May, 1919 
FOREST AND S T R E A :\I 
243 
THE COLORS OF 
FISHES 
(CONTINUED FROM PAGE 220) 
nocturnal red fishes have red deep-water 
relatives, and an explanation of their 
color should rather be considered a prob- 
lem corrolary to that of the red deep- 
water fish. Possibly it is a mere in- 
heritance from deep-water ancestors. 
Then there are many fishes whose haoitat 
and colors are intermediate between the 
different groups, or we find on the reefs 
bottom species (a variety of small blen- 
nies comes to mind), adapted to the 
reef in habits and colors just as they 
and their relatives are to other types 
of bottom. 
S O far any mention of the great var- 
iation of color found within many 
species of fishes has been avoided. 
The males of many species assume high 
colors in the breeding season or when 
stimulated by breeding activities. My 
observations of such males are sufficient 
for me to conclude that in some species 
they have a higher visibility than when 
in normal, more neutral color, and I as- 
sume that this is ordinarily the case. It 
is safe to assume also that an explanation 
of the high colors of such males should 
be homologous with that of the more per- 
manent high colors found in the plumage 
of many male birds. The Darwinian 
hypothesis of sexual selection is so far 
the most satisfactory explanation of the 
phenomenon, though from some aspects 
an unsatisfactory explanation, at least in 
its unmodified form. 
Extensive, rapid, color and pattern 
changes in individual flounders have been 
experimentally proved to be an adapta- 
tion for concealment, rendering the fish 
equally inconspicious on various bottoms. 
Fishes from the white bottoms near 
Key West I have found, as a, rule, to 
harmonize in general color with the tone 
of the bottom, individuals from here 
being often very much whiter than those 
of the same species taken elsewhere on 
darker bottoms. From these considera- 
tions I would expect many color changes 
undergone by individual bottom and weed 
fishes to be correlated with concealment. 
Observations, particularly in aquaria, 
prove that there are color changes corre- 
lated with the fish’s mental or physiolog- 
ical condition and apparently with no 
other bearing. 
Many fishes undergo considerable color 
change with age. For instance, the 
young of the dolphin which hides about 
weed and other drift has a dull mottled 
color quite unlike that of the free-swim- 
ming adult, young and old belonging to 
quite different groups, according to my 
classification, and with colors correspond- 
ingly different. 
In many, not all, of the boldly colored 
reef fishes, individuals undergo consider- 
able and rapid changes of color. Prof. 
Longley finds that the Red Parrotfish, 
Sparihoma abildgaardi,' (which I be- 
lieve to be a typical reef fish, usually con- 
picious, though my experience with the 
species in life is limited) has gray and 
brown probably concealing phases, and 
= Longley, Journal Exp. Zool, 23. 1917: 547. 
(CONTINUED ON PAGE 249) 
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