Chapter Zircono to Zoöpathology of Z by Webster's Dictionary (1913 Edition)

Zona pellucida

. [NL.] (Biol.) (a) The outer transparent layer, or envelope, of the ovum. It is a more or less elastic membrane with radiating striæ, and corresponds to the cell wall of an ordinary cell. See Ovum, and Illust. of Microscope. (b) The zona radiata. — Zona radiata[NL.] (Biol.), a radiately striated membrane situated next the yolk of an ovum, or separated from it by a very delicate membrane only.

Zonal
(Zon"al) a. [L. zonalis.] Of or pertaining to a zone; having the form of a zone or zones.

Zonal equation (Crystallog.), the mathematical relation which belongs to all the planes of a zone, and expresses their common position with reference to the axes. — Zonal structure (Crystallog.), a structure characterized by the arrangements of color, inclusions, etc., of a crystal in parallel or concentric layers, which usually follow the outline of the crystal, and mark the changes that have taken place during its growth. — Zonal symmetry. (Biol.) See the Note under Symmetry.

Zonar
(Zo"nar) n. [Mod. Gr. a girdle, fr. Gr. dim. of a girdle. See Zone.] A belt or girdle which the Christians and Jews of the Levant were obliged to wear to distinguish them from Mohammedans. [Written also zonnar.]

Zonaria
(||Zo*na"ri*a) n. pl. [NL.] (Zoöl.) A division of Mammalia in which the placenta is zonelike.

Zonate
(Zon"ate) a. (Bot.) Divided by parallel planes; as, zonate tetraspores, found in certain red algæ.

Zone
(Zone) n. [F. zone, L. zona, Gr. zw`nh; akin to zwnny`nai to gird, Lith. j&uringsta a girdle, j&uringsti to gird, Zend yah.]

1. A girdle; a cincture. [Poetic]

An embroidered zone surrounds her waist.

Dryden.

Loose were her tresses seen, her zone unbound.

Collins.

2. (Geog.) One of the five great divisions of the earth, with respect to latitude and temperature.

The zones are five: the torrid zone, extending from tropic to tropic 46° 56&min, or 23° 28&min on each side of the equator; two temperate or variable zones, situated between the tropics and the polar circles; and two frigid zones, situated between the polar circles and the poles.

Commerce . . . defies every wind, outrides every tempest, and invades.

Bancroft.

3. (Math.) The portion of the surface of a sphere included between two parallel planes; the portion of a surface of revolution included between two planes perpendicular to the axis. Davies & Peck (Math. Dict.)

4. (Nat. Hist.) (a) A band or stripe extending around a body. (b) A band or area of growth encircling anything; as, a zone of evergreens on a mountain; the zone of animal or vegetable life in the ocean around an island or a continent; the Alpine zone, that part of mountains which is above the limit of tree growth.

5. (Crystallog.) A series of planes having mutually parallel intersections.

6. Circuit; circumference. [R.] Milton.

Abyssal zone. (Phys. Geog.) See under Abyssal. — Zone axis (Crystallog.), a straight line passing through the center of a crystal, to which all the planes of a given zone are parallel.

Zone
(Zone), v. t. To girdle; to encircle. [R.] Keats.