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in PROTECTIVE RESEMBLANCES AMONG ANIMALS 41protective tint would be useless to them, and they accordinglyretain the more usual reptilian hues.Fishes present similar instances. Many flat fish, as forexample the flounder and the skate, are exactly the colour ofthe gravel or sand on which they habitually rest. Amongthe marine flower gardens of an Eastern coral reef the fishespresent every variety of gorgeous colour, while the river fisheven of the tropics rarely if ever have gay or conspicuousmarkings. A very curious case of this kind of adaptationoccurs in the sea-horses (Hippocampus) of Australia, some ofwhich bear long foliaceous appendages resembling seaweed,and are of a brilliant red colour ;and they are known to liveamong seaweed of the same hue, so that when at rest theymust be quite invisible. There are now in the aquarium ofthe Zoological Society some slender green pipe-fish whichfasten themselves to any object at the bottom by theirprehensile tails, and float about with the current, lookingexactly like some simple cylindrical algae.It is, however, in the insect world that this principle ofthe adaptation of animals to their environment is most fullyand strikingly developed. In order to understand howgeneral this is, it is necessary to enter somewhat into details,as we shall thereby be better able to appreciate the significanceof the still more remarkable phenomena we shallpresently have to discuss. It seems to be in proportion totheir sluggish motions or the absence of other means ofdefence, that insects possess the protective colouring. In thetropics there are thousands of species of insects which restduring the day clinging to the bark of dead or fallen trees ;and the greater portion of these are delicately mottled withgray and brown tints, which, though symmetrically disposedand infinitely varied, yet blend so completely with the usualcolours of the bark, that at two or three feet distance theyare quite undistinguishable. In some cases a species isknown to frequent only one species of tree. This is the casewith the common South American long -horned beetle(Onychocerus scorpio), which, Mr. Bates informed me, isfound only on a rough -barked tree, called Tapiriba, on theAmazon. It is very abundant, but so exactly does it resemblethe bark in colour and rugosity, and so closely does it cling