Cephalopoda

“ For the plaited fibres encircle an object in a slackened condition, and when they are put on the stretch they grasp and cling tightly to whatever it may be that is in contact with their inner surface. Since, then, the Cephalopoda have no other instruments with which to convey anything to themselves from without, than either twining tentacles, as in some species, or proboscises as in others, they are provided with these to serve as hands for offence and defence and other necessary uses. ”

“ Hermaphroditism is unknown in Cephalopoda; male and female individuals always being differentiated. The genital aperture and duct is sometimes single, when it is the left; sometimes the typical pair is developed right and left of the anus. The males of nearly all Cephalopoda have been shown to be characterized by a peculiar modification of the arm-like processes or lobes of the fore-foot, connected with the copulative function. ”

“ They are very widely distributed; the garden snail is a familiar instance of a terrestrial Gasteropod.
c. Cephalopoda (feet around the head) .—The mollusca of « 379 » this order have powerful muscular arms, or tentacula, which surround the head, or upper part of the body; some genera have no shell, but possess an internal skeleton, as the recent Sepiadæ and the fossil Belemnitidæ. Most of the testaceous Cephalopoda have a discoidal, univalve shell, which is divided internally by septa or partitions; as the Nautilus. ”

“ The mouth of the Cephalopoda is singularly formidable,—it is armed with a pair of powerful horny jaws, having within them a fleshy tongue, the whole apparatus being not unlike the bill and mouth of a parrot, forming, as may readily be imagined, most destructive instruments amongst the young crustaceous and testaceous animals on which they prey at the bottom of the ocean, where by day they establish themselves, but roaming gregariously after nightfall. ”

“ The Cephalopoda, with arms covered by suckers surrounding the head of the animal, have generally symmetrical convolute shells. The Cephalopoda are divided into C. polythalamia, which have the internal cavity divided into chambers by septa, as in the Nautilus; and the C. Monothalamia, which are not so divided, as the Argonauta. The order Heteropoda contains the genus Carinaria alone. ”

“ FOSSIL CEPHALOPODA
The molluscous animals named Cephalopoda (from their organs of prehension being arranged around the upper part « 448 » of the body) are the most ancient, numerous, and interesting of this division of animated nature; and their fossil remains comprehend the most varied and striking forms of extinct beings that occur in the sedimentary strata, from the earliest Secondary to the latest Tertiary formations. The living species are but a feeble representation of the countless myriads which swarmed in the ancient seas ”

“ The Hectocotylus Arm.—Perhaps the most remarkable feature in the sexual relations of all the Mollusca is the so-called hectocotylus of the Cephalopoda. In the great majority of the male Cephalopoda, one of the ‘arms,’ which is modified for the purpose in various ways and to a greater or less extent, becomes charged with spermatophores, and sometimes, during union, becomes detached and remains within the mantle of the female, preserving for some considerable time its power of movement. ”

“ Cephalopoda.—The special characteristic of the reproductive organs in female Cephalopoda is the development of various glands, some of considerable size, in connexion with the ovary and oviduct. Sepia, Loligo, and Sepiola are furnished with two [137] large nidamental glands, which open into the mantle cavity independently of the oviduct. Their purpose is to produce a viscid mucus, which envelops the ova at the moment of their emission and eventually hardens into the egg-capsules. ”

“ In the carabi and their like the females produce their eggs so as to keep them attached to themselves, which is why the side-flaps of the females are larger than those of the males, to protect the eggs; the cephalopoda lay them away from themselves. The males of the cephalopoda sprinkle their milt over the females, as the male fish do over the eggs, and it becomes a sticky and glutinous mass, but in the carabi and their like nothing of the sort has been seen or can be naturally expected, for the egg is under the female and is hard-shelled. ”

“ Certain Cephalopoda, however, are characterised by one extraordinary sexual character, namely that the male element collects within one of the arms or tentacles, which is then cast off, and clinging by its sucking-discs to the female, lives for a time an independent life. ”

