STUDIES ON REACTIONS TO STIMULI IN UNICEL- 

 LULAR ORGANISMS. X. THE MOVEMENTS AND 

 REACTIONS OF PIECES OF CILIATE INFUSORIA. 



H. S. JENNINGS AND CLARA JAMIESON. 



The present paper records an attempt to investigate by opera- 

 tive procedure the division of labor among the organs of locomo- 

 tion of the ciliate body ; to determine the part played by cilia of 

 different position or structure in the usual movements and reac- 

 tions. In many of the Ciliata the body is much differentiated, 

 often bearing a number of different sorts of simple or compound 

 cilia, variously distinguished as membranellae, cirri, sets, cilia 

 proper, and the like. In such organisms as StylonycJiia (Fig. i) 

 and Stcntor these different structures have a characteristic distri- 

 bution, and apparently differ markedly in function. Even in less 

 differentiated infusoria a distinction between oral or peristomal 

 cilia and body cilia can usually be made. 



Observation of the behavior of these animals indicates that 

 there is a division of labor among these cilia in the production 

 of the usual movements. The organisms as they swim through 

 the water follow a spiral course, usually swerving continually 

 toward one side, but compensating the deviation thus caused by 

 rotating on the long axis. The swerving is as a rule (though not 

 invariably) toward the side away from the peristome or the oral 

 cilia. The stroke of the oral cilia is of such a character as to 

 tend to turn the body toward the side opposite to that on which 

 they are situated, so that the swerving appears to be due to these 

 cilia, aided, as a rule, by the form of the body. 



In reacting to most stimuli, these organisms turn toward a 

 structurally defined side (see Jennings, 1900), and, as a rule, this 

 is again the aboral side, or that opposite the oral or peristomal 

 cilia. Observation indicates that this is due to the stroke of the 

 oral cilia, or in some cases to a still smaller and more localized 

 group of cilia. This has been set forth by a number of authors, 



; Contributions from the Zoological Laboratory of the University of Michigan, 

 No. 56. 



