Part 18

The external changes of form are as follows:--The mantle is the middle of the embryonic area, and in its centre is the shell-gland, which, however, behaves in a different way from that seen in other Molluscs. Its borders grow inwards and approach each other to form the shell-sac. E. Ray Lankester showed that in _Argonauta_ and other Octopods the shell-sac disappears before it is closed up, but in other forms except _Spirula_ it closes completely and the shell develops within it. The lateral and posterior borders of the embryo form the foot, and these borders grow out into ten or eight lobes which become the arms, and which at first, as seen in fig. 35 (8), are entirely posterior to the mouth. Development actually shows the anterior arms gradually growing round the mouth and uniting in front of it. Between the mantle and the foot are two ridges which form the funnel, and their position shows them to be the epipodia. The otocysts and eyes are formed as invaginations of ectoderm, the former behind the eyes, at the sides of the funnel. All the nerve-centres, cerebral, visceral, pedal and optic, are formed as proliferations of the ectoderm. At the sides of the optic ganglia a pair of ectodermic invaginations are formed, which in the adult become the white bodies of the eyes, surrounding the optic ganglion. These are vestiges of lateral cerebral lobes which degenerate in the course of development.

[Illustration: FIG. 35.--Development of _Loligo_.

1. View of the cleavage of the egg during the first formation of embryonic cells.

2. Lateral view of the egg at a little later stage. a, Limit to which the layer of cleavage-cells has spread over the egg; b, portion of the egg (shaded) as yet uncovered by cleavage-cells; ap, the auto-plasts; kp, cleavage-pole where first cells were formed.

3. Later stage, the limit (a) now extended so as to leave but little of the egg-surface (b) unenclosed. The eyes (d), mouth (e) and mantle-sac (u) have appeared.

4. Later stage, anterior surface, the embryo is becoming nipped off from the yolk-sac (g).

5. View of an embryo similar to (3) from the cleavage-pole or centro-dorsal area.

6. Later stage, posterior surface.

7. Section in a median dorso-ventral and antero-posterior plane of an embryo of the same age as (4).

8. View of the anterior face of an older embryo.

9. View of the posterior face of an embryo of the same age as (8).

Letters in (3) to (9):--a, lateral fins of the mantle; b, mantle-skirt; c, supra-ocular invagination to form the "white body"; d, the eye; e, the mouth; f^1, f^2, f^3, f^4, f^5, the five paired processes of the fore-foot; g, rhythmically contractile area of the yolk-sac, which is itself a hernia-like protrusion of the median portion of the fore-foot; h, dotted line showing internal area occupied by yolk (food-material of the egg); k, first rudiment of the epipodia (paired ridges which unite to form the siphon or funnel); l, sac of the radula or lingual ribbon; m, stomach; n, rudiments of the gills (paired ctenidia); o, the otocysts--a pair of invaginations of the surface of the epipodia; p, the optic ganglion; q, the distal portion of the ridges which form the siphon, k being the basal portion of the same structure; r, the vesicle-like rudiment of the intestine formed independently of the parts connected with the mouth, s, k, m, and without invagination; s, rudiment of the salivary glands; t in (7), the shell-sac at an earlier stage open (see fig. 36), now closed up; u, the open shell-sac formed by an uprising ring-like growth of the centro-dorsal area; w in (5), the mantle-skirt commencing to be raised up around the area of the shell-sac. In (7) mes points to the middle cell-layer of the embryo, ep to the outer layer, and h to the deep layer of fusiform cells which separates everywhere the embryo from the yolk or food-material lying within it.]

The coelomic cavity appears as a symmetrical pair of spaces in the mesoderm, right and left of the intestine, and from it grow out the genital ducts and the renal organs. The gonad develops from the wall of the coelom.

[Illustration: FIG. 36.--Section through aboral end of embryo of _Loligo_ showing shell-sac still open. ep, ectoderm; m, mesoderm; m', endoderm; shs, shell-sac; y, yolk.]

