332 ELSA SHADALL 



Temperature reactions were also studied by siphoning water 

 of various temperatures through an exceedingly fine capillary 

 U-shaped tube. With this apparatus a more uniform and defi- 

 nite temperature was obtained. The tube which rested on the 

 slide was observed under a microscope. Opalina swims in- 

 differently up to the cold or warm tube, rests along the surface 

 or may move along in close contact with it. 



REACTIONS TO LIGHT 



Light induces no change in the movements of Opalina as is 

 also true of Paramoecium and other colorless ciliates. Neither 

 an increase in intensity nor a decrease causes a response. Con- 

 trary to what Entz ('88) observed, Opalina may be suddenly 

 exposed to very bright sunlight and then quickly shaded with- 

 out causing it to react. There was no evidence that it oriented 

 in horizontal rays of light. In one instance, where a number 

 were oriented in the direction of the source of light, there was 

 no response when the slide was turned 180°. Polarized light or 

 red light have no effect on movement. 



In some of the experiments with light a Nernst lamp of about 



650 candle power was used in a dark room. By moving the 



light to various distances, varying from 12-178 inches from the 



Opalinas, different intensities were obtained but no reaction 



was noted. 



SUMMARY 



1. Opalina usually swims in a spiral, though it frequently 

 travels long distances without rotation, or moves along the 

 surface of some object without turning over. When feeding it 

 remains in contact with the debris and keeps the cilia vibrating 

 rapidly. 



2. The spiral course is due to the forward movement of the 

 organism and the rotation on its long axis. Opalina often 

 makes half a revolution and then turns back the same distance. 



3. Opalina reacts to stimuli by moving backward a short 

 distance without rotating and then turning to the right at an 

 angle to the original course. If it is stimulated, it " tries " 

 many different directions until one is found which proves satis- 

 factory. When stimulated Opalina often swims in a circle, 

 without revolving, keeping the left side turned away from the 

 center. 



