1902 Encyclopedia > Cuttlefish


CUTTLE-FISH. The cuttle-fishes are the " Dinten-fische " of the Germans and the " Seiches " of the French, and they constitute the most highly organized members of the class of the Cephalopoda. The great class of animals now known to naturalists under the name of Cephalopoda was fully recognized by Aristotle as a well-marked division of animals, under the name of Malahia. Even at the early period at which he lived (384-322 B.C.), this acute observer recognized at least nine species of Cephalopods—including the Argonaut and the Pearly Nautilus ; and he also recorded the singular phenomena of reproduction, phenomena which were not scientifically confirmed and fully established till the year 1850, by the researches of Verany and H. Miiller. The other classical writers (e.g., Pliny) added nothing to Aristotle's observations. The next contribution of importance to the elucidation of the history of the Cephalopods was made by Rumph (1705) in his Rariteit-Kamer, describing the curiosities of Amboyna. The old Dutch naturalist gives in this work an account of the structure and habits of the Pearly Nautilus, which, though long discredited, is now known to be in the main correct, and which is accompanied by a fair figure of the soft parts of the animal. The relations of various fossil forms (such as Ammonites) to the Cepludopoda were first recognized in the earlier portion of the 18th century; and Breynius (1732) detected the true affinities of the Belemnite. Lin-naeus gives a summary of the knowledge of his time as to these animals, but separates the naked from the testaceous forms. The first establishment of the class Cephalopoda, however, as a definite natural group, is due to the genius of Cuvier (1798), to which we also owe this now universally accepted name. Cuvier's researches on this subject are contained in his Leçons d'Anal. Comparée (1799—1805), and were subsequently republished in an enlarged form in his Mémoire sur les Céplialopodes et leur Anatomie (1817). Since the appearance of this classical work, our knowledge of the natural history of the Cephalopods has been immensely increased by the researches of Delle Chiaje, Meckel, Von Siebold, De Blaiuville, Owen, Van Beneden, Peters, Van der Hoeven, Gray, Huxley, A. Hancock, Milne-Edwards, Kolliker, H. Miiller, Leuckart, Steenstrup, Keferstein, Férussac, D'Orbigny, &c. ; and, as regards fossil forms, by Buckland, D'Orbigny, Quenstedt, Oppel, Owen, Huxley, Phillips, Von Buck, Munster, Barrande, Von Hauer, Von Meyer, Hyatt, Hall, Meek, and many other palaeontologists. One of the principal steps in advance upon the knowledge possessed by Cuvier was taken in 1835, when Dujardin showed that the Foraminifera, previously included by Plancus, Soldani, Fichtel, Linnaeus, and others in the Cephalopoda, were in reality of a much lower grade of organization, and were not systematically related to the true Mollusca.
The class Cephalopoda comprises Mollusca in which there is a distinct head, and a toothed " tongue " or " odontophore," whilst the hinder extremity of the body is inclosed in a muscular mantle-sac, which may or may not secrete an external shell. The mouth is placed near the centre of the " foot," and the margins of this structure are split up into 8 (Octopod Cuttle-fishes), 10 (Decapod Cuttle-fishes), or numerous (Pearly Nautilus) muscular pro-cesses, or " arms." The lateral margins of the foot (" epipodia ") constitute, by apposition or fusion, a muscular tube (the " funnel ") through which the effete water of respiration is expelled.

The class Cephalopoda is divided into the two great orders of the Tetrabranchiata and the Dibranchiata.

The Tetrabranchiate order comprises only the living species, or varieties, of the Pearly Nautilus (Nautilus pom-pilius), along with a vast number of fossil forms, and is characterized by the possession of an external, many-cham-bered, siphunculate shell ; by the presence of numerous arms, which are devoid of suckers ; by the possession of four branchiae ; by the absence of an ink-sac ; and by the fact that the " funnel " does not form a complete tube.
The order Dibranchiata, with which alone we are con-cerned here, comprises the true cuttle-fishes, in which there are either 8 or 10 arms, provided with suctorial discs ; there is no external shell, or, in the single case in which such a structure is present (the female Argonaut), it is single-chambered, and is not secreted by the mantle ; there are only two branchiae ; an ink-sac is present ; and the " funnel " forms a complete tube.

FIG. 1.—A. Lolc'go vulgaris; a,arms; t, tentacles. B, pen of the same reduced In size ; C, side-view of one of the suckers, showing the horny hooks surrounding the margin; D, view of the head from in front, showing the arms (a), the tentacles (0, the mouth (m), and the funnel (/).