_Phylogeny and Classification._--The order is divided into two sub-orders, Decapoda and Octopoda, by the presence or absence of the tentacular arms. The Decapoda are more adapted for swimming than the Octopoda, the body being usually provided with fins. In the former also there is generally an internal shell of considerable size, often calcined, while in the Octopoda only the merest vestiges of a shell remain. There can be no doubt that the Octopoda were derived from the Decapoda, although from the absence of skeletal structures fossil remains of Octopods are almost entirely unknown. _Palaeoctopus_, however, occurs in the Cretaceous, while shells of _Argonauta_ do not appear before the Pliocene. The Decapoda are abundantly represented in the Secondary formations by the _Belemnitidae_, whose shell (fig. 19) consists of a straight conical phragmacone covered posteriorly by a very thick rostrum, and produced anteriorly into a thin long proöstracum which is only occasionally preserved. In certain cases remains of the arms provided with hooks, and of the ink-sac, have been recognized. The _Belemnitidae_ appear first in the Upper Trias, attain their maximum development in the Jurassic rocks, and are not continued into the Tertiary period, though represented in the Eocene by a few allied forms.

There is no difficulty in deriving the typical existing Decapoda from _Belemnitidae_, and many of the extinct forms may have been directly ancestral. Chitinous "pens" like that of _Loligo_, however, begin to appear in the Jurassic and Cretaceous rocks, so that in this case as in many others the parent form and the modified form existed contemporaneously, and the latter alone has survived. The oldest shells of the _Sepia_ type are from the Eocene, and it is perhaps possible that the _Sepiidae_ arose separately from the Belemnites.

It is a curious fact that no fossil specimens of the genus _Spirula_ have been found, but this may be due to the fact that it occurs only in deep water. At any rate there is no evidence that the shell of _Spirula_ has lost a rostrum and a proöstracum; its characters must be regarded as primitive, not secondary. In the characters of the protoconch and of the commencement of the siphuncle, the shell of _Spirula_ agrees with that of the Ammonoids, and in both its position is ventral, although in most Ammonoids the shell being exogastric the ventral side is the convex or external, while in _Spirula_ the shell is endogastric and the siphuncle internal. The fact that the shell is not completely enclosed by the mantle is also a primitive character.

With regard to the general morphology of the Cephalopoda, it is difficult to reconcile the existence of two pairs of renal tubes as well as a pair of genital ducts in _Nautilus_ with the view that the original Mollusc was unsegmented and had only one pair of coelomoducts. Considering the great specialization, however, and high degree of organization of the Cephalopods, it is evident that the earliest Nautiloid whose remains are known to us must have had a long evolutionary history behind it, and such metamerism as exists may have been developed in the course of its own history. In the other direction the evidence seems to prove that the Dibranchiata with only two renal ducts have been derived from the Tetrabranchiata.

SUBORDER 1. DECAPODA.--Four pairs of ordinary non-retractile arms which are shorter than the body, and one pair of tentacular arms, situated between the third and fourth normal arms on each side and retractile within special pouches. Suckers pedunculated and provided with horny rings, on the tentacular arms confined usually to the distal extremities. Usually a well-developed internal shell, and lateral fins on the edges of the body. Heart in a coelomic cavity; nidamentary glands usually present.

[Illustration: FIG. 37.--Right and left sections through embryos of _Loligo_. (After Lankester.)

A, Same stage as fig. 35 (4).

B, Same stage as fig. 35 (8); only the left side of the sections is drawn, and the food-material which occupies the space internal to the membrane ym is omitted.

al, Rectum.

is, Ink-sac.

ep, Outer cell-layer.

mes, Middle cell-layer.

ym, Deep cell-layer of fusiform cells (yolk-membrane).

ng, Optic nerve-ganglion.

ot, Otocyst.

wb, The "white body" of the adult ocular capsule forming as an invagination of the outer cell-layer.

mtf, Mantle-skirt.

g, Gill.

ps, Pen-sac or shell-sac, now closed.

dg, Dorsal groove.

poc. Primitive optic vesicle, now closed (see fig. 34).

l, Lens.

r, Retina.

soc, Second or anterior optic chamber still open.

if, Iridean folds.

