Sym"me*try (?), n. [L. symmetria,
Gr. &?;; sy`n with, together + &?; a measure: cf. F.
symétrie. See Syn-, and Meter rhythm.]
1. A due proportion of the several parts of a
body to each other; adaptation of the form or dimensions of the
several parts of a thing to each other; the union and conformity of
the members of a work to the whole.
2. (Biol.) The law of likeness;
similarity of structure; regularity in form and arrangement; orderly
and similar distribution of parts, such that an animal may be divided
into parts which are structurally symmetrical.
&fist; Bilateral symmetry, or two-sidedness, in
vertebrates, etc., is that in which the body can be divided into
symmetrical halves by a vertical plane passing through the middle;
radial symmetry, as in echinoderms, is that in which the
individual parts are arranged symmetrically around a central axis;
serial symmetry, or zonal symmetry, as in earthworms, is
that in which the segments or metameres of the body are disposed in a
zonal manner one after the other in a longitudinal axis. This last is
sometimes called metamerism.
3. (Bot.) (a) Equality
in the number of parts of the successive circles in a flower.
(b) Likeness in the form and size of floral
organs of the same kind; regularity.
Axis of symmetry. (Geom.) See under
Axis. -- Respective symmetry, that
disposition of parts in which only the opposite sides are equal to
each other.
Sym"me*try (?), n. [L. symmetria,
Gr. &?;; sy`n with, together + &?; a measure: cf. F.
symétrie. See Syn-, and Meter rhythm.]
1. A due proportion of the several parts of a
body to each other; adaptation of the form or dimensions of the
several parts of a thing to each other; the union and conformity of
the members of a work to the whole.
2. (Biol.) The law of likeness;
similarity of structure; regularity in form and arrangement; orderly
and similar distribution of parts, such that an animal may be divided
into parts which are structurally symmetrical.
&fist; Bilateral symmetry, or two-sidedness, in
vertebrates, etc., is that in which the body can be divided into
symmetrical halves by a vertical plane passing through the middle;
radial symmetry, as in echinoderms, is that in which the
individual parts are arranged symmetrically around a central axis;
serial symmetry, or zonal symmetry, as in earthworms, is
that in which the segments or metameres of the body are disposed in a
zonal manner one after the other in a longitudinal axis. This last is
sometimes called metamerism.
3. (Bot.) (a) Equality
in the number of parts of the successive circles in a flower.
(b) Likeness in the form and size of floral
organs of the same kind; regularity.
Axis of symmetry. (Geom.) See under
Axis. -- Respective symmetry, that
disposition of parts in which only the opposite sides are equal to
each other.
