POLYZOA , in See also:

• ZOOLOGY (from Gr. Nov, a living thing, and ?byos, theory)

Reproductive organs with ducts leading to the vesti- bule. Zooids possessing a high degree of individuality. Loxosoma Pedicellina (fig. 1), Ur satella. Class II. ECTOPROCTA (Nitsche). Lophophore circular or horseshoe shaped, including the mouth but not the anus. Tentacles retractile into an introvert (" tentacle-sheath "). Body- wall membranous or calcified, body- cavity distinct. Specific excretory organs absent, with the doubtful exception of the Phylactolaemata. Reproductive organs not continuous with ducts. Zooids usually connected laterally with their neighbours.

See also:

• ORDER
• ORDER (through Fr. ordre, for earlier ordene, from Lat. ordo, ordinis, rank, service, arrangement; the ultimate source is generally taken to be the root seen in Lat. oriri, rise, arise, begin; cf. " origin ")
• ORDER, HOLY

Crisis (fig. 2), Tubulipore, Hornera, Lichenopora. ub•order . CTEIQOSTOMATA (Busk).—Zooecia with soft unoalci-fiedl walls, the See also:

• EXTERNAL

Membranipora, Flustra, Onychocella, Lunulites, Steganoporella, Scrupocellaria, Menipea, Caberea, Bicellaria, Bugula, Beania, (After Hincks.) The tentacles are See also:

• EXPANDED

Against this view may be urged the essential similarity between the processes of budding in Entoprocta and Ectoprocta (cf. Seeliger, Zeitschr. wiss. Zool. xlix. 168; 1., 56o), and the resemblances in the development of the two classes. Of the forms above indicated there is no palaeontological See also:

• EVIDENCE (Lat. evidentia, evideri, to appear clearly)

They are the dominant group at the present day, and are ?.jepresented by a large number of genera and species. The Phylactolaemata are a small group confined to fresh See also:

• WATER

The rigid Cheilostomes which have this See also:

• HABIT (through the French from Lat. habitus, from habere, to have, hold, or, in a reflective sense, to be in a certain condition; in many of the English senses the French use habitude, not habit)

It is one of the most remarkable facts in the natural See also:

• HISTORY

In the Ectoprocta they are retractile into an introvert, the " tentacle-sheath " (fig. 9), the external opening of which is the " orifice " of the zooecium. In the Cyclostomata, further distinguished by the cylindrical or prismatic form of their highly calcified zooecia, the orifice is typically circular, without any definite closing organ. In the Cheilostomata it is closed by a chitinous (rarely calcareous) " operculum " (fig. 9, C), while in the Ctenostomata it is guarded by a delicate membrane similar to a piece of See also:

• PAPER
• PAPER (Fr. papier, from Lat. papyrus)

Even the ectoderm can rarely be recognized as an obvious epithelium except in regions where budding is taking place, while muscular layers are always absent and a coelomic epithelium can seldom be observed. The body-cavity is, however, traversed by muscles, and by, strands of mesodermic " funicular tissue," usually irregular, but sometimes constituting definite funiculi (fig. 6, x, x'). This tissue is continuous from zooecium to zooecium (After Allman.) a, Anus. br, Expanded tentacles. i, Ectocyst. in, r', Parietovaginal muscles. mr, Retractor muscle. o, Ovary. oe, Oesophagus. v, Caecum of stomach. t, testis. x, x', Funiculi.

through perforated " rosette-plates " in the dividing walls. In the Phylactolaemata a single definite funiculus passes from the body-wall to the See also:

• APEX

The mesodermic portion becomes charged with a yolk-like material (y), and, on the germination of the statoblast, gives rise to the outer layer (See also:

• MES

The parietal muscles (p.m.), which pass from the vertical walls to the frontal wall, thus See also:

• ACT (Lat. actus, actum)

The operculum retains its op continuity with the frontal membrane (fig. 9, B) into which the parietal muscles are still inserted. As indications that the conditions described in Membranipora and Cribrilina are of special significance may be noted the fact that the ancestrula of many genera which have well-developed compensation-sacs in the rest of their zooecia is a Membranipora-like individual with a series of marginal calcareous spines, and the further fact that a considerable proportion of the Cretaceous Cheilostomes belong either to the Membraniporidae or to the Cribrilinidae. (ii.) In Scrupocellaria, Menipea and Caberea a single, greatly dilated marginal spine, the FIG. to. Zooecium " scutum " or " fornix," may protect the of Cribrilina, showing frontal membrane. (iii.) In Umbonula the entrance to the the frontal membrane and parietal the muscles of the young zooecium are like th e pemol side sac on the of the those of Membranipora, but they become exi ntrant operculum (o p). covered by the growth, from the proximal aand lateral sides, of a calcareous lamina covered externally by a soft membrane. The arrangement is perhaps derivable from a Cribrilina-like condition in which the outer layer of the spines has become membranous while the spines themselves are laterally united from the first. (iv.) In the Microporidae and Steganoporellidae the body-cavity becomes partially subdivided by a calcareous lamina (" cryptocyst," Jullien) which grows from the proximal and lateral sides in a See also:

