J J UL TIXUCL EAT.i: 291 



Braun — Verjiingung in der Natur, 1851, p. 136 (Ray Soc, Bot. and Phys. Mem., 



1853)- 

 Woronin — Ann. Sc. Nat. (Bot.), xvi., 1862, p. 200. 



Pringsheim — Monber. Berlin Akad., 1 87 1, p. 240. 



Arcangeli — Nuov. Giorn. Bot. Ital. , 1874, p. 174. 



De Bary u. Strasburger — (Acetabularia) Bot. Zeit., p. 713 et seq. 



Cornu — Compt. Rend., Ixxxix., 1879, p. 1049. 



Schmitz — Sitzber, Niederrhein. Gesell. , 1879 ^i^^l 1881. 



Berthold — Bot. Zeit., 18S0, p. 648 ; and ^^littheil. Zool. Stat. Xeapel, 18S0, p. 72. 



Murray — (Rhipilia Ktz. = Avrainvillea Dene.) Trans. Linn. Soc, ii., 18S6, p. 225 



AYakker — (Caulerpa), VersL Akad. Weten. Amsterdam, 1886, p. 251 ; and 1887, 



p. 251. 



Agardh — Till Algernes Systematik, Siphoneae, 1887. 



Cramer — Ueber die verticillirten Siphoneen (Xeomeris und Cymopolia), 1887. 



Noll— Bot. Zeit., 1887, p. 473. 



^Murray and Boodle — (Struvea) Ann. of Bot,, ii., 1S88. 



Class XVII.— Coenobiese. 



In this class are included a small number of minute (mostly micro- 

 scopic) fresh-water organisms, characterised by the cells being associated 

 together into a ccenobe, i.e. into a colony of more or less equivalent ceils 

 resulting from the division of a common mother-cell. As this division 

 always takes the form of repeated bipartition, the number of cells con- 

 stituting a colony is necessarily, when perfect, a power of 2, viz. 4. 8, 16, 32, 

 64, &c. The cells constituting the coenobe are more or less imbedded 

 in a gelatinous envelope, which is sometimes enclosed in a membrane 

 common to the whole colony ; in the higher forms the cells, or some of 

 them, are ciliated, the cilia protruding through the enveloping mem- 

 brane, and the colony moves about in the water with very great activity ; 

 the lower forms are not ciliated, but the colony is nevertheless endowed 

 with a very considerable power of motion. The coenobe is always of 

 an exceedingly beautiful regular fcrm, spherical, or less often discoid 

 or cubical, or, in the Hydrodictyeae, in the form of a net. The five 

 orders of which it is composed, the Sorastrese, Pandorinese, Pediastreae, 

 Hydrodictyese, and Yolvocineje, form a series of ascending develop- 

 ment. Very little is known about the reproduction of the first ; the 

 Pandorineae, Pediastrese, and Hydrodictyeae multiply by the conjugation 

 of zoogametes ; while in the Yolvocinere, which represent the highest 

 type attained by organisms of the coenobe type, the mode of sexual 

 reproduction is much more complicated, the male and female reproduc- 

 tive cells being separately formed in distinct antherids and oogones. 



u 2 



