medusoid's Usage Examples:

The Anthozoa differ from the Scyphomedusae in having no medusoid form; they all more or less resemble a sea-anemone, and may be termed actinioid.

It has been maintained that the gonads of Hydra represent sporosacs or gonophores greatly reduced, with the last traces of medusoid structure completely obliterated.

There is, however, no evidence whatever for this, the gonads of Hydra being purely ectodermal structures, while all medusoid gono phores have an endodermal portion.

- Simple polyps which become sexually mature and which also reproduce non-sexually, but without any medusoid stage in the life-cycle.

Polyp 7 has proof sense, 1 o c oduced as its first bud, 8; as its second bud, a7, motion and nutriwhich starts a uniserial pinnule; and as a third t i on, until its bud I', which starts a biserial branch (I I'-VI') medusoid nature that repeats the structure of the main stem and and organization gives off pinnules.

They typically present two structural forms, the non-sexual hydroid and the sexual medusoid; in such a case there is an alternation of generations (metagenesis), the hydroid giving rise to the medusoid by a sexual gemmation, the medusoid bearing sexual cells which develop into a hydroid.

The most usual condition, however, is that in which sessile medusoid gonophores or sporosacs are produced.

The medusoids have no true velum; in some cases a structure more or less resembling this organ, termed a velarium, is present, permeated by endodermal canals.

The entocodon is usually formed, proving the medusoid nature of the bud, but in sporosacs the entocodon may be rudimentary or absent altogether.

Here the medusoid, attached by the centre of its ex-umbral surface, has lost its velum and sub-umbral muscles, its sense organs and mouth, though still retaining rudimentary tentacles.

In this way the medusa sinks from an independent per sonality to an organ of the polyp-colony, becoming a so-called medusoid gonophore, or bearer of the reproductive organs, and losing gradually all organs necessary for an independent existence, namely those of sense, locomotion and nutrition.

Haeckel, on the other hand, is in accordance with Balfour in regarding a Siphonophore as a medusome, that is to say, as a colony composed of medusoid persons or organs entirely.