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TUGAS UNTUK TGL 3 DESEMBER 08 MK KKH I: terjemahkan perorangan dan kumpulkan pada ketua tingkat.

Colonial hydroids
Unlike hydra most members of the class Hydrozoa, are marine and colonial. They include the hydroids, the stinging corals, some jellyfishes, and the free-floating siphonophones, obelia (Fig.18-7) is a typical hydroid, of mossy or hairy form, found on rocks or shells or piling in the shallow waters of seacoasts. The small whitish or brownish colony isfastened by a rootlike base (hydrorhiza) bearing slender branched stems (hydrocauli) on which grow hundreds of microscopic polyps of two kinds. The feeding polyp, or hydranth, is hydra-like, with 20 or more solid tentacles, and is set in a transparent vase-shaped hydrotheca that affords it protection. These polyps capture minute animals by use of their nematocysts and tentacles. The reproductive polyp, or gonangium, is of cylindrical form, covered by a transparent gonotheca, and contains an axis or blastostyle on which lateral buds form that develop into medusae. The common stem supporting both kinds of polyps comprises an external transparent and noncellular parisarc that is continuous with the hydrotheca and gonotheca and an internal hollow coenosarc (common enteron) of cellular structure connecting the enterons of various polyps. Digested food circulates through the coenosarc. Both types of polyps are produced by buds on the stem.
The medusa is a minute jellyfish, shaped like an umbrella and rimmed with tentacles; on its concave side his containns is a central projecting manubrium, This contains the mouth, which leads to an enteron in the middle of the bell, whence four radial canals eextend to a ring canal in the bell margin. A gelatinous mesoglea fills the space between the epidermis over the bell, tentacles and manubrium and the gastrodermis that lines the digestive tract and its branches. Although the feeding polyps and the medusae differ markedly in appearance their basic structure is essentially the same.
The medusae escape from the gonangia to float and feed in the sea. They are of separate sexes, and their gonads develop in the enteron, whence eggs and sperm are released into the water. There each zygote develops into a minute ciliated planula larva. This soon settles and attaches with is blastophore uppermost, then grows to be a small polyp, which by asexual budding begins a new colony. Such an alternation of sexual an asexual generqations is termed metagenesis.