ON the left of the cuttle-arm is the common Limpet, shown as it appears when adhering to the rocks. Every visitor to the seaside who has attempted to remove the Limpets may remember how difficult it is to stir them when they have once taken their hold. If they can be taken by surprise, they come away with a touch; but if they become alarmed, they press the edges of the foot firmly against the rock, withdraw the centre, and thus create the necessary vacuum. * * * * * NEXT follows a Star-fish, shown as it appears when in the act of walking, or rather, gliding along. This movement is obtained by the use of a vast number of long suckers, exactly resembling the pneumatic peg, except that they are flexible, and can be curved in any direction. It is really beautiful to see the manner in which a Star-fish will glide along by means of its suckers, its arms accommodating themselves to the irregularities of the ground, and its multitudinous suckers protruded and withdrawn with a never-ceasing movement. And, as the Star-fish is apparently blind, not having any organs which can even be conjectured to serve the purpose of vision, this mode of directing its course is not easily understood. Yet, blind though it may be, it guides itself with as much accuracy as if it possessed eyes, and evidently does so with a definite purpose, using its suckers with as much decision as a centipede uses its legs. These suckers can be seen very well by placing a Star-fish in a shallow vessel of sea-water, and laying it on its back. The suckers immediately protrude themselves from their little apertures, and the arms slowly curve themselves so as to find something to which the suckers can adhere. Presently one or two of the suckers will take hold of the bottom of the vessel. Others soon follow, and in a very short time the Star-fish is on its legs, if we may so call them, and is quietly gliding on its way. * * * * * BELOW the Star-fish is seen the celebrated Sucking-fish (_Echeneis remora_) about which so many strange tales have been told, and which is possessed of a structure remarkable enough to need no aid from invention. The dorsal fin of this fish is modified in a most singular manner. The spines of which it is so largely composed are metamorphosed into flattened plates very much resembling the laths of a Venetian blind, and form an instrument of suction identical in principle, though not in form, with those which have already been described. When the sucker is pressed against a smooth surface, a vacuum is formed, and the fish in consequence adheres firmly to the object.