PHYSIOLOGY OF CHROMATOPHORES OF FISHES 569 



7. ELECTRICAL EFFECTS 



The following authors have recorded a contraction of the 

 chromatophores following an electrical stimulation. Briicke ('52) 

 in excised pieces of the skin of the chameleon; Buchholz ('63) 

 in the tails of Cyprinodon fishes (quoted by v. Rynberk '06 b, 

 p. 530); Pouchet ('71) in Cottus embryos (quoted by v. Ryn- 

 berk '06 b, p. 533); Bert ('75) in pieces of the skin of chameleon; 

 Krukenberg ('81) in flat-fishes (Pleuronectidae) ; Lode ('90, p. 

 133), in pieces of the fins of medium-sized trout; Biedermann 

 ('92) in the frog (Rana, p. 493); v. Rynberk ('06 a) in Solea and 

 Rhomboidichthys species (quoted by v. Rynberk '06 b, pp. 549 

 -550); Mayerhofer ('09) in Esox lucius Lin.; Winkler ('10) in 

 the toad (Hyla) by an induction current;* v. Frisch ('11 a) in 

 Phoxinus laevis L., upon stimulation of the medulla and v. 

 Frisch ('12) in Trigla corax and Crenilabrus pavo by local 

 stimulation. 



The melanophores of F. heteroclitus readily respond to an in- 

 duction stimulus. If this be applied at the medulla just pos- 

 terior to the cerebellum, a rapid lightening of the fish follows 

 immediately. Other experiments were carried out with scales 

 immersed in NaCl solutions in the usual way until the melano- 

 phores were all completely expanded. The stimulus was here 

 applied to the bony portion of the scale. The time of the con- 

 traction varied with the strength of the salt solution. When 

 the scales were immersed in sea-water no response followed. 



August 8, 1912 



A Harvard inductorium with closed secondary (one Mesco 'A' dry 

 cell) produced a complete contraction of the melanophores of scales in 

 0.25 M NaCl solution in thirty seconds and this was reversible. A 

 thirty second stimulus of scales in 0.5 M NaCl solution showed only a 

 very slight and doubtful contraction. In sea-water trials with one, two 

 and three dry cells (in series) and closed secondary gave no reaction. 

 The melanophores remained fully expanded. 



* Winkler records an expansion of the pigment when stimulated by a galvanic 

 current. 



