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in PROTECTIVE RESEMBLANCES AMONG ANIMALS 47this insect belongs, is more or less imitative, and a greatnumber of the species are called " walking-stick insects," fromtheir singular resemblance to twigs and branches. Some ofthese are a foot long and as thick as one's finger, and theirwhole colouring, form, rugosity, and the arrangement of thehead, legs,and antennae are such as to render them absolutelyidentical in appearance with dead sticks.They hang looselyabout shrubs in the forest, and have the extraordinary habitof stretching out their legs unsymmetrically, so as to renderthe deception more complete. One of these creatures obtainedby myself in Borneo (Ceroxylus laceratus) was coveredover with foliaceous excrescences of a clear olive green colour,so as exactly to resemble a stick grown over by a creepingmoss or jungermannia. The Dyak who brought it meassured me it was grown over with moss although alive, andit was only after a most minute examination that I couldconvince myself it was not so.We need not adduce any more examples to show howimportant are the details of form and of colouring in animals,and that their very existence may often depend upon theirbeing by these means concealed from their enemies. Thiskind of protection is found apparently in every class andorder, for it has been noticed wherever we can obtain sufficientknowledge of the details of an animal's life-history. Itvaries in degree, from the mere absence of conspicuous colouror a general harmony with the prevailing tints of nature, upto such a minute and detailed resemblance to inorganic orvegetable structures as to realise the talisman of the fairytale, and to give its possessor the power of rendering itselfinvisible.Theory of Protective ColouringWe will now endeavour to show how these wonderfulresemblances have most probably been brought about. Returningto the higher animals, let us consider the remarkablefact of the rarity of white colouring in the mammalia or birdsof the temperate or tropical zones in a state of nature. Thereis not a single white land-bird or quadruped in Europe, exceptthe few arctic or alpine species, to which white is a protectivecolour.of these creatures there seems to be noYet in many