ZOOLOGY: W. H. LONGLEY 
735 
Those fishes in whose coloration red normally predominates are noc- 
turnal, and, in proportion to their numbers, are rarely seen by day. 
Gray appears with very different frequency among reef-ranging species 
and those whose diurnal activity is centered among the coral heads. 
The ratio of its occurrence in the two cases is roughly commensurate 
with that of its appearance in the environment of the contrasted groups. 
Among thirty-one reef-rangers, to state the facts in detail, fourteen 
show evident adaptive gray color phases or have permanent gray mark- 
ings, while the same is true of only three of twenty-one species which 
remain near the coral heads by day. This is equivalent to saying 
that according to present information gray markings or color phases 
are about three times as common among reef-ranging fishes as they are 
among those which live close to the coral heads. 
Brown appears so frequently in combination with gray in the pat- 
terns of fishes which adapt their coloration almost instantaneously to 
gray or brown bottoms, whenever the character of their surroundings 
changes, that in default of special evidence to that effect no functional 
conspicuousness may be imputed to either color alone, or m combina- 
tion with the other. The same seems to be true of yellow. 
Among the Tortugas fishes the lighter blues at least are correlated 
with the habit of swimming habitually well above the bottom in water 
of moderate depth. These tints are peculiarly inconspicuous in the 
eyes of an observer at a lower level, and photographs of fishes banded 
with other colors show that the effect of the blue is to blot out its pos- 
sessor's contour under that condition, since at a distance of a few feet 
the blue-gray elements in patterns are indistinguishable from the color 
of the watery background. 
Finally, two-thirds of the species seined upon the green grass-flats 
along shore, and with any show of reason considered typical members 
of the bionomic association inhabiting such places, are wholly or largely 
of a green color, or regularly show a green color phase amid green sur- 
roundings. If the forms that swim at a high level in open water be 
excluded, no other such aggregation of green fishes as may be secured 
on the grass flats may be named from the entire fish fauna of the region, 
though this includes more than two hundred species. 
It seems significant that the suggestion from the observations so far 
recorded is uniform. The obliterative effect of countershading is dem- 
onstrated by Thayer's experiments. That adaptive color changes are 
very common and minister to the same end, although they occur among 
bright colored species, is a fair inference from my own experience. 
The colors of the fishes, also, are correlated with their habits in such 