The body of a cuttle-fish is symmetrical, and is divisible into an anterior cephalic portion (prosoma) and a posterior abdominal portion (metasoma). The former of these is developed into a distinct head, furnished on its sides with large and prominent eyes, and having the mouth in the centre of its anterior surface, surrounded by eight or ten " arms." The latter incloses the various viscera, and is en-veloped in an integumentary sac, which corresponds to the " mantle " ("pallium ") of the Gasteropods and Lamelli-branchs. The mantle-sac is formed by the coalescence of the two pallia] lobes along the ventral surface of the body, and it is attached directly to the metasoma along the dorsal surface, whilst it is free inferiorly, and incloses a space (the " pallial chamber ") which contains the gills, and into which the intestine and the ducts of the generative organs and ink-sac open.
The integument of the cuttle-fishes consists of several layers, of which the most important is one which corre-sponds to the lowermost layer of the epidermis, and which is distinguished by the possession of numerous large-sized cells filled with pigment-granules (" chromatophores "). These pigment-cells are capable of expanding and contract-ing in their dimensions, and of altering in shape, and below them are other flattened nucleated refracting cells, which co-operate with the former in the production of the mar-vellous play of changing colours which the cuttle-fishes exhibit under excitement or irritation.

The muscular system of the cuttle-fishes is well developed, the fibres being long and spindle-shaped, and only in certain situations (e.g., in the branchial hearts) transversely striated. The mantle is in all highly muscular, but the most important muscular organs are the " arms," the "tentacles," the " fins," and the "funnel." The "arms" are long processes produced by the splitting up of the antero-lateral margins of the foot, and the mouth is placed in the centre of their bases. In all the cuttle-fishes eight arms are present, but the so-called Decapods have in addition the " tentacles," whilst the Octopods are devoid of these supplementary processes. The arms are longer or shorter-pointed processes, formed principally of longitudinal muscles, with well-marked radial bundles of fibres, and having a nerve and an artery occupying the axis of each. They are placed symmetrically round the mouth, forming a dorsal pair, a ventral pair, and two lateral pairs on each side ; and their bases are connected by an inter-brachial membrane, which in some instances (Girrhoteuthis) extends nearly to their points. On the inner surface of the arms are placed the suckers (" acetabula "), in the form of muscular cup-like discs, which may be sessile or stalked, and which are arranged generally in one or two, or rarely in four, rows. Each acetabulum consists of a cup, the margin of which is formed by a muscular ring, sometimes strengthened by a horny girdle (which may be smooth or may be pro-duced into teeth), whilst its centre is occupied by an elevated papilla composed mainly of radial muscular fibres. When the sucker is applied to any object, the contraction of the muscular fibres causes the depression of this muscular papilla, and creates a partial vacuum, thus enabling each sucker to act as a most efficient organ of prehension—their action being sometimes supplemented (as in Onychoteuthis) by the conversion of the central papilla into a horny hook. The so-called "tentacles" of the Decapod Cuttle-fishes resemble the true arms in structure, but are very much longer, and only carry suckers on their swollen and club-shaped extremities. They are placed on the ventral surface of the animal, between the third and fourth pairs of arms (counting from the middle line of the back); they may or may not be retractile into pouches placed below the eyes ; and they may attain a length many times greater than that of the body itself. The tentacles are organs of prehension, and the arms are, in addition, employed by the animal in locomotion, enabling it to walk head downwards, at the bottom of the sea, or, when webbed, to swim through the water in a retrograde manner. One of the arms of the male cuttle-fishes, as will subsequently appear, is also more or less largely engaged in the work of reproduction, and may for this reason be greatly modified.

The sides of the body in all the Decapod Cuttle-fishes, and in a few of the Octopods (e.g., Pinnoctopus), are more or less extensively produced into muscular expansions or fins, supported internally by a cartilaginous basis. These fins are employed by the animal in swimming head fore-most, and they may extend along the whole length of the metasoma (as in Sepia), or they may be confined to the hinder end of the body (as in Loligo, Gheiroteuthis, Onychoteuthis, ifcc.)

The " funnel " of the cuttle-fishes is a muscular tube, formed by the union of the " epipodia," and placed on the lower surface of the body, with its anterior extremity pro-jecting beyond the mantle, whilst it opens posteriorly into the paliial chamber. It serves for the extrusion (by means of the outgoing respiratory currents) of the undigested portions of the food and of the excretions of the kidneys and ink-sac ; whilst the water which has passed over the gills is expelled through it in a succession of jets, subserv-ing in this way the secondary purpose of driving the animal backwards through the water.

