(Hy*dat"i*form) a. [Hydatid + -form.] Resembling a hydatid.
(Hy"da*toid) a. [Gr. "y`dwr, "y`datos, water + -oid.] (Anat.) Resembling water; watery; aqueous; hyaloid.
(Hy"dr-) See under Hydro-.
(Hy"dra) n.; pl. E. Hydras L. Hydræ [L. hydra, Gr. "y`dra; akin to "y`dwr water. See Otter the
1. (Class. Myth.) A serpent or monster in the lake or marsh of Lerna, in the Peloponnesus, represented
as having many heads, one of which, when cut off, was immediately succeeded by two others, unless
the wound was cauterized. It was slain by Hercules. Hence, a terrible monster.
Gorgons, and Hydras, and Chimeras dire.Milton.
2. Hence: A multifarious evil, or an evil having many sources; not to be overcome by a single effort.
3. (Zoöl.) Any small fresh-water hydroid of the genus Hydra, usually found attached to sticks, stones,
etc., by a basal sucker.
The body is a simple tube, having a mouth at one extremity, surrounded by a circle of tentacles with
which it captures its prey. Young hydras bud out from the sides of the older ones, but soon become
detached and are then like their parent. Hydras are remarkable for their power of repairing injuries; for
if the body be divided in pieces, each piece will grow into a complete hydra, to which fact the name
alludes. The zooids or hydranths of marine hydroids are sometimes called hydras.
4. (Astron.) A southern constellation of great length lying southerly from Cancer, Leo, and Virgo.
(Hy*drach"nid) n. [Hydr- + arachnid.] (Zoöl.) An aquatic mite of the genus Hydrachna.
The hydrachnids, while young, are parasitic on fresh-water mussels.
(Hy*drac"id) n. [Hydr- + acid: cf. F. hydracide.] (Chem.) An acid containing hydrogen;
sometimes applied to distinguish acids like hydrochloric, hydrofluoric, and the like, which contain no
oxygen, from the oxygen acids or oxacids. See Acid.
(Hy`dra*cryl"ic) a. [Hydr- + acrylic.] (Chem.) Pertaining to, or designating, an isomeric
variety of lactic acid that breaks down into acrylic acid and water.
(Hy`drac*tin"i*an) n. [See Hydra, and Actinia.] (Zoöl.) Any species or marine hydroids,
of the genus Hydractinia and allied genera. These hydroids form, by their rootstalks, a firm, chitinous
coating on shells and stones, and esp. on spiral shells occupied by hermit crabs. See Illust. of Athecata.
(||Hy*dræ"mi*a) n. [NL., fr. Gr. "y`dwr water + a"i^ma blood.] (Med.) An abnormally watery
state of the blood; anæmia.
(Hy"dra*gogue) a. [L. hydragogus conveying off water, Gr. "y`dwr water + to lead: cf. F.
hydragogue.] (Med.) Causing a discharge of water; expelling serum effused into any part of the body,
as in dropsy. n. A hydragogue medicine, usually a cathartic or diuretic.
(Hy*dram"ide) n. [Hydr- + -amide.] (Chem.) One of a group of crystalline bodies produced
by the action of ammonia on certain aldehydes.