C, The primitive invagination to form one of the otocysts, as seen in fig. 35 (5) and (6).]

Tribe 1. _Oigopsida_.--A wide aperture in the cornea. Two oviducts in the female. In fossil genera and _Spirula_, shell has a multilocular phragmacone with a siphuncle; initial chamber globular and larger than the second chamber. The most ancient forms characterized by the small size of the rostrum and proöstracum, and large size of the phragmacone. In the living genera, except _Spirula_, the shell is a chitinous gladius.

Fam. 1. _Belemnoteuthidae_. Extinct; shell with well-developed phragmacone, and rostrum merely a calcareous envelope; siphuncular necks directed backwards as in Nautiloidea; ten equal arms provided with hooks. _Phragmoteuthis_, Trias. _Belemnoteuthis_, Jurassic and Cretaceous. _Acanthoteuthis_, Jurassic.

Fam. 2. _Aulacoceratidae_. Extinct; phragmacone with widely separated septa; rostrum well developed and claviform. _Aulacoceras_, Trias. _Atractites_, Trias and Jurassic. _Xiphoteuthis_, Lias.

Fam. 3. _Belemnitidae_. Extinct; phragmacone short with ventral siphuncle, prolonged dorsally into long proöstracum; rostrum large and cylindrical. _Belemnites_, 350 species from Jurassic and Cretaceous. _Diploconus_, Upper Jurassic.

Fam. 4. _Belopteridae_. Extinct; rostrum and phragmacone well developed, phragmacone often curved; initial chamber small. _Beloptera_, Eocene. _Bayanoteuthis_, Eocene. _Spirulirostra_, Miocene.

Fam. 5. _Spirulidae_. Dorsal and ventral sides of posterior extremity of shell uncovered by mantle; no rostrum or proöstracum; shell calcareous, coiled endogastrically and sipnunculated; fins posterior. _Spirula_, three living species known, abyssal.

Fam. 6. _Ommatostrephidae_. Shell internal and chitinous, ending aborally in a little narrow cone; tentacular arms short and thick; suckers with denticulate rings. _Ommatostrephes_, fins aboral, simple and rhomboidal, British. _Ctenopteryx_, fins pectinate, as long as the body; _Bathyteuthis_, fins terminal, rudimentary; tentacular arms, filiform; abyssal. _Rhynchoteuthis_, tentacular arms united to form a beak-shaped appendage. _Symplectoteuthis. Tracheloteuthis. Doridicus. Architeuthis_; this is the largest of Cephalopoda, reaching 60 ft. in length including arms.

Fam. 7. _Thysanoteuthidae_. Arms enlarged, bearing two rows of suckers and filaments; fins triangular, extending whole length of body. _Thysanoteuthis_, Mediterranean.

Fam. 8. _Onychoteuthidae_. Fins terminal; tentacular arms long; suckers with hooks. _Onychoteuthis_, hook-bearing suckers on tentacular arms only. _Enoploteuthis_, hook-bearing suckers on all the arms. _Veranya_, body very short, tentacular arms atrophied in the adult, Mediterranean. _Chaunoteuthis_, body elongated, tentacular arms atrophied. _Pterygioteuthis. Ancistroteuthis. Abralia. Teleoteuthis. Lepidoteuthis._

Fam. 9. _Gonatidae_. Body elongated; fins terminal; radula with only two lateral teeth. _Gonatus_.

Fam. 10. _Cheiroteuthidae_. Tentacular arms long, not retractile; resisting apparatus well developed. _Cheiroteuthis_, suckers along the whole length of the tentacular arms. _Doratopsis_, body very long and slender with aboral spine, dorsal arms very short. _Histioteuthis_, six dorsal arms united by membrane, photogenous organs present. _Histiopsis_, membrane of dorsal arms only half-way up the arms, photogenous organs present. _Calliteuthis_, no brachial membrane, photogenous organs present. _Grimalditeuthis_, two fins on each bide, no tentacular arms.

