rhagonn.

Brit.

/ˈreɪɡɒn/, U.S.

/ˈreɪˌɡɑn/

Origin: A borrowing from Greek, combined with an English element. Etymons: Greek ῥαγ- , ῥάξ , sycon n.

Etymology: < ancient Greek ῥαγ-, ῥάξ grape, of uncertain origin (probably a loanword from another language of the Mediterranean) + -on (in sycon n.); so called on account of its shape: see quot. 1887 at sense 1.

Zoology.

1. Originally: a hypothetical stage in the development of sponges, having a simple pyramidal form with an apical osculum and rounded flagellated chambers like those of a mature leuconoid sponge (see sense 2). In later use: a young sponge at a stage of development in which the larva has settled to form a flattened pyramid with a functional system of water canals (irrespective of its internal organization).

ΘΚΠ

the world > life > biology > biological processes > development, growth, or degeneration > [noun] > growth > stage of growth

stage1882

rhagon1887

sensitive period1905

scotophase1939

1887 W. J. Sollas in Encycl. Brit. XXII. 414/2 Such a form, called by Haeckel ‘dyssycus’, may be more briefly named a Rhagon from the grape-like form of its flagellated chambers.

1900 E. A. Minchin Sponges 125 The Rhagon is a little sponge organism, in shape like a cake or bun, being usually slightly flattened and spread out.

1928 Amer. Midland Naturalist 11 285 The ideal rhagon does not exist as an entity in nature, but certain of the fresh water sponges approach it very closely.

1957 Systematic Zool. 6 179/1 This development is the simplest known in the Demospongiae and results in the formation of a sack with double walls, opening by an osculum, that is, an asconoid rhagon.

2001 Invertebr. Biol. 120 299/1 Functional rhagons were completed within a week after settling.

2. The most complex type of sponge structure, characterized by small rounded flagellated chambers and a high degree of folding; a sponge of this type. Also called leucon. Usually attributive.

ΘΚΠ

the world > animals > invertebrates > subkingdom Parazoa > phylum Porifera > [noun] > member of > rhagon

ascon1881

leucon1881

rhagon1887

1887 W. J. Sollas in Encycl. Brit. XXII. 422/2 The canal system belongs to the eurypylous Rhagon type.

1906 Amer. Museum Jrnl. 6 226 The great majority of sponges, including those having ‘glass’ skeletons, horny skeletons or no skeletons at all, belong to the Rhagon type. In this case the flagellate chambers are very small and numerous and, instead of being tubular, are spherical.

1966 Jrnl. Paleontol. 40 1373/2 One of the most distinctive features of the sponges at hand is their sycon, or very simple rhagon, structure.

1979 E. N. K. Clarkson Invertebr. Palaeontol. & Evol. (1981) iv. 50/1 The vast majority of sponges are of leucon (rhagon) type..in which a number of sycon-like elements open into the large central cavity.

This entry has been updated (OED Third Edition, June 2010; most recently modified version published online March 2022).

单词	rhagon
释义	rhagonn. Brit. /ˈreɪɡɒn/, U.S. /ˈreɪˌɡɑn/ Origin: A borrowing from Greek, combined with an English element. Etymons: Greek ῥαγ- , ῥάξ , sycon n. Etymology: < ancient Greek ῥαγ-, ῥάξ grape, of uncertain origin (probably a loanword from another language of the Mediterranean) + -on (in sycon n.); so called on account of its shape: see quot. 1887 at sense 1. Zoology. 1. Originally: a hypothetical stage in the development of sponges, having a simple pyramidal form with an apical osculum and rounded flagellated chambers like those of a mature leuconoid sponge (see sense 2). In later use: a young sponge at a stage of development in which the larva has settled to form a flattened pyramid with a functional system of water canals (irrespective of its internal organization). ΘΚΠ the world > life > biology > biological processes > development, growth, or degeneration > [noun] > growth > stage of growth stage1882 rhagon1887 sensitive period1905 scotophase1939 1887 W. J. Sollas in Encycl. Brit. XXII. 414/2 Such a form, called by Haeckel ‘dyssycus’, may be more briefly named a Rhagon from the grape-like form of its flagellated chambers. 1900 E. A. Minchin Sponges 125 The Rhagon is a little sponge organism, in shape like a cake or bun, being usually slightly flattened and spread out. 1928 Amer. Midland Naturalist 11 285 The ideal rhagon does not exist as an entity in nature, but certain of the fresh water sponges approach it very closely. 1957 Systematic Zool. 6 179/1 This development is the simplest known in the Demospongiae and results in the formation of a sack with double walls, opening by an osculum, that is, an asconoid rhagon. 2001 Invertebr. Biol. 120 299/1 Functional rhagons were completed within a week after settling. 2. The most complex type of sponge structure, characterized by small rounded flagellated chambers and a high degree of folding; a sponge of this type. Also called leucon. Usually attributive. ΘΚΠ the world > animals > invertebrates > subkingdom Parazoa > phylum Porifera > [noun] > member of > rhagon ascon1881 leucon1881 rhagon1887 1887 W. J. Sollas in Encycl. Brit. XXII. 422/2 The canal system belongs to the eurypylous Rhagon type. 1906 Amer. Museum Jrnl. 6 226 The great majority of sponges, including those having ‘glass’ skeletons, horny skeletons or no skeletons at all, belong to the Rhagon type. In this case the flagellate chambers are very small and numerous and, instead of being tubular, are spherical. 1966 Jrnl. Paleontol. 40 1373/2 One of the most distinctive features of the sponges at hand is their sycon, or very simple rhagon, structure. 1979 E. N. K. Clarkson Invertebr. Palaeontol. & Evol. (1981) iv. 50/1 The vast majority of sponges are of leucon (rhagon) type..in which a number of sycon-like elements open into the large central cavity. This entry has been updated (OED Third Edition, June 2010; most recently modified version published online March 2022). < n.1887
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