Definitions of polyzoa
-
A
class
of
animals
forming
the
lowest
members
of
the
Mollusca,
and
generally
known
by
the
popular
names
of "
sea-
mosses"
and "
sea-
mats."
They
are
invariably
compound,
forming
associated
growths
or
colonies
produced
by
gemmation
from
a
single
primordial
individual,
and
inhabit
a
polyzoarium,
corresponding
to
the
polypidom
of
the
composite
hydroids.
The
typical
polypide
of
a
polyzoon
differs
from
the
polypite
of
the
Hydrozoa
in
having
a
distinct
alimentary
canal
suspended
freely
in
a
body
cavity,
and
in
having
the
reproductive
organs
contained
within
the
body.
The
body
is
inclosed
in
a
doublewalled
sac,
the
outer
layer (
ectocyst)
of
which
is
chitinous
or
calcareous,
and
the
inner (
endocyst)
a
delicate
membranous
layer.
All
the
Polyzoa
are
hermaphrodite.
Besides
true
sexual
reproduction,
and
besides
the
power
of
producing
colonies
by
continous
budding,
fresh
individuals
are
in
many
cases
produced
by
a
process
of
discontinuous
gemmation.
The
Polyzoa
are
chiefly
marine,
encrusting
stones,
old
shells,
and
sea-
weeds;
but
some
are
fresh-
water.
-
marine
or
freshwater
animals
that
form
colonies
of
zooids
-
A
numerous
living
class
of
mollusca
or
plant
like
animals,
chiefly
inhabitants
of
the
sea,
found
fossil
in
all
formations;
known
also
as
bryozoa.
-
Molluscous
animals
growing
together,
and
produced
by
germination
from
a
single
one.
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