370 SUMMARY OF CURRENT RESEARCHES RELATING TO 



are sometimes slightly curved. The length of a medium-sized specimen 

 is 5 fx, the breadth 2-2 • 5 /x. It is possible in longer specimens to 

 distinguish a slight constriction in the middle, standing out as a light 

 cross-line, and this indicates the beginning of cross-division. Sometimes 

 two halves are found which have parted from one another but are still 

 not wholly disconnected. A further likeness to Chromatium is found 

 in the granular contents, and in the manner of movement, which is 

 lengthwise and accompanied by continual revolution round the axis. 

 Other analogies with Chromatium are described. A detailed account is 

 given of Chloronium mirabile both on a light and on a dark field, and 

 as a stained object. The result of these investigations shows that 

 Chloronium is not a one- but a many-celled organism, consisting of a 

 colourless central cell with polar cilia and numerous green peripheral 

 cells. Various experiments were made to determine the relationship of 

 these two component parts of the organism, and the possibility of their 

 separate existence. The author found that the green cells are capable 

 of living for some time separately, and the central cell for a short 

 period. He therefore concludes that Chloronium represents a new type 

 of symbiotic connexion. Finally, the author gives information as to 

 its habitat and distribution. It is fairly common in suitable localities 

 and conditions. 



The Genus Cylindrocystis.* — J. Liitkemiiller publishes a revision 

 of the genus Cylindrocystis. It has no special and exclusive character- 

 istic. The structure of the cell membrane and its behaviour during 

 cell-division and conjugation decide whether a species belongs to the 

 placoderm or saccoderm Desmidiacese , and in the latter case, again 

 whether it belongs to the Gonatozygeai or to the Spirotaeniese. The 

 chlorophores of Cylindrocystis resembles those of Netrium, but are 

 smaller and less regular. Cylindrocystis has a gelatinous sheath, which 

 in Netrium is wanting. No placoderm species can be placed in Cylin- 

 drocystis, therefore, only Fenium and Cosmarium are left to be con- 

 sidered ; and the author points out the distinguishing characters which 

 separate these genera from Cylindrocystis. He considers that it contains 

 fourteen good species, and he transfers five other species to Cosmarium. 



Stigonema.f — F. N. Blanchard describes in detail a new species 

 of Stiyonema, S. anomalum, from Massachusetts. It is a typical 

 Stiyonema ; and it is allied to Fischerella and Hapalosiphon by certain 

 characters set forth by the author. It is sufficiently like Stiyonema 

 ocellatum to be confused with that species, but can be distinguished 

 from it by seven different characters, which are given Another new 

 species of Stiyonema is here described, 8. medium, from the same locality. 

 This plant shows characteristics of Hapalosiphon as well as of Stiyonema. 

 A table of comparison showing the chief characteristics of these two 

 genera and Fischerella is given, founded on reproduction, width of 

 filament, length of hormogones, number of rows in filaments, style of 

 branching, sheath, cells, heterocysts. Hapalosiphon grows free-floating 



* Verb. k.k. Zool. Bot. Ges. Wieu, bdii. (1913) pp. 212-30. 

 t Tuft's Coll. Studies, iii. (1914) pp. 117-24 (1 pi.). 



