98 SUMMARY OF CURRENT RESEARCHES RELATING TO 



A comparison of various lakes has proved that mineral " constituents of 

 the water have no noticeable influence on the production of plankton, 

 but the development of " water bloom " goes certainly hand-in-hand 

 with the presence of organic substances washed out from the mud. The 

 lake water was often changed by the running in of fresh water, but this 

 only produced a diminution of the quantity, not the quality, of the 

 plankton. Animal enemies of the algae appeared to be absent. Details 

 are given of the analysis of the water and mud. 



Marine Plankton.* — G. Stiasny embodies in book form his own know- 

 ledge, gained by a study of Adriatic plankton, together with the latest 

 information on the subject in general. The treatment is as follows : 

 History of plankton investigation, conditions of life of marine plankton, 

 organisms (both plant and animal), comparison of fresh-water and marine 

 plankton, methods of investigation, phenomena of adaptation, methods 

 of life, animals and plants in their respective relations, horizontal, 

 vertical and geographical distribution, variations, density of plankton- 

 swarms, plankton -streaming, bipolarity, role of plankton in marine 

 economy, importance for mankind, and practical hints for the study and 

 observation of plankton on sea-voyages. 



Colonies of Bacillariaceae.f — G. Funk discusses the movements of 

 colonies of Bacillariaceae and their dependence on outward stimuli. The 

 colonies of Bacillaria paradoxa and Homoiocladia Martiana take on 

 resting stages under certain conditions ; and in these states the in- 

 dividuals are separated as much as possible. As a result of mechanical 

 stimulus the separate individuals of a Bacillaria colony slide past each 

 other and change the form of the colony from rows to that of a ribbon, 

 while a colony of Homoiocladia shortens itself by a half to a third of its 

 original length. After a short period in the new form they change back 

 to the original resting shape. The colonies of Bacillaria take preferably 

 during the day long stretched-out positions, during the night contracted 

 positions. The author notices that in Homoiocladia single individuals, 

 in Bacillaria single colonies, carry out apparently autonomous move- 

 ments. The author was unable to establish proof of any reaction to 

 mechanical stimuli in Schizonema and Berlceleya ; he only found autono- 

 mous movements. 



Isolation of Algae from Collemaceae.:}: — V, Uhlir has succeeded in 

 cultivating Nostocaceae from the lichen genus Collema, in silicic acid 

 lighted by electric light. The cultures grew quickly and luxuriantly. 

 The two points which the author emphasizes are the lighting by elec- 

 tricity and the poverty of the nutritive medium. The algae need only a 

 certain amount of dampness, which can be obtained by evaporating 

 water under the bell-jar. 



* Sammlung Goschen., No. 675. G. J. Goschen's Verlagshandl. (1913) 160 pp., 

 83 figs. See also Bot. Centralbl, cxxix. (1915) pp. 407-8. 



t Mitt. Zool. Stat. Neapel, 1914, Berlin, 15 pp. (1 pi.). See also Bot. Cen- 

 tralbl., cxxix. (1915) p. 4. 



X Ziva. Praze, 1914-[1915] p. 233. See also Bot. Centralbl., cxxix. (1915) p. 879. 



