Fig. 325. Pinnoctopus corolliformis (D'Orbigny). Fig. 326. Cirrotheutis Mittleri (Eschricht).
It is a singular fact that the creature notably changes colour under any exertion, so that the animal at rest and in motion are two different beings. When walking under water the tube is directed behind, its arms are spread out, the head is raised, and the body slightly inclined forward; its mantle is then of a pearly grey, and the spots take the tint of wine lees. When at rest the shades disappear.
The Pinnoctopus (Fig. 325), another genera of this family, have the body oblong, with lateral expansions, as represented in the accompanying figure.
In Cirrotheutis the arms are completely united in their whole extent by a thin membrane furnished with cirri, which alternate with certain suckers arranged in one row. Only one species of this genera is known as an inhabitant of northern seas, which is represented in Fig. 326.
The sixth family, Argonautidæ, contains only Argonauta.
The Argonauta, or Paper-nautilus. Floating gracefully on the surface of the sea, trimming its tiny sail to the breeze, just sufficient to ruffle the surface of the waves, behold the exquisite living shallop. The elegant little bark which thus plays with the current is no work of human hands, but a child of Nature: it is the Argonaut, whose tribes, decked in a thousand brilliant shades of colour, are wanderers of the night in innumerable swarms on the ocean's surface.
The marine shell which Linnæus called the Argonaut enjoyed great renown among the ancient Greeks and Romans. It was the subject of graceful legends; it had inspired great poets; it occupied the attention of Aristotle, who called it the Nautilus and Nauticos, and of Pliny, who called it Pompylius. Few animals, indeed, have been so celebrated, so anciently known. The Greek and Roman poets saw in it an elegant model of the ship which the skill and audacity of the man constructed who first braved the fury of the waves; in the words of the poet, "armour of triple oak and triple brass covered the heart of him who first confided himself in a frail bark to the relentless waves:"
"Illi robur et æs triplex
Circa pectus erat, qui fragilem truci