162 JOHN N. LOWE 



Na + and the potassium cation K + and not between the po- 

 tassium cation and the chlorine anion K + CI — . This is sup- 

 ported in part by the foregoing experiments on the pigment 

 cells of trout embryos. The pigment cells are expanded in 

 sodium salts after a potassium salt contraction. But this is not 

 true of all the salts of sodium. If the pigment cells are con- 

 tracted in KCl or KI and are now placed in Nal there is no ex- 

 pansion. Apparently there is an antagonism between the 

 dissociated anions of (CI — and I — ) and the sodium cation 

 (Na +) for from the conditions of the experiment we should get 

 an expansion. It is probable that Loeb underestimated the 

 antagonism between the positive ions of K + and Na + and 

 their negative ions CI — . The longevity of the fish is better 

 protected in sodium salts than in potassium salts. But again 

 some of the sodium salts are more protective (Na2S04 or NaCl) 

 than others (Nal). That the potassium and sodium cations do 

 exert some such modifying action is undeniable, but to say that 

 it IS independent of its anion is not warranted by the facts at 

 our command. 



3) That it is the residual undissociated molecules in the 

 solution that modify the action of the salt. 



In 0.2 M, KI the degree of dissociation is much greater than 

 in an equivalent 0.2 M, solution of K2SO4. Correspondingly KI 

 initiates more intense responsiveness of the pigment cells than 

 does K2SO4. The rate and degree of the reactions of the pigment 

 cells decline as the number of the undissociated molecules in- 

 creases. In the potassium salts the primary contraction and the 

 expansion vary with undissociated molecule, thus, 



S04> Cl> Br> NO3 I 



The degree of dissociation for 0.2 M solutions are 



66.03 82.98 83.44 78.05 84.82 



The fact that the nitrate is out of place was mentioned before. 

 As already stated, this may be due to the independent activity 

 of the nitrate, which may break down to form a nitrite. 



In sodium salts the dissociation percentages are slightly less 

 than in potassium salts. The rate of contraction is much slower. 



