Such medusæ are the reproductive zooids or gonophores, either male or female, of the hydroid from which they arise, whether they become free or remain attached to the hydroid colony.
Also applied to the proboscis or manubrium of a hydroid medusa.
All the zooids of a hydroid colony collectively, including the nutritive and reproductive zooids, and often other kinds.
The rootstock or decumbent stem by which a hydroid is attached to other objects.
The reproductive zooids of a hydroid colony, collectively.
Defn: Any small fresh-water hydroid of the genus Hydra, usually found attached to sticks, stones, etc.
Note: Such medusæ are the reproductive zooids or gonophores, either male or female, of the hydroidfrom which they arise, whether they become free or remain attached to the hydroid colony.
Defn: Any hydroid belonging to Plumularia and other genera of the family Plumularidæ.
Defn: A branch of a plumularian hydroid specially modified in structure for the protection of the gonothecæ.
Defn: The rootstock or decumbent stem by which a hydroid is attached to other objects.
Especially: (a) The circular membrane that partially incloses the space beneath the umbrella of hydroid medusæ.
Defn: A division of acalephs in which the development is direct from the eggs, without a hydroid stage.
Defn: One of the nutritive zooids of a hydroid colony.
Defn: The reproductive zooids of a hydroid colony, collectively.
Defn: Any one of numerous species of delicate, usually pink, calcareous hydroid corals of the genus Stylaster.
Defn: Any hydroid which has tubular chitinous stems.
Defn: All the zooids of a hydroidcolony collectively, including the nutritive and reproductive zooids, and often other kinds.
Defn: A hydroid coral of the genus Millepora, especially M.
It is thus possible to force upon this hydroid an arrangement of organs which is altogether different from the hereditary arrangement.
This hydroid consists of a long straight main stem which grows vertically upwards and which has at regular intervals very fine and short bristle-like lateral branches, on the upper side of which the polyps grow.
One of the feeding or nutritive zooids of a hydroid or coral.
A branch of a plumularian hydroid specially modified in structure for the protection of the gonothec\'91.
Such medus\'91 are the reproductive zooids or gonophores, either male or female, of the hydroid from which they arise, whether they become free or remain attached to the hydroid colony.
A division of acalephs in which the development is direct from the eggs, without a hydroid stage.
The entire community is connected at its base by a horny net-work, uniting all the Hydroid stems in its meshes, and spreading over the whole surface on which the colony has established itself.
They swim about for a time, until they have found a resting-place, where they attach themselves, each one founding a Hydroid stock of its own, which will in time produce a new brood of Medusae.
In the Hydroids, the organization does not rise above the simple digestive cavity inclosed by the double body-wall; and we might not suspect their relation to the Acalephs, did we not see the Jelly-Fish born from the Hydroid stock.
There are other Hydroids giving rise to Medusae buds, from which, however, the Medusae do not separate to begin a new life, but wither on the Hydroid stock, after having come to maturity and dropped their eggs.
Long ago, Trembley attempted to cause, by grafting, the union of two pieces of hydroid polyps into a single individual.
In Tubularia mesembryanthemum, a hydroid polyp, there are stalk, root, and polyp-head.
If a piece cut from the stem of Antennularia (a hydroid polyp) be placed vertically, in a short time new branches and new 'roots' spring from it.
Bourne, describing the hydroid stage of the fresh-water Medusa (Proc.
Allman, "Note on the Structure of Certain Hydroid Medusae," "Brit.
Amongst the Coelenterates, the "Hydroid Zoophytes" are represented by a species of the encrusting genus Hydractinia, the horny polypary of which is so commonly found at the present day adhering to the exterior of shells.
The only Hydroid Zoophytes or Polyzoans which have a similar free mode of existence, have either no skeleton at all, or have hard structures quite unlike the horny sheaths of the Graptolites.
Footnote 19: A singular fossil has been described by Professor Martin Duncan and Mr Jenkins from the Carboniferous rocks under the name of Paloeocoryne, and has been referred to the Hydroid Zoophytes (Corynida).
Zoaria of the entoproct Loxosomatoides colonialis and colonies of the hydroid Irene ceylonensis are also found entangled with the zoaria of V.
Niger, has been found and it is doubtful whether a hydroid generation exists.
Among the most remarkable instances of such isolation is the occurrence in Lake Qurun in the Fayum of Egypt of Cordylophora lacustris and of the peculiar littlehydroid recently described by Mr. C.
America and in Germany, possesses both an asexual hydroid and a sexual medusoid generation.
This is a branching hydroid that does not produce free medusae.
In addition to these four species a minute hydroid belonging to the order Gymnoblastea and now being described by Mr. J.
The medusa was originally taken off the coast of Ceylon, while the hydroid was discovered in ponds of brackish water at Port Canning.
