456 PROCEEDINGS OF THE AMERICAN ACADEMY. 



logically active substances, and alkaloids. A possible analogy suggested 

 itself between the artificially stimulated egg, beginning and continuing 

 its cleavages after an initial impulse, and a possible acceleration in the 

 rate of division in Stentor after similar treatment. I set the question, 

 *' Can a temporary impulse due to a substance accelerate the rate of divi- 

 sion in Stentor or Paramaecium ? " The first two of the following 

 experiments were made with this question in view and gave an afiirma- 

 tive answer. It seemed reasonable that the same eflPects might be kept 

 up by the continuous application of the same substance, and such proved 

 to be tlie case. I therefore describe these experiments, among others 

 made with a different aim, because they are interesting from another 

 point of view. The comparison of the reaction to a temporarily applied 

 substance with one continuously applied will make clearer the mode of 

 action in the former case. The experiments whose main result was the 

 acceleration of division in Stentor and Paramaecium were as follows. 



The Specific Action of Potassic Chloride on Stentor. 

 Expt. No. 6, Oct. 21, 1901. 



For the purpose of applying a liquid medium for a limited time, and 

 to enable me both to apply and to withdraw the medium rapidly, I made 

 use of the apparatus I have elsewhere (Peters, :01) described as a U-cell. 

 This was, essentially, two slides, between which there was placed, in U- 

 form, a properly selected piece of yarn. This cell was placed in an 

 inclined position, the open end of the U uppermost, in a vessel containing 

 enough liquid to permit the immersion of the lower part or the whole 

 of the cell when desirable. By this arrangement liquid can be passed 

 throuofh the wall of the cell without the production of excessive down- 

 ward pressure upon the contained organisms. The cell was filled with 

 0.05 m. potassic chloride by means of a capillary pipette, and into it were 

 introduced a considerable number of Stentors, all from the same culture. 

 To this solution the organisms were subjected for ten minutes. During 

 the next ten minutes tap-water was passed through the cell to remove 

 the potassic chloride, and the Stentors were then transferred to a glass 

 vessel containing about 18 cc. of their original culture medium free from 

 other Stentors. In this medium they were mounted in hanging drops, 

 as described in this paper under General Methods and Technique (p. 444). 

 The results are shown in the following table. The time stated is 

 reckoned from the beginning of the experiment. The Mean Result 

 expresses the number to which on the average one Stentor increased or 

 diminished. 