As regards the digestive system, the mouth is placed centrally, surrounded by the bases of the arms ; and it conducts into a powerfully muscular buccal cavity, in which are contained two strong horny jaws and a well-developed " tongue." Thejaws, or " mandibles," are purely horny (not partially calcareous, as in the Pearly Nautilus), and they have very much the form of a parrot's beak, working vertically, the lower one projecting most and receiving the upper mandible within it in the act of biting. The so-called " tongue " is a muscular organ, part of which is covered with numerous papillfe, and is apparently an organ of taste; whilst another portion is developed into a lingua] ribbon essentially similar in its structure to the " odontophore " of the Gasteropoda. The oesophagus— sometimes simple (Decapoda), sometimes provided with proventricular or crop-like dilatations (Octopoda)—con-ducts from the buccal chamber to the stomach, the latter organ being of large size, highly muscular, of a generally rounded shape, and having appended to its pyloric ex-tremity a capacious diverticulum, into which the bile-ducts open. Into the oesophagus open the ducts of one or two pairs of salivary glands; and the liver is of large size and highly developed, whilst certain glandular structures which pour their secretion into the bile-ducts are believed to re-present the pancreas. The intestine is usually short, mostly of nearly uniform calibre, straight or slightly con-voluted, and terminates in an anal aperture placed in the median line of the paliial chamber close to the base of the funnel.

The excretory organs of the cuttle-fishes are the kidneys and the ink-sac; and the integumentary sinuses in connection with the so-called " aquiferous pores " may possibly also have an excretory function. The kidneys (r, r, fig. 2) are spongy, cellular, tufted, or massive organs appended to the two posterior branches of the vena cava, and sometimes developed on others of the principal veins, just before they open into the branchial hearts. They are contained, along with the veins to which they are attached and the corresponding branchial heart on each side, in two serous sacs, which are separated centrally by the chamber containing the systemic heart, and which open by distinct apertures into the paliial chamber. The renal appendices are in direct communication with the veins on which they are situated, and have the form of membranous, often plicated sacs, covered externally with a layer of glandular cells which secrete a yellowish fluid. This fluid escapes into the serous sacs surrounding the kidneys, and is thence expelled into the mantle-cavity by the apertures before mentioned. The identity of this fluid with the renal secretion of the higher animals is shown by its containing uric acid (as proved by Harless).

The ink-sac is a glandular organ, present in all known Dibranchiates, generally of a pyriform shape, situated in different portions of the visceral chamber, but communicat-ing by a longer or shorter duct either with the terminal portion of the intestine, or, more commonly, directly with the paliial cavity by a special aperture of its own, situated close beside the anus and at the base of the funnel. The ink-sac has strong fibrous walls, often with a silvery lustre, and its secretion is a brown or black fluid, containing a large amount of a carbonaceous pigment ("sepia"), along with various mineral salts. It is employed by the cuttle-fishes as a means of protection against their enemies, as they have the power of at will expelling jets of it into the surrounding water, and thus raising a cloud under cover of which they make their escape. The colouring matter of the ink is highly indestructible, is often found preserved in fossil Dibranchiates, and was formerly employed in the manufacture of the paint " sepia."

FIG. 2.—Central organs of the circulation, gills, and renal organs of Sepia offici-nalis (after John Hunter), a, aorta; v, vena cava; r', tj', visceral veins; c, systemic heart; a\ d, dilatations of branchial veins on entering the heart; e, e, branchial hearts; 6, 6, branchiae; r, r, renal organs.

