The royal natural history . g a kindof transition form connecting the Discomedusseand the polyps, are the Calycozoa, or cup-shapedmedusae, which either swim about freely or areattached by their apices, where the firm gelatinousdisc attains its greatest thickness. At the marginof the disc, these forms carry eight to sixteenarm - like processes. In the attached forms(Lucernaria) the ends of these processes areprovided with short tentacles, occasionally broad-ened into discs and used for attachment, andalso with stinging-capsules. The Calycozoa mayleave their place of attachment and swim aboutfor
The royal natural history . g a kindof transition form connecting the Discomedusseand the polyps, are the Calycozoa, or cup-shapedmedusae, which either swim about freely or areattached by their apices, where the firm gelatinousdisc attains its greatest thickness. At the marginof the disc, these forms carry eight to sixteenarm - like processes. In the attached forms(Lucernaria) the ends of these processes areprovided with short tentacles, occasionally broad-ened into discs and used for attachment, andalso with stinging-capsules. The Calycozoa mayleave their place of attachment and swim aboutfor a time, with a rotatory motion, and then againsettle down. Lucernaria has been found as deepas three thousand three hundred feet, but appearsto prefer to settle in shallower water. Thenearest relations of Lucernaria are the Tesseridce. These creatures are small andswim about freely, having an elegant long bell-like shape. The edge of the disc isdrawn out into alternately longer and shorter arms, eight to sixteen in Tessera (20 times size) The Sea-Anemones and Corals,—Class Anthozoa. We turn from the free-swimming Scyphomedusae to the permanently fixedpolyp forms, namely, the sea-anemones and corals; the latter of which leavebehind them monuments compared with which the pyramids sink into insigniii- 496 CCELENTERA TES. cance. Wherever these often minute animals settle, they build up great masses ofrock which may form part of the solid ground of the globe. Although Aristotle and his contemporaries recognised the sea-anemones as animals, almost two thousandyears elapsed before corals were considered tobe related to them. In describing the develop-ment of a small coral discovered on the Arabiancoast, and named Monoxenia darwini, Haeckelstates that the polyp, which is one-eighth ofan inch long, is of strictly radiate structure, themouth, which lies at the upper end of thecylindrical body, being surrounded by eightfeathered tentacles. It is attached to somesubstratu
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Keywords: ., bookcentury1800, booksubjectnaturalhistory, booksubjectzoology
