314 CHAS. W. HARGITT. 



play. Still others have contended that various species react very 

 differently to a given stimulus, and that an element which may 

 prove a stimulus in one case may prove inhibitory or even toxic 

 in another case. It is quite certain, therefore, that the last word 

 has not yet been said concerning this perplexing problem. And 

 so far from the rather dogmatic declaration that " it is only the 

 presence of Ca ions in the blood which prevents the muscles of 

 our skeleton from beating rhythmically in our body " we may 

 better assume an attitude of open skepticism, or at least suspend 

 judgment long enough to perform a few more experiments ! In 

 the lack of material for such experimentation in the present case 

 it occurred to me to try in a very simple fashion the effects of 

 perfectly pure, that is distilled, water on the medusae. In the 

 absence of the ions of the aforementioned elements, Na, Ca, K, 

 etc., in such water should we get any of the results usually 

 attributed to them ? The problem seemed simple enough, but 

 not too simple to be unworthy of a trial. Accordingly the fol- 

 lowing experiments were made : 



1. Specimens were transferred from the water in which they 

 had been sent from the aquarium to that of the ordinary tap- 

 water of the laboratory in order to see whether any appreciable 

 effect would follow. But none could be observed; hence they 

 were thereafter freely transferred to such water as circumstances 

 seemed to suggest from day to day. Later tests of this water 

 showed it to be so free from any of the salts in question as to be 

 indistinguishable by the ordinary chemical tests. 



2. A single specimen was next transferred to a jar of distilled 

 water. It moved rhythmically for thirteen beats, then paused. 

 Then followed six beats succeeded by another pause of longer 

 extent during which it floated downward sinking to the bottom. 

 Here there followed five beats and a pause of five minutes. At 

 this time it was transferred back to normal water with the result 

 of prompt resumption of rhythmic activity, but of a more rapid 

 rate, nearly or quite twice that before the experiment was begun. 

 This continued for nearly ten minutes, when the rhythm grad- 

 ually returned to the normal rate. 



3. Another specimen tested in the same way gave almost 

 identically the same reactions. 