The circulatory organs of the cuttle-fishes consist of arteries, veins, generally an intermediate system of capillaries, a more or less extensively developed system of sinuses or lacunae amongst the tissues, a central systemic heart, and two accessory or " branchial " hearts, whereby the venous blood is propelled through the breathing organs. The general course of the circulation is as follows. The venous blood returned from the arms, the anterior portion of the body and mantle generally, and the funnel is collected into a main ventrally-placed vein (the vena cava). This is reinforced by a great vein (canalis venosus), which brings the blood from a venous sinus surrounding the buccal chamber, the gullet, stomach, and liver in the Octopods, but which is of comparatively small dimensions in the Decapods. The great venous channel thus formed splits into two branches (the so-called "branchial arteries"), which further receive the venous blood returned from the posterior viscera and hinder portion of the mantle by special vessels (the " visceral veins"). The branchial arteries then pour their contents by valvular apertures into two special muscular contractile chambers, which are termed the " branchial hearts," and are situated, one on each side, at the bases of the gills. The branchial hearts drive the blood through the gills, where it is aerated, and whence it issues, as arterial blood, by the so-called " branchial veins," which convey it to the true systemic heart. This organ is placed in the middle line of the body, between the renal sinuses on each side, and below the bifurcation of the vena cava. The two branchial veins open into it by contractile dilatations, which may be regarded as auricles, and it con-sists of a single muscular cavity, which propels the blood into the systemic aorta. By this vessel the aerated blood is distributed to the tissues generally, finding its way back to the veins mostly through the intervention of a system of capillaries, but partly by the venous sinuses and lacunae before-mentioned. Besides the true aorta there arise from the systemic heart minor arterial vessels, by which the blood is conveyed to the mantle, fins, and reproductive organs. The blood contains microscopic corpuscles, and is remarkable in containing a notable amount of copper.

The respiratory organs of the cuttle-fishes consist of two gills or branchiae, one of each side of the body, placed in the cavity of the mantle-sac. The branchiae are of an elong-ated pyramidal figure, and each consists of a central stem, attached below to the visceral mass and along one side to the mantle, the other side being free. The central stem bears a larger or smaller number of triangular laminae, in turn supporting similar secondary laminae, which finally carry still smaller tertiary laminae ; and the blood is thus minutely distributed through the gill. In the absence of a ciliated branchial surface, the necessary respiratory currents are maintained by the alternate contractions and expansions of the muscular walls of the pallial chamber. As the mantle dilates, the water from the exterior makes its way into the mantle-cavity by the opening between the rim of the mantle and the nock. The water, after passing over 'the gills, is then expelled through the funnel by the contraction of the mantle. The course of the out-going current through the funnel is determined either by the presence of suitable valves at the base of this organ, which permit the egress of water, but do not permit its ingress, or by the articulation of the sides of the funnel with the rim of the mantle-sac, in such a manner that the opening into the mantle-cavity is completely closed during the exspiratory act, the funnel alone remaining open. As before remarked, the outgoing respiratory currents serve to take with them the excrementitious portions of the food and the secretions of the kidneys and ink-sac; and they are also concerned in swimming, as the animal can by their means propel itself backwards through the water.

The nervous system of the cuttle-fishes consists of the three principal pairs of ganglia characteristic of the Lamelli-branchs and Gasteropods—namely, the cephalic, pedal, and parieto-splanchnic. These form an oesophageal collar, which consists of a smaller dorsal mass (the cephalic ganglia), and a larger ventral mass (the pedal and parieto-splanchnic ganglia), united by commissures. The central organs of the nervous system are protected by a cartilage, foreshadowing ^he cranium of the vertebrate animals ; and the cerebral ganglia supply the nerves to the buccal mass and eyes, whilst the pedal ganglia supply nerves to the auditory organs, funnel, and arms, and the nervous supply of the mantle and viscera generally is derived from the-parieto-splanchnic ganglia. The organs of sense of the cuttle-fishes are highly developed, and consist of the eyes,, auditory sacs, and perhaps of an olfactory apparatus. Space will not permit of a description of these, and it must suffice to say that the organs of vision are of large-size, and more highly developed than in any other inverte-brate animals, consisting of a sclerotic, choroid, retina, vitreous humour, aqueous humour, and cr3rstalline lens ; the organs of hearing are two chambers hollowed out of the cartilage of the cranial plate, each containing a membranous sac with an otolith; and the organs of smell have been doubtfully sought in certain cavities which open by small apertures behind the eye, and are supplied with filaments from the cephalic ganglia.

Of the skeletal structures which these animals possess, some are integumentary and exoskeletal, whilst others may be regarded as constituting a true endoskeleton. In the latter category are the various internal cartilaginous structures which are found in the cuttle-fishes, protecting vital organs, or serving as a base of insertion for muscles. Some of these, such as the cartilages which strengthen the anterior rim of the mantle-sac, and serve for its articulation in some forms with the funnel, and the cartilages of the fins (when present) need no further notice ; but the cranial cartilage is of greater importance. This latter forms a plate, which surrounds the gullet, and incloses and protects \ the great oesophageal nerve-collar, and which sends off prolongations which strengthen and protect the eye, thus ! discharging the functions of the orbits of higher animals.

