Tunicata \Tu`ni*ca"ta\, pr. n. pl. [NL. See Tunicate.] (Zool.)
A grand division of the animal kingdom, intermediate, in some
respects, between the invertebrates and vertebrates, and in
modern classifications considered a subphylum of the
vertebrates; called also urochordata. They were formerly
classed with acephalous mollusks. The body is usually covered
with a firm external tunic, consisting in part of cellulose,
and having two openings, one for the entrance and one for the
exit of water. The pharynx is usually dilated in the form of
a sac, pierced by several series of ciliated slits, and
serves as a gill.
[1913 Webster]
Note: Most of the species when mature are firmly attached to
foreign substances, but have free-swimming larvae which
are furnished with an elongated tail and somewhat
resemble a tadpole. In this state the larva has a
urochord and certain other structures resembling some
embryonic vertebrates. See Ascidian, Doliolum,
Salpa, Urochord, and Illust. of Social ascidian,
under Social.
[1913 Webster] Tunicate
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