111 
Researches on the Coloration of the Skins of Flat- 
fishes. 
By 
J. T. Cunningham, M.A., 
Naturalist to the Association. 
In the year 18901 tried an experiment upon young flounders, with 
the object of discovering what would be the effect upon the lower 
sides of the fish if these sides were continually exposed to daylight. 
Under ordinary conditions the upper side of the fish is dark-coloured, 
the lower side white ; and the upper side is exposed to light, while 
the lower side being usually in contact with the ground, and always 
turned away from the sky, is protected from the light. A connection 
between the difference of the two sides in relation to light and in 
coloration naturally suggests itself. If the difference in coloration 
is due to the difference in the exposure of the sides to light, when 
the lower side of the fish is kept exposed to the light it ought to 
become coloured. 
When the flounder or other flat-fish is first hatched it has chroma- 
tophores on both sides equally, and these chromatophores disappear 
from the lower side during the metamorphosis. It seemed more 
likely that illumination of the lower side would prevent to some 
extent this disappearance, than that it would cause the reappearance 
of chromatophores on the lower sides of older specimens. My first 
experiment (described in the Zool. Anzeiger, 1891) consisted, there- 
fore, in taking a few young flounders which had not completed their 
metamorphosis and rearing them in a glass bottle supported on a 
plate of glass, underneath which was placed an inclined mirror 
reflecting the light from a window vertically upwards. I covered 
the sides and top of the bottle with an opaque cover made first of 
brown paper, afterwards of cloth, so that the hght was to a great 
extent prevented from entering the bottle in any direction except 
from the mirror. The rearing of flounders from this stage 
to maturity, although requiring minute and constant attention, 
presents no great difficulty. The methods of feeding them and main- 
taining a circulation of the water containing them were described 
