102 The American Naturalist. [February, 
Nocturnal and Diurnal changes in the Colors of Certain Fishes, 
and of the Squid (Loligo), with notes on their Sleeping Habits. 
—These observations were mostly made in the U. S. Fish 
Commission Laboratory, at Wood’s Holl, Mass., in 1885 to 
1887, when the laboratory was in excellent condition for bio- 
logical studies. In order to observe the nocturnal habits of 
the fishes, ete.,in the aquaria, the gas was turned down low, so 
as to give a light just sufficient for distinct vision, after every 
one except myself had retired. Great care was also taken not 
to jar the floor or furniture. Under these conditions many 
interesting observations were made. It was noticed that while 
many species became very active others took this opportunity 
to sleep, and in doing so, assumed unusual colors and positions. 
Several species of fishes, while asleep, had colors very different 
from those seen in the day time. Others showed a decided 
increase in the intensity or contrast of their colors, without 
changing the pattern. The latter was the more common habit, 
and was noticed especially in the case of species that have 
longitudinal, transverse, or oblique dark bands or stripes or 
irregular mottlings. As previously explained, these dark 
stripes are highly protective colors for fishes that rest at night 
among weeds and grasses. Among those showing this change 
are several species of minnows (Fundulus), and the king-fish 
(Menticirrus nebulosus), in which the blackish stripes come out 
more strongly and clearly when asleep than when awake. The 
black sea-bass, (Serranus furvus), especially when young, shows 
its black markings more clearly when asleep. The sea robins 
(Prionotus palmipes and P. evolans), and various species of 
flounders show more strongly contrasted and darker colors 
than in the day time. But the scup or porgy (Stenotomus chry- 
sops) shows much more remarkable changes in color. This 
fish, in the day time, usually has a bright silvery color, with a 
brilliant pearly iridescence, but at night, while asleep, it be- 
comes dull bronzy or gray, and is crossed by about six trans- 
verse black bands, colors very effective for concealment among 
the stalks of eel-grass or sea-weeds. If aroused by suddenly 
turning up the gas, it immediately resumes its day time colors. 
If killed in alcohol this fish, and many others, as well as the 