“ Bellerophon.—It has been already stated, that the animals of one genus of the existing dibranchiate Cephalopoda are protected by a thin, flexible, symmetrical, keeled shell, convoluted on a vertical plane, and having but one chamber—this is the Argonaut, or Paper Nautilus, an inhabitant of the Mediterranean. This animal belongs to the Octopoda, or those which have eight arms; and in one pair of these processes the extremities expand into broad and thin membranes, by which the delicate, elastic, calcareous envelopement, or shell, « 466 » is secreted. ”

“ Cephalopoda, sef-al-op′od-a, n.pl. the highest class of molluscs, usually large animals, exclusively marine, with well-developed head region, but having the ventral surface grown round the mouth and split up into arms bearing suckers—more commonly cuttlefish.—adj. Ceph′alopod. [Gr. kephalē, the head, pous, podos, the foot.]
Cephaloptera, sef-a-lop′tėr-a, n. a name formerly used for a genus of rays. [Gr. kephalē, the head, ptera, wings.] ”

“ Cephalopoda with four branchiae and four kidneys; animal inhabiting the last chamber of an external multilocular shell; [392] funnel consisting of two separate lobes; tentacles numerous, without suckers or hooks; no ink-sac.
The shell consists of two layers, the outer being porcellanous, and the inner, as well as the walls of the chambers or septa, nacreous. The septa vary greatly in shape. In most of the Nautiloidea they are regularly curved, as in Nautilus, or straight, as in Orthoceras, but in the Ammonoidea they are often exceedingly complex. ”

“ The peculiarities of the Gastropoda are all due to the torsion of the shell and body. The Cephalopoda can be derived without much difficulty from the schematic Mollusc, if we assume that some metameric repetition of organs has occurred, as explained above in reference to the coelom. The foot has been developed into long processes which have extended in a circle round the mouth; all the ganglia, including the visceral, have been concentrated around the oesophagus. ”

“ Whilst studying the history of the development of Cephalopoda he found that they had embryonic layers similar to those of Vertebrates; this was the first time that the fact was established. It was extremely important, for it constituted a concrete and indisputable proof of the existence of a genetic connection between inferior and superior animals. Metchnikoff chose this subject for his thesis, and, having completed his researches, he returned to Russia in 1867. ”

“ Whether the closed primitive shell-sac of the slugs (and with it the transient embryonic shell-gland of all other Mollusca) is precisely the same thing as the closed sac in which the calcareous pen or shell of the Cephalopod Sepia and its allies is formed, is a further question which we shall consider when dealing with the Cephalopoda. It is important here to note that Clausilia furnishes us with an exceptional instance of the continuity of the shell or secreted product of the primitive shell-sac with the adult shell. ”

“ A genus of Cephalopoda. The shell is called paper nautilus or paper sailor.
Note: The animal has much resemblance to an Octopus. It has eight arms, two of which are expanded at the end and clasp the shell, but are never elevated in the air for sails as was formerly supposed. The creature swims beneath the surface by means of a jet of water, like other cephalopods. The male has no shell, and is much smaller than the female. ”

“ This species of Cephalopoda is thus armed with those kind of teeth at the termination of the tentacles in order to secure the agile, slippery, and mucous-clad fishes on which it preys; and there is an instance recorded in the works of a celebrated author on Excursions in the Mediterranean, by which we perceive that these terrible creatures sometimes prey upon men. ”

“ All Cephalopoda. Gasteropoda Amphineura (except Neomeniidae) . Gasteropoda Prosobranchiata (except Valvata and some species of Marsenia) . Scaphopoda. Many Pelecypoda.
[134]
2. The sexes are united in
Gasteropoda Opisthobranchiata. Gasteropoda Pulmonata. Certain Pelecypoda. [254]
In the dioecious Mollusca, sexual union is the rule, but is by no means universal. In some instances,—e.g. Vermetus, Magilus, Patella, Haliotis, Crepidula, Chiton, the Scaphopoda—the form and habits of the animal do not admit of it; in others (many Trochus) a male copulative organ is wanting. ”

