Hydranth sentence example

hydranth
  • Just below the crown of tentacles, however, the body widens out to form a " head," termed the hydranth (a), containing a stomach-like dilatation of the digestive cavity.

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  • On the upper face of the hydranth the crown of tentacles (t) surrounds the peristome, from which rises the conical hypostome, bearing the mouth at its extremity.

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  • The perisarc when, present invests the hydrorhiza and hydrocaulus; it may stop short below the hydranth, or it may extend farther.

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  • Amphibrachium grows in the tissues of a sponge, Euplectella, and protrudes its hydranth into the canal-system of the sponge; and Lar grows on the tubes of the worm Sabella.

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  • As a general rule polyp-buds are produced from the hydrorhiza and hydrocaulus, while medusa-buds are formed on the hydranth.

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  • In Tubularia by a process of decapitation the hydranths may separate off and give rise to a separate individual, while the remainder of the body grows a new hydranth.

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  • The body bears tentacles, but shows no division into hydrorhiza, hydrocaulus or hydranth; it is temporarily fixed and has no perisarc. The polyp is usually hermaphrodite, developing both ovaries and testes in the same individual.

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  • The gymnoblastic polyp usually has a distinct perisarc investing the hydrorhiza and the hydrocaulus, sometimes also the hydranth as far as the bases of the tentacles (Bimeria); but in such cases the perisarc forms a closely-fitting investment or cuticule on the hydranth, never a hydrotheca standing off from it, as in the next sub-order.

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  • In this sub-order the characters of the hydranth are very variable, probably owing to the fact that it is exposed and not protected by a hydrotheca,.

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  • Speaking generally, three principal types of hydranth can be distinguished, each with subordinate varieties of form.

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  • Hydranth (hydriform person)expanded.

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  • Hydranth (hydriform person) contracted.

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  • The body, representing the hydranth of an ordinary hydroid, has the aboral portion modified into a float, from which hangs down a proboscis bearing the mouth.

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  • Thus the affinities of the hydranth are clearly, as Dendy points out, After Haeckel, System der Medusen, by permission of Gustav Fischer.

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  • The hydranth almost always has a single circlet of tentacles, like the Bougainvillea-type in the preceding sub-order; an exception is the curious genus Clathrozoon, in which the hydranth has a single tentacle.

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  • In both cases the hydranth is extremely reduced and has no tentacles, and the polyp forms a colony by budding from the base.

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  • The polyp usually has the body distinctly divisible into hydranth, hydrocaulus and hydrorhiza, and is usually clothed in a perisarc. The medusae may be set free or may remain attached to the polyp-colony and degenerate into a gonophore.

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