82 THE BEHAVIOR OF PROTOZOA 
ahead in another direction. To a degree unusual among 
infusoria Stentor has the power of changing the form of 
its body. It may extend into the form of a very long slender 
trumpet, or contract almost into a sphere. The ability 
to undergo these changes is due to the presence of numerous 
contractile threads or myonemes which extend for the most 
part longitudinally just beneath the outer layer of ecto- 
plasm. Food taking in Stentor is accomplished with the aid 
of the cilia at the anterior end of the body and the membran- 
elle leading to the oral opening. The currents set up by 
the beating of these organs carry bodies to the mouth 
which has the power of taking in comparatively large ob- 
jects, for one often sees rotifers, diatoms, alge, and various 
protozoans in the endoplasm of the animal. 
While swimming freely in the water the behavior of 
Stentor is in general similar to that of Paramcecium. The 
spiral swimming and the motor reflex in response to chemical, 
mechanical, thermal and electrical stimuli are much the 
‘same in both organisms. Stentors as a rule react to light 
which has little effect on Paramcecia. In Stentor ceruleus, 
which is negatively phototactic, sudden illumination evokes 
the motor reflex which after one or more trials enables the 
animal to reach a more shaded region. The anterior end is 
the region most sensitive to light and when the organism 
is pointed toward the light it gives the motor reflex, and 
swims in a different direction. If still pointing obliquely 
toward the light it may repeat the motor reflex and continue 
to do so until its anterior end is directed away from the 
source of stimulation, when the Stentor swims off in the 
direction of the rays. 
When Stentor is attached it exhibits several peculiar types 
of activity. It may contract or extend the body, and it 
often sways about in various directions in a more or less 
