THE REACTIONS OF THE FLAGELLATE PERANEMA 



93 



side of the object. Under such conditions these creatures usually 

 slide by or through the obstruction, their course being altered 

 only in so far as the mechanical resistance requires. Ordinarily, 



o.l rn m. 



Figure 1. Camera drawings of specimens of Peranema representing the reaction 

 to contact or chemical stimulation. A, Outline of four individuals selected 

 from many suddenly killed in Worcester's fluid in different stages of the 

 response. B, Outline of the same individuals superimposed to represent 

 the relative positions of a specimen in different stages of the response; 0, 

 solid object; 1, specimen crawling in the direction of the arrow, only the bent 

 tip of the flagellum is active; c, contractile vacuole; 2, position taken imme- 

 diately after stimulation; the flagellum is inactive, the turning of the anterior 

 end being due to contraction on one side of the body; 3 and 4, later positions 

 assumed, the body gradually straightens and the tip of the flagellum again 

 becomes active. Note that the response results in a change in the direction 

 of motion of approximately ninety degrees. 



however, there is a definite response when the flagellum touches 

 an object. The organism stops, the body bends sharply always 

 toward the larger lip, throwing the anterior end with the flagel- 

 lum, usually more or less curved and inactive, to one side 



