ION-PROTEID COMPOUNDS 553 



poisonous character of a pure NaCl solution would not have 

 been possible except in a marine animal like Fundulus for 

 which distilled water is not poisonous. Another possibility 

 might have been the presence of a trace of acid. My 

 colleague, Professor Stieglitz, was kind enough to test the 

 NaCl used, for acids, but it was found to be absolutely free 

 from acids. Hence I do not see any other possible explana- 

 tion of the results than the theory from which we started. 



What is true for pure NaCl solutions is, of course, still 

 more true for equimolecular pure solutions of KC1 and 

 CaCl g . They act like poisons. I have not yet been able to 

 convince myself that their poisonous effect can be prevented 

 by the addition of small amounts of other metal ions. 



The fact that Fundulus can be thrown from sea-water 

 into distilled water without any considerable swelling, or 

 without any visible injurious effects, may find its explanation 

 through the influence that various ions have upon the ab- 

 sorption of liquids. The above-mentioned experiments on 

 the absorption of liquids by the muscle have shown that the 

 simple osmotic theory of absorption which has been accepted 

 by botanists cannot possibly be correct. I shall deal with 

 this problem in another paper. 



III. EXPERIMENTS ON JELLYFISH (GONIONEMUS) 



The locomotion of Medusae is due to rhythmical con- 

 tractions of their swimming-bell. I experimented on a 

 form which is very abundant at Woods Hole, Gonionemus. 

 If we put a Gonionemus into a |- n solution of NaCl, it soon 

 stops contracting rhythmically. Too many Na ions take the 

 place of Ca and K ions, and this alters the physical properties 

 of the tissues to such an extent that no more contractions are 

 possible. If such a Medusa is brought back into normal 

 sea-water, it begins to beat again after a short time. In 

 this case Ca and K ions take the place of some of the Na ions 



