Nu"cle*us (?), n.; pl. E.
Nucleuses (#), L. Nuclei (#).
[L., a kernel, dim. fr. nux, nucis, nut. Cf.
Newel post.]
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.
It must contain within itself a nucleus of
truth.
I. Taylor.
2. (Astron.) The body or the head of a
comet.
3. (Bot.) (a) An
incipient ovule of soft cellular tissue. (b)
A whole seed, as contained within the seed coats.
4. (Biol.) A body, usually spheroidal,
in a cell or a protozoan, distinguished from the surrounding
protoplasm by a difference in refrangibility and in behavior towards
chemical reagents. 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.
&fist; 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.
5. (Zoöl.) (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.
