504 PROCEEDINGS OF THE AMERICAN ACADEMY. 



electrode in the measuring tube W" as read directly against a millimeter 

 scale placed behind it. The fifth column shows the position of the 

 electrode as determined by means of the disk placed upon W". The 

 latter reading is accurate to within 0.02 mm. The physical relations 

 of the apparatus are such that an increased reading in the position of 

 the electrode is due to increased conductivity through the test-cell, and 

 vice versa, when the latter is connected in parallel with the measuring 

 tube. The absolute values of the conductivity would not add to the 

 significance of the experiment and are not determined. Without the 

 presence of Stentor in the test-cell the following record was obtained. 



This test shows that the conditions in the test-cell are nearly constant 

 for a period of one hour. 



Corresponding measurements, made under the same. conditions, except 

 that the 5 cc. of the medium contained about fifty Stentors, gave the 



1 hr. 0.00 .343 mm. 



After the experiment fifty-two live Stentors in apparently good con- 

 dition were recovered. Only one dead animal was observed. 



The results show that in a period of one hour the conductivity of 5 cc. 

 of this salt medium containing about fifty Stentors had increased by an 

 amount far above the limit of error of the measurement. 



