The divers, however, have terrible combats with the dog-fish, which attack with avidity the groin, the heels, and all the whiter parts of the body. The only means of ensuring safety, is to go boldly to meet them, and so, by taking the initiative, strike them with alarm: for, in fact, this animal is just as frightened at man, as man is at it; and they are on quite an equal footing when beneath the water. But the moment the diver has reached the surface, the danger is much more imminent; for he loses the power of boldly meeting his adversary while he is endeavouring to make his way out of the water, and his only chance of safety is in his companions, who draw him along by a cord that is fastened under his shoulders. While he is engaging with the enemy, he keeps pulling this cord with his left hand, according as there may be any sign of immediate peril, while with the right he wields the stiletto, which he is using in his defence. At first they draw him along at a moderate pace, but as soon as ever they have got him close to the ship, if they do not whip him out in an instant, with the greatest possible celerity, they see him snapped asunder; and many a time, too, the diver, even when already drawn out, is dragged from their hands, through neglecting to aid the efforts of those who are assisting him, by rolling up his body in the shape of a ball. The others, it is true, are in the meantime brandishing their pronged fish-spears; but the monster has the craftiness to place himself beneath the ship, and so wage the warfare in safety. Consequently, every possible care is taken by the divers to look out[2751] for the approach of this enemy. (47.) It is the surest sign of safety to see flat-fish, which never frequent the spots where these noxious monsters are found: and it is for this reason that the divers[2752] call them sacred. CHAP. 71.—FISHES WHICH ARE ENCLOSED IN A STONY SHELL—SEA ANIMALS WHICH HAVE NO SENSATION—-OTHER ANIMALS WHICH LIVE IN THE MUD. Those animals, however, it must be admitted, which lie enclosed in a stony shell, have no sensation whatever—such as the oyster,[2753] for instance. Many, again, have the same nature as vegetables; such as the holothuria,[2754] the pulmones,[2755] and the sea-stars.[2756] Indeed, I may say that there is no land production which has not its like in the sea;[2757] no, not even those insects which frequent our public-houses[2758] in summer, and are so troublesome with their nimble leaps, nor yet those which more especially make the human hair their place of refuge; for these are often drawn up in a mass[2759] collected around the bait. This, too, is supposed to be the reason why the sleep of fish is sometimes so troubled in the night. Upon some fish, indeed, these animals breed[2760] as parasites: among these, we find the fish known as the chalcis.[2761] CHAP. 72. (48.)—VENOMOUS SEA-ANIMALS.