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nuclei 音標拼音: [n'ukli ,ɑɪ] n. nucleus的復數形 nucleus的復數形 Nucleus \ Nu" cle* us\, n.; pl. E. { Nucleuses}, L. { Nuclei}. [ L., a kernel, dim. fr. nux, nucis, nut. Cf. { Newel} post.] [ 1913 Webster] 1. A kernel; hence, a central mass or point about which matter is gathered, or to which accretion is made; the central or material portion; -- used both literally and figuratively. [ 1913 Webster] It must contain within itself a nucleus of truth. -- I. Taylor. [ 1913 Webster] 2. ( Astron.) The body or the head of a comet. [ 1913 Webster] 3. ( Bot.) ( a) An incipient ovule of soft cellular tissue. ( b) A whole seed, as contained within the seed coats. [ 1913 Webster] 4. ( Biol.) A body, usually spheroidal, in a eukaryotic cell, distinguished from the surrounding protoplasm by a difference in refrangibility and in behavior towards chemical reagents, which contains the chromosomal genetic material, including the chromosomal DNA. It is more or less protoplasmic, and consists of a clear fluid ( achromatin) through which extends a network of fibers ( chromatin) in which may be suspended a second rounded body, the nucleolus ( see { Nucleoplasm}). See { Cell division}, under { Division}. [ 1913 Webster PJC] Note: The nucleus is sometimes termed the endoplast or endoblast, and in the protozoa is supposed to be concerned in the female part of the reproductive process. See { Karyokinesis}. [ 1913 Webster] 5. ( Zool.) ( a) The tip, or earliest part, of a univalve or bivalve shell. ( b) The central part around which additional growths are added, as of an operculum. ( c) A visceral mass, containing the stomach and other organs, in Tunicata and some mollusks. [ 1913 Webster]
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