THE BEHAVIOR OF PROTOZOA 



81 



the object. Then there are righting movements which are 

 brought into play when Loxophyllum is turned over on 

 its left side. There is not, as we might be led to expect, 

 but a single stereotyped method of righting. The organism 

 rights itself by a number of very different methods which 

 present an indefinite number of modifications. One cannot 

 but wonder when watching the varied movements of this 

 graceful and supple infusorian that a single cell is capable 

 of such behavior. 



One of the most highly developed 

 types of behavior which has been 

 carefully studied in the protozoa is 

 exhibited by the large infusorian 

 Stentor. There are several species 

 of this genus, but all are trumpet- 

 shaped, with a mouth situated at 

 the bottom of a depression at one 

 side of the anterior end. The oral 

 end of the organism is surrounded 

 by a zone of membranellaB which at 

 one end descends in a spiral course 

 toward the mouth. The whole sur- 

 face of the body is covered by uni- 

 form cilia, with the exception of a 

 small area of naked protoplasm at 

 the small end or foot, by means of 

 which Stentor is able to attach itself 

 to foreign objects. When free in the 



i -, ! morphus. (After Stein.) 



water Stentor is able to swim by 



the action of its cilia and membranellae. Like Paramce- 

 cium it follows a spiral course and when stimulated it may 

 perform the motor reflex, backing off by reversing the 

 beat of its cilia, turning to the aboral side and then going 



FIG. 11. Stentor poly- 