Preliminary Note on the occurrence of a Medusa (Irene ceylonensis, Browne) in a brackish pool in the Ganges Delta and on the Hydroid Stage of the species," J.
The medusa has been found in tanks in hot-houses in England, France and Germany, and a minute hydroid closely resembling that of Microhydra ryderi has been associated with it provisionally.
Both hydroid and medusae were found in a small pool of brackish water at Port Canning.
I subjoin a woodcut of a Silurian Coral, which does not, however, show the peculiar internal structure, but gives some idea of the general appearance of the old Hydroid Corals.
They are called graptolites (from their resemblance to pens), an extinct group of hydroid zoophytes, apparently resembling the sertularians of our own seas.
A branch of a plumularian hydroid specially modified in structure for the protection of the gonothecæ.
Any free-swimming gonophore of a hydroid; a hydroid medusa.
The Acalephæ of Cuvier are now regarded as belonging to the same class as the Hydroid Polyps.
All of you have seen common sea-anemones or sea-roses, and many of you will also be familiar with the so-called hydroid polyps.
Whereas primitively any polyp in a colony may produce medusa-buds, in many hydroid colonies medusae are budded only by certain polyps termed blastostyles (fig.
In a great many Leptomedusae the hydroid stage is as yet unknown, and it is by no means certain even that they possess one.
In the curious hydroid Monobrachium a single tentacle is present, and the same is the case in Clathrozoon; in Amphibrachium and in Lar (fig.
A hydrocoralline may be regarded as a form of hydroid colony in which the coenosarc forms a felt-work ramifying in all planes, and in which the chitinous perisarc is replaced by a massive calcareous skeleton.
This common British hydroid belongs by its characters to the family Bougainvillidae; it produces, however, a medusa of the genus Tiara (fig.
The gonostyles have been compared to the blastostyles of a hydroid colony, or to the manubrium of a medusa which produces free or sessile medusa-buds.
Moreover, all the medusae budded from a given hydroid colony are either male or female, so that even the non-sexual polyp must be considered to have a latent sex.
They show every transition between free medusae and sporosacs, as already described, for hydroid colonies.
So far as the trophosome is concerned, the step from an encrusting hydroid such as Hydractinia to the hydrocoralline Millepora is not great.
Hydra is, moreover, bisexual, in contrast with what is known of hydroid colonies.
In some cases both free medusae and gonophores may be produced from the same hydroid colony.
I know of no form in which so many of the characteristic features of a typical hydroid are more finely expressed than in this beautiful species.
Scarcely distinguishable from the Hydra are the adherent Hydroid polyps (Campanularia, Tubularia), which produce freely swimming medusae by budding, and out of the eggs of these there again arise adherent polyps.
On the upper half of the plate is a swarm of swimming medusae and ctenophora; on the lower half a few bunches of corals and hydroid polyps adhering to the bottom of the sea.
Out of the Archydra there first developed the different Hydroid polyps, some of which became the primary forms of Corals, others the primary forms of Hydromedusae.
You see the hydroid does not in the least resemble a jelly-fish.
A hydroid about one inch high, growing in patches and appearing like tufts of moss on rocks between tide-marks.
The illustration shows a plant on which thehydroid /Sertularia pumila/ is growing.
The hydroid /Hydractinia polyclina/ often covers the exterior of such shells with a brown, velvety growth.
These are spherical bodies covered with cilia (hairs), by means of which they swim about for a time; but they finally attach themselves to some object, there to grow and develop into hydroid colonies.
In the sertularians the zooeids perish on the stem and have no medusa life, their reproductive element giving rise to the hydroid form without metamorphosis.
It lives in colonies, but, unlike the hydroid colonies, each polyp of the community is a complete organism, and in the reef-building corals all the individual polyps of a colony are alike.
The typical hydroid colony is attached by a kind of creeping stem from which arises a vertical axis, which gives off short lateral, alternate branches bearing zooeids at their ends.
This hydroid is found in tide-pools on the New England coast, growing in clusters, about two inches high, attached to rocks or to mussel-shells.
The medusa which this hydroid liberates is called /Thaumatias diaphana/.
Hydroid colony beyond the lip of the shell relieves the Hermit from the necessity of so frequently changing to a larger shell as it grows.
Other species of Hermit Crabs constantly have their shells covered with a horny crust formed byHydroid zoophytes (Hydractinia, etc.
The vegetable kingdom has its root in the simple earths, especially the hydroid argillaceous earths; the animal kingdom in the divided calcareous earths.
All abide by the signification of water, or are conversions of elements or earths by oxydation into an hydroid condition.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "hydroid" in a variety of sentences. We hope that you will now be able to make sentences using this word.
