leuconn.

Brit.

/ˈl(j)uːkɒn/, U.S.

/ˈlukɑn/

Origin: A borrowing from German. Etymon: German Leucones.

Etymology: < German Leucones, the name of a ‘natural family’ of sponges (E. Haeckel 1871, in Jenaische Zeitschr. f. Med. u. Naturwissensch. 6 648) < leucon- (in scientific Latin Leuconia , proposed genus name of sponges (R. E. Grant in Lancet (1833) 2 Nov. 199/2) < ancient Greek λευκός white (see leuco- comb. form) + scientific Latin -ia -ia suffix², with inserted -n- , perhaps after ancient Greek λευκόν , neuter singular of λευκός ) + -es , probably after Sycones (see sycon n.). Compare earlier scientific Latin leucon, specific name of a beetle (1826).

Zoology.

The most complex type of sponge structure, in which chambers lined with flagellated cells (choanocytes) are connected to the exterior and the central cavity by a network of canals (= rhagon n. 2); a stage in sponge development typified by this structure (= rhagon n. 1); a sponge of this type or stage. Frequently attributive. Cf. ascon n., sycon n. 2.

ΘΚΠ

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

ascon1881

leucon1881

rhagon1887

1873 W. S. Dallas tr. E. Häckel in Ann. & Mag. Nat. Hist. 11 424 D. IV. Natural system with average extension of the idea of species (in the fourth degree): three families (Ascones, Leucones, Sycones) with 21 genera.]

1881 Jrnl. Royal Microsc. Soc. 1 612 A simple Leucon is the homologue of a simple Sycon, and therefore with an Ascon.

1892 Jrnl. Elisha Mitchell Sci. Soc. 9 36 The subdermal cavities.., communicating with the exterior by numerous pores,..are found in certain Leucons.

1932 L. A. Borradaile & F. A. Potts Invertebrata iii. 113 The three grades of sponge structure..are known as the ‘Ascon’, ‘Sycon’, and ‘Leucon’ grades.

1989 Encycl. Brit. XXVIII. 109/1 In the leucon type..the radial canals are replaced by numerous small flagellated chambers in which the choanocytes are localized.

2010 C. Milsom & S. Rigby Fossils at Glance (ed. 2) iii. 22 There is a leucon grade of organization, with a series of canals within the thick wall of the tulip head.

This is a new entry (OED Third Edition, June 2010; most recently modified version published online March 2022).

单词	leucon
释义	leuconn. Brit. /ˈl(j)uːkɒn/, U.S. /ˈlukɑn/ Origin: A borrowing from German. Etymon: German Leucones. Etymology: < German Leucones, the name of a ‘natural family’ of sponges (E. Haeckel 1871, in Jenaische Zeitschr. f. Med. u. Naturwissensch. 6 648) < leucon- (in scientific Latin Leuconia , proposed genus name of sponges (R. E. Grant in Lancet (1833) 2 Nov. 199/2) < ancient Greek λευκός white (see leuco- comb. form) + scientific Latin -ia -ia suffix², with inserted -n- , perhaps after ancient Greek λευκόν , neuter singular of λευκός ) + -es , probably after Sycones (see sycon n.). Compare earlier scientific Latin leucon, specific name of a beetle (1826). Zoology. The most complex type of sponge structure, in which chambers lined with flagellated cells (choanocytes) are connected to the exterior and the central cavity by a network of canals (= rhagon n. 2); a stage in sponge development typified by this structure (= rhagon n. 1); a sponge of this type or stage. Frequently attributive. Cf. ascon n., sycon n. 2. ΘΚΠ the world > animals > invertebrates > subkingdom Parazoa > phylum Porifera > [noun] > member of > rhagon ascon1881 leucon1881 rhagon1887 1873 W. S. Dallas tr. E. Häckel in Ann. & Mag. Nat. Hist. 11 424 D. IV. Natural system with average extension of the idea of species (in the fourth degree): three families (Ascones, Leucones, Sycones) with 21 genera.] 1881 Jrnl. Royal Microsc. Soc. 1 612 A simple Leucon is the homologue of a simple Sycon, and therefore with an Ascon. 1892 Jrnl. Elisha Mitchell Sci. Soc. 9 36 The subdermal cavities.., communicating with the exterior by numerous pores,..are found in certain Leucons. 1932 L. A. Borradaile & F. A. Potts Invertebrata iii. 113 The three grades of sponge structure..are known as the ‘Ascon’, ‘Sycon’, and ‘Leucon’ grades. 1989 Encycl. Brit. XXVIII. 109/1 In the leucon type..the radial canals are replaced by numerous small flagellated chambers in which the choanocytes are localized. 2010 C. Milsom & S. Rigby Fossils at Glance (ed. 2) iii. 22 There is a leucon grade of organization, with a series of canals within the thick wall of the tulip head. This is a new entry (OED Third Edition, June 2010; most recently modified version published online March 2022). < n.1881
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