544 R. A. SPAETH 



The time of contraction in KCl solution of different strengths 

 varies with the concentration. 



September 5, 1912 



9.26 A.M. Scales from an 8 cm. female were immersed in 0.1 M NaCI. 

 10.45 A.M. Sets of 3 matched scales were removed to 8 cc. of 0.2, 0.1, 

 and 0.05 M KCl. The average time of the contracting 

 for nine trials in each solution was as follows: 



Solution stren^tk mi^^::'' IZnds 



0^2 M 4 2 9 



0.1 M 3 9 



0.05 M 4 58 



All concentrations of KCl from 0.85 to 0.02 M clearly show a 

 contracting effect upon the melanophores, while NaCl solutions 

 of the same strength produce an expansion of the pigment in 

 every case. Since this cannot be an osmotic effect and the chlor- 

 anion is common to the two salts, it seemed possible, that the 

 contraction might be the specific effect of the K+ ion and the ex- 

 pansion that of the Na+ ion. If this were so, other neutral K 

 salts might also be expected to exert a contracting influence upon 

 the melanophores. 



Trials were now made with 0.1 M KCl and KBr. Both solu- 

 tions contracted the melanophores in the same time. Not the 

 slightest constant difference in the contraction-time could be 

 detected. The evidence for the specificity of the K+ ion was this 

 strengthened. A chance observation gave a clue to the differ- 

 ence in the effects of the two anions. After three hours immer- 

 sion in 0.1 M KCl and 0.1 M KBr solutions, all the scales in the 

 KBr solution showed the melanophores to be slightly expanded 

 while all of those in the KCl remained completely contracted. 

 This difference was quite striking, sufficiently so to be seen clearly 

 with the naked eye. Further experiments proved it to be con- 

 stant. In KBr a secondary expansion and subsequent degenera- 

 tion of the melanophores always appeared sooner than in KCl. 

 This secondary expansion was in no way comparable to the ex- 

 pansion produced by NaCl for in the case of the potassium salts 

 it was irreversible. 