Fam. 11. _Cranchiidae_. Eight normal arms, very short; eyes prominent; fins small and terminal. _Cranchia_, body short, purse-shaped, normal arms short, fins entirely aboral. _Loligopsis_, body elongated, conical, tentacular arms slender. _Leachia_, tentacular arms absent, funnel without a valve. _Taonius_, body elongated, normal arms, rather short, eyes pedunculated.

[Illustration: FIG. 38.--Octopodous Cephalopods.

A, _Pinnoctopus cordiformis_, Quoy and Gain (from New Zealand).

B, _Tremoctopus violaceus_, Ver. (from the Mediterranean).

C, _Cranchia scabra_, Owen (from the Atlantic Ocean; one of the Decapoda).

D, _Cirrhoteuthis Mulleri_, Esch. (from the Greenland coast).]

Tribe 2. _Myopsida_.--No aperture in the cornea. Left oviduct only developed in female. Internal shell without a distinct phragmacone, calcified or simply chitinous.

Fam. 1. _Sepiidae_. Body wide and flat; fins narrow, extending the whole length of the body; shell calcareous and laminated. _Belosepia_, a rudiment of rostrum and phragmacone present in shell, Eocene. _Sepia_, shell with a rostrum, British. _Sepiella_, shell without a rostrum.

Fam. 2. _Sepiolidae_. Body short, rounded at the aboral end; fins rounded, inserted in middle of body-length; shell chitinous, small or absent. _Sepiola_, head united to mantle dorsally, British. _Rossia_, head not united to mantle, British. _Stoloteuthis_ and _Inioteuthis_, without shell. _Heteroteuthis. Euprymna._

Fam. 3. _Idiosepiidae_. Body elongated, with rudimentary terminal fins; internal shell almost lost. _Idiosepius_, 1.5 cm. long, Indian Ocean.

Fam. 4. _Sepiadariidae_. Body short; mantle united to head dorsally; no shell. _Sepiadarium_, Pacific Ocean. _Sepioloidea_, Australian.

Fam. 5. _Loliginidae_. Body elongated and conical; fins extending forward beyond the middle of body-length; shell chitinous, well developed. _Loligo_, fins triangular, aboral, British. _Sepioteuthis_, fins rounded, extending along whole of body-length. _Loliolus. Loliguncula._ The following fossil genera, known only by their gladius and ink-sac, have been placed near _Loligo_:--_Teuthopsis, Beloteuthis_ and _Geoteuthis_, Lias; _Phylloteuthis_, Cretaceous; _Plesioteuthis_, Jurassic and Cretaceous.

SUBORDER 2. OCTOPODA.--Only four pairs of arms, all similar and longer than the body. Body short and rounded aborally. Suckers sessile. Heart not contained in coelom. No nidamentary glands.

[Illustration: FIG. 39.--_Palaeoctopus Newboldi_, the oldest Octopod known. From the Cretaceous rocks of Lebanon. (After H. Woodward.)]

Tribe I. _Leioglossa_.--No radula. Arms united by a complete membrane. Fins on sides of body.

Fam. _Cirrhoteuthidae_. Tentacular filaments on either side of the suckers. _Cirrhoteuthis_, pallial sac prominent, fins large, pelagic. _Opisthoteuthis_, body flattened, with small fins, deep-sea. _Vampyroteuthis_, four fins. _Palaeoctopus_, fossil, Cretaceous.

Tribe 2. _Trachyglossa._--Radula present. No fins.

Fam. 1. _Amphitretidae_. Arms united by membrane; funnel attached to mantle, dividing the pallial aperture into two. _Amphitretus_, pelagic.

Fam. 2. _Alloposidae_. All arms united by membrane; mantle joined to head by dorsal band and two lateral commissures. _Alloposus_, pelagic.