FIG. 3.—a, Internal skeleton (" sepiostaire ") of Sepia ornata, Rang. ; b. Internal skeleton ("pen") of Histioteuihis Bonelliana, D'Orb.; c, Internal skeleton (" phragmacone ") of Spirula fragilis, Lamarck; a, Animal of Spirula J>eronii.

The integumentary skeleton of the cuttle-fishes consists of ?an external shell only in the Paper Nautilus (Argonaida), but in all others in which it is present at all it is composed . of certain horny or calcareous structures, which are lodged in the substance of the mantle, and are therefore concealed from view. This internal skeleton, so characteristic of the Dibranchiates, is well developed in all the Decapods, but is either absent or rudimentary in the Octopods, in which it never consists of more than " two short rudimental styles encysted in the dorso-lateral parts of the mantle" (Owen). In the typical Decapods (such as Loligo, Sepioteuthis, Enoploteuthis, Histioteuthis, &c), the skeleton is horny, and . consists of a feather-shaped " pen " (b, fig. 3) composed of a central shaft and two more or less extensively developed lateral expansions or wings, the whole imbedded in the mantle in the middle line of the back. In some cases (Ony-choteuthis, 0mmastrephes, Loligopsis) the hinder end of the pen is developed into hollow conical appendix or cup, form-ing a rudimentary "splanchnoskeleton." In the genus Sepia, the internal skeleton (a, fig. 3) consists of a horny oval plate, strengthened by calcareous matter, which is deposited principally on its internal surface, and consists of numerous thin plates separated by vertical fibres. The " cuttle-bone," or " sepiostaire," is of a porous, spongy consistence, and is concave on its inner surface behind, terminating posteriorly in a small cone (" mucro "), from which a thin, wing-like margin is prolonged forwards on both sides. In rthe singular genus Spirula the internal skeleton (c, fig. 3) has tihe form of a calcareous and nacreous tube, coiled up into a 'flat spiral, the coils of which are not in contact. The internal cavity of the shell is partitioned off by a succession of pearly septa, which are perforated on the ventral or con-cave side of the shell by a tube (" siphuncle ") running the whole length of the spiral. In its general construction, the skeleton of the Spirula is very like the shell of the Pearly Nautilus : but it is quite certain that its relations to the animal are quite different. Though the shell itself is exceedingly abundant in certain regions, the animal is at present only known by some very imperfect examples, and its connection with the shell is not precisely clear. The last chamber of the shell, however, is little or not at all larger than those behind it, and it is certain that the animal in no sense lives in the shell. On the contrary the last chamber simply lodged the extremity of the visceral sac, and the shell is to all iutents and purposes an internal one, though possibly it is only partially concealed from view by folds of the mantle, and is not absolutely encysted.

Diagram of IJelenmite (after Phillips). ;o, horny pel] or" pro-ostracum;" a, conical cavity or " alveolus," in which the chambered " phragmacone " ip) is contained ;</," guard,' or "rostrum."

Of the three types of internal skeleton characteristic of living cuttle-fishes—namely, the horny pen of the Calamaries, the calcareous " bone " of the Sepice, and the spiral cham-bered and siphunculate shell of Spjirula—two appear under various forms in the Secondary and Tertiary rocks, whilst the third, comprising the Spirulce, is so far unknown in the fossil condition. Thus, we find fossil " pens," in all essential respects identical with those of the ordinary living Decapods, to be by no means very rare in deposits of Secondary age, and such genera as Teudopsis, Leptoteuthis, Geoteuthis, and Beloteu-tlds have been founded on these remains. Similarly, the calcareous " cuttle-bones " from the Tertiary rocks, upon which are founded the genera Spiridirostra, Beloptera, and Belemnosis, appear to be referable to the Sepiadce. In Spiridirostra, however, the skeleton consists partly of a spirally bent, chambered, and siphonate " phragmacone," protected by a pointed calcareous " guard," and it thus reminds us on the one hand of the living Spirula, and on the other hand of the extinct Be-lemnites. By far the most import-ant of the fossil cuttle-fishes, how-ever, are those which form the family of the Belemnitidee, a group wholly Secondary in its distribution, which has a type of skeleton peculiar to itself. This skeleton consists of a conical chambered Fl(5 shell—the " phragmacone "—which is partitioned off by calcareous septa into distinct air-chambers, pierced ventrally by a tube or "siphuncle." The conical phrag-macone is placed in a corresponding excavation in the anterior end of a longer or shorter, sub-cylindrical, calcareous, and fibrous structure, which is known as the " guard," or "rostrum," and which protects the delicate phragmacone from injury. The guard is the part of the skeleton which is most frequently found in the fossil condi-tion, and in perfect specimens it is prolonged forwards anteriorly into a longer or shorter horny or shelly plate, which corresponds with the front portion of the " pen " of the Calamaries, and is known as the " pro-ostracum." The various genera of the Belemnitidee—Belemnites, Belemnitella, Xiphoteuthis, Conoteuthis, Acanthoteuthis, Belemnoteuthis—are founded on differences in the uature of the internal skeleton. We know, however, from specimens preserved in such fine-grained deposits as the Oxford clay, that the cuttle-fishes of this family possessed lateral fins, and two " tentacles " in addition to the eight proper " arms;" that the suckers were provided with horny hooks ; and that there was an ink-sac.

