PHYSIOLOGY OF CHROMATOPHORES OF FISHES 



567 



Cell with 

 Q,uartz Windov/ 

 1 min. Thick 



Microscope 

 Stage^ 



^Scales in 

 //Sodium Chloride 



.Ultra-violet 

 Rays 



Fig. C Diagram of apparatus for subjecting melanophores to ultra-violet 

 light. 



May 7, 1912 



2.15 P.M. Scales from an 8 cm. female were immersed in 0.1 M NaCl. 



2.35 P.M. 4 scales were exposed to ultra-violet light; 2 inverted and 

 2 face up. (4 control scales were similarly arranged with- 

 out exposure to the ultra-violet light). All those scales 

 were immersed in a 0.1 M NaCl solution during the ex- 

 posure. After 7 minutes both inverted scales in ultra- 

 violet light showed a decided contraction of the melan- 

 ophores. Neither face-up scale in ultra-violet light 

 showed any contraction. After twenty-one minutes a 

 very decided contraction was visible in both inverted 

 scales in ultra-violet light. The face-up scales showed 

 a very slight contraction at 2 points on the periphery at 

 this time. All four control scales had completely ex- 

 panded melanophores throughout the experiment. These 

 8 scales were now fixed in 95 per cent alcohol (Plate 4) . 



The failure of the response in the scales which were turned 

 face-up suggested that the ultra-violet rays might be absorbed 

 by the bony plate of the scale exactly as they are absorbed by 

 glass. In order to test this point an experiment similar to the 

 last was performed but in this case a thin cover-glass was placed 

 at the bottom of the cell between the scales and the quartz-bottom. 



