Notes and Queries. 26 
In this connection it will be of interest to 
quote Giinther as to the cause of variation in 
color obtaining in fishes: 
“The changes of colors are produced in two 
ways; either by an increase or decrease of the 
black, red, yellow, etc., pigment-cells or chrom- 
atophers, in the skin of the fish, or by the rapid 
contraction or expansion of the chromatophers 
which happen to be developed ‘The former 
change is gradual, like every kind of growth or 
development: the latter rapid, owing to the 
great sensitiveness of the cells, but certainly 
involuntary. In many bright-shining fishes— 
as mackerels, mullets—the colors appear to be 
brightest in the time intervening between the 
capture of the fish and its death, a phenomena 
clearly due to the pressure of the convulsively- 
contracted muscles on the chromatophers. 
(This will answer the query of W. D., who 
~~ 
wishes to know why the dolphin rapidly 
changes color when dying.) External irrita- 
tion readily excites the chromatophers to ex- 
pand—a fact unconsciously utilized by fisher- 
men, who, by scaling the red mullet im- 
mediately before its death, produce the desired 
intensity of the red color of the skin, without 
which the fish would not be saleable. How- 
ever, it does not require such stronz measures 
to prove the sensitiveness of the chromatophers 
to external irritation; the mere change from 
darkness into light is sufficient to induce them 
to contract, the fish appearing paler, and vice 
versa. In trout which are kept in dark places, 
the black chromatophers are expanded, and 
consequently such specimens are very dark 
colored; when removed to the light they be- 
come paler almost instantly ”’ 

