548 R. A. SPAETH 



• 



At 0.9 M concentration a few melanophores show the beginning 

 of an expansion but the centrifugal migration soon ceases. No 

 constant reaction occurs in a molecular solution of NaCl. The 

 epidermis very quickly becomes entirely opaque and the migra- 

 tion of the pigment is completely inhibited. 



WTien scales have been immersed in a 0.1 M NaCl solution 

 for about an hour the xanthophores are completely contracted 

 while the melanophores are widely expanded. Here again is 

 a case in which the melanophores and xanthophores react recip- 

 rocally to the same stimulus. This contraction of the xan- 

 thophores is quite as characteristic a NaCl reaction as is the 

 expansion of the melanophores. 



The expansion produced by a solution of NaCl is dependent 

 upon both the temperature and the oxygen supply Above 30°C. 

 the specific effect of heat overcomes the expanding tendency of 

 a 0.1 M NaCl solution (p. 563). Similarly in an atmosphere of 

 pure hydrogen the melanophores immersed in a 0.1 M NaCl con- 

 tract (p. 563). If the temperature and oxygen supply remain 

 constant the chromatophores retain their irritability much longer 

 in a 0.1 M NaCl solution than in KCl of the same concentration. 



Believing the expansion in the NaCl solution to be due to a 

 specific effect of the Na'^^ ion, experiments were made with other 

 neutral salts of sodium. 



June 22, 1912 



11.43 A.M. Scales from a light, 8 cm. female were removed to sea-water. 

 11.48 A.M. 4 sets of three scales each were tran,sf erred to 8 cc. of 0.1 



M NaCl, NaBr, and NaSCN and 8 cc. of 0.105 M NaNOg. 

 12.25 P.M. All these scales showed expanding melanophores and the 



order of darkness was 



Cl>Br>N03>SCN 



Very little expansion was seen in the NaSCN solution. 



1.30 P.M. Both the NaNOs and the NaSCN solutions had the melan- 

 ophores contracted. In NaCl they were still widely ex- 

 panded. 



2.40 P.M. The melanophores in all four solutions were contracted. 



In further experiments of this type the same order of darkness 

 appeared repeatedly. Scales were started from both KCl and 



