64 
unmistakable (— the zoologists in Manila were well acquainted with 
it —); it is a most admirable case of protective resemblance, no 
less admirable than the numerous cases of butterflies mimicking 
dead leaves. It is true, the resemblance in the shape of the body 
and in the coloration is not nearly so perfect as is generally the 
case in butterflies; but the movements of the fish outweigh com- 
pletely the lack of perfectness in shape and colour, and the com- 
bined result of shape, colour and habits of the fish is a very per- 
fect disguise as an old Mangrove-leaf, swaying for the movements 
of the water. 
Another, very peculiar instance of protective resemblance in 
fishes was observed in the Bay of Panama. Around the little island 
Taboga driftwood is often seen in the sea, now large trees, now 
smaller stems or branches; but, especially, the sea may ”often be 
covered to a large extent by quite small particles of old wood, 
driftwood which has been washed ashore and ground to pieces, 
the pieces then being brought afloat again at spring tide and swept 
together in large patches or long streaks by the currents. 
Being aware from previous experience, as related below, that 
many young fishes use to seek a shelter under anything floating 
in the surface of the water, I expected to find them here also and 
looked carefully out for them. It proved, however, to be not quite 
the same simple thing I had observed before. The young fishes 
were there, sure enough, but they did not hide themselves beneath 
the wooden fragments; they were swimming or rather floating free 
among the fragments. Still it was almost impossible to discover 
them. The body was dark coloured, exactly like the wet wooden 
fragments, while the tail and other fins were perfectly transparent, 
the result being that only the dark coloured part could be disting- 
uished. Furthermore they are generally floating on the side. The 
resemblance between these young fishes and the wooden fragments 
is so perfect, that I found it almost impossible to distinguish the 
fishes, except when they started to swim. Numerous persons, to whom 
I showed such fishes, caught and put into a dish together with the 
wooden fragments, found it equally impossible to tell the fishes 
from the fragments. — Also somewhat larger specimens were found 
In the same way among the fragments. 
This resemblance of the young fishes to the wooden fragments 
