28 3 



By decanting and renovating the saltpetre solution as soon as the evolution 

 of gas diminishes, the activity returns 1 ). This being repeated a few times the 

 precipitate changes into a slimy mass, so rich in slime-forming bacteria that at 

 heating on a platinum plate in the Bun sen burner carbon is separated. With 

 concentrated sulfuric acid carbonisation is also easily demonstrated. As the rate 

 of nitrogen of this slime is less than 3%, it must chiefly consist of wall substance, 

 which is evidently the chief product of the chemosynthesis *). It results from 

 the carbonic acid after the same formula as the starch in the chlorophyll granules 

 by photosynthesis, thus 



6 COa + 5 Ha O = = C Hiu Or, + 6 Oa 



so that oxygen is set free, which explains the ready course of the process in a closed 

 bottle, when considering that all denitrifying bacteria require a little free oxygen. 



Just as the organic denitrification, that with sulfur may as well take place 

 in the dark as in the light. After pasteurisation no sulfur-denitrification or oxy- 

 dation is observed. 



The quantitative estimation of the carbon fixed by chemosynthesis was made 

 as follows. The sediment was treated with hydrochloric acid and later with alkali 

 to remove the chalk and the sulfur, whereby certainly a great portion of the 

 organic substance ist lost. In the remaining precipitate, which still contains gypsum, 

 the organic matter was determined as carbonic acid after the method of Herz- 

 feld-Wolff-Degener 3 ), by oxydation with bichromate and sulfuric acid. After 

 a culture of about six weeks there was in this way found about 0.05 gram of 

 carbonic acid per gram of oxidised sulfur, which corresponds to 0.013 gr. of 

 organic carbon 4 ). This quantity, however, must certainly be doubled, for at the 

 extraction of the chalk and sulfur at least half the weight of the bacterial sub- 

 stance in lost. I therefore esteem the production of organic carbon in relation 

 to the oxidised sulfur at 2% in weight. 



Old cultures containing much organic matter and in which the nitrate has 

 disappeared produce H'2S, obviously in consequence of sulfate reduction, and 

 perhaps, too, directly from the still present sulfur, whilst the hydrogen wanted 

 for this originates from the organic material formed by chemosynthesis. Such 

 liquids finally teem with infusoria and monads, and various other members of 

 the so remarkable sulfur-flora and -fauna. 



') Addition of soda instead of decantation and renovation, also acts favourably. 

 Evidently the dissolved sulfuric acid is difficultly neutralised by the chalk of the precipitate 



-) See also: A. J. Lebedeff, Ueber die Assimilation des Kohlenstoffs durch Wasser- 

 stoff-oxydierende Bakterien. Berichte d. Deutschen Botan. Gesellsch. Bd. 27, pag. 598, 

 1909. He says that the bacterium can oxidise hydrogen in absence of COa; this, however, 

 is manifestly erroneous. Nor does he take into consideration the oxygen produced at 

 the denitrification by the hydrogen of the saltpetre, used by him as source of nitrogen. 

 His fear that by using ammonsalts nitrification would follow, is under these conditions 

 unfounded. 



3 ) F. Tiemann und A. Gartner. Die chemische, mikroskop. und bakteriol. Unter- 

 suchungen des Wassers. 3. Aufl., pag. 247, 1889. 



4 ) The quantity found by Mr. Jacobsen at the direct oxidation of sulfur by bacteria 

 was of the same order. (Die Oxydation des elementaren Schwefels durch Bakterien. 

 Folia Microbiol. Jahrg. i, pag. 487, 1912.) 



