July 31, 1916 Life Cycles of the Bacteria 69 1 



the typical spore-forming rods as reproduced in the atlas of Lehmann 

 and Neumann (11, pi. 47, fig. V). Figure 25 (PL E) was made from a 

 preparate from a 2-day-old agar slant. Spores dissolve into stage D; 

 and thick-walled, more or less irregular regenerative bodies are being 

 formed. This process is going on in the 6-day-old culture (fig. 26 of 

 PL E). The "melting" of the spores is clearly visible. The regenera- 

 tive bodies have increased in number as well as in size. Some forms 

 resemble very much those of B. radicicola. After eight days (fig. 27 of 

 PL E) these regenerative bodies are either dissolved entirely into a 

 readily stainable symplasm or they produce bright granulated spores 

 (type H), which later also pass over into the symplastic stage. Some- 

 times the unstainable content of the regenerative bodies slips out of the 

 dark-stained cell wall, forming an unstainable symplasm like that fre- 

 quently produced by cells of the C type of B. azotobacter (fig. 6 of PL A; 

 fig. 7 of PL B. See also the mixture of stained and unstained symplasm 

 in fig. 19, PL D). The new set of regenerative bodies developing from 

 the symplasm, especially from the dark-stained material derived from 

 those irregular forms, usually showed rodlike forms stretching out into 

 long granulated threads, which, in their turn, divided themselves into the 

 normal spore-forming rods typical of B. subtilis. 



This behavior was observed, only slightly modified, with all cultures of 

 spore-forming rods. Figure 28 (PL E) shows this regerneration of the new 

 threads from the symplastic stage as it was found in a 2-day-old transfer 

 of the "yellow bacillus" (No. 41), made from a 12-day-old peptone- 

 glycerin solution into the same liquid substrate. The thread on the right 

 side of the field illustrates the situation especially well. As the upper 

 part is broken off, the gonidia inside the cell, which caused the formation 

 of the short branch on the lower part, become visible. The symplasm 

 Still contains several regenerative units which apparently are checked by 

 the vigorous absorptive action of the thread. 



The special appearance of many types of growth of Bad. bulgaricum is 

 plainly discernible in figure 29 (PL E), made from a 6-day-old stab culture 

 in yeast-whey agar. Large and small rods (types L. and F), pointed 

 forms (type M), the formation of regenerative bodies (type I) budding 

 (type K) are clearly visible. On the left side of the figure two long, thin 

 threads grow ("branch" or "bud") out of the same point in a larger rod. 

 Below this another thick rod, showing granular decomposition (type C), 

 is reproduced. In the middle of the field some thin, pale symplasm (D) 

 is spread out. Above, a thin pale thread containing darker stained 

 bodies (type G) crosses the field. Some small cells of type E are lying 

 close to it. That the round cells budding out of the rods are indeed 

 regenerative bodies is proved by their germination, the new rods growing 

 out in one or in two directions. This frequently happens when the 

 regenerative bodies are still connected with their mother cell. 

 42721°— 16 2 



