Siphonophora

Century Dictionary and Cyclopedia

1. n. A genus of myriapods, typical of the unused family Siphonophoridæ.
2. n. A notable genus of plantlice (Aphididæ), erected by Koch in 1855, having long nectaries, and the antennæ usnally longer than the body. It contains numerous species, many of which are common to Europe and America, as the grain plant-louse, S. avenæ, and the rose plant-louse, S. rosæ.
3. n. Oceanic hydrozoans, a subclass of Hydrozoa or an order of Hydromedusæ, containing free pelagic forms in which hydriform persons and sterile mednsiform persons (in one family only the former) are united in colonies or aggregates under many special modifications, but definite and constant in each instance. The medusiform or sexual persons are usually only in the form of sporosacs, hut sometimes are matured before they are set free from the colony. The structure is essentially a hollow stem or stock, badding into many different kinds of appendages, representing modified hydranths, hydriform persons, or undeveloped medusiforms. The appendages which a siphonophoran may or does have are the float, pneumatophore orpneumatocyst, which may be absent or replaced by an inflation of the whole stem, the somatocyst, as in the Portuguese man-of-war; the swimming-bell or nectocalyx; the hydrophyllium, covering some of the other parts; the dactylozoöid, or tentaculiform person; the gastrozoöid or nutritive person, which may be highly differentiated into oral, pharyngeal, gastric, and basal parts, which latter may bear long tentacles; and the sexual persons, medusiform buds proper, or gonophores. The arrangement of these elements is very diverse in the different forms of the order. The Siphonophora are sometimes divided into two orders, Calycophora and Physophora, or into four suborders. Re cognized families are Athorybiidæ, Agalmidæ, Apolemiidæ, Physophoridæ, Rhizophysidæ, Physaliidæ, Hippapodiidæ, Monophyidæ, Diphyidæ, and Velellidæ. See cuts under hydrophyllium, Physalia, hydranth, tentacular, Athorybia, gonoblastidium, gonophore, and nematocyst.

Wiktionary

1. n. A taxonomic order within the class Hydrozoa — the siphonophores.

GNU Webster's 1913

1. n. (Zoöl.) An order of pelagic Hydrozoa including species which form complex free-swimming communities composed of numerous zooids of various kinds, some of which act as floats or as swimming organs, others as feeding or nutritive zooids, and others as reproductive zooids. See Illust. under physallia, and porpita.

WordNet 3.0

1. n. marine colonial hydrozoans