The membranes, when unfurled, as it were, in the rays of the sun, certainly display a variety of delicate colours, that the famous “Judson” himself might envy but could never imitate; but they are only seen to perfection on a calm sea; the least disturbance sends them precipitately into the inmost recesses of their shells, when they instantly sink to the depths, presumably by some specially devised apparatus, that enables them to exhaust the air, since they cannot contract the volume of their habitat. Perhaps the same arrangement permits of their generating some kind of gas when they feel inclined to go to the surface for a sail and a “look round.” Sailors not infrequently confuse them with the so-called “Portuguese man-o’-war,” which is, however, a much lower and headless organization, living by suction, and bearing but slight resemblance to the delicate and many-coloured argonaut. This name will doubtless recall to the reader’s mind that fabulous band of Greek heroes who, under the leadership of Jason—not the aforesaid Judson!—sailed forth to Colchis for the lofty purpose of hoodwinking the sleepless dragon and stealing the ram’s Golden Fleece. At the time when the Exhibition of 1851 gave such an impetus to Science and Art, the “argonaut,” “Portuguese man-o’-war,” “Paper”-, and True-Nautilus were very much confused in the minds of men generally, and of sailors in particular. The shell of the last named was sent from the East, and its nacred interior excited the admiration of all. In lieu of the discs common to the cephalopods, it is provided with calcareous mandibles with which it crushes the numerous small crustaceans, on which it feeds as greedily as the octopus of the Mediterranean and Southern Seas, or the “squid” that plays such havoc in the Channel trawl-nets.