I had no fear of _Aurelia_, but when another free-swimming species of jelly-fish, _Cyanea_, or the blue-jelly, appeared, I swam ashore with all speed. This great jelly is usually more of a reddish liver-colour than a purple, and is much to be dreaded. Its tentacles are of enormous length. I have seen specimens which measured two feet across the disc, with streamers fully forty feet long, and one has been recorded seven feet across and no less than one hundred and twelve feet to the tip of the cruel tentacles! These trail behind in eight bunches and form a living, tangled labyrinth as deadly as the hair of the fabled Medusa--whose name indeed has been so appropriately applied to this division of animals. The touch of each tentacle to the skin is like a lash of nettle, and there would be little hope for a diver whose path crossed such a fiery tangle. The untold myriads of little darts which are shot out secrete a poison which is terribly irritating. On the crevice bottoms a sight now and then meets my eyes which brings the "devil-fish" of Victor Hugo's romance vividly to mind,--a misshapen squid making its way snakily over the shells and seaweed. Its large eyes gaze fixedly around and the arms reach alternately forward, the sucking cups lined with their cruel teeth closing over the inequalities of the bottom. The creature may suddenly change its mode of progression and shoot like an arrow, backward and upward. If we watch one in its passage over areas of seaweed and sand, a wonderful adaptation becomes apparent. Its colour changes continually; when near sand it is of a sombre brown hue, then blushes of colour pass over it and the tint changes, corresponding to the seaweed or patches of pink sponge over which it swims. The way in which this is accomplished is very ingenious and loses nothing by examination. Beneath the skin are numerous cells filled with liquid pigment. When at rest these contract until they are almost invisible, appearing as very small specks or dots on the surface of the body. When the animal wishes to change its hue, certain muscles which radiate from these colour cells are shortened, drawing the cells out in all directions until they seem confluent. It is as if the freckles on a person's face should be all joined together, when an ordinary tan would result.