434 Gary N. Calkins. 



Average number of divisions per day after stimulation. 



K.HPO^. KCI. MgCU. CaCl,. NaCl. 



May 6-10 1.60 1. 00 1. 00 0.60 1.20 



May 11-15 1. 00 1.20 0.60 1.20 1.20 



May 16-21 1.50 1.50 1. 00 1.50 1.66 



May 22-26 1.80 2.00 1.80 1.80 2.00 



May 27-June I . . . . 1.25 1.03 1.25 0.75 1.50 



June2-6 1.33 1.33 1.33 0.16 1.33 



June 7-12 0.20 0.40 1.60 dead 0.40 



dead dead living dead 



All were normal solutions, diluted 25 times, one drop to twelve 

 drops of hay infusion and the treatment lasted for 30 minutes in 

 case of KCI, and for 25 minutes in each of the other solutions. 

 Definite conclusions cannot be drawn from one set of compari- 

 sons for it may have been pure accident that the magnesium 

 chloride specimens continued to live. The effect of MgClj upon 

 the protoplasmic structures is shown in Fig. 12. 



Comparatively few experiments were made with acids. Hydro- 

 chloric and nitric acids were tried during the period of depression 

 in October, 1902, but the results were negative, the individuals 

 dying within twenty-four to forty-eight hours. An interesting 

 effect was produced by treatment with dilute phosphoric acid. 

 The dense endoplasm was broken up and with it the macro- 

 nucleus which, after the treatment, appeared as many small 

 fragments (see Fig. 16). 



Of the other unsuccessful attempts to rejuvenate the race during 

 the last period of depression I will mention only those with gal- 

 vanic stimuli, with nitro-glycerine, and with dried and powdered 

 Paramoecium of an entirely foreign race. 



3. Galvanic Stimuli. 



A small cell was made and connected with two Mesco batteries. 

 Four individuals were treated on November 28, three different 

 times to the full current and for a period of one minute each time. 

 The usual reaction followed the treatment, migration to the nega- 

 tive pole, and when the current was reversed, migration from the 



