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aterial portion; -- used both literally and figuratively. It must contain within itself a nucleus of truth. I. Taylor.

Some as Nucleolus.

s or nuclei (called male and female pronuclei) which unite to form the first segmentation nucleus of an impregnated ovum.

A genus of Lower Silurian trilobites in which the glabella and cheeks form three rounded elevations on the head.

Cell division in which there is first a simple cleavage of the nucleus without change in its structure (such as the formation of chromosomes), followed by the division of the cytoplasm; direct cell division; -- opposed to mitosis. It is not the usual mode of division, and is believed by many to occur chiefly in highly…

(Bot.) A small body situated on or near the nucleus in the cells of some of the lower plants, consisting of two centrospheres containing centrosomes. It exercises an important function in mitosis.

roduct or benzole, and also, but rarely, to a similar mixed product of petroleum. Benzene nucleus, Benzene ring (Chem.), a closed chain or ring, consisting of six carbon atoms, each with one hydrogen atom attached, regarded as the type from which the aromatic compounds are derived. This ring formula is provisionally ac…

A small, clear space in the segments of the ovum, the precursor of the nucleus.

t is often represented in graphic formulæ by a short line or dash. See Diagram of Benzene nucleus, and Valence. Arbitration bond. See under Arbitration. -- Bond crediter (Law), a creditor whose debt is secured by a bond. Blackstone. -- Bond debt (Law), a debt contracted under the obligation of a bond. Burrows. -- Bo…

nic heteropod Mollusca, having a thin, glassy, bonnet-shaped shell, which covers only the nucleus and gills.

A principal or important point of concentration; the nucleus around which things are gathered or to which they tend; an object of attention, action, or force; as, a center of attaction.

A peculiar rounded body lying near the nucleus of a cell. It is regarded as the dynamic element by means of which the machinery of cell division is organized.

The nucleus or central part of the earth, forming most of its mass; -- disting. from lithosphere, hydrosphere, etc.

whose rational formulæ are written respectively in the form of a closed ring (see Benzene nucleus, under Benzene), or in an open extended form. -- Endless chain, a chain whose ends have been united by a link.

The place on an ovule, or seed, where its outer coats cohere with each other and the nucleus.

ceæ and Juglandaceæ. Partial chalazogamy is found in Ulmus, the tube here penetrating the nucleus midway between the chalaza and micropyle. --Chal`a*zo*gam"ic (#), a.

A hairlike envelope. The nucleus and chevelure of nebulous star. Sir. W. Hershel.

One of the minute bodies into which the chromatin of the nucleus is resolved during mitotic cell division; the idant of Weismann.

The envelope of a comet; a nebulous covering, which surrounds the nucleus or body of a comet.

ery great distance from it at its aphelion. A comet commonly consists of three parts: the nucleus, the envelope, or coma, and the tail; but one or more of these parts is frequently wanting. See Illustration in Appendix.