This section is from the book "General Outline Of The Organization Of The Animal Kingdom, And Manual Of Comparative Anatomy", by Thomas Rymer Jones. Also available from Amazon: A General Outline of the Animal Kingdom and Manual of Comparative Anatomy.
* Magazine of Natural History, April 1839, "Observations on the Poulpe of the Argonaut," by Madame Jeannette Power.
(1536). It has been already stated that in all Cephalopods the aperture of the mouth is situated in the centre of the disk formed by the union of the origins of the feet (figs. 282,289.) The oral orifice is generally surrounded by a broad circular lip (fig. 287, a, a), which being not unfrequently fringed or papillose, there is little doubt of its possessing sufficient sensibility to render it of material assistance in manducation.
(1537). The circular lip partially conceals a pair of strong horny mandibles, not unlike the beak of a parrot, but differing in this particular, that in the Cephalopod the upper mandible is the shorter of the two, and is overlapped by the lower jaw. The mandibles detached from the soft part are represented in fig. 287, b, a, b.) There is likewise another important difference between the structure of the beak of the Cuttle-fish and that of the Bird, inasmuch as in the former there is no bony support to the horny jaws, and consequently some other means of sustaining them must be had recourse to. We accordingly find the place of the jaw-bones supplied by a fibrocartilaginous substance (fig. 288, c) that fills the interior of each mandible, and thus gives it sufficient solidity for all required purposes.
Fig. 287. Jaws of the Cuttle-fish. A: a, fleshy orifice of the mouth; b, muscular mass of the mouth; e, mandibles; d, oesophagus. B, horny beak of the Cuttlefish, in outline.
Externally the jaws are imbedded to a considerable depth in a strong mass of muscle (fig. 287, b), composed of several layers of fibres variously disposed, so as to open or close the jaws with a degree of force proportioned to their large size. Here therefore is an apparatus fully adequate to cooperate with the elaborately-constructed prehensile arms whereby these predatory animals seize their prey; and a victim once involved in the tenacious grasp of the tentacula, and dragged to this powerful beak, can have but little chance of resisting means of destruction so formidable as those granted to the Cephalopoda.
(1538). The mandibles of Nautilus Pompilius, instead of being entirely composed of horn (as is invariably the case in those genera that, being provided with tentacula armed with suckers, are thus capable of seizing active and slippery animals), would seem to be rather calculated to break to pieces the testaceous coverings of Mollusca or the armour of the Crustacea. They possess, indeed, the shape of the jaws already described, but are blunt at their extremities (fig. 289, n, o), and thickened by a covering of a dense calcareous substance; so that they appear manifestly adapted to crush hard substances rather than to cut or lacerate the tender bodies of fishes*. The jaws of the Nautilus, like those of the Octopus above described, are imbedded in a powerful mass of muscles (p) whereby they are opened and shut with great force, and are also provided with a distinct muscular apparatus destined to protrude them when in use, and again to retract the whole mass of the mouth deeply into the body when unemployed. The mechanism provided for the protrusion of the mandibles is a strong semicircular muscle (r r), which firmly embraces the base of the oral apparatus, and by its contraction pushes it outwards among the labial tentacula (h, k); while, on the other hand, four retractor muscles, the upper pair of which are represented in the figure referred to (q q), arise from the extremities of the cranial cartilage, and, running forwards to be inserted into the oral mass, are the agents whereby the whole is again withdrawn and thus concealed from view.
(1539). The tongue of the Cephalopoda, as in the Mollusca described in the last two chapters, is an exceedingly important instrument, and from its construction would here seem to be an organ of taste, as well as a necessary assistant in deglutition. In the annexed figure, representing a vertical section of the beak of a very large Onychoteuthis, the shape and disposition of the different parts of the tongue are well seen. The substance of the tongue itself is fleshy (fig. 288, e, i), and its movements are principally performed by the action of its own intrinsic muscular fibres: its surface is divided into several lobes (f, g, h), partially invested with a delicate and papillose membrane; but a large portion of the organ is covered with sharp recurved horny hooklets, so disposed that with their assistance the morsels of food taken into the mouth are seized and dragged backwards, by a kind of peristaltic motion, to the commencement of the oesophagus (I.) The necessity of the provision thus made for enabling the Cephalopods to swallow the substances upon which they feed must be at once apparent; for, seeing that the walls of the mouth are formed entirely by the hard and inflexible horny beak, it is difficult to conceive how deglutition could have been accomplished by any other contrivance.
* Owen, 'Memoir on the Pearly Nautilus.' London, 1832, 4to.
Fig. 288. Section of the oral apparatus of Onychoteuthis: a, circular lip surrounding the mouth; b, d, horny beak; c, cartilaginous substance forming the bulk of the mandible; e, i, muscular tongue; f,g, h, lobes upon its surface; k, salivary glands; I, oesophagus.
(1540). Four salivary glands pour a copious supply of saliva into the oral chamber: of these, two, situated on the sides of the root of the tongue, give off distinct ducts, which terminate near the commencement of the oesophagus; while the other pair, generally larger than the superior, are lodged in the visceral sac on each side of the upper part of the crop. The inferior salivary glands each furnish an excretory canal; but their two ducts soon unite into a single tube which, with the oesophagus, passes through the ring formed by the cranial cartilage, and, piercing the fleshy mass of the mouth, opens in the neighbourhood of the spiny portion of the tongue, so that the secretion furnished at this point serves to moisten the aliment as it is taken up by the lingual hooks to be swallowed. In Onychoteuthis two salivary glands (fig. 288, k) are situated at the root of the tongue; and their ducts are pointed out in the drawing by pins introduced into their orifices.