The octopus

by Henry Lee

Fig. 3. Mandibles of Octopus.
(O. vulgaris).

So says the novelist. The naturalist knows that it has a complete and perfect muscular organisation; muscles which serve to retract and depress the funnel, bundles of strong muscles passing along the arms and branching to each of the suckers, within which other fasciculi of muscular fibres converge from the circumference to the centre, and by their contraction produce the vacuum which gives to the animal its power of adhesion,—muscles all over its body, and a mass of muscles of such strength to work the powerful beak, that if anyone, believing the fictionist, were to place his finger in the small circular orifice in the centre of the base of the arms, he would possibly learn practically that it is not “an empty flask with nothing in it.” A sharp nip might perhaps teach him that it has not only muscles, but a mouth and head also. For just within the oral cavity lie, retracted and hidden, but ready for use when wanted, a pair of horny mandibles which bite vertically, like the beak of a parrot or turtle, except that the lower mandible is the longest and overlaps the upper, and are so hard that they can not only tear the softer animals the octopus is able to catch, but also break up the shells of lobsters, crabs, and mussels, which are its usual food. The head contains a brain, from which arises the system of nerves; and the animal has a sense of smell, and organs of hearing and taste, besides those which are apparent on its exterior, namely, of sight and touch. Instead of having “no blood,” it is furnished with a complete circulatory apparatus consisting of one systemic and two branchial hearts, arteries which distribute the blood through all parts of the body, and a system of veins or canals by which it returns towards the gills, of which breathing organs the animal has two—one on each side. By the alternate expansion and contraction of the bladder-like mantle-sac—an action resembling that of a pair of bellows—the water is pumped into contact with these gills, which convey to the blood the oxygen contained in it; and when its life-giving, purifying gas has been extracted from it, it is expelled by the muscular, valved funnel, or syphon tube, which has also another function, to be presently described. Far from being “a skin with nothing inside it,” from the beak and mouth (within which is a tongue like a rasp, having recurved spines or teeth) is continued the alimentary canal, œsophagus, crop, gizzard, stomach, and intestines; and within this so-called “empty pouch” are also the liver, and the organs of reproduction and respiration. The “tentacles,” or arms, cannot be “turned inside out like the fingers of a glove.” On making a section across one of them, it will be seen that it is composed of close muscles, the fibres of some of which run longitudinally, and others transversely. The arm, therefore, is more like the strong flexible lash of a stout hunting whip than the finger of a glove, and is solid, except that it has a perforation along the centre of its axis for the lodgment of its nerve and artery.

Fig. 4. Tongue of the Octopus
(O. vulgaris).
Magnified 12 diameters.

The author accurately describes the action and movement of the octopus, and its utilisation of its eight arms when crawling at the bottom, or on ledges of rocks. The globose body is then turned upward, the mouth downward, and the arms sprawl along, and by grappling some fresh object drag the body after them. But he is mistaken concerning its mode of progression when swimming. After stating that in swimming, it, so to speak, sheaths and draws close together its arms, which is quite true, he continues:—

“Figure to yourself a sleeve sewn up with a fist in it. This fist, which is the head, pushes through the water, and advances with an undulating movement.”

That which M. Hugo supposes to be the head is the body of the animal. He appears to have received this impression from Pliny,[13] who writes:—“The head, which is directed obliquely when they swim, is, in the living animal, hard and distended like a balloon.” The cuttle-fishes, and the octopus amongst them, propel themselves rapidly backward, when swimming, by the forcible expulsion from the funnel, in sudden and frequent jets, of the water drawn in at the branchial, or gill openings. Thus the organs of respiration become those of locomotion as well, and the funnel has also another function, being the orifice from which the excreta are expelled. It has been asserted by various writers—and the statement has been repeated by many able naturalists—that the octopus swims by vigorous flappings of the expanded membrane which extends from the sheath of the mouth along the arms, and connects the bases of the latter like the web of a duck’s foot. It is true that this sometimes, though very rarely, takes place, but its proper and usual mode of progression is with the body in advance, the arms closely packed together, and directed backward horizontally in its wake, whilst the jets of water, pumped out at frequent intervals from the funnel, propel it at a considerable speed. I have had opportunities of watching the habits of at least a hundred individuals of this species, yet have only three or four times seen them progress, when swimming, by powerful contraction of the web-like membrane, and then but for a very short distance. Still less frequently does the octopus reverse its usual course; but I have twice seen one swim with its arms extended in advance of it, by bending the syphon tube beneath its body so as to present the orifice in a direction exactly contrary to its normal position.

Fig. 5. The Octopus swimming.