The littoral area as defined is not a large haunt of life; it occupies only about 9 million square miles, a small fraction of the 197,000,000 of the whole earth's surface. But it is a very long haunt, some 150,000 miles, winding in and out by bay and fiord, estuary and creek. Where deep water comes close to cliffs there may be no shore at all; in other places the relatively shallow water, with seaweeds growing over the bottom, may extend outwards for miles. The nature of the shore varies greatly according to the nature of the rocks, according to what the streams bring down from inland, and according to the jetsam that is brought in by the tides. The shore is a changeful place; there is, in the upper reaches, a striking difference between "tide in" and "tide out"; there are vicissitudes due to storms, to freshwater floods, to wind-blown sand, and to slow changes of level, up and down. The shore is a very crowded haunt, for it is comparatively narrow, and every niche among the rocks may be precious. [Illustration: AN EIGHT-ARMED CUTTLEFISH OR OCTOPUS ATTACKING A SMALL CRAB These molluscs are particularly fond of crustaceans, which they crunch with their parrot's beak-like jaws. Their salivary juice has a paralysing effect on their prey. To one side, below the eye, may be seen the funnel through which water is very forcibly ejected in the process of locomotion.] [Illustration: A COMMON STARFISH, WHICH HAS LOST THREE ARMS AND IS REGROWING THEM The lowest arm is being regrown double. (_After Professor W. C. McIntosh._)] [Illustration: A PHOTOGRAPH SHOWING A STARFISH (_Asterias Forreri_) WHICH HAS CAPTURED A LARGE FISH The suctorial tube-feet are seen gripping the fish firmly. (After an observation on the Californian coast.)] [Illustration: _Photo: J. J. Ward, F.E.S._ THE PAPER NAUTILUS (ARGONAUTA), AN ANIMAL OF THE OPEN SEA The delicate shell is made by the female only, and is used as a shelter for the eggs and young ones. It is secreted by two of the arms, not by the mantle as other mollusc shells are. It is a single-chambered shell, very different from that of the Pearly Nautilus.] Keen Struggle for Existence