Diagram of IJelenmite (after Phillips). ;o, horny pel] or" pro-ostracum;" a, coni-cal cavity or " alveolus," in which the chambered " phragmacone " ip) is contained ;</," guard,' or "ros-trum."

As before remarked, the only known Dibranchiat^ Ceplialopod in which an external shell is present is the Paper Nautilus (Argonauta). The shell, moreover, is only possessed by the female Argonaut—the male being shell-less—and it is in no way comparable as regards its mode of origin and its morphological sig-nificance with the shell of the ordi-nary testaceous Mollusks in gene-ral, or of the Tetra-branchiate Cepha-lopods in particu-lar. The shell of the Argonaut is in-volute, one-cham-bered, and calcare-ous, of most grace-ful outlines and ornamentation. It is not secreted by the mantle, nor is the animal attach-ed to it by any organic connection —hence the long controversy as to whether the ArüO- *'IG' 5'—Argonauta argo, the " Paper Nautilus,

o female. The animal is represented in its shell, liaut truly Owned but the webbed dorsal arms are separated from the

the shell it iuha- 8he11'which they "''^'^ «*»™°-bited, or had not rather simply obtained it by plunder, as the Hermit-Crab seizes any empty shell which may be suitable for its temporary habitation. It is, however, now known that the shell of the Argonaut is secreted by the two dorsal arms of the female, which are expanded or webbed, and closely embrace the shell which they produce. These two arms, in their natural position, are bent backwards, so as to allow the animal to inhabit the shell. The animal sits in the shell, with its funnel turned towards the keel, and the apex of the shell is empty, and is used simply as a receptacle for the clustered eggs.

The processes of reproduction and development in the cuttle-fishes are of great interest. The males and females are generally more or less unlike externally—this difference being most marked in the Argonaut, in which the male is very much smaller than the female, and in addition possesses no shell. The reproductive organs of the female consist of a single ovary, situated at the hinder end of the body, and inclosed in a pouch of the peritoneum, from which one or two oviducts are continued to open into the mantle-cavity, generally near the base of the funnel. The eggs are discharged into the peritoneal sac surrounding the ovary, and are then taken up by the oviducts and conveyed into the mantle-cavity. "When finally extruded, the impregnated eggs are found to be inclosed, singly or many together, in special capsules, which are usually attached in bunches to some foreign body. These egg-capsules are produced by the so-called " nidamental glands," which in some genera (e.g., Sepia and Loligo) are of large size, and are appended to the proper gene-rative organs. The reproductive organs of the male cuttle-fishes consist of a testis placed at the hinder extremity, like the ovary of the female, and inclosed in a peritoneal sac. The spermatozoids are discharged into this sac by the rupture of the secreting tubes, and are conveyed to the exterior by a tubular " vas deferens," which is dilated in its course into a "vesícula seminalis," and ulti-mately opens into the mantle-cavity by a papilliform " penis" situated close to the anus. Before the vas deferens finally termin-ates in this way, it is usually expanded into a special dilatation ("bursa spermatophorum "), in which are packed away the so-called " spermatophores," or " moving filaments of Needham." These singular bodies are whitish filaments, 6 or 8 lines in length, composed of aggregations of spermatozoids inclosed in a covering originally of an albuminous nature, but ultimately becoming deve-loped into two membranes which have a complicated arrangement. When set free and moistened, the spermatophores exhibit active ver-micular movements, and under suitable circumstances rupture and discharge their contained spermatozoa.

