Fig. 123.—Giant octopus, radial spread twenty-two feet.
The octopus swims when forced to do so, using a weblike membrane which is seen to connect the base of the eight arms or by forcing water from its siphon. These arms, when extended, give the octopus a faint resemblance to an umbrella without a handle, and with very long supports. The octopus preys upon very small animals, particularly crabs. I have lain among the bowlders on the shores of the Californian islands and watched the octopus hunting. They selected the flood tide and crept near the shore, moving along slowly, on the watch for a species of Grapsus very common here, a land crab which occasionally enters the water. The crabs crept down to the water's edge, and often entered, and in this moment of incaution were pounced upon by the disagreeable creature so well named the devilfish. Sometimes they were caught at the very edge; a long, livid tentacle would come shooting out of the water like a flame and seize the victim. Despite its struggles, it was soon hauled in, the octopus immediately covering it with its umbrellalike bag, doubtless bringing its nippers into play. I have seen an octopus dash out of water two or three feet and scramble up the dry rocks with remarkable speed after an escaping crab. At these times the octopus can be caught by seizing it quickly, but some experience is required before one can grasp a large octopus and retain the hold, so disagreeable is the sensation of the snakelike tentacles winding about hand and arm. The very appearance of the octopus is like a horrible dream, and so intensely repulsive is the animal that in an actual test not one person in fifty who passed a tank containing an octopus with arms a foot long and a hideous striped body, could be induced to touch the animal, though assured that it was absolutely harmless and would merely squeeze the hand.
While the devilfish is the type of all that is hideous and repulsive in nature, it has a near relative, the paper nautilus, which is a very dainty and beautiful creature. It appears to be an octopus which lives in a shell. The argonaut, as it is called, has eight short arms, the upper pair being largely developed at their tips, forming fanlike or saillike organs. It was formerly believed that these were really sails, held aloft to catch the breeze to blow the fairy argonaut along. So fixed in the public mind was this erroneous belief that illustrations in various works otherwise correct, display the argonaut in this incorrect position. The animal is the female, which, to protect and carry its eggs, is provided with a dainty shell which it secretes, but is not attached to, and would lose were it not for the two large-ended tentacles with which it grasps the beak of the shell (Fig. 124). These arms also bear the shell-making and repairing glands. The argonaut can crawl upon the rocks at the bottom, swim through the water, forced along by its siphon stream, or float calmly at the surface. About nine species are known; generally in some tropical waters. Every year a few are found stranded upon Santa Catalina Island, California.
Fig. 124.—Argonaut in natural position, arms holding the shell.
Figs. 125, 126.—Sections of an ammonite.
In many of the fossil deposits are found gigantic shells resembling the wheels of a cart, and enormously heavy. These are ammonites (Figs. 125, 126), and ancestors of the nautilus (Fig. 127), another member of this wonderful family of animals, with feet attached to their heads. It has a shell of radiant pearl, divided, like the little Spirula, by pearly septa or partitions, into rooms or chambers (C) all of which surround a small tube (s) called the siphuncle. This contains a long, fleshy pedicel, hence the nautilus is attached to its shell and can not leave it. The shell chambers are filled with gas, and the animal has the power to change its specific gravity, to float or rise. The nautilus forces itself along by a current from its siphon, and in a general way resembles others of the group. It has no ink bag, and its eye is not the striking object seen in the other forms. It is merely an elevation bearing a minute hole which leads into the globe of the eye, which during the life of the nautilus is filled with water. According to Doctor Hensen, in place of a refracting lens and a cornea, the animal has an arrangement for forming an image on the principle of a pin-hole camera. We might imagine the nautilus easy to capture; but it is very timid and rarely caught. Instead of eight or ten arms the nautilus has ninety-four. The shell is a beautiful object when cleaned and polished, being a vase of pearl of a chaste and elegant design, often copied, and in great demand by native artisans who carve and engrave it, and mount it in gold and silver. The nautilus, aside from its beauty, is a most interesting animal, being the last or almost the last of its race of fifteen hundred species, which have lived in former periods of the earth. Only two are still alive, and these in all probability are doomed to extinction.