M UL T1NUCLEA T^E 291 



BraunVerj tingung in der Natur, 1851, p. 136 (Ray Soc., Bot. and Phys. Mem., 



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



Pringsheim Member. Berlin Akad., 1871, 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 and 1881. 



Berthold Bot. Zeit., 1880, p. 648 ; and Mittheil. Zool. Stat. Neapel, 1880, p. 72. 



Murray (Rhipilia Ktz. =Avrainvillea Dene.) Trans. Linn. Soc., ii., 1886, p. 225 



Wakker (Caulerpa), Versl. Akad. Weten. Amsterdam, 1886, p. 251 ; and 1887, 



p. 251. 



Agardh Till Algernes Systematik, Siphoneae, 1887. 



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

 Noll Bot. Zeit., 1887, p. 473. 

 Murray and Boodle (Struvea) Ann. of Bot., ii. , 1888. 



Class XVII. Ccenobieae. 



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 cxnobe, i.e. into a colony of more or less equivalent cells 

 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 ccenobe is always of 

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

 or cubical, or, in the Hyo^rodictyeae, in the form af a net. The five 

 orders of which it is composed, the Sorastreae, Pandorineas, Pediastreae. 

 Hydrodictyeae, and Volvocineae, form a series of ascending develop- 

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

 Pandorineae, Pediastreae, and Hydrodictyeae multiply by the conjugation 

 of zoogametes ; while in the Volvocineae, 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 



