There are numerous kinds of polypi. The land polypus is larger than that of the sea; they all of them use their arms as feet and hands. The polypus has a sort of passage in the back, by which it lets in and discharges the water, and which it shifts from side to side, sometimes carrying it on the right, and sometimes on the left. It swims obliquely, with the head on one side, which is of surprising hardness while the animal is alive, being puffed out with air. In addition to this, they have cavities dispersed throughout the claws, by means of which, through suction, they can adhere to objects, with the head upwards, so tightly, that they cannot be torn away. They cannot attach themselves, however, to the bottom of the sea, and their retentive powers are weaker in the larger ones. These are the only soft fish that come on dry land, and then only where the surface is rugged: a smooth surface they will not come near. They feed upon the flesh of shellfish, the shells of which they can easily break in the embrace of their arms: their retreat may be easily detected by the pieces of shell which lie before it. Although, in other respects, this is looked upon as a remarkably stupid kind of animal, so much so, that it will swim towards the hand of a man, in its own domestic matters it manifests considerable intelligence. It carries its prey to its home, and after eating all the flesh, throws out the debris, and then pursues such small fish as may chance to swim towards them. It also changes its color, according to the aspect of the place where it is, and more especially when it is alarmed. The notion is entirely unfounded that it gnaws its own arms; this mischance befalls it from the congers; but it is perfectly true that its arms shoot forth again, like the tail in the colotus and the lizard. Among the most remarkable curiosities among all the inhabitants of the sea is the animal which has the name of nautilus, or, as some people call it, the pompilos. Lying with the head upwards, it rises to the surface of the water, raising itself little by little, while, by means of a certain conduit in its body, it discharges all the water, and this being got rid of like so much bilge-water as it were, it finds no difficulty in sailing along the surface. Then, extending backwards its two front arms, it stretches out between them a membrane of marvellous thinness, which acts as a sail spread out to the wind, while with the rest of its arms it paddles along below, steering itself with its tail in the middle, which acts as a rudder. Thus does it make its way along the deep, mimicking the appearance of a light Liburnian bark; while, if anything chances to cause it alarm, in an instant it draws in the water, and sinks out of sight.