PHvsi()L<)(;v OK (;hh(jmat()I'H(jkes of fishes 575 



an expansion, of the molanophores. This expansion is due to 

 the specific effect of NaCl (p. 540, pi. 1, figs. l-G and p. 547). 

 The irritabihty is maintained longer (> eighteen hours) in sea- 

 water than in distilled water (one hour) (p. 541 and sununary of 

 section 2, 1, p. 543). 



3. The neutral salts K("l, KBr, KNO, KI and KSCN all 

 cause a contraction of exi)anded melanophores and an expansion 

 of the xanthophores which is scMumdarily follow(nl by a cytolytic 

 degeneration. The time required for the begimiing of this de- 

 generation varies in the order 



(n>Br>N03>I>SCN 



(j). 547 and i)ls. 2 and 3)- The first contraction of the melano- 

 phores is pr()))ably specific for the K+ ion (p. 547). There is ap- 

 parently an antagonism l)etween cation and anion of the same 

 salt in these cases which varies with the nature of the anion. 



4. The neutral salts NaC^l, NaBr, NaNO,, and NaSCN pro- 

 duce an expansion of contracted melanophores. The duration 

 of this expansion is greatest in NaC'l and least in NaSCJN. The 

 other Na salts show an intermediate expansion in the order 



Cn>Br>NO,>SCN 



Degeneration appears first in the NaSCN. In the other solul 

 tions the chromatophores may retain their irritability for more; 

 than five days after removal from the fish. The ex})ansion is 

 the specific effect of the Na+ ion. In contrast to tlie neutra- 

 salts of potassium the cationic effect is distinctly influenced by 

 the nature of the anion. 



5. The alkahne chlorides KCl, (RbCl), NH4CI, (C's(n), LiCl 

 and NaCl vary in th(ur initial effe(;t upon the chromatophores. 

 The first five salts (KCl-Li(U) all bring about contraction of the 

 melanophores and the rapidity of this contraction varies in the 

 order 



K, Rb>NH4, ('s>Li>Na 



In Na(4 the melanophores expand. The irritability is preserved 

 longest in NaCU solutions. The exact positions in the series of 



TIIIO .IOUR\ Vr, or KXPKIlIMK.VTAr, ZOOI.OOy, VOL. 15, .vo. 4 



