PLATE 1 



EFFECTS OF DISTILLED WATER 

 EXPLANATION OF FIGURES 



The first five figures are consecutive photographs of a scale from the median 

 dorsal head-region of a 9.3 cm. light female. They show the characteristic pe- 

 ripheral encroachment of distilled water. 



1 All melanophores contracted. Photograph taken 1 minute, 49 seconds after 

 the removal of the scale. 



2 The characteristic expansion which follows the loss of the nerve tonus. 

 This is the cause of the darkening seen in decapitated fish. Taken 10 minutes, 

 20 seconds after the removal of the scale. 



3 The distilled-vvater effect is clearly visible at the periphery of the scale 

 where the melanophores have all contracted. Taken 27 minutes, 40 seconds 

 after the removal of the scale. 



4 The melanophores at the center of the scale are being contracted by tlio 

 advancing distilled water. Taken 34 minutes, 15 seconds after the removal of 

 the scale. 



5 All the melanophores are contracted. Taken 80 minutes, 44 seconds after 

 the removal of the scale. 



6 A single melanophore and a groups of xanthophores. In the former the 

 empty processes may be seen, a characteristic effect of the distilled-water con- 

 traction. 



PLATES 2 AND 3 



EFFECTS OF POTASSIUM SALTS 

 EXPLANATION OF FIGURES 



These figures show the effects of five neutral salts of potassium. Five sets 

 of four scales each were immersed in isotonic solutions of KCl, KBr, KNO3, 

 Kl, and KSCN, for one, two, three, and four hours respectively. 



After one hour the melanophores of the KCl and KBr scales were still con- 

 tracted; in KNO3 a few peripheral melanophores showed an expansion which 

 was more advanced in the KI while all the melanophores of the KSCN scale had 

 begun to expand. 



After Ui'o hours there was still no expansion in KCl, a slight expansion was 

 beginning in the KBr; in KNO3 all but the most central melanophores showed 

 an expansion and all were expanded in KI and KSCN. 



After three hours, there was still no expansion in KCl; all the others were 

 fully expanded and degeneration was well advanced in KSCN. 



After four hours all five scales showed expanded melanophores; in KI and 

 KSCN degeneration was well advanced. 



These figures show clearly the protective anion sequence: 



Cl>Br>N03>I>SCN. 



5S0 



