Directly we look at the ground in the neighbourhood of Port Sudan or Suakin, or indeed anywhere on this part of the Red Sea coast, we see that it is largely composed of shells and fragments of coral. Further, it is easy to see that these differ from the fossils of home limestones in their extreme abundance, in their lying loose among the surrounding sand, and in their being familiar to the collector of shells as common species still living in the neighbouring sea. The same is true of the corals, though in this case the identification is not quite so obvious. The fact is we are walking upon a coral-reef, almost exactly like those still forming and growing in the sea, which has been elevated by earth movements above the water, and every grain of the earth was once part of a living creature. Such elevated coral-reefs are common in the world, but they rarely remain so little altered by the upheaval as here. All this dry land and these splendid harbours, many mountain masses in different parts of the world, innumerable islands in the Pacific and Indian Oceans rising from enormous depths of water, are monuments of the life-activity of certain lowly organisms. So much is generally understood, but too often the vision is of “patient insects building islands in the deep.” At least the visitor to the new town of Port Sudan must recognise the coral organism as the fundamental fact of all that he has come so far to see. They are the builders of those foundations of which the great quay-walls are but a trimming and straightening of an infinitesimal portion, but it is no more possible to directly observe the building action of the coral polyps than to see the growth of the bones in a child. Fig. 52. A simple sea-anemone. Figs. 53 and 54. Young and fully developed colonial anemones. Figs. 55 and 56. Two views of a living coral polyp (_Caryophyllia smithii_) from above and from the side. The radial plates of limestone, conspicuous in Fig. 57, are seen through the transparent body wall. Otherwise the animal is like Fig. 52. (Drawn from living animal by H. C. Chadwick, A.L.S.) Fig. 57. The stony cup of _Caryophyllia_, seen from above and from the side, after removal of the polyp’s flesh. _Plate XXV_ [Illustration: Fig. 52] [Illustration: Fig. 53] [Illustration: Fig. 54] [Illustration: Fig. 55] [Illustration: Fig. 56] [Illustration: Fig. 57 Sea-anemones and corals]