272 



C. J. BROKAW 



IOJJ 



Fig. 1. Left, one-half second time exposure and two sets of triple Hash 

 exposures of an isolated flagellum attached to the slide at its basal end. 

 Right, a triple flash exposure of an unattached isolated flagellum, showing 

 forward progression. Interval between flashes is about 2 sec. 



ured at 29°C by the dark-ground-track method (Brokaw, 1958). The 

 swimming speed decreases markedly with viscosity, as expected if the 

 cells are operating efficiently and using most of the available energy 

 to move against the viscous resistance of the medium. The viscosi- 

 ties were varied with methyl cellulose and measured with a standard 

 capillary tube viscometer. This represents a naive approach to vis- 

 cosity, which may require modification on further study. In Fig. 2, 

 viscosity is expressed on a logarithmic scale. 