“ I have never seen these “sea-mops” attached to anything, and the pelagic [77] habits of the calamaries render it probable that they are left floating on the surface of the sea.
A remarkable organ with which some of the cephalopoda are provided is a sac, popularly called the “ink-bag,” in which is stored a deep black secretion, which they are able to employ at will as a protection from rapacious enemies. ”

“ Cephalopoda with two symmetrical branchiae, funnel completely tubular, mouth surrounded by 8 or 10 arms furnished with suckers or hooks, ink-sac and fins usually present, eyes with a lens; shell internal or absent.
The Dibranchiata are not known from Palaeozoic strata, and first appear (Belemnites, Belemnoteuthis) in the Trias. Whether they are to be regarded as derived from some form of Tetrabranchiata, e.g. Orthoceras, or as possessing an independent origin from some common stock, cannot at present be decided. They attain their highest development at the present time. ”

“ How far the term Cephalopoda-bed for the fossiliferous portion of this section may be justified will at once be seen from the following list of the family of fossils after which it has been named, the whole of which have been found at Bradford Abbas, or the equivalent bed near Sherborne. ”

“ In some genera the shell is a simple cavity, spirally disposed, as in the Snail; in others, it is conical, consisting of one or many pieces, as in the Limpet and Chiton. In the Cephalopoda it is internally divided into cells, or chambers, as, for example, in the Nautilus.
The Encephalous Mollusca are subdivided into the following classes; viz.—
a. Pteropoda (wing-feet) .—In these the organs of progression are two wing-like muscular expansions, proceeding from the sides of the neck, by which they can swim and float in the open sea: all the species are of small size. ”

“ Part 15 The cephalopoda entwine together at the mouth, pushing against one another and enfolding their arms. This attitude is necessary, because Nature has bent backwards the end of the intestine and brought it round near the mouth, as has been said before in the treatise on the parts of animals. The female has a part corresponding to the uterus, plainly to be seen in each of these animals, for it contains an egg which is at first indivisible to the eye but afterwards splits up into many; each of these eggs is imperfect when deposited, as with the oviparous fishes. ”

“ The third and highest class of Mollusks has been called Cephalopoda, in reference again to a special feature of their structure. They have long arms or feelers around the head, serving as organs of locomotion, by which they propel themselves through the water with a velocity that is quite extraordinary, when compared with the sluggishness of the other Mollusks. In these animals the head is distinctly marked,—being separated, by a contraction or depression behind it, from the rest of the body. ”

“ He had just remarked to a companion that it must be a Trigonia, and his companion had laughed at the idea, reminding him that all known Trigonia were fossil, when the shell in question baffled their efforts to discover its generic position by suddenly leaping into the sea, and it was three months before Mr. Stutchbury succeeded in obtaining another.
Some genera possess more than merely passive means of defence. Many Cephalopoda emit a cloud of inky fluid, which is of a somewhat viscous nature, and perhaps, besides being a means of covering retreat, serves to entangle or impede the pursuer. ”

“ In the Pteropoda they are very varied; in the snail-like Heteropoda they are mostly pectiniform or tuft-shaped; in the Sepiæ or Cephalopoda phylliform or fin-shaped.
The external character ccommon to the whole class is the cylindrical body, unto which may be aptly conjoined the possession of special organs of motion; whether such organs be prehensile in function, media of support, or veritable instruments of progression.
The snail-like Pteropoda, Heteropoda, and Cephalopoda, have a head, but this is wanting in the mussel-like Salpæ, Ascidiæ, Cirripedia, and Brachiopoda. ”

“ As to the Mollusca, which afford the most unbroken series of geological medals, the highest of that class, the Cephalopoda, abounded in older Silurian times, comprising several hundred species of chambered univalves. Had there been strong prepossessions against the progressive theory, it would probably have been argued that when these cephalopods abounded, and the siphonated gasteropods were absent, a higher order of zoophagous mollusca discharged the functions afterwards performed by an inferior order in the Secondary, Tertiary, and Post-Tertiary seas. ”