The explanation is not to be found in any laxity in either the Admiralty or the Sudan Government surveyors. Considering that the country is an absolutely unproductive desert, traversed only by a sparse population of nomads, that no steamer passes within miles of the outermost reefs, that the native vessels sail by perhaps at the rate of one a month, the existing chart is a monument to the greatness of the Admiralty’s conception of taking the whole world for its province, even the most useless desert coasts. Perhaps the fact that this country, though so near to Europe, is only artificially made habitable at all, may add interest to my account; but besides the description of things and peoples more or less unique and peculiar to this country, I have aimed at giving information of general interest. For instance, in treating of the coral reefs I describe features of the barrier system which may be unique in the world, but I have combined with the description of this special point a general account of coral animals and the reefs which they build. This may recall and complete the interesting conversations I have had on such subjects with friends both at home and in those places where the very streets and houses were once parts of coral reefs. Biologists have one way of justifying their existence which has to some extent been neglected. Their reply to the eternal question “What good is it? where does the money come in?” should be, in some cases, that of the artist. Just as there are those to whom the love of beauty in pictures, sculpture and architecture is one of the things in life they would least wish to lose, to whom the existence of professional artists is more than justified, so there are many outside the ranks of professional biologists, to whom the romance of the beginnings of life, and of strange lowly forms of being, might become an absorbing interest, an enrichment of life in which money does not necessarily “come in” at all. This is an interest especially accessible to the exiles of the coral seas, where ordinary amusements are so restricted that their repetition produces a sense of loneliness and monotony scarcely conceivable by the man of normal surroundings. For these among my friends I have written, beginning from the beginning and omitting as not pertinent to the questions they ask me, many points vital to the science of animal anatomy, but not essential to their understanding perfectly such questions as, “What is the coral organism? How does it build up these rocks?”