54 



\VM. A. KEPXER AND W. H. TALIAFERRO. 



on top of a paraffin bath which kept the water at a constant 

 temperature of 86 F. Although these specimens were kept at 

 this high temperature for twenty-four hours they gave us reac- 

 tions which showed that they had not lost their physiological tone. 



FIG. ii. Diagrams indicating the paths of specimens when placed in .05 per 

 cent, salt solution and encountering a drop of fresh water. The dotted line indicates 

 the contour of the fresh water surrounded by .05 per cent, salt solution. 



Text-figure ii-b shows the path of one of these when treated like 

 the one placed in bacteria. As soon as this specimen entered 

 the fresh water it remained there by continually reacting to the 

 salt solution. We watched such a specimen remain in the drop 

 of fresh water for thirty minutes and then stopped observations 

 because the salt solution began to diffuse into the fresh water. 

 A comparison of text-figures n-a and ii-b shows the difference 

 between the reactions of the above two lots of specimens. 

 From these experiments we conclude that : 



(a) Microstomas lose their physiological tone chiefly from the 

 toxins thrown off by the bacteria. 



(b) If change of temperature is a factor in this loss of physio- 

 logical tone it is a very small one and they in time become 

 adjusted to the new factor in their environment. 



This change of physiological condition is somewhat analogous 

 to the different physiological states found in the flat-worm 

 Planaria by Pearl ('03) and summarized by Jennings in his 

 "Behavior of the Lower Organisms" (p. 253, '06). 



Finally a second class of experiments was carried out in order 

 to test the value of the bilateral arrangement of the ciliated pits. 



