r .
h .
:.íl! r
368 DESMIDEÆ.
o f which is occupied hy a vesicle filled with active mole-
cides.
Derivation. From KXmcrryp, a fine thread ; in allusion to
the attenuated form of the frond.
The two peculiarities which distinguish the genus Clos-
tcrium from all other Desmideæ are the crescentic form of
the fronds and the presence in the free extremity of each
of the segments, of the vesicle filled with revolving particles.
These particles occasionally escape from the vesicle, and circulate
vaguely and irregularly round the circumference of
the frond. The use of these particles is not determined : it
may be conjectured tha t they arc in some way or other connected
with reproduction.
The existence of motive papillæ or processes issuing from
the open extremities of the segments has been denied by
most recent observers.
Conjugation has been noticed to occur hy Ehrenherg in
Closterium Dianæ, Cl. lineatum, Cl. striolatum, and Cl.
inoequale.
Ehrenherg, by whom the genus Closterium is placed
amongst the polygastric animalcula, thus defines it: —
“ Animalia polygastrica anentera (tubo intestinal! destituía
) gymnica (non appendiculata), et corpore uniformi in-
volucrato sen loricato, cryptomonadibus simillima, cum lorica
sponte et imperfecte dividua, hinc in polyparium bacilliforme
(aut fusiforme) abeuntia, papillis denique in loricæ apertura
discretis. ”
Independently of the irregular motion of the particles
escaped from the cells, a circulation has been noticed, consisting
of two opposite currents, the one along the side of the
shell, and the other along the periphery of the internal gelatinous
matter, which is invested with an elastic envelope.
By some systematists the Closteria are placed next to the
Conjugateoe, with which in the occasional conjugation of the
fronds of two Closteria and formation of sporangia they do
indeed exhibit a certain degree of relationship.
Through Closterium cylindrus Ehr., Infus. pi. v. fig. 6.
this genus would appear to be united to the genus Cosma-
CLOSTEKIUM. 369
rium : it is most probable, however, that tha t species ought
to be referred to the latter genus.
a. Closteria curved, smooth, not appendaged.
1. Closterium E hrenbergii Menegh.
Plate L X X X V I I . Figo. 1.
Char. Frond semilunar, thinned, and rounded at the extremities.
Granules scattered. Endochrome fasciated.
Bands two or three in each segment.
Der halbe Mond, Eichorn, Kleinste Wassenthiere, p. 48.
taf. 5. fig. c. 1775, 1781, 1784. Vibrio Lunula Miiller,
Naturforscher, 20. p. 142. 1784. ; Herman (after Müller)
ebenda, p. 169. taf. 3. fig. 59. V. Lunula Müller,
Animale.Infus. p.55. taf. vii. figs. 13.and 15. 1717? Mid-
leria? LunulaVeclexQ, 1802 ? Conferve inedite. No. 77,
{Zygnema deciminum) Gerod Chantrans, Recherche sur les
Conferves, t.33. 1802. Mülleria Lunula Schrank, Fauna
boica, iii. 2. p. 47. 1803. Closterium Lunula XitzscAi,
Beiträge, ^ Infusarienkunde, 60. and 67. 1817? Vibrio
Lunula Gruithulsen, Acta Nat. Curios, x. 2. p. 449.
1821. cfr. Cl. moniliferum. Bacillaria Lunula, Acta Nat.
Curios, xi. 2. p. 533. 1823. Lunulina vulgaris Bory,
Fncyc. Method. 1824, and in Diet. Class. d’Hist. Nat.
1826. Lunulina vulgaris Turpin, Diet. d’Hist. Nat.
Planches Végétaux, i. p. 3. 1828. Closterium L^unula
Hemprich et Ehrenberg, Symbolse Physica;, Ever-
tebrat. i. Phytozoa, tab. ii. iv. fig. 6. 1828. Closterium
Lunula, Isis, 1830, p. 168. Closterium Lunula, Abhandl.
der Academic d. Wissensch. zu Berlin, 1829, p. 7. 15.
1830, p. 40. 56. 62., 1831, p. 67. Closterium Lunula,
Symbola; Physica;, text 1830 (1831), fol. b. a. 2. Closterium
Lunula Kütz., Alga; Aquat. siccata;, dec. iii.
No. 22. 1833, and Synopsis Diatomearum, Linna;a,
1833, p. 596. Closterium Lunula and acuminatum Corda,
Almanac de Carlsbad, 1835, p. 190. tafel 5. f. 56—60.
B B