82 SUMMARY OF CUERENT RESEARCHES RELATING TO 



and the presentation of a new scheme. The author regards as neces- 

 sary the determination, quantitatively and qualitatively, of the organic 

 and inorganic floating matter, Plankton and Tripton. He dis- 

 tinguishes three groups : I. Euplankton (Kolkwitz) and Eutripton. 

 In size the two are analogous. Both are found in the clearest water as 

 Nannoplankton and Nannotripton. II. Pseudoplankton and Pseudo- 

 tripton. Under the former he understands all organisms which may 

 live in water but do not actually find therein the true conditions essen- 

 tial to life ; such as organisms torn from the bank or the bottom and 

 able to exist for a certain time, or those attached to Euplankton 

 individuals, or those dependent on sewage (Saproplankton). III. Hemi- 

 plankton and Periplankton. All organisms which pass a certain stage 

 of their development as a plankton unit. The auto-purification of 

 sewage is more difficult to bring about in the sea than in fresh-water. 

 Impurities of harbours and of bays in tideless seas cause an enormous 

 development of Ulva Lactuca through a rich supply of nitrogen, and it 

 fouls the water and spreads disease. E. S. G. 



Fresh-water Biological Institute at Aneboda, and the Scientific 

 Investigations carried out there. — E. Naumann {Skrift. Sodra Sver. 

 Fisherifor. Lund, 1916, No. 13, 17 pp. ; see also Bot. Centralbl., 1918, 

 137, 134-5). In connexion with the Swedish Fishery Association a 

 laboratory was opened at Aneboda in 1907, for the investigation of 

 problems of fresh-water biology and fishery. The influence of the food 

 supply on planktological conditions of the water was examined. It was 

 shown to produce a more or less marked change of the chemical medium, 

 and in a mildly saprobihzing direction, which caused an increase in 

 certain plankton forms, often in extreme degree. These culture for- 

 mations have a two-fold importance. They bring about a normal 

 biochemical automatic regulation of the water — a sort of automatic 

 protection against otherwise harmful remains of nutrition ; and the in- 

 creased production of phyto-plankton provides a larger supply of food 

 for the pelagic and benthic fauna. E. S. G. 



Simple arrangement for obtaining Biological Samples of Water 

 from the deeper Water Strata. — E. Naumann {Skrift. Sodra Sver. 

 Fiskerifor. Lund, 1916, No. 13, 8 pp. ; see also Bot. Centralbl., 1918, 

 137, 135). A description of a new type of dipping-bottle used by 

 the author for some years for biological purposes. The appearance of 

 the apparatus is described and figured. It is specially adapted for the 

 •collection of quantitative samples of water from various depths. 



E. S. G. 



Lietzensee, near Berlin : An example of Applied Hydrobiology. — 

 E. Naumann {Skrift. Sodra Sver. Fiskerifor. Lund, 1916, No. 13, 

 34 pp. ; see also Bot. Centralbl., 1918, 137, 135). An exhaustive 

 report on the investigations of R. Kolkwitz on the plankton production 

 of the Lietzensee, together with a discussion of the measures undertaken 

 by him for the reduction of the surplus production. An original 

 drawing is given of Oscillatoria Agardhii Gom. E. S. G. 