he reproductive act in the cuttle-fishes is only imperfectly known ; but true intromission is certainly impossible. According to ths observations of Aristotle, the poulpes and calamaries perform this act by clinging to each other, fhouth to mouth, with the suckers of the arms in mutual apposition, the former seeking the bottom, whilst the latter move fre'ely in the water. It is known now, in this connection, that one of the arms of the male cuttle-fishes is pecu-liarly modified, the arm thus affected beins said to be " hecto-eotylized." In some forms, this hectoeotylized arm—differing in its position in different cases—is not so conspicuously altered as to attract immediate attention, and it does not appear clear that it plays necessarily any part in the reproductive act, though the alteration of form is undoubtedly primarily sexual. In certain forms, however (viz. Argonauta argo, Tremoctopus violoxeus, T. Quoyanus, and Octopus carena) the hectoeotylized arm is the efficient agent in the act of reproduction. It is longer and thicker than the other arms, prolonged at its extremity into a long filament, and possessing posteriorly a sac which is filled with spermatophores. During the act of reproduction, the hectoeotylized arm is detached by the male, and is deposited, with its freight of spermatophores, within the mantle-cavity of the female. The terminal filament is perforated by a tube, by which the spermatophores are conveyed to the ova, and impregnation is thus effected. When thus detached, the hectoeotylized arm is capable of independent movement, and when first found in this free condition within the mantle-sac of the female Argonaut it was regarded as a parasitic worm. Under this belief Delle Chiaje described it as the Triclioceplialus acetabularis, and Cuvier called it (in the Octopus) the Eectocotylus Octopodis. Both these names are in allusion to the suckers which the arm carries, and the name of " hectocotylus" is still applied to the detached arm, whereas the arm, if not detached, is simply said to be " hectoeotylized." As before remarked, it is not absolutely certain that the hectoeotylized arm is invariably employed as a repro-ductive agent ; and certainly it is only occasionally detached. According to Steenstrup, however, the hectoeotylized arm, when not detached, is employed by the male to transfer the spermatophores to the female during the act of reproduction, the spermatic filaments being either placed within the mantle-cavity, or fixed to

FIG. 6.—a.Male of Argonauta argo. with the hectoeotylized arm still contained in its enveloping cyst, four times enlarged (after H. Muller). b, Hectocotylus of Tremoctopus violaceus (after Kolliker).

the internal surface of the buccal cavity of the females. How the spermatophores are transferred from the seminal ducts of the male to the sac contained in the interior of the hectoeotylized arm is still uncertain ; but Leuckart has shown that the sac in question does actually communicate with the surface by a distinct aperture.

The development of the cuttle-fishes can be barely touched upon here. After fertilization the ovum undergoes a partial segmentation, as in birds and reptiles, and there is formed at one pole a germinal disc ("blastoderm"), which is at first divided into two parts by a primitive furrow, then into four by a secondary furrow intersecting the first at right angles, and then into eight. An inner germinal layer is then formed (according to the researches of Kay Lankester on Loligo) quite independently of the outer one ; and the two layers then grow over the entire yolk and completely inclose it. The un-segmented portion of the yolk is gradually absorbed by the grow-ing embryo, but obtains no direct connection with the alimentary tube, the latter originating from the primitive invagination of the outer layer of the blastoderm, instead of being formed, as in verte-brates, by its inner layer.

As regards their distribution in space, the cuttle-fishes are all marine, active, rapacious, and carnivorous in their habits, swim-ming vigorously by means of the jets of water emitted from the funnel, or in an opposite direction by means of fins, and creep-ing about the sea-bottom by means of the prehensile arms.

Some forms (such, as the Odopodidœ and Sepia) are essen-tially littoral 'animals, frequenting shallow seas, living in the vicinity of the land, and specially affecting rocky bottoms. Others (such as Tremoctopus, Sepiola, Argonauta, Spirula, Archi-teidhis, Onychoteuthis, &e. ) are pelagic animals, living in the open ocean, often far from land, and swimming at or near the surface. Though more varied as regards their specific and generic types in the warmer seas of the globe, cuttle-fishes are found in almost all seas, and are sometimes extremely numerous individually even in the colder oceans. It seems also certain that our present knowledge as to the pelagic forms is only very imperfect. As to their dimensions, none are extremely minute, and some attain truly gigantic dimensions. Not to speak of the fabulous accounts of colossal cuttle-fishes given by many of the older writers, such as Pontoppidan and Olaus Magnus, we are now acquainted through the observations and descriptions of scientific witnesses, such as Banks and Solander, Quoy and Gaimard, Steenstrup, Verrill, &c, with various huge cuttlefishes, inhabiting both the Atlantic and Pacific Oceans. Some of these, though only known by imperfect specimens, certainly attain a length of 15 feet or upwards to the body and head, and" from 30 to 40 feet or upwards in the long ten-tacles. All these giant cuttlefishes appear to belong to the suborder of the Dxapoda.
As regards their distribution in time, the order of the Dihranchiate Cephalopoda does not seem to have come into existence during the Palaeozoic period. And in this case the negative evidence is of considerable value, seeing that so many members of the order are provided with structures capable of preservation in the fossil state. During the Mesozoio period the Dibranchiates attained ahigh deve-lopment, being principally represented by the exclusively Secondary family of the Belemnitidas, which began to exist in the Trias and sur-vived to the Chalk. The genus Belemnites itself extends from the Upper Trias to the Upper Greensand, and its place is taken in the Chalk by the nearly allied Belemnitella, distinguished by a fissure in the side of the alveolus of the guard. The Secondary rocks have also yielded the pens of Teuthidce (Teudopsis, BetvuiMids, &c. ), and of Sepiadce (Sepia itself, and Coccoteuthis). In the Tertiary rocks, the three curious extinct genera Belosepia, Spiruli-rostra, and Bdemnosis appear to be referable to the Sepiadœ, and Sepia itself still continues to exist ; whilst the Teuthidoe are not wholly unrepresented. The family of the Spirulidce has no certain fossil representative ; but two species of Argonaut have been detected in the later Tertiaries. With this last-mentioned exception, no remains certainly referable to the sub-order of the Octopoda have hitherto been met with.

BIBLIOGRAPHY.—The following list comprises some of tire more important
works and memoirs which may be consulted with regard to the living and fossil
Dibranchiafe Cepiialopods:—Aristotle, Historia de Animations: Meyer, Aristo-
teles Thierkunde, Berlin, 1855; Needham, An Account of some new Microscopical
Discoveries, 1745 ; Monro {secundus), " On the Anatomy of the Sagirtated Cala-
mary," in The Structure and Physiology of Fishes, 1785; Cuvier, Leçons cVAnat.
Comparée, and Mémoire sur les Céphalopodes et sur leur Anatomie; St. delle
Chiaje, Memoria su' Cefalopedi, 1829; Meckel, System der vergleichenden Ana-
tomie, Owen, " Cephalopoda,'1 in Todd and Bowman's Cyclopedia of Anatomy
and Physiology, 183-5-36; Von Siebold, " Anatomy of Cephalopoda," in Sicbold
and Stannius's Lehrbuch der vergleichenden Anatomie, 1848; Milne-Edwards,
Leçons surla Physiologie et l'Anatomie comparée, 1857; Kcferstein, "Cephalo-
poda," in Bronn'a K'assen und Ordnungen des Thierreichs, 1S62; Férussac and
Ale. d'Orbigny, Histoire nature/le des Céphalopodes acétabulifères rivants et
fossiles, 1835-48; Poli, "Anatomy of Argonauta," in Iiis Testacea utriusque
Siciliee, 1826 ; Jeanette Power, " The Animal of Argonauta argo," Archiv, f.
Naturgesch., Ì337; Van Beneden, " Mém. sur l'Argonauta," in Nouv. Mem, de
l'Acad. roy. de Bruxelles, 1838; J. E. Gray, " The Animal of Spirula" Ann. and
Mag. Nat. Hist., 1845 ; Kò'lliker, Entwichet ungsgeschicìil'e der Cephalopoden. 1841,
and "Observations on the Hectocotyli of Tremoctopus violaceus and Argonauta
argo," in Trans. Linn. Soc. 1846; lì. Müller, " lieber das .Männchen von Argo-
nauta argo und die Hectocotylen," in Zeitsch. f. Wiss. Zool., 1852; Verrill, "Col-
ossal Cepiialopods of the North Atlantic," in American Naturalist, 1S75 ; Wagner,
" Die fossilen Ueberreste von nackten Diatentisehen aus den Lithographischen
Schiefer," in Ablandl. d. Math. phys. Cl. der K. Bayer. Akad. Wiss., 1860 ; Owen,
" Belemnites from the Oxford Clav," Phil. Trans., 1S44 ; Huxley, " Structure
of Belemnites," in Mem. Oeol. Survey, 1864; Phillips, Monograph of the Belem-
nitidx (Palaeontographical Society). 1865-69. (H. A. N.)

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