ION-PKOTEID COMPOUNDS 555 



Medusa the same is true as for Fundulus. Na ions are poi- 

 sonous in a pure NaCl solution, while the same solution is 

 harmless if a certain amount of K and Ca ions are present. 

 Our theory that the irritability of tissues depends upon the 

 presence in definite proportions of Na, K, and Ca ions is 

 once more verified. It goes without saying that a pure -|n 

 KC1 and a pure y n CaCl 2 solution was still more poisonous 

 than a -| n NaCl solution. 



IV. EXPERIMENTS ON CILIARY MOTION 



The conditions for ciliary movements were studied in the 

 young larvae (blastula, gastrula, and pluteus) of the sea- 

 urchin. The movements of these larvae are due to cilia 

 which are incessantly active. I found that these larvae do 

 not die rapidly in a f n NaCl solution. They may live 

 twenty-four hours. But if we add a small amount of f n 

 KC1 and *-n CaCl 2 , they may be kept alive and in motion 

 for ten days or more. In the latter solution their develop- 

 ment can continue, while in the pure NaCl solution this is 

 not possible. 



I was, however, surprised to find that this ciliary motion 

 continued in solutions in which no muscular contractions of 

 Fundulus or Gonionemus were possible. Larvae which were 

 twenty hours old were able to swim for about forty-eight hours 

 in the following solutions: 



90 c.c. V n MgCl 2 + 10 c.c. V n CaCl 2 

 80 +20 



50 " +50 



The reader will notice that these solutions contain no NaCl. 

 I tried the effects of these solutions on Gonionemus. As 

 was to be expected, not one contraction was possible in these 

 solutions. The following observation is equally astonishing. 

 Combinations of NaCl and KC1 were tried: 



(1) 80 c.c. in NaCl + 20 cc. f n KC1 



(2) 20 c.c. " +80 