• PLANE

9, C), the compensation-sac being developed See also:

• ROUND (O. Fr. rond, Lat. rotundus, the Fr. is the source also of Du. rond; Ger., Swed., Dan. and Nor. rond)

sp, Anchoring spines of the statoblast. y, The yolk-like rnesodermic mass. B, of an Cribrilina ; A Sections. A, of Membranipora; immature zooecium of p.m., Parietal muscles. ha, gB, 1, Hatschek.) i 1.—Larva of Pedicellina. Anus. Apical sense-organ. Intestine. Ventral wall of stomach. POLYZOA 45 pora pilosa, the pelagic larva is known as Cyphonautes, and it has a structure not unlike that of the larval Pedicellina. The See also:

• PRINCIPAL

The pyriform organ has probably assisted the larva to find an appropriate place for fixation (cf. Kupelwieser, 18) ; but, like the alimentary canal and most of the other larval organs, it undergoes a process of histolysis, and the larva becomes the ancestrula, containing the primary brown body derived from the purely larval organs. The polypide is formed, as in an ordinary zooecium after the loss of its polypide, from a polypide-bud. The Cyphonautes type has been shown by Prouho (24) to occur in two or three widely different species of Cheilostomata and Ctenostomata in which the eggs are laid and develop in the external water. In most Ectoprocta, however, the development takes place internally or in an ovicell, and a considerable quantity of yolk is present. The alimentary canal, which may be represented by a vestigial structure, is accordingly not functional, and the larva does not become pelagic. A pyriform organ is present in most Gymnolaemata as well as the sucker by which fixation is effected. As ,in the case of Cyphonautes, the larval organs degenerate and the larva becomes the ancestrula from which a polypide is developed as a bud. In the Cyclostomata the primary embryo undergoes repeated fission without developing definite organs, and each of the numerous pieces so formed becomes a free larva, which possesses no alimentary canal. Finally, in the Phylactolaemata, the larva becomes an ancestrula before it is hatched, and one or several polypides, may be present when fixation is effected. The development of the Ectoprocta is intelligible on the hypo-thesis that the Entoprocta form the starting-point of the series.' On the view that the Phylactolaemata are nearly related to Phoronis (see See also:

• PHORONIDEA

It seems more natural to draw the conclusion that the resemblances of the Phylactolaemata to Phoronis are devoid of phylogenetic significance. References to important See also:

• WORKS

(4) Busk, " See also:

• REPORT (O.Fr. report or raport, modern rapport, from O.Fr. reporter, mod. rap porter, Lat. reportare, to bring back, in poetical use only, of bringing back an account, news, &c.)

(7) See also:

• CORI (anc. Cora)

(To) Davenport, " Urnatella," ibid. (1893), See also:

• XXIV

Brit. (loth ed., 1902), xxxi. 826. (13) Harmer, " Morph. Cheilostomata," Quart. Journ. Mic. Sci. (1903), xlvi. 263. (14) Hincks, " Hist. Brit.

See also:

• MAR, EARLDOM OF
• MAR, JOHN ERSKINE, 1ST OR 6TH EARL OF (d. 1572)
• MAR, JOHN ERSKINE, 2ND OR 7TH EARL
• MAR, JOHN ERSKINE, 6TH OR 11TH EARL OF (1675-1732)

(19) Lankester, art, " Polyzoa," Ency. Brit. (9th ed., 1885), xix. 429. (20) Levinsen, " Bryozoa," Vid. Medd. Naturh. Foren. (See also:

• COPENHAGEN (Danish Kjobenhavn)

See also:

• VICTORIA
• VICTORIA (or VITTORIA), TOMMASSO LUDOVICO DA (C. I540-C. 1613)
• VICTORIA [ALEXANDRINA VICTORIA]

(23) See also:

• PACE (through O. Fr. pas, from Lat. passus, step, properly the stretch of the leg in walking, from pandere, to stretch)
• PACE, RICHARD (c. 1482-1536)

(25) Prouho, " Bryozoaires," ibid. (2) (1892), x. 557. (26) Seeliger,"Larven u. Verwandtschaft," Zeitschr. wiss. Zoo'. 1906), lxxxiv. I. (27) See also:

• ULRICH

F. H.) or " mandible " can be opened and closed. It is regarded as a modified zooecium, the polypide of which has become vestigial, although it is commonly represented by a sense-organ, bearing tactile hairs, situated on what may be termed the See also:

• PALATE (Lat. palatum, possibly from the root of pascere, to feed)

They occur in particular in relation with the orifice of the zooecium, and with that of the compensation-sac. This delicate structure is frequently guarded by an avicularium at its entrance, while avicularia are also commonly found on either side of the operculum or in other positions See also:

• CLOSE
• CLOSE (from Lat. clausum, shut)
• CLOSE, MAXWELL HENRY (1822-1903)

II) constitutes the greater part of the larva and contains most of the viscera. It is terminated by a well-developed structure (fg) corresponding with the apical sense-organ of ordinary Trocho-T See also:

• SPHERES, MUSIC OF THE