Mr Stark on Changes in the Colour of Fishes. 829 



the minnows appeared of a mottled grey and brown colour, with 

 the fins of a bluish tinge. 



July 18. — Colours on the back dark brown, approaching to 

 black, so as to be with difficulty distinguished from the colour 

 of the jar when looking down ; fins purpKsh, inchning to blue. 



The same minnows remained in the dark jar till the 21st. 

 On that day, I covered the bottom and two slips on the side 

 two inches high with tinfoil, leaving the minnows in the shade 

 as before. 



July 22. — One of the minnows which had kept at the bottom 

 over the tinfoil, had this day lost much of its dark colours, the 

 back appearing brownish-coloured, fading into silvery on the 

 sides, with no appearances of the dark interrupted bars. The 

 other minnow, which kept above, and by the side of the vessel 

 where it was not covered with tinfoil, retained its original co- 

 lours and markings. 



July 24. — I removed the tinfoil this morning, and at night 

 both minnows had assumed on the back, when looked down 

 upon, the same dark colour as before, and nearly approaching 

 that of the jar. 



The minnows remained in this jar till the 3d of August, 

 some time previous to which, I had put others of the same spe- 

 cies into the j'ar ; and they were now uniformly of the same 

 dark colour on the back, with black variegations and golden re- 

 flections on the sides. The belly in all cases retained its silvery 

 appearance. 



All these experiments were conducted in a dark corner of the 

 room. I repeated the same experiments in a perfectly light 

 place of the room, but excluded from the sun's rays ; and again 

 by exposing the vessels and animals to the direct rays of the 

 sun, with the same results ; — that is, when placed in a dark 

 vessel, the colours of the animals assumed much of the colour 

 of the vessel they were placed in ; and when transferred to a 

 white basin, they uniformly became in a very short period of 

 a light sandy colour, and their characteristic markings disap- 

 peared. In crystal vessels, when exposed to the light, little 

 change of colour takes place, though I have often observed, at 

 different periods of the day, and in different minnows in the 

 same vessel, a change to a certain extent in the brightness of 



JULY— SEPTEMBER 1830. Y 



