RHODO-THIOBACTERIA 157 



the latter being evidently deri\-ed from tlie former. In division, 

 the coccus elongates slightly, and becomes constricted in the 

 middle (Fig. 34^ and Fig. 33tj. In many cells the process of 

 constriction does not proceed any further, and the cell con- 

 tinues its existence as a diplococcus. In others, the constric- 

 tion continues until complete separation of the two daughter 

 cells takes place. Whilst division is in process, the cells are 

 also increasing in size so that when separation take place, the 

 daugliter cells are as large as the parent coccus before division. 

 More rarely tricocci are formed (Fig. ^2)^ and h ; Fig. 2^6 at a). 

 The three units in a tricoccus are usually arranged in triangu- 

 lar formation (Fig. 33a; Fig. 36 at a) ; more seldom the linear 

 arrangement holds (Fig. 33^). It is probable that the formation 

 of a tricoccus from a diplococcus results from a process similar 

 to that by which a diploccocus is formed from a unicoccus. 



(B) Budding. — This method of reproduction, normal to the 

 yeast plant, has not hitherto been recorded for bacteria. 

 Under natural conditions, the organism occasionally shows a 

 'very marked increase in reproductive activity, which is 

 marked macroscopically by an intense deepening of the 

 purple colour. During this period more individuals are formed 

 in a few days than are normally formed in several weeks. On 

 the occasion of such a marked increase, it was found that 

 the normal method of reproduction had been superseded by 

 a method of bud production. The buds are considerably 

 smaller than the normal form, and much more numerous. If 

 seen apart, and in aggregated masses, they would have been 

 denominated as a species of Lamprocystis. Compare Fig. 

 36 (i) with Fig. 36 (2). 



Stages in Bud Formation. 



(i) A more or less rounded space near the surface, marked 

 off from the rest of the cell by a difference in colour, is the 

 first indication that budding has commenced. This space is 

 clearer than the rest, and shows a greater resistance to the 

 penetration of stains (Fig. 35fl). We may apply the name 

 of Regional Rejuvenescence to this differentiation of the plasma, • 



