the spring they delight in swimming up the great rivers, fighting the currents of the Volga, Danube, Po, Rhine, Loire, and Oder, while feeding on herring, mackerel, salmon, and codfish; although they belong to the class of cartilaginous fish, they rate as a delicacy; they’re eaten fresh, dried, marinated, or salt-preserved, and in olden times they were borne in triumph to the table of the Roman epicure Lucullus. But whenever the Nautilus drew near the surface, those denizens of the Mediterranean I could observe most productively belonged to the sixty-third genus of bony fish. These were tuna from the genus Scomber, blue-black on top, silver on the belly armor, their dorsal stripes giving off a golden gleam. They are said to follow ships in search of refreshing shade from the hot tropical sun, and they did just that with the Nautilus, as they had once done with the vessels of the Count de La Pérouse. For long hours they competed in speed with our submersible. I couldn’t stop marveling at these animals so perfectly cut out for racing, their heads small, their bodies sleek, spindle-shaped, and in some cases over three meters long, their pectoral fins gifted with remarkable strength, their caudal fins forked. Like certain flocks of birds, whose speed they equal, these tuna swim in triangle formation, which prompted the ancients to say they’d boned up on geometry and military strategy. And yet they can’t escape the Provençal fishermen, who prize them as highly as did the ancient inhabitants of Turkey and Italy; and these valuable animals, as oblivious as if they were deaf and blind, leap right into the Marseilles tuna nets and perish by the thousands. Just for the record, I’ll mention those Mediterranean fish that Conseil and I barely glimpsed. There were whitish eels of the species Gymnotus fasciatus that passed like elusive wisps of steam, conger eels three to four meters long that were tricked out in green, blue, and yellow, three-foot hake with a liver that makes a dainty morsel, wormfish drifting like thin seaweed, sea robins that poets call lyrefish and seamen pipers and whose snouts have two jagged triangular plates shaped like old Homer’s lyre, swallowfish swimming as fast as the bird they’re named after, redheaded groupers whose dorsal fins are trimmed with filaments, some shad (spotted with black, gray, brown, blue, yellow, and green) that actually respond to tinkling handbells, splendid diamond-shaped turbot that were like aquatic pheasants with yellowish fins stippled in brown and the left topside mostly marbled in brown and yellow, finally schools of wonderful red mullet, real oceanic birds of paradise that ancient Romans bought for as much as 10,000 sesterces apiece, and which they killed at the table, so they could heartlessly watch it change color from cinnabar red when alive to pallid white when dead.