Fam. 3. _Octopodidae_. Arms long and equal, without membrane; hectocotylus not autotomous. No cephalic aquiferous pores. _Octopus_, two rows of suckers on each arm, British. _Eledone_, single row of suckers on each arm. _Scaeurgus. Pinnoctopus. Cistopus. Japetella._

Fam. 4. _Philonexidae_. Hectocotylus autotomous; arms unequal in size; aquiferous pores on head and funnel. _Tremoctopus_, two dorsal pairs of arms united by membrane. _Ocythoë_, without interbrachial membrane.

Fam. 5. _Argonautidae_. Hectocotylus autotomous; no interbrachial membrane; extremities of dorsal arms in female expanded and secreting a shell; males very small, without shell. _Argonauta_.

LITERATURE.--Use has been freely made above of the article by E. Ray Lankester, on _Mollusca_, in the 9th edition of this Encyclopedia. For the chief modern works, see Bashford Dean, "Notes on Living Nautilus," _Amer. Nat._ xxxv., 1901; Arthur Willey, "Contribution to the Natural History of the Pearly Nautilus," A. Willey's _Zoological Results_, pt. vi. (1902); Foord, _Cat. Fossil Cephalopoda in British Museum_; Alpheus Hyatt, "Fossil Cephalopods of the Museum of Comp. Zoology," _Bull. Mus. Comp. Zool._ (Cambridge, U.S., 1868); Jalta, "I Cefalopodi viventi nel golfo di Napoli," _Fauna und Flora des Golfes von Neapel_, xxiii. (1896); Joubin, "Céphalopodes de l'atlantique nord," "Céph. de la Princesse Alice," _Camp. sci. Albert I^er de Monaco_, ix. (1895), xxii. (1900); Paul Pelseneer, "Mollusca," in the _Treatise on Zoology_, edited by E. Ray Lankester. (J. T. C.)

CEPHEUS, in Greek mythology, the father of Andromeda (q.v.); in astronomy, a constellation of the northern hemisphere, mentioned by Eudoxus (4th century B.C.) and Aratus (3rd century B.C.). Ptolemy catalogued 13 stars in this constellation, Tycho n, and Hevelius 51. The most interesting star in it is [delta] _Cephei_, a remarkable double star, the brighter component of which is a short period variable (5.37 days), with a range in magnitude of 3.7 to 4.9; it is also a spectroscopic binary.

CEPHISODOTUS, the name of the father and of the son of Praxiteles, both sculptors like himself. The former must have flourished about 400 B.C. A noted work of his was Peace bearing the infant Wealth, of which a copy exists at Munich. Peace is a Madonna-like figure of a somewhat conservative type; the child Wealth is less successful. Cephisodotus also made, like his son, a figure of Hermes carrying the child Dionysus, unless indeed ancient critics have made two works of one. He made certain statues for the city of Megalopolis, founded in 370 B.C. Of the work of the younger Cephisodotus, his grandson, we have no remains; he was a prolific sculptor of the latter part of the 4th century B.C., especially noted for portraits, of Menander, of the orator Lycurgus, and others (see J. Overbeck, _Antike Schriftquellen_, p. 255).

