THE BEHAVIOR OF OTHER INFUSORIA 



in 



A . Flagellata 



-nu 



The free swimming flagellates move in a spiral, keeping a certain 

 side of the body always toward the outside of the spiral, 1 just as Para- 

 mecium does. By means of the flagella they draw a cone of water from 

 in front to the anterior end of the body, as happens in Paramecium. 

 Among the flagellates the behavior has 

 been most precisely studied in Chilomonas 

 and Euglena (Jennings, 1900, 1900 a 

 and b). 



Chilomonas. — Chilomonas is an un- 

 symmetrical organism, of an irregularly 

 oblong form. The body is compressed 

 sideways and bears an oblique notch at the 

 broader anterior end (Fig. 72). Of the two 

 anterior angles which He on either side of 

 the notch, one (x) is larger and lies more 

 to the right than the other (y). From the 

 notch arise two long flagella, by the aid of 

 which the animal swims. Chilomonas 

 often occurs in uncounted millions in water 

 containing decaying vegetation. 



In swimming, Chilomonas revolves on 

 its long axis, at the same time swerving 

 toward the smaller of the two angles at 

 the anterior end (Fig. 72, y). The path 

 followed thus becomes a spiral (Fig. 73). 

 The animal often comes to rest against solid objects; it is then attached 

 by one of the two flagella, while the other is free. 



To most effective stimuli Chilomonas responds by an avoiding re- 

 action similar to that of Paramecium. Its forward movement becomes 

 slower, ceases, or is transformed into a movement backward. Then 

 the animal turns more strongly toward the side which bears the smaller 

 angle, and finally starts forward again. Thus the path is altered. The 

 reaction consists essentially in pointing the anterior end successively in 

 many directions, toward one of which the animal finally swims. The 

 different factors in the reaction vary with the intensity of the stimula- 

 tion, just as they do in Paramecium. The reaction may be repeated, 

 as in the animal last named, until it finally carries the organism away 

 from the stimulating region. Thus it is clear that in Chilomonas, as in 



1 This was first observed by Naegeli (i860). 



Fig. 72. — Chilomonas, side view. 

 c. v., contractile vacuole; ft, flagella; 

 g, gullet; nu, nucleus; x, dorsal or 

 upper lip; y, ventral or lower lip. 



