FORMS OF BACTERIA 



packets (Fig. 4a) or Staphylococci (Fig. 4&). If these species are non- 

 motile they belong to the Sarcina group, but if motile they belong to 

 the Planosardna group. 1 



Turning now to the bacillus, or rod-shaped individuals, we find that 

 they also show great variety in form, and in the ways in which they 



FIG. 5. 



PIG. 6. 



a 



combine together. It has already been said that there is no constancy 

 in the length or breadth of the individuals of any one species. A 

 species which, cultivated in one medium, exhibits short thick rods, may 

 develop into long thin threads in 

 another medium. When culti- 

 vated in wort, Bacillus Kiitzin- 

 gianum shows very short, thick 

 individuals as seen in Fig. 5, but 

 when cultivated in a solution 

 containing flesh extract and pep- 

 tone, long threads are developed 

 similar to those shown in Fig. 6. 

 In sub-dividing the rod-shaped 

 species, advantage is taken of 

 the fact that some are not motile, 

 whilst others possess motility ; 

 and, further, that those that are 

 motile show differences in the 

 mode of insertion of the organs 

 of motion. These organs of 

 motion, sometimes called cilia, 

 and sometimes flagellae (singular 



dlium and flagdlum) are whip- Fio 7 



like filaments of living matter 



thrust out from the sides of the organisms, and it is the lashing of 

 the cilia that causes the movement of the organism to which they are 



1 The author has lately shown the probability that the distinction between 

 Micrococcus and Planococcus, and between Sarcina and Planosarcina, is not a 

 real one, for all the species belonging to the immotile Micrococcus and Sarcina 



