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 to 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 