CERAM (_Sirang_), an island of the Dutch East Indies, in the Molucca group, lying about 3° S., and between 127° 45' and 131° E. Its length is a little over 200 m., its greatest breadth about 50 m., and its area, including neighbouring islets, 6621 sq. m. It consists of two parts, Great Ceram and Little Ceram or Huvamohel, united by the isthmus of Taruno; and, for administrative purposes, is assigned to the residency of Amboyna, being divided into Kairatu or West Ceram, Wahai and Amahai, the northern and the southern parts of Middle Ceram, and Waru or Eastern Ceram. No central chain of mountains stretches west and east through the island, but near the north coast hills, rising 2300 to 2600 ft., slope steeply to the shore. Near the south coast, west of the Bay of Elpaputeh, a complex mass of mountains forms a colossal pyramid, with peaks rising to nearly 5000 ft. The isthmus connecting the two parts of the island is very narrow, and has a height of only 460 to 490 ft. The chief rivers flow north and south into bays, but are navigable only for a few miles during the rainy season. The rainfall is very heavy, amounting to 121 in. (mean annual) on the south coast. On the north coast the bays of Savai and Waru are accessible for small vessels. The geological structure, consisting chiefly of eruptive rocks and crystalline limestone, is similar to that of northern Amboyna. In the eastern section the prevailing rock is crystalline chalk, similar to that of Buru. Several hot springs occur, and earthquakes are not infrequent. About 4000 persons perished in the earthquake of 1899. A large part of the interior is covered with dense forests, and except along the coast the population is scanty. For the naturalist Ceram is without much interest, lacking characteristic species or abundance of specimens. The Bandanese pay occasional visits to shoot bears and deer; there are numbers of wild goats and cattle; and among birds are mentioned cassowaries, cockatoos, birds of paradise, and the swallows that furnish edible nests. A large number of fish are to be found in the various rivers; and as early as 1860 no fewer than 213 species were described. The most valuable timber tree is the iron-wood. Rice, maize, cocoa-nuts, sugar-cane and a variety of fruits are grown; and some tobacco is exported to Europe; but by far the most important production is the sago palm, which grows abundantly in the swampy districts, especially of Eastern Ceram, and furnishes a vast supply of food, not only to Ceram itself, but to other islands to the east. The Dutch have established cocoa and coffee plantations at various points. The coast-villages are inhabited by a mixed Malay population, Buginese, Macassars, Balinese and other races of the archipelago. The interior is occupied by the aborigines, a people of Papuan stock. They are savages and head-hunters. The introduction of Christianity was hampered by the baneful influence of a secret society called the Kakian Union, to which pagans, Mahommedans and Christians indiscriminately attached themselves; and it has several times cost the Dutch authorities considerable efforts to frustrate their machinations (see _Tijdschrift van Ned. Ind._, fifth year). The total population is estimated at 100,000, including 12,000 Christians and 16,000 Mahommedans. The chief settlements are Savai at the north and Elpaputeh at the south end of the isthmus of Taruno. There was a Dutch fort at Kambello, on the west side of Little Ceram, as early as 1646.

CERAMICS, or KERAMICS ([Greek: keramos], earthenware), a general term for the study of the art of pottery. It is adopted for this purpose both in French (_céramique_) and in German (_Keramik_), and thus has its convenience in English as representing an international form of description for a study which owes much to the art experts of all nations, though "ceramic" and "ceramics" do not appear in English as technical terms till the middle of the 19th century.

The word "pottery" (Fr. _poterie_) in its widest sense includes all objects fashioned from clay and then hardened by fire, though there is a growing tendency to restrict the word to the commoner articles of this great class and to apply the word "porcelain" to all the finer varieties. This tendency is to be deprecated, as it is founded on a misconception; the word "porcelain" should only be applied to certain well-marked varieties of pottery. The very existence of pottery is dependent on two important natural properties of that great and widespread group of rocky or earthy substances known as clays, viz. the property of plasticity (the power of being readily kneaded or moulded while moist), and the property of being converted when fired into one of the most indestructible of ordinary things.

The clays form such an important group of mineral substances that the reader must refer to the article CLAY for an account of their occurrence, composition and properties. In this article we shall only deal with the various clays as they have affected the problems of the potter throughout the ages. The clays found on or close to the earth's surface are so varied in composition and properties that we may see in them one of the vital factors that has determined the nature of the pottery of different countries and different peoples. They vary in plasticity, and in the hardness, colour and texture of the fired product, through an astonishingly wide range. To-day the fine, plastic, white-burning clays of the south of England are carried all over Europe and America for the fabrication of modern wares, but that is a state of affairs which has only been attained in recent times. Even down to the 18th century, the potters of every country could only use on an extensive scale the clays of their own immediate district, and the influence of this controlling factor on the pottery of bygone centuries has never yet received the attention it deserves.[1]