Page:The New International Encyclopædia 1st ed. v. 04.djvu/501

* CEPHALIZATION. 429 CEPHALOPODA. three iiietaineies. Ahtady. Iiowovev, tlic prin- cipal sense-organs are lotaled in the head, and the central nervous system is enlarged there to lorni a brain. In the Arthropoda and the verte- brates the number ol" nietanieres in the head is increased, there Vieing live head-melameres in the eraylish. jirobalily five in insects, and from nine to thirteen in vertebrates. The head now takes on the principal sensory and psychical (unctions, which are abandoned by the rest of the body. The sense-organs become more and more concentrated at the head and they become larger: the nerve-centres at the head become relatively more important, and so the brain in- creases in size, while the interrelation of parts bec(nnes more intimate, so »hat the head not cmly becomes hirger, but also more of a unit, an<l the brain more elVniiiit as a controlling factor. CEPHALOCHORDA, s.M'iil-.'.-kor'da i Xeo- l.at. nom. pi., from (ik. (ct^aXii, l.cithuU', head + Xopd-q. chorilf. cord), . small class of chordate animals, including the lancelet. These are usu- ally regarded as oll'shoots of the primary verte- brate type, although some maintain that they are pioneer or ancestral types themselves and fore- shadow fishes. See Amphioxis, CEPHALODIS'CUS. An extraordinary deep- sea animal, regarded as allied to Balanoglossus (q.v. ), and classed, with a related genus, Rhabdo- pleura, among the .delochorda, as the lowest of the phylum fhordata. They were formerly re- garded as polyzoans, but resemble Balanoglos- sus in structure, having a proboscis, a collar and eoUar-cavity, and a trunk, containing a structure resend)ling a notochord. '"Cephalodiscus has an investment in the form of a branching gelatinous structure, which is beset with numerous short, filiform processes, and contains a number of cavities occupied by zooids. The latter are not in organic continuity, so that, though inclosed in a common investment, they do not form a colony in the sense in which the word is used of the Polyzoa or hydroid polyps, . . . They mul- tiply by buds, but these become detached before they are mature. . . . Rhabdopleura occurs in colonies of zooids organically connected to- gether, and inclosed in, th<nigh not in organic continuity Avith, a system of branching mem- branous tvibes." Consult Parker and Haswell. Tej-t-Hook of Zoology (London and New York. ISfC). CEPHALO'NIA, or KEPH ALLE'NIA (Gk. Ke0aXX7;Wa, from Kf(/)a^, kcphnlC, head + 6vos, Olios, donkey). The largest of the Ionian Islands (q.v. I, situated off the coast of Greece, be- tween latitudes 38°aml ,38° ,30' X, and longitudes '20° 21' and 20° 49' E, (.Map: Greece, B 3). Its greatest length is about 32 miles, and its total area 302 square miles. The surface is mountain- ous, rising near the centre to an altitude of 3714 feet. The soil is for the most part thin, and water scarce and the rainfall slight, The climate is warm and dry, but agreeable. Earthquakes are not infrequent. The inhabitants are industri- ous and enterprising, and have planted vineyards wherever the grape will grow. There is little available land for the cultivation of grain, but the output of fruit is considerable. The chief prod- ucts are olives, currants, and other southern fruits and vegetables, wine, and oil. The popula- tion in 1800 was ,80,178. The language spoken is a Greek dialect. The chief towns are .Argostoli (q.v.), the capital, and Lixuri, on the Bay ot l.ivada, on the southwest coast, C'ephalonia is called, by Homer, Same or Sanios, Later the island appears under the name of C'ephallenia, derived from its inhabitants. It successively fell into the hands of the .thenians, Romans, Byz;intines, Normans, and Venetians, from the last of whom it was repeatedly wrested by the Turks. On the fall of the Venetian Rc- iniblic, in 1707, it was seized by the French, who were in their turn dislodged by the Russians. Tn 1809 it came into the possession of England. It was ceded to Greece in IStU. With Ithaca and some neighboring islets Cephalonia now forms a nomarchy of that kingdom. CEPH'ALOP'ODA (Xeo-Lat. nom. pi., from Gk. K«t>ar], hrphalr, head + irovs, potts, foot). The highest and most specialized class of JIol- lusca, characterized by the presence of a circlet of lleshy arms surrounding the mouth on the front of the head. These arms, also called 'tentacles' and 'feet,' are modifications of the 'foot' which, as the muscular organ of locomotion of the Gas- tropoda and the Velecypoda, occupies a ventral position on the body of the animal in those classes. In the Cephalopoda the foot has moved forward and become divided into two sections. The anterior section forms the circlet of arms that serve both as accessory mouth-parts, to catch and hold the prey, and as organs of creeping loco- motion. The posterior section has become de- veloped into part of a most eflicient hydrostatic organ of propulsion, called the 'hypimome' or 'siphon.' The body of the cephalopod is essen- tially a bag formed of the 'mantle,' which entirely incloses the visceral organs, and which is open only at the end to which the head is attached. In some genera this bag is almost spherical, and creeping locomotion is accomplished chiefly by the a])pendages of the head: in others, the body is elongated, and furnished with tw'o fin-like ex- pansions on the sides, and the animal propels it- self through the water by means of the hydro- static organ, the hyponome. The ordinary posi- tion of the cephalopod in water is quite different from that of any other mollusk, A chiton, a ^nail, or a clam moves with the foot down, the mouth at the anterior end, and the visceral hump uppermost on the dorsal surface. A cephalopod when creeping has a very similar position, ex- cept that the mouth is ventral. In swinmiing, however, ce[)!ialo])ods liave the mouth at the an- terior end. and what was the anterior side is now the dorsal side of the animal. Thus the cephalo- pod, in taking to an active swimming life, has lipped backward through an angle of 90°, Cepha- lopods are able to swim forward or backward, often with great rapidity, the most important means of locomotion being the hyponome, near the under side of the head. The mantle is at- tached to the neck only on the dorsal side; else- where there is free commimication between the mantle-cavity and the outside. When the numtle relaxes, water fills the cavity: when it contracts it closes tight about the neck: there is no exit for the contained water save through the hypo- nome. and, as contraction takes place suddenly and forcibly, a jet of water is expelled from the hyponome, causing the animal to dart backward through the water. The head of a cephalopod is roundish, more distinct from the rest of the body than it is in