research, July, 1916, a remarkable paper entitled 

 "Life Cycles of the Bacteria." In this article the authors state 

 that the life cycle of many, if not all, species of bacteria is much 

 more complex than has been generally considered to be the case. 



The theory which they advance is that 



All bacteria studied live in an organized and in an amorphous stage. 

 The latter has been called the "symplastic stage," because at this time 

 the living matter previously enclosed in the separate cells undergoes a 

 thorough mixing either by a complete disintegration of the 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 stainable, in the latter case an unstainable symplasin 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 

 germinating or stretching, become cells of normal shape. In some 

 cases the regenerative bodies also return temporarily into the sym- 

 plastic stage. 



Beside the formation of the symplasm another mode of interaction 

 between the plasmatic substances in bacterial cells has been observed, 

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

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

 first mentioned. 



Whilst Lohnis and Smith base their conclusions on many 

 observations which they made on cultures of various species 

 of bacteria including such diverse forms as B. subtilis (Pseud.) 



