RESEMBLANCES AMONG ANIMALS, 55 
harmless genera; but almost all of them are of a 
beautiful green colour, sometimes more or less adorned 
with white or dusky bands and spots. There can 
be little doubt that this colour is doubly useful to 
them, since it will tend to conceal them from their 
enemies, and will lead their prey to approach them 
unconscious of danger. Dr. Gunther informs me 
that there is only one genus of true arboreal snakes 
(Dipsas) whose colours are rarely green, but are of 
various shades of black, brown, and olive, and these 
are all nocturnal reptiles, and there can be little doubt 
conceal themselves during the day in holes, so that the 
green protective tint would be useless to them, and 
they accordingly retain the more usual reptilian hues. 
Fishes present similar instances. Many flat fish, as 
for example the flounder and the skate, are exactly 
the colour of the gravel or sand on which they 
habitually rest. Among the marine flower gardens 
of an Eastern coral reef the fishes present every 
variety of gorgeous colour, while the. river fish even 
of the tropics rarely if ever have gay or conspicuous 
markings. A very curious case of this kind of ad- 
aptation occurs in the sea-horses (Hippocampus) of 
Australia, some of which bear long foliaceous ap- 
pendages resembling seaweed, and are of a brilliant 
red colour; and they are known tv live among sea- 
weed of the same hue, so that when at rest they 
must be quite invisible. There are now in the aqua- 
rium of the Zoological Society some slender green 
pipe-fish which fasten themselves to any object at 
