wavelength averaging 1.7 microns. The ratio of the two wave- 

 lengths is thus almost exactly 2:1. By plating in semisolid agar, 

 colonies showing much and little spreading were found. When 

 these were fished the small spreading colonies showed bacteria 

 mainly with the undulant type of polar llagellum while the bac- 

 teria from the larger spreaders had mainly the normal type of 

 polar flagellum. However the cultures from the fished colonies 

 were not pure for one or the other type of flagella, and variation 

 from the one type to the other must take place at a high rate. 

 Individuals with both types of flagella are occasionally seen, even 

 at the same pole, as illustrated in Fig. 20d. The undulant flagel- 

 lum is apparently less efficient for locomotion than the normal 

 flagellum. Individuals with coiled polar flagella were occasionally 

 observed. In one strain (Kluyver L-417) the coiled flagella were 

 very common and often multiple as illustrated in Figs. 20h and i. 

 The peritrichous variant with coiled flagella may have originated 

 from this type with multiple coiled polar flagella. However, a 

 mutation from polar to peritrichous was not observed in the au- 

 thor's laboratory. 



The most unique feature of Aeromonas flagellation is the forma- 

 tion of lateral flagella in very young cultures. This phenomenon, 

 to a variable extent, has been observed in all but one of the strains 

 studied. In one strain (Kluyver L-417) the lateral flagella had the 

 same wavelength as the polar flagellum. With the other strains 

 the lateral flagella had a definitely shorter wavelength than the 

 polar flagellum. In all the strains studied the lateral flagella 

 showed the same wavelength of 1.5 microns irrespective of the 

 wavelength of the polar flagellum. Individuals with undulant, nor- 

 mal, or coiled polar flagella produced normal lateral flagella of 

 the same wavelength. Coiled or undulant lateral flagella were 

 never observed in the young cultures. 



